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Influence-cjdns/src/lib/json/json.hpp
Denis Davydov 4d8e28b55d Added a library for working with JSON.
2018-05-10 18:54:01 +03:00

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/*
__ _____ _____ _____
__| | __| | | | JSON for Modern C++
| | |__ | | | | | | version 3.1.2
|_____|_____|_____|_|___| https://github.com/nlohmann/json
Licensed under the MIT License <http://opensource.org/licenses/MIT>.
Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
#ifndef NLOHMANN_JSON_HPP
#define NLOHMANN_JSON_HPP
#define NLOHMANN_JSON_VERSION_MAJOR 3
#define NLOHMANN_JSON_VERSION_MINOR 1
#define NLOHMANN_JSON_VERSION_PATCH 2
#include <algorithm> // all_of, find, for_each
#include <cassert> // assert
#include <ciso646> // and, not, or
#include <cstddef> // nullptr_t, ptrdiff_t, size_t
#include <functional> // hash, less
#include <initializer_list> // initializer_list
#include <iosfwd> // istream, ostream
#include <iterator> // iterator_traits, random_access_iterator_tag
#include <numeric> // accumulate
#include <string> // string, stoi, to_string
#include <utility> // declval, forward, move, pair, swap
#include <nlohmann/json_fwd.hpp>
#include <nlohmann/detail/macro_scope.hpp>
#include <nlohmann/detail/meta.hpp>
#include <nlohmann/detail/exceptions.hpp>
#include <nlohmann/detail/value_t.hpp>
#include <nlohmann/detail/conversions/from_json.hpp>
#include <nlohmann/detail/conversions/to_json.hpp>
#include <nlohmann/detail/input/input_adapters.hpp>
#include <nlohmann/detail/input/lexer.hpp>
#include <nlohmann/detail/input/parser.hpp>
#include <nlohmann/detail/iterators/primitive_iterator.hpp>
#include <nlohmann/detail/iterators/internal_iterator.hpp>
#include <nlohmann/detail/iterators/iter_impl.hpp>
#include <nlohmann/detail/iterators/iteration_proxy.hpp>
#include <nlohmann/detail/iterators/json_reverse_iterator.hpp>
#include <nlohmann/detail/output/output_adapters.hpp>
#include <nlohmann/detail/input/binary_reader.hpp>
#include <nlohmann/detail/output/binary_writer.hpp>
#include <nlohmann/detail/output/serializer.hpp>
#include <nlohmann/detail/json_ref.hpp>
#include <nlohmann/detail/json_pointer.hpp>
#include <nlohmann/adl_serializer.hpp>
/*!
@brief namespace for Niels Lohmann
@see https://github.com/nlohmann
@since version 1.0.0
*/
namespace nlohmann
{
/*!
@brief a class to store JSON values
@tparam ObjectType type for JSON objects (`std::map` by default; will be used
in @ref object_t)
@tparam ArrayType type for JSON arrays (`std::vector` by default; will be used
in @ref array_t)
@tparam StringType type for JSON strings and object keys (`std::string` by
default; will be used in @ref string_t)
@tparam BooleanType type for JSON booleans (`bool` by default; will be used
in @ref boolean_t)
@tparam NumberIntegerType type for JSON integer numbers (`int64_t` by
default; will be used in @ref number_integer_t)
@tparam NumberUnsignedType type for JSON unsigned integer numbers (@c
`uint64_t` by default; will be used in @ref number_unsigned_t)
@tparam NumberFloatType type for JSON floating-point numbers (`double` by
default; will be used in @ref number_float_t)
@tparam AllocatorType type of the allocator to use (`std::allocator` by
default)
@tparam JSONSerializer the serializer to resolve internal calls to `to_json()`
and `from_json()` (@ref adl_serializer by default)
@requirement The class satisfies the following concept requirements:
- Basic
- [DefaultConstructible](http://en.cppreference.com/w/cpp/concept/DefaultConstructible):
JSON values can be default constructed. The result will be a JSON null
value.
- [MoveConstructible](http://en.cppreference.com/w/cpp/concept/MoveConstructible):
A JSON value can be constructed from an rvalue argument.
- [CopyConstructible](http://en.cppreference.com/w/cpp/concept/CopyConstructible):
A JSON value can be copy-constructed from an lvalue expression.
- [MoveAssignable](http://en.cppreference.com/w/cpp/concept/MoveAssignable):
A JSON value van be assigned from an rvalue argument.
- [CopyAssignable](http://en.cppreference.com/w/cpp/concept/CopyAssignable):
A JSON value can be copy-assigned from an lvalue expression.
- [Destructible](http://en.cppreference.com/w/cpp/concept/Destructible):
JSON values can be destructed.
- Layout
- [StandardLayoutType](http://en.cppreference.com/w/cpp/concept/StandardLayoutType):
JSON values have
[standard layout](http://en.cppreference.com/w/cpp/language/data_members#Standard_layout):
All non-static data members are private and standard layout types, the
class has no virtual functions or (virtual) base classes.
- Library-wide
- [EqualityComparable](http://en.cppreference.com/w/cpp/concept/EqualityComparable):
JSON values can be compared with `==`, see @ref
operator==(const_reference,const_reference).
- [LessThanComparable](http://en.cppreference.com/w/cpp/concept/LessThanComparable):
JSON values can be compared with `<`, see @ref
operator<(const_reference,const_reference).
- [Swappable](http://en.cppreference.com/w/cpp/concept/Swappable):
Any JSON lvalue or rvalue of can be swapped with any lvalue or rvalue of
other compatible types, using unqualified function call @ref swap().
- [NullablePointer](http://en.cppreference.com/w/cpp/concept/NullablePointer):
JSON values can be compared against `std::nullptr_t` objects which are used
to model the `null` value.
- Container
- [Container](http://en.cppreference.com/w/cpp/concept/Container):
JSON values can be used like STL containers and provide iterator access.
- [ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer);
JSON values can be used like STL containers and provide reverse iterator
access.
@invariant The member variables @a m_value and @a m_type have the following
relationship:
- If `m_type == value_t::object`, then `m_value.object != nullptr`.
- If `m_type == value_t::array`, then `m_value.array != nullptr`.
- If `m_type == value_t::string`, then `m_value.string != nullptr`.
The invariants are checked by member function assert_invariant().
@internal
@note ObjectType trick from http://stackoverflow.com/a/9860911
@endinternal
@see [RFC 7159: The JavaScript Object Notation (JSON) Data Interchange
Format](http://rfc7159.net/rfc7159)
@since version 1.0.0
@nosubgrouping
*/
NLOHMANN_BASIC_JSON_TPL_DECLARATION
class basic_json
{
private:
template<detail::value_t> friend struct detail::external_constructor;
friend ::nlohmann::json_pointer<basic_json>;
friend ::nlohmann::detail::parser<basic_json>;
friend ::nlohmann::detail::serializer<basic_json>;
template<typename BasicJsonType>
friend class ::nlohmann::detail::iter_impl;
template<typename BasicJsonType, typename CharType>
friend class ::nlohmann::detail::binary_writer;
template<typename BasicJsonType>
friend class ::nlohmann::detail::binary_reader;
/// workaround type for MSVC
using basic_json_t = NLOHMANN_BASIC_JSON_TPL;
// convenience aliases for types residing in namespace detail;
using lexer = ::nlohmann::detail::lexer<basic_json>;
using parser = ::nlohmann::detail::parser<basic_json>;
using primitive_iterator_t = ::nlohmann::detail::primitive_iterator_t;
template<typename BasicJsonType>
using internal_iterator = ::nlohmann::detail::internal_iterator<BasicJsonType>;
template<typename BasicJsonType>
using iter_impl = ::nlohmann::detail::iter_impl<BasicJsonType>;
template<typename Iterator>
using iteration_proxy = ::nlohmann::detail::iteration_proxy<Iterator>;
template<typename Base> using json_reverse_iterator = ::nlohmann::detail::json_reverse_iterator<Base>;
template<typename CharType>
using output_adapter_t = ::nlohmann::detail::output_adapter_t<CharType>;
using binary_reader = ::nlohmann::detail::binary_reader<basic_json>;
template<typename CharType> using binary_writer = ::nlohmann::detail::binary_writer<basic_json, CharType>;
using serializer = ::nlohmann::detail::serializer<basic_json>;
public:
using value_t = detail::value_t;
/// @copydoc nlohmann::json_pointer
using json_pointer = ::nlohmann::json_pointer<basic_json>;
template<typename T, typename SFINAE>
using json_serializer = JSONSerializer<T, SFINAE>;
/// helper type for initializer lists of basic_json values
using initializer_list_t = std::initializer_list<detail::json_ref<basic_json>>;
////////////////
// exceptions //
////////////////
/// @name exceptions
/// Classes to implement user-defined exceptions.
/// @{
/// @copydoc detail::exception
using exception = detail::exception;
/// @copydoc detail::parse_error
using parse_error = detail::parse_error;
/// @copydoc detail::invalid_iterator
using invalid_iterator = detail::invalid_iterator;
/// @copydoc detail::type_error
using type_error = detail::type_error;
/// @copydoc detail::out_of_range
using out_of_range = detail::out_of_range;
/// @copydoc detail::other_error
using other_error = detail::other_error;
/// @}
/////////////////////
// container types //
/////////////////////
/// @name container types
/// The canonic container types to use @ref basic_json like any other STL
/// container.
/// @{
/// the type of elements in a basic_json container
using value_type = basic_json;
/// the type of an element reference
using reference = value_type&;
/// the type of an element const reference
using const_reference = const value_type&;
/// a type to represent differences between iterators
using difference_type = std::ptrdiff_t;
/// a type to represent container sizes
using size_type = std::size_t;
/// the allocator type
using allocator_type = AllocatorType<basic_json>;
/// the type of an element pointer
using pointer = typename std::allocator_traits<allocator_type>::pointer;
/// the type of an element const pointer
using const_pointer = typename std::allocator_traits<allocator_type>::const_pointer;
/// an iterator for a basic_json container
using iterator = iter_impl<basic_json>;
/// a const iterator for a basic_json container
using const_iterator = iter_impl<const basic_json>;
/// a reverse iterator for a basic_json container
using reverse_iterator = json_reverse_iterator<typename basic_json::iterator>;
/// a const reverse iterator for a basic_json container
using const_reverse_iterator = json_reverse_iterator<typename basic_json::const_iterator>;
/// @}
/*!
@brief returns the allocator associated with the container
*/
static allocator_type get_allocator()
{
return allocator_type();
}
/*!
@brief returns version information on the library
This function returns a JSON object with information about the library,
including the version number and information on the platform and compiler.
@return JSON object holding version information
key | description
----------- | ---------------
`compiler` | Information on the used compiler. It is an object with the following keys: `c++` (the used C++ standard), `family` (the compiler family; possible values are `clang`, `icc`, `gcc`, `ilecpp`, `msvc`, `pgcpp`, `sunpro`, and `unknown`), and `version` (the compiler version).
`copyright` | The copyright line for the library as string.
`name` | The name of the library as string.
`platform` | The used platform as string. Possible values are `win32`, `linux`, `apple`, `unix`, and `unknown`.
`url` | The URL of the project as string.
`version` | The version of the library. It is an object with the following keys: `major`, `minor`, and `patch` as defined by [Semantic Versioning](http://semver.org), and `string` (the version string).
@liveexample{The following code shows an example output of the `meta()`
function.,meta}
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes to any JSON value.
@complexity Constant.
@since 2.1.0
*/
static basic_json meta()
{
basic_json result;
result["copyright"] = "(C) 2013-2017 Niels Lohmann";
result["name"] = "JSON for Modern C++";
result["url"] = "https://github.com/nlohmann/json";
result["version"]["string"] =
std::to_string(NLOHMANN_JSON_VERSION_MAJOR) + "." +
std::to_string(NLOHMANN_JSON_VERSION_MINOR) + "." +
std::to_string(NLOHMANN_JSON_VERSION_PATCH);
result["version"]["major"] = NLOHMANN_JSON_VERSION_MAJOR;
result["version"]["minor"] = NLOHMANN_JSON_VERSION_MINOR;
result["version"]["patch"] = NLOHMANN_JSON_VERSION_PATCH;
#ifdef _WIN32
result["platform"] = "win32";
#elif defined __linux__
result["platform"] = "linux";
#elif defined __APPLE__
result["platform"] = "apple";
#elif defined __unix__
result["platform"] = "unix";
#else
result["platform"] = "unknown";
#endif
#if defined(__ICC) || defined(__INTEL_COMPILER)
result["compiler"] = {{"family", "icc"}, {"version", __INTEL_COMPILER}};
#elif defined(__clang__)
result["compiler"] = {{"family", "clang"}, {"version", __clang_version__}};
#elif defined(__GNUC__) || defined(__GNUG__)
result["compiler"] = {{"family", "gcc"}, {"version", std::to_string(__GNUC__) + "." + std::to_string(__GNUC_MINOR__) + "." + std::to_string(__GNUC_PATCHLEVEL__)}};
#elif defined(__HP_cc) || defined(__HP_aCC)
result["compiler"] = "hp"
#elif defined(__IBMCPP__)
result["compiler"] = {{"family", "ilecpp"}, {"version", __IBMCPP__}};
#elif defined(_MSC_VER)
result["compiler"] = {{"family", "msvc"}, {"version", _MSC_VER}};
#elif defined(__PGI)
result["compiler"] = {{"family", "pgcpp"}, {"version", __PGI}};
#elif defined(__SUNPRO_CC)
result["compiler"] = {{"family", "sunpro"}, {"version", __SUNPRO_CC}};
#else
result["compiler"] = {{"family", "unknown"}, {"version", "unknown"}};
#endif
#ifdef __cplusplus
result["compiler"]["c++"] = std::to_string(__cplusplus);
#else
result["compiler"]["c++"] = "unknown";
#endif
return result;
}
///////////////////////////
// JSON value data types //
///////////////////////////
/// @name JSON value data types
/// The data types to store a JSON value. These types are derived from
/// the template arguments passed to class @ref basic_json.
/// @{
#if defined(JSON_HAS_CPP_14)
// Use transparent comparator if possible, combined with perfect forwarding
// on find() and count() calls prevents unnecessary string construction.
using object_comparator_t = std::less<>;
#else
using object_comparator_t = std::less<StringType>;
#endif
/*!
@brief a type for an object
[RFC 7159](http://rfc7159.net/rfc7159) describes JSON objects as follows:
> An object is an unordered collection of zero or more name/value pairs,
> where a name is a string and a value is a string, number, boolean, null,
> object, or array.
To store objects in C++, a type is defined by the template parameters
described below.
@tparam ObjectType the container to store objects (e.g., `std::map` or
`std::unordered_map`)
@tparam StringType the type of the keys or names (e.g., `std::string`).
The comparison function `std::less<StringType>` is used to order elements
inside the container.
@tparam AllocatorType the allocator to use for objects (e.g.,
`std::allocator`)
#### Default type
With the default values for @a ObjectType (`std::map`), @a StringType
(`std::string`), and @a AllocatorType (`std::allocator`), the default
value for @a object_t is:
@code {.cpp}
std::map<
std::string, // key_type
basic_json, // value_type
std::less<std::string>, // key_compare
std::allocator<std::pair<const std::string, basic_json>> // allocator_type
>
@endcode
#### Behavior
The choice of @a object_t influences the behavior of the JSON class. With
the default type, objects have the following behavior:
- When all names are unique, objects will be interoperable in the sense
that all software implementations receiving that object will agree on
the name-value mappings.
- When the names within an object are not unique, it is unspecified which
one of the values for a given key will be chosen. For instance,
`{"key": 2, "key": 1}` could be equal to either `{"key": 1}` or
`{"key": 2}`.
- Internally, name/value pairs are stored in lexicographical order of the
names. Objects will also be serialized (see @ref dump) in this order.
For instance, `{"b": 1, "a": 2}` and `{"a": 2, "b": 1}` will be stored
and serialized as `{"a": 2, "b": 1}`.
- When comparing objects, the order of the name/value pairs is irrelevant.
This makes objects interoperable in the sense that they will not be
affected by these differences. For instance, `{"b": 1, "a": 2}` and
`{"a": 2, "b": 1}` will be treated as equal.
#### Limits
[RFC 7159](http://rfc7159.net/rfc7159) specifies:
> An implementation may set limits on the maximum depth of nesting.
In this class, the object's limit of nesting is not explicitly constrained.
However, a maximum depth of nesting may be introduced by the compiler or
runtime environment. A theoretical limit can be queried by calling the
@ref max_size function of a JSON object.
#### Storage
Objects are stored as pointers in a @ref basic_json type. That is, for any
access to object values, a pointer of type `object_t*` must be
dereferenced.
@sa @ref array_t -- type for an array value
@since version 1.0.0
@note The order name/value pairs are added to the object is *not*
preserved by the library. Therefore, iterating an object may return
name/value pairs in a different order than they were originally stored. In
fact, keys will be traversed in alphabetical order as `std::map` with
`std::less` is used by default. Please note this behavior conforms to [RFC
7159](http://rfc7159.net/rfc7159), because any order implements the
specified "unordered" nature of JSON objects.
*/
using object_t = ObjectType<StringType,
basic_json,
object_comparator_t,
AllocatorType<std::pair<const StringType,
basic_json>>>;
/*!
@brief a type for an array
[RFC 7159](http://rfc7159.net/rfc7159) describes JSON arrays as follows:
> An array is an ordered sequence of zero or more values.
To store objects in C++, a type is defined by the template parameters
explained below.
@tparam ArrayType container type to store arrays (e.g., `std::vector` or
`std::list`)
@tparam AllocatorType allocator to use for arrays (e.g., `std::allocator`)
#### Default type
With the default values for @a ArrayType (`std::vector`) and @a
AllocatorType (`std::allocator`), the default value for @a array_t is:
@code {.cpp}
std::vector<
basic_json, // value_type
std::allocator<basic_json> // allocator_type
>
@endcode
#### Limits
[RFC 7159](http://rfc7159.net/rfc7159) specifies:
> An implementation may set limits on the maximum depth of nesting.
In this class, the array's limit of nesting is not explicitly constrained.
However, a maximum depth of nesting may be introduced by the compiler or
runtime environment. A theoretical limit can be queried by calling the
@ref max_size function of a JSON array.
#### Storage
Arrays are stored as pointers in a @ref basic_json type. That is, for any
access to array values, a pointer of type `array_t*` must be dereferenced.
@sa @ref object_t -- type for an object value
@since version 1.0.0
*/
using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
/*!
@brief a type for a string
[RFC 7159](http://rfc7159.net/rfc7159) describes JSON strings as follows:
> A string is a sequence of zero or more Unicode characters.
To store objects in C++, a type is defined by the template parameter
described below. Unicode values are split by the JSON class into
byte-sized characters during deserialization.
@tparam StringType the container to store strings (e.g., `std::string`).
Note this container is used for keys/names in objects, see @ref object_t.
#### Default type
With the default values for @a StringType (`std::string`), the default
value for @a string_t is:
@code {.cpp}
std::string
@endcode
#### Encoding
Strings are stored in UTF-8 encoding. Therefore, functions like
`std::string::size()` or `std::string::length()` return the number of
bytes in the string rather than the number of characters or glyphs.
#### String comparison
[RFC 7159](http://rfc7159.net/rfc7159) states:
> Software implementations are typically required to test names of object
> members for equality. Implementations that transform the textual
> representation into sequences of Unicode code units and then perform the
> comparison numerically, code unit by code unit, are interoperable in the
> sense that implementations will agree in all cases on equality or
> inequality of two strings. For example, implementations that compare
> strings with escaped characters unconverted may incorrectly find that
> `"a\\b"` and `"a\u005Cb"` are not equal.
This implementation is interoperable as it does compare strings code unit
by code unit.
#### Storage
String values are stored as pointers in a @ref basic_json type. That is,
for any access to string values, a pointer of type `string_t*` must be
dereferenced.
@since version 1.0.0
*/
using string_t = StringType;
/*!
@brief a type for a boolean
[RFC 7159](http://rfc7159.net/rfc7159) implicitly describes a boolean as a
type which differentiates the two literals `true` and `false`.
To store objects in C++, a type is defined by the template parameter @a
BooleanType which chooses the type to use.
#### Default type
With the default values for @a BooleanType (`bool`), the default value for
@a boolean_t is:
@code {.cpp}
bool
@endcode
#### Storage
Boolean values are stored directly inside a @ref basic_json type.
@since version 1.0.0
*/
using boolean_t = BooleanType;
/*!
@brief a type for a number (integer)
[RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
> The representation of numbers is similar to that used in most
> programming languages. A number is represented in base 10 using decimal
> digits. It contains an integer component that may be prefixed with an
> optional minus sign, which may be followed by a fraction part and/or an
> exponent part. Leading zeros are not allowed. (...) Numeric values that
> cannot be represented in the grammar below (such as Infinity and NaN)
> are not permitted.
This description includes both integer and floating-point numbers.
However, C++ allows more precise storage if it is known whether the number
is a signed integer, an unsigned integer or a floating-point number.
Therefore, three different types, @ref number_integer_t, @ref
number_unsigned_t and @ref number_float_t are used.
To store integer numbers in C++, a type is defined by the template
parameter @a NumberIntegerType which chooses the type to use.
#### Default type
With the default values for @a NumberIntegerType (`int64_t`), the default
value for @a number_integer_t is:
@code {.cpp}
int64_t
@endcode
#### Default behavior
- The restrictions about leading zeros is not enforced in C++. Instead,
leading zeros in integer literals lead to an interpretation as octal
number. Internally, the value will be stored as decimal number. For
instance, the C++ integer literal `010` will be serialized to `8`.
During deserialization, leading zeros yield an error.
- Not-a-number (NaN) values will be serialized to `null`.
#### Limits
[RFC 7159](http://rfc7159.net/rfc7159) specifies:
> An implementation may set limits on the range and precision of numbers.
When the default type is used, the maximal integer number that can be
stored is `9223372036854775807` (INT64_MAX) and the minimal integer number
that can be stored is `-9223372036854775808` (INT64_MIN). Integer numbers
that are out of range will yield over/underflow when used in a
constructor. During deserialization, too large or small integer numbers
will be automatically be stored as @ref number_unsigned_t or @ref
number_float_t.
[RFC 7159](http://rfc7159.net/rfc7159) further states:
> Note that when such software is used, numbers that are integers and are
> in the range \f$[-2^{53}+1, 2^{53}-1]\f$ are interoperable in the sense
> that implementations will agree exactly on their numeric values.
As this range is a subrange of the exactly supported range [INT64_MIN,
INT64_MAX], this class's integer type is interoperable.
#### Storage
Integer number values are stored directly inside a @ref basic_json type.
@sa @ref number_float_t -- type for number values (floating-point)
@sa @ref number_unsigned_t -- type for number values (unsigned integer)
@since version 1.0.0
*/
using number_integer_t = NumberIntegerType;
/*!
@brief a type for a number (unsigned)
[RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
> The representation of numbers is similar to that used in most
> programming languages. A number is represented in base 10 using decimal
> digits. It contains an integer component that may be prefixed with an
> optional minus sign, which may be followed by a fraction part and/or an
> exponent part. Leading zeros are not allowed. (...) Numeric values that
> cannot be represented in the grammar below (such as Infinity and NaN)
> are not permitted.
This description includes both integer and floating-point numbers.
However, C++ allows more precise storage if it is known whether the number
is a signed integer, an unsigned integer or a floating-point number.
Therefore, three different types, @ref number_integer_t, @ref
number_unsigned_t and @ref number_float_t are used.
To store unsigned integer numbers in C++, a type is defined by the
template parameter @a NumberUnsignedType which chooses the type to use.
#### Default type
With the default values for @a NumberUnsignedType (`uint64_t`), the
default value for @a number_unsigned_t is:
@code {.cpp}
uint64_t
@endcode
#### Default behavior
- The restrictions about leading zeros is not enforced in C++. Instead,
leading zeros in integer literals lead to an interpretation as octal
number. Internally, the value will be stored as decimal number. For
instance, the C++ integer literal `010` will be serialized to `8`.
During deserialization, leading zeros yield an error.
- Not-a-number (NaN) values will be serialized to `null`.
#### Limits
[RFC 7159](http://rfc7159.net/rfc7159) specifies:
> An implementation may set limits on the range and precision of numbers.
When the default type is used, the maximal integer number that can be
stored is `18446744073709551615` (UINT64_MAX) and the minimal integer
number that can be stored is `0`. Integer numbers that are out of range
will yield over/underflow when used in a constructor. During
deserialization, too large or small integer numbers will be automatically
be stored as @ref number_integer_t or @ref number_float_t.
[RFC 7159](http://rfc7159.net/rfc7159) further states:
> Note that when such software is used, numbers that are integers and are
> in the range \f$[-2^{53}+1, 2^{53}-1]\f$ are interoperable in the sense
> that implementations will agree exactly on their numeric values.
As this range is a subrange (when considered in conjunction with the
number_integer_t type) of the exactly supported range [0, UINT64_MAX],
this class's integer type is interoperable.
#### Storage
Integer number values are stored directly inside a @ref basic_json type.
@sa @ref number_float_t -- type for number values (floating-point)
@sa @ref number_integer_t -- type for number values (integer)
@since version 2.0.0
*/
using number_unsigned_t = NumberUnsignedType;
/*!
@brief a type for a number (floating-point)
[RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
> The representation of numbers is similar to that used in most
> programming languages. A number is represented in base 10 using decimal
> digits. It contains an integer component that may be prefixed with an
> optional minus sign, which may be followed by a fraction part and/or an
> exponent part. Leading zeros are not allowed. (...) Numeric values that
> cannot be represented in the grammar below (such as Infinity and NaN)
> are not permitted.
This description includes both integer and floating-point numbers.
However, C++ allows more precise storage if it is known whether the number
is a signed integer, an unsigned integer or a floating-point number.
Therefore, three different types, @ref number_integer_t, @ref
number_unsigned_t and @ref number_float_t are used.
To store floating-point numbers in C++, a type is defined by the template
parameter @a NumberFloatType which chooses the type to use.
#### Default type
With the default values for @a NumberFloatType (`double`), the default
value for @a number_float_t is:
@code {.cpp}
double
@endcode
#### Default behavior
- The restrictions about leading zeros is not enforced in C++. Instead,
leading zeros in floating-point literals will be ignored. Internally,
the value will be stored as decimal number. For instance, the C++
floating-point literal `01.2` will be serialized to `1.2`. During
deserialization, leading zeros yield an error.
- Not-a-number (NaN) values will be serialized to `null`.
#### Limits
[RFC 7159](http://rfc7159.net/rfc7159) states:
> This specification allows implementations to set limits on the range and
> precision of numbers accepted. Since software that implements IEEE
> 754-2008 binary64 (double precision) numbers is generally available and
> widely used, good interoperability can be achieved by implementations
> that expect no more precision or range than these provide, in the sense
> that implementations will approximate JSON numbers within the expected
> precision.
This implementation does exactly follow this approach, as it uses double
precision floating-point numbers. Note values smaller than
`-1.79769313486232e+308` and values greater than `1.79769313486232e+308`
will be stored as NaN internally and be serialized to `null`.
#### Storage
Floating-point number values are stored directly inside a @ref basic_json
type.
@sa @ref number_integer_t -- type for number values (integer)
@sa @ref number_unsigned_t -- type for number values (unsigned integer)
@since version 1.0.0
*/
using number_float_t = NumberFloatType;
/// @}
private:
/// helper for exception-safe object creation
template<typename T, typename... Args>
static T* create(Args&& ... args)
{
AllocatorType<T> alloc;
using AllocatorTraits = std::allocator_traits<AllocatorType<T>>;
auto deleter = [&](T * object)
{
AllocatorTraits::deallocate(alloc, object, 1);
};
std::unique_ptr<T, decltype(deleter)> object(AllocatorTraits::allocate(alloc, 1), deleter);
AllocatorTraits::construct(alloc, object.get(), std::forward<Args>(args)...);
assert(object != nullptr);
return object.release();
}
////////////////////////
// JSON value storage //
////////////////////////
/*!
@brief a JSON value
The actual storage for a JSON value of the @ref basic_json class. This
union combines the different storage types for the JSON value types
defined in @ref value_t.
JSON type | value_t type | used type
--------- | --------------- | ------------------------
object | object | pointer to @ref object_t
array | array | pointer to @ref array_t
string | string | pointer to @ref string_t
boolean | boolean | @ref boolean_t
number | number_integer | @ref number_integer_t
number | number_unsigned | @ref number_unsigned_t
number | number_float | @ref number_float_t
null | null | *no value is stored*
@note Variable-length types (objects, arrays, and strings) are stored as
pointers. The size of the union should not exceed 64 bits if the default
value types are used.
@since version 1.0.0
*/
union json_value
{
/// object (stored with pointer to save storage)
object_t* object;
/// array (stored with pointer to save storage)
array_t* array;
/// string (stored with pointer to save storage)
string_t* string;
/// boolean
boolean_t boolean;
/// number (integer)
number_integer_t number_integer;
/// number (unsigned integer)
number_unsigned_t number_unsigned;
/// number (floating-point)
number_float_t number_float;
/// default constructor (for null values)
json_value() = default;
/// constructor for booleans
json_value(boolean_t v) noexcept : boolean(v) {}
/// constructor for numbers (integer)
json_value(number_integer_t v) noexcept : number_integer(v) {}
/// constructor for numbers (unsigned)
json_value(number_unsigned_t v) noexcept : number_unsigned(v) {}
/// constructor for numbers (floating-point)
json_value(number_float_t v) noexcept : number_float(v) {}
/// constructor for empty values of a given type
json_value(value_t t)
{
switch (t)
{
case value_t::object:
{
object = create<object_t>();
break;
}
case value_t::array:
{
array = create<array_t>();
break;
}
case value_t::string:
{
string = create<string_t>("");
break;
}
case value_t::boolean:
{
boolean = boolean_t(false);
break;
}
case value_t::number_integer:
{
number_integer = number_integer_t(0);
break;
}
case value_t::number_unsigned:
{
number_unsigned = number_unsigned_t(0);
break;
}
case value_t::number_float:
{
number_float = number_float_t(0.0);
break;
}
case value_t::null:
{
object = nullptr; // silence warning, see #821
break;
}
default:
{
object = nullptr; // silence warning, see #821
if (JSON_UNLIKELY(t == value_t::null))
{
JSON_THROW(other_error::create(500, "961c151d2e87f2686a955a9be24d316f1362bf21 3.1.2")); // LCOV_EXCL_LINE
}
break;
}
}
}
/// constructor for strings
json_value(const string_t& value)
{
string = create<string_t>(value);
}
/// constructor for rvalue strings
json_value(string_t&& value)
{
string = create<string_t>(std::move(value));
}
/// constructor for objects
json_value(const object_t& value)
{
object = create<object_t>(value);
}
/// constructor for rvalue objects
json_value(object_t&& value)
{
object = create<object_t>(std::move(value));
}
/// constructor for arrays
json_value(const array_t& value)
{
array = create<array_t>(value);
}
/// constructor for rvalue arrays
json_value(array_t&& value)
{
array = create<array_t>(std::move(value));
}
void destroy(value_t t) noexcept
{
switch (t)
{
case value_t::object:
{
AllocatorType<object_t> alloc;
std::allocator_traits<decltype(alloc)>::destroy(alloc, object);
std::allocator_traits<decltype(alloc)>::deallocate(alloc, object, 1);
break;
}
case value_t::array:
{
AllocatorType<array_t> alloc;
std::allocator_traits<decltype(alloc)>::destroy(alloc, array);
std::allocator_traits<decltype(alloc)>::deallocate(alloc, array, 1);
break;
}
case value_t::string:
{
AllocatorType<string_t> alloc;
std::allocator_traits<decltype(alloc)>::destroy(alloc, string);
std::allocator_traits<decltype(alloc)>::deallocate(alloc, string, 1);
break;
}
default:
{
break;
}
}
}
};
/*!
@brief checks the class invariants
This function asserts the class invariants. It needs to be called at the
end of every constructor to make sure that created objects respect the
invariant. Furthermore, it has to be called each time the type of a JSON
value is changed, because the invariant expresses a relationship between
@a m_type and @a m_value.
*/
void assert_invariant() const noexcept
{
assert(m_type != value_t::object or m_value.object != nullptr);
assert(m_type != value_t::array or m_value.array != nullptr);
assert(m_type != value_t::string or m_value.string != nullptr);
}
public:
//////////////////////////
// JSON parser callback //
//////////////////////////
/*!
@brief parser event types
The parser callback distinguishes the following events:
- `object_start`: the parser read `{` and started to process a JSON object
- `key`: the parser read a key of a value in an object
- `object_end`: the parser read `}` and finished processing a JSON object
- `array_start`: the parser read `[` and started to process a JSON array
- `array_end`: the parser read `]` and finished processing a JSON array
- `value`: the parser finished reading a JSON value
@image html callback_events.png "Example when certain parse events are triggered"
@sa @ref parser_callback_t for more information and examples
*/
using parse_event_t = typename parser::parse_event_t;
/*!
@brief per-element parser callback type
With a parser callback function, the result of parsing a JSON text can be
influenced. When passed to @ref parse, it is called on certain events
(passed as @ref parse_event_t via parameter @a event) with a set recursion
depth @a depth and context JSON value @a parsed. The return value of the
callback function is a boolean indicating whether the element that emitted
the callback shall be kept or not.
We distinguish six scenarios (determined by the event type) in which the
callback function can be called. The following table describes the values
of the parameters @a depth, @a event, and @a parsed.
parameter @a event | description | parameter @a depth | parameter @a parsed
------------------ | ----------- | ------------------ | -------------------
parse_event_t::object_start | the parser read `{` and started to process a JSON object | depth of the parent of the JSON object | a JSON value with type discarded
parse_event_t::key | the parser read a key of a value in an object | depth of the currently parsed JSON object | a JSON string containing the key
parse_event_t::object_end | the parser read `}` and finished processing a JSON object | depth of the parent of the JSON object | the parsed JSON object
parse_event_t::array_start | the parser read `[` and started to process a JSON array | depth of the parent of the JSON array | a JSON value with type discarded
parse_event_t::array_end | the parser read `]` and finished processing a JSON array | depth of the parent of the JSON array | the parsed JSON array
parse_event_t::value | the parser finished reading a JSON value | depth of the value | the parsed JSON value
@image html callback_events.png "Example when certain parse events are triggered"
Discarding a value (i.e., returning `false`) has different effects
depending on the context in which function was called:
- Discarded values in structured types are skipped. That is, the parser
will behave as if the discarded value was never read.
- In case a value outside a structured type is skipped, it is replaced
with `null`. This case happens if the top-level element is skipped.
@param[in] depth the depth of the recursion during parsing
@param[in] event an event of type parse_event_t indicating the context in
the callback function has been called
@param[in,out] parsed the current intermediate parse result; note that
writing to this value has no effect for parse_event_t::key events
@return Whether the JSON value which called the function during parsing
should be kept (`true`) or not (`false`). In the latter case, it is either
skipped completely or replaced by an empty discarded object.
@sa @ref parse for examples
@since version 1.0.0
*/
using parser_callback_t = typename parser::parser_callback_t;
//////////////////
// constructors //
//////////////////
/// @name constructors and destructors
/// Constructors of class @ref basic_json, copy/move constructor, copy
/// assignment, static functions creating objects, and the destructor.
/// @{
/*!
@brief create an empty value with a given type
Create an empty JSON value with a given type. The value will be default
initialized with an empty value which depends on the type:
Value type | initial value
----------- | -------------
null | `null`
boolean | `false`
string | `""`
number | `0`
object | `{}`
array | `[]`
@param[in] v the type of the value to create
@complexity Constant.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes to any JSON value.
@liveexample{The following code shows the constructor for different @ref
value_t values,basic_json__value_t}
@sa @ref clear() -- restores the postcondition of this constructor
@since version 1.0.0
*/
basic_json(const value_t v)
: m_type(v), m_value(v)
{
assert_invariant();
}
/*!
@brief create a null object
Create a `null` JSON value. It either takes a null pointer as parameter
(explicitly creating `null`) or no parameter (implicitly creating `null`).
The passed null pointer itself is not read -- it is only used to choose
the right constructor.
@complexity Constant.
@exceptionsafety No-throw guarantee: this constructor never throws
exceptions.
@liveexample{The following code shows the constructor with and without a
null pointer parameter.,basic_json__nullptr_t}
@since version 1.0.0
*/
basic_json(std::nullptr_t = nullptr) noexcept
: basic_json(value_t::null)
{
assert_invariant();
}
/*!
@brief create a JSON value
This is a "catch all" constructor for all compatible JSON types; that is,
types for which a `to_json()` method exists. The constructor forwards the
parameter @a val to that method (to `json_serializer<U>::to_json` method
with `U = uncvref_t<CompatibleType>`, to be exact).
Template type @a CompatibleType includes, but is not limited to, the
following types:
- **arrays**: @ref array_t and all kinds of compatible containers such as
`std::vector`, `std::deque`, `std::list`, `std::forward_list`,
`std::array`, `std::valarray`, `std::set`, `std::unordered_set`,
`std::multiset`, and `std::unordered_multiset` with a `value_type` from
which a @ref basic_json value can be constructed.
- **objects**: @ref object_t and all kinds of compatible associative
containers such as `std::map`, `std::unordered_map`, `std::multimap`,
and `std::unordered_multimap` with a `key_type` compatible to
@ref string_t and a `value_type` from which a @ref basic_json value can
be constructed.
- **strings**: @ref string_t, string literals, and all compatible string
containers can be used.
- **numbers**: @ref number_integer_t, @ref number_unsigned_t,
@ref number_float_t, and all convertible number types such as `int`,
`size_t`, `int64_t`, `float` or `double` can be used.
- **boolean**: @ref boolean_t / `bool` can be used.
See the examples below.
@tparam CompatibleType a type such that:
- @a CompatibleType is not derived from `std::istream`,
- @a CompatibleType is not @ref basic_json (to avoid hijacking copy/move
constructors),
- @a CompatibleType is not a different @ref basic_json type (i.e. with different template arguments)
- @a CompatibleType is not a @ref basic_json nested type (e.g.,
@ref json_pointer, @ref iterator, etc ...)
- @ref @ref json_serializer<U> has a
`to_json(basic_json_t&, CompatibleType&&)` method
@tparam U = `uncvref_t<CompatibleType>`
@param[in] val the value to be forwarded to the respective constructor
@complexity Usually linear in the size of the passed @a val, also
depending on the implementation of the called `to_json()`
method.
@exceptionsafety Depends on the called constructor. For types directly
supported by the library (i.e., all types for which no `to_json()` function
was provided), strong guarantee holds: if an exception is thrown, there are
no changes to any JSON value.
@liveexample{The following code shows the constructor with several
compatible types.,basic_json__CompatibleType}
@since version 2.1.0
*/
template <typename CompatibleType,
typename U = detail::uncvref_t<CompatibleType>,
detail::enable_if_t<
detail::is_compatible_type<basic_json_t, U>::value, int> = 0>
basic_json(CompatibleType && val) noexcept(noexcept(
JSONSerializer<U>::to_json(std::declval<basic_json_t&>(),
std::forward<CompatibleType>(val))))
{
JSONSerializer<U>::to_json(*this, std::forward<CompatibleType>(val));
assert_invariant();
}
/*!
@brief create a JSON value from an existing one
This is a constructor for existing @ref basic_json types.
It does not hijack copy/move constructors, since the parameter has different
template arguments than the current ones.
The constructor tries to convert the internal @ref m_value of the parameter.
@tparam BasicJsonType a type such that:
- @a BasicJsonType is a @ref basic_json type.
- @a BasicJsonType has different template arguments than @ref basic_json_t.
@param[in] val the @ref basic_json value to be converted.
@complexity Usually linear in the size of the passed @a val, also
depending on the implementation of the called `to_json()`
method.
@exceptionsafety Depends on the called constructor. For types directly
supported by the library (i.e., all types for which no `to_json()` function
was provided), strong guarantee holds: if an exception is thrown, there are
no changes to any JSON value.
@since version 3.1.2
*/
template <typename BasicJsonType,
detail::enable_if_t<
detail::is_basic_json<BasicJsonType>::value and not std::is_same<basic_json, BasicJsonType>::value, int> = 0>
basic_json(const BasicJsonType& val)
{
using other_boolean_t = typename BasicJsonType::boolean_t;
using other_number_float_t = typename BasicJsonType::number_float_t;
using other_number_integer_t = typename BasicJsonType::number_integer_t;
using other_number_unsigned_t = typename BasicJsonType::number_unsigned_t;
using other_string_t = typename BasicJsonType::string_t;
using other_object_t = typename BasicJsonType::object_t;
using other_array_t = typename BasicJsonType::array_t;
switch (val.type())
{
case value_t::boolean:
JSONSerializer<other_boolean_t>::to_json(*this, val.template get<other_boolean_t>());
break;
case value_t::number_float:
JSONSerializer<other_number_float_t>::to_json(*this, val.template get<other_number_float_t>());
break;
case value_t::number_integer:
JSONSerializer<other_number_integer_t>::to_json(*this, val.template get<other_number_integer_t>());
break;
case value_t::number_unsigned:
JSONSerializer<other_number_unsigned_t>::to_json(*this, val.template get<other_number_unsigned_t>());
break;
case value_t::string:
JSONSerializer<other_string_t>::to_json(*this, val.template get_ref<const other_string_t&>());
break;
case value_t::object:
JSONSerializer<other_object_t>::to_json(*this, val.template get_ref<const other_object_t&>());
break;
case value_t::array:
JSONSerializer<other_array_t>::to_json(*this, val.template get_ref<const other_array_t&>());
break;
case value_t::null:
*this = nullptr;
break;
case value_t::discarded:
m_type = value_t::discarded;
break;
}
assert_invariant();
}
/*!
@brief create a container (array or object) from an initializer list
Creates a JSON value of type array or object from the passed initializer
list @a init. In case @a type_deduction is `true` (default), the type of
the JSON value to be created is deducted from the initializer list @a init
according to the following rules:
1. If the list is empty, an empty JSON object value `{}` is created.
2. If the list consists of pairs whose first element is a string, a JSON
object value is created where the first elements of the pairs are
treated as keys and the second elements are as values.
3. In all other cases, an array is created.
The rules aim to create the best fit between a C++ initializer list and
JSON values. The rationale is as follows:
1. The empty initializer list is written as `{}` which is exactly an empty
JSON object.
2. C++ has no way of describing mapped types other than to list a list of
pairs. As JSON requires that keys must be of type string, rule 2 is the
weakest constraint one can pose on initializer lists to interpret them
as an object.
3. In all other cases, the initializer list could not be interpreted as
JSON object type, so interpreting it as JSON array type is safe.
With the rules described above, the following JSON values cannot be
expressed by an initializer list:
- the empty array (`[]`): use @ref array(initializer_list_t)
with an empty initializer list in this case
- arrays whose elements satisfy rule 2: use @ref
array(initializer_list_t) with the same initializer list
in this case
@note When used without parentheses around an empty initializer list, @ref
basic_json() is called instead of this function, yielding the JSON null
value.
@param[in] init initializer list with JSON values
@param[in] type_deduction internal parameter; when set to `true`, the type
of the JSON value is deducted from the initializer list @a init; when set
to `false`, the type provided via @a manual_type is forced. This mode is
used by the functions @ref array(initializer_list_t) and
@ref object(initializer_list_t).
@param[in] manual_type internal parameter; when @a type_deduction is set
to `false`, the created JSON value will use the provided type (only @ref
value_t::array and @ref value_t::object are valid); when @a type_deduction
is set to `true`, this parameter has no effect
@throw type_error.301 if @a type_deduction is `false`, @a manual_type is
`value_t::object`, but @a init contains an element which is not a pair
whose first element is a string. In this case, the constructor could not
create an object. If @a type_deduction would have be `true`, an array
would have been created. See @ref object(initializer_list_t)
for an example.
@complexity Linear in the size of the initializer list @a init.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes to any JSON value.
@liveexample{The example below shows how JSON values are created from
initializer lists.,basic_json__list_init_t}
@sa @ref array(initializer_list_t) -- create a JSON array
value from an initializer list
@sa @ref object(initializer_list_t) -- create a JSON object
value from an initializer list
@since version 1.0.0
*/
basic_json(initializer_list_t init,
bool type_deduction = true,
value_t manual_type = value_t::array)
{
// check if each element is an array with two elements whose first
// element is a string
bool is_an_object = std::all_of(init.begin(), init.end(),
[](const detail::json_ref<basic_json>& element_ref)
{
return (element_ref->is_array() and element_ref->size() == 2 and (*element_ref)[0].is_string());
});
// adjust type if type deduction is not wanted
if (not type_deduction)
{
// if array is wanted, do not create an object though possible
if (manual_type == value_t::array)
{
is_an_object = false;
}
// if object is wanted but impossible, throw an exception
if (JSON_UNLIKELY(manual_type == value_t::object and not is_an_object))
{
JSON_THROW(type_error::create(301, "cannot create object from initializer list"));
}
}
if (is_an_object)
{
// the initializer list is a list of pairs -> create object
m_type = value_t::object;
m_value = value_t::object;
std::for_each(init.begin(), init.end(), [this](const detail::json_ref<basic_json>& element_ref)
{
auto element = element_ref.moved_or_copied();
m_value.object->emplace(
std::move(*((*element.m_value.array)[0].m_value.string)),
std::move((*element.m_value.array)[1]));
});
}
else
{
// the initializer list describes an array -> create array
m_type = value_t::array;
m_value.array = create<array_t>(init.begin(), init.end());
}
assert_invariant();
}
/*!
@brief explicitly create an array from an initializer list
Creates a JSON array value from a given initializer list. That is, given a
list of values `a, b, c`, creates the JSON value `[a, b, c]`. If the
initializer list is empty, the empty array `[]` is created.
@note This function is only needed to express two edge cases that cannot
be realized with the initializer list constructor (@ref
basic_json(initializer_list_t, bool, value_t)). These cases
are:
1. creating an array whose elements are all pairs whose first element is a
string -- in this case, the initializer list constructor would create an
object, taking the first elements as keys
2. creating an empty array -- passing the empty initializer list to the
initializer list constructor yields an empty object
@param[in] init initializer list with JSON values to create an array from
(optional)
@return JSON array value
@complexity Linear in the size of @a init.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes to any JSON value.
@liveexample{The following code shows an example for the `array`
function.,array}
@sa @ref basic_json(initializer_list_t, bool, value_t) --
create a JSON value from an initializer list
@sa @ref object(initializer_list_t) -- create a JSON object
value from an initializer list
@since version 1.0.0
*/
static basic_json array(initializer_list_t init = {})
{
return basic_json(init, false, value_t::array);
}
/*!
@brief explicitly create an object from an initializer list
Creates a JSON object value from a given initializer list. The initializer
lists elements must be pairs, and their first elements must be strings. If
the initializer list is empty, the empty object `{}` is created.
@note This function is only added for symmetry reasons. In contrast to the
related function @ref array(initializer_list_t), there are
no cases which can only be expressed by this function. That is, any
initializer list @a init can also be passed to the initializer list
constructor @ref basic_json(initializer_list_t, bool, value_t).
@param[in] init initializer list to create an object from (optional)
@return JSON object value
@throw type_error.301 if @a init is not a list of pairs whose first
elements are strings. In this case, no object can be created. When such a
value is passed to @ref basic_json(initializer_list_t, bool, value_t),
an array would have been created from the passed initializer list @a init.
See example below.
@complexity Linear in the size of @a init.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes to any JSON value.
@liveexample{The following code shows an example for the `object`
function.,object}
@sa @ref basic_json(initializer_list_t, bool, value_t) --
create a JSON value from an initializer list
@sa @ref array(initializer_list_t) -- create a JSON array
value from an initializer list
@since version 1.0.0
*/
static basic_json object(initializer_list_t init = {})
{
return basic_json(init, false, value_t::object);
}
/*!
@brief construct an array with count copies of given value
Constructs a JSON array value by creating @a cnt copies of a passed value.
In case @a cnt is `0`, an empty array is created.
@param[in] cnt the number of JSON copies of @a val to create
@param[in] val the JSON value to copy
@post `std::distance(begin(),end()) == cnt` holds.
@complexity Linear in @a cnt.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes to any JSON value.
@liveexample{The following code shows examples for the @ref
basic_json(size_type\, const basic_json&)
constructor.,basic_json__size_type_basic_json}
@since version 1.0.0
*/
basic_json(size_type cnt, const basic_json& val)
: m_type(value_t::array)
{
m_value.array = create<array_t>(cnt, val);
assert_invariant();
}
/*!
@brief construct a JSON container given an iterator range
Constructs the JSON value with the contents of the range `[first, last)`.
The semantics depends on the different types a JSON value can have:
- In case of a null type, invalid_iterator.206 is thrown.
- In case of other primitive types (number, boolean, or string), @a first
must be `begin()` and @a last must be `end()`. In this case, the value is
copied. Otherwise, invalid_iterator.204 is thrown.
- In case of structured types (array, object), the constructor behaves as
similar versions for `std::vector` or `std::map`; that is, a JSON array
or object is constructed from the values in the range.
@tparam InputIT an input iterator type (@ref iterator or @ref
const_iterator)
@param[in] first begin of the range to copy from (included)
@param[in] last end of the range to copy from (excluded)
@pre Iterators @a first and @a last must be initialized. **This
precondition is enforced with an assertion (see warning).** If
assertions are switched off, a violation of this precondition yields
undefined behavior.
@pre Range `[first, last)` is valid. Usually, this precondition cannot be
checked efficiently. Only certain edge cases are detected; see the
description of the exceptions below. A violation of this precondition
yields undefined behavior.
@warning A precondition is enforced with a runtime assertion that will
result in calling `std::abort` if this precondition is not met.
Assertions can be disabled by defining `NDEBUG` at compile time.
See http://en.cppreference.com/w/cpp/error/assert for more
information.
@throw invalid_iterator.201 if iterators @a first and @a last are not
compatible (i.e., do not belong to the same JSON value). In this case,
the range `[first, last)` is undefined.
@throw invalid_iterator.204 if iterators @a first and @a last belong to a
primitive type (number, boolean, or string), but @a first does not point
to the first element any more. In this case, the range `[first, last)` is
undefined. See example code below.
@throw invalid_iterator.206 if iterators @a first and @a last belong to a
null value. In this case, the range `[first, last)` is undefined.
@complexity Linear in distance between @a first and @a last.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes to any JSON value.
@liveexample{The example below shows several ways to create JSON values by
specifying a subrange with iterators.,basic_json__InputIt_InputIt}
@since version 1.0.0
*/
template<class InputIT, typename std::enable_if<
std::is_same<InputIT, typename basic_json_t::iterator>::value or
std::is_same<InputIT, typename basic_json_t::const_iterator>::value, int>::type = 0>
basic_json(InputIT first, InputIT last)
{
assert(first.m_object != nullptr);
assert(last.m_object != nullptr);
// make sure iterator fits the current value
if (JSON_UNLIKELY(first.m_object != last.m_object))
{
JSON_THROW(invalid_iterator::create(201, "iterators are not compatible"));
}
// copy type from first iterator
m_type = first.m_object->m_type;
// check if iterator range is complete for primitive values
switch (m_type)
{
case value_t::boolean:
case value_t::number_float:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::string:
{
if (JSON_UNLIKELY(not first.m_it.primitive_iterator.is_begin()
or not last.m_it.primitive_iterator.is_end()))
{
JSON_THROW(invalid_iterator::create(204, "iterators out of range"));
}
break;
}
default:
break;
}
switch (m_type)
{
case value_t::number_integer:
{
m_value.number_integer = first.m_object->m_value.number_integer;
break;
}
case value_t::number_unsigned:
{
m_value.number_unsigned = first.m_object->m_value.number_unsigned;
break;
}
case value_t::number_float:
{
m_value.number_float = first.m_object->m_value.number_float;
break;
}
case value_t::boolean:
{
m_value.boolean = first.m_object->m_value.boolean;
break;
}
case value_t::string:
{
m_value = *first.m_object->m_value.string;
break;
}
case value_t::object:
{
m_value.object = create<object_t>(first.m_it.object_iterator,
last.m_it.object_iterator);
break;
}
case value_t::array:
{
m_value.array = create<array_t>(first.m_it.array_iterator,
last.m_it.array_iterator);
break;
}
default:
JSON_THROW(invalid_iterator::create(206, "cannot construct with iterators from " +
std::string(first.m_object->type_name())));
}
assert_invariant();
}
///////////////////////////////////////
// other constructors and destructor //
///////////////////////////////////////
/// @private
basic_json(const detail::json_ref<basic_json>& ref)
: basic_json(ref.moved_or_copied())
{}
/*!
@brief copy constructor
Creates a copy of a given JSON value.
@param[in] other the JSON value to copy
@post `*this == other`
@complexity Linear in the size of @a other.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes to any JSON value.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is linear.
- As postcondition, it holds: `other == basic_json(other)`.
@liveexample{The following code shows an example for the copy
constructor.,basic_json__basic_json}
@since version 1.0.0
*/
basic_json(const basic_json& other)
: m_type(other.m_type)
{
// check of passed value is valid
other.assert_invariant();
switch (m_type)
{
case value_t::object:
{
m_value = *other.m_value.object;
break;
}
case value_t::array:
{
m_value = *other.m_value.array;
break;
}
case value_t::string:
{
m_value = *other.m_value.string;
break;
}
case value_t::boolean:
{
m_value = other.m_value.boolean;
break;
}
case value_t::number_integer:
{
m_value = other.m_value.number_integer;
break;
}
case value_t::number_unsigned:
{
m_value = other.m_value.number_unsigned;
break;
}
case value_t::number_float:
{
m_value = other.m_value.number_float;
break;
}
default:
break;
}
assert_invariant();
}
/*!
@brief move constructor
Move constructor. Constructs a JSON value with the contents of the given
value @a other using move semantics. It "steals" the resources from @a
other and leaves it as JSON null value.
@param[in,out] other value to move to this object
@post `*this` has the same value as @a other before the call.
@post @a other is a JSON null value.
@complexity Constant.
@exceptionsafety No-throw guarantee: this constructor never throws
exceptions.
@requirement This function helps `basic_json` satisfying the
[MoveConstructible](http://en.cppreference.com/w/cpp/concept/MoveConstructible)
requirements.
@liveexample{The code below shows the move constructor explicitly called
via std::move.,basic_json__moveconstructor}
@since version 1.0.0
*/
basic_json(basic_json&& other) noexcept
: m_type(std::move(other.m_type)),
m_value(std::move(other.m_value))
{
// check that passed value is valid
other.assert_invariant();
// invalidate payload
other.m_type = value_t::null;
other.m_value = {};
assert_invariant();
}
/*!
@brief copy assignment
Copy assignment operator. Copies a JSON value via the "copy and swap"
strategy: It is expressed in terms of the copy constructor, destructor,
and the `swap()` member function.
@param[in] other value to copy from
@complexity Linear.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is linear.
@liveexample{The code below shows and example for the copy assignment. It
creates a copy of value `a` which is then swapped with `b`. Finally\, the
copy of `a` (which is the null value after the swap) is
destroyed.,basic_json__copyassignment}
@since version 1.0.0
*/
reference& operator=(basic_json other) noexcept (
std::is_nothrow_move_constructible<value_t>::value and
std::is_nothrow_move_assignable<value_t>::value and
std::is_nothrow_move_constructible<json_value>::value and
std::is_nothrow_move_assignable<json_value>::value
)
{
// check that passed value is valid
other.assert_invariant();
using std::swap;
swap(m_type, other.m_type);
swap(m_value, other.m_value);
assert_invariant();
return *this;
}
/*!
@brief destructor
Destroys the JSON value and frees all allocated memory.
@complexity Linear.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is linear.
- All stored elements are destroyed and all memory is freed.
@since version 1.0.0
*/
~basic_json() noexcept
{
assert_invariant();
m_value.destroy(m_type);
}
/// @}
public:
///////////////////////
// object inspection //
///////////////////////
/// @name object inspection
/// Functions to inspect the type of a JSON value.
/// @{
/*!
@brief serialization
Serialization function for JSON values. The function tries to mimic
Python's `json.dumps()` function, and currently supports its @a indent
and @a ensure_ascii parameters.
@param[in] indent If indent is nonnegative, then array elements and object
members will be pretty-printed with that indent level. An indent level of
`0` will only insert newlines. `-1` (the default) selects the most compact
representation.
@param[in] indent_char The character to use for indentation if @a indent is
greater than `0`. The default is ` ` (space).
@param[in] ensure_ascii If @a ensure_ascii is true, all non-ASCII characters
in the output are escaped with `\uXXXX` sequences, and the result consists
of ASCII characters only.
@return string containing the serialization of the JSON value
@throw type_error.316 if a string stored inside the JSON value is not
UTF-8 encoded
@complexity Linear.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@liveexample{The following example shows the effect of different @a indent\,
@a indent_char\, and @a ensure_ascii parameters to the result of the
serialization.,dump}
@see https://docs.python.org/2/library/json.html#json.dump
@since version 1.0.0; indentation character @a indent_char, option
@a ensure_ascii and exceptions added in version 3.0.0
*/
string_t dump(const int indent = -1, const char indent_char = ' ',
const bool ensure_ascii = false) const
{
string_t result;
serializer s(detail::output_adapter<char, string_t>(result), indent_char);
if (indent >= 0)
{
s.dump(*this, true, ensure_ascii, static_cast<unsigned int>(indent));
}
else
{
s.dump(*this, false, ensure_ascii, 0);
}
return result;
}
/*!
@brief return the type of the JSON value (explicit)
Return the type of the JSON value as a value from the @ref value_t
enumeration.
@return the type of the JSON value
Value type | return value
------------------------- | -------------------------
null | value_t::null
boolean | value_t::boolean
string | value_t::string
number (integer) | value_t::number_integer
number (unsigned integer) | value_t::number_unsigned
number (floating-point) | value_t::number_float
object | value_t::object
array | value_t::array
discarded | value_t::discarded
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `type()` for all JSON
types.,type}
@sa @ref operator value_t() -- return the type of the JSON value (implicit)
@sa @ref type_name() -- return the type as string
@since version 1.0.0
*/
constexpr value_t type() const noexcept
{
return m_type;
}
/*!
@brief return whether type is primitive
This function returns true if and only if the JSON type is primitive
(string, number, boolean, or null).
@return `true` if type is primitive (string, number, boolean, or null),
`false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_primitive()` for all JSON
types.,is_primitive}
@sa @ref is_structured() -- returns whether JSON value is structured
@sa @ref is_null() -- returns whether JSON value is `null`
@sa @ref is_string() -- returns whether JSON value is a string
@sa @ref is_boolean() -- returns whether JSON value is a boolean
@sa @ref is_number() -- returns whether JSON value is a number
@since version 1.0.0
*/
constexpr bool is_primitive() const noexcept
{
return is_null() or is_string() or is_boolean() or is_number();
}
/*!
@brief return whether type is structured
This function returns true if and only if the JSON type is structured
(array or object).
@return `true` if type is structured (array or object), `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_structured()` for all JSON
types.,is_structured}
@sa @ref is_primitive() -- returns whether value is primitive
@sa @ref is_array() -- returns whether value is an array
@sa @ref is_object() -- returns whether value is an object
@since version 1.0.0
*/
constexpr bool is_structured() const noexcept
{
return is_array() or is_object();
}
/*!
@brief return whether value is null
This function returns true if and only if the JSON value is null.
@return `true` if type is null, `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_null()` for all JSON
types.,is_null}
@since version 1.0.0
*/
constexpr bool is_null() const noexcept
{
return (m_type == value_t::null);
}
/*!
@brief return whether value is a boolean
This function returns true if and only if the JSON value is a boolean.
@return `true` if type is boolean, `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_boolean()` for all JSON
types.,is_boolean}
@since version 1.0.0
*/
constexpr bool is_boolean() const noexcept
{
return (m_type == value_t::boolean);
}
/*!
@brief return whether value is a number
This function returns true if and only if the JSON value is a number. This
includes both integer (signed and unsigned) and floating-point values.
@return `true` if type is number (regardless whether integer, unsigned
integer or floating-type), `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_number()` for all JSON
types.,is_number}
@sa @ref is_number_integer() -- check if value is an integer or unsigned
integer number
@sa @ref is_number_unsigned() -- check if value is an unsigned integer
number
@sa @ref is_number_float() -- check if value is a floating-point number
@since version 1.0.0
*/
constexpr bool is_number() const noexcept
{
return is_number_integer() or is_number_float();
}
/*!
@brief return whether value is an integer number
This function returns true if and only if the JSON value is a signed or
unsigned integer number. This excludes floating-point values.
@return `true` if type is an integer or unsigned integer number, `false`
otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_number_integer()` for all
JSON types.,is_number_integer}
@sa @ref is_number() -- check if value is a number
@sa @ref is_number_unsigned() -- check if value is an unsigned integer
number
@sa @ref is_number_float() -- check if value is a floating-point number
@since version 1.0.0
*/
constexpr bool is_number_integer() const noexcept
{
return (m_type == value_t::number_integer or m_type == value_t::number_unsigned);
}
/*!
@brief return whether value is an unsigned integer number
This function returns true if and only if the JSON value is an unsigned
integer number. This excludes floating-point and signed integer values.
@return `true` if type is an unsigned integer number, `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_number_unsigned()` for all
JSON types.,is_number_unsigned}
@sa @ref is_number() -- check if value is a number
@sa @ref is_number_integer() -- check if value is an integer or unsigned
integer number
@sa @ref is_number_float() -- check if value is a floating-point number
@since version 2.0.0
*/
constexpr bool is_number_unsigned() const noexcept
{
return (m_type == value_t::number_unsigned);
}
/*!
@brief return whether value is a floating-point number
This function returns true if and only if the JSON value is a
floating-point number. This excludes signed and unsigned integer values.
@return `true` if type is a floating-point number, `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_number_float()` for all
JSON types.,is_number_float}
@sa @ref is_number() -- check if value is number
@sa @ref is_number_integer() -- check if value is an integer number
@sa @ref is_number_unsigned() -- check if value is an unsigned integer
number
@since version 1.0.0
*/
constexpr bool is_number_float() const noexcept
{
return (m_type == value_t::number_float);
}
/*!
@brief return whether value is an object
This function returns true if and only if the JSON value is an object.
@return `true` if type is object, `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_object()` for all JSON
types.,is_object}
@since version 1.0.0
*/
constexpr bool is_object() const noexcept
{
return (m_type == value_t::object);
}
/*!
@brief return whether value is an array
This function returns true if and only if the JSON value is an array.
@return `true` if type is array, `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_array()` for all JSON
types.,is_array}
@since version 1.0.0
*/
constexpr bool is_array() const noexcept
{
return (m_type == value_t::array);
}
/*!
@brief return whether value is a string
This function returns true if and only if the JSON value is a string.
@return `true` if type is string, `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_string()` for all JSON
types.,is_string}
@since version 1.0.0
*/
constexpr bool is_string() const noexcept
{
return (m_type == value_t::string);
}
/*!
@brief return whether value is discarded
This function returns true if and only if the JSON value was discarded
during parsing with a callback function (see @ref parser_callback_t).
@note This function will always be `false` for JSON values after parsing.
That is, discarded values can only occur during parsing, but will be
removed when inside a structured value or replaced by null in other cases.
@return `true` if type is discarded, `false` otherwise.
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies `is_discarded()` for all JSON
types.,is_discarded}
@since version 1.0.0
*/
constexpr bool is_discarded() const noexcept
{
return (m_type == value_t::discarded);
}
/*!
@brief return the type of the JSON value (implicit)
Implicitly return the type of the JSON value as a value from the @ref
value_t enumeration.
@return the type of the JSON value
@complexity Constant.
@exceptionsafety No-throw guarantee: this member function never throws
exceptions.
@liveexample{The following code exemplifies the @ref value_t operator for
all JSON types.,operator__value_t}
@sa @ref type() -- return the type of the JSON value (explicit)
@sa @ref type_name() -- return the type as string
@since version 1.0.0
*/
constexpr operator value_t() const noexcept
{
return m_type;
}
/// @}
private:
//////////////////
// value access //
//////////////////
/// get a boolean (explicit)
boolean_t get_impl(boolean_t* /*unused*/) const
{
if (JSON_LIKELY(is_boolean()))
{
return m_value.boolean;
}
JSON_THROW(type_error::create(302, "type must be boolean, but is " + std::string(type_name())));
}
/// get a pointer to the value (object)
object_t* get_impl_ptr(object_t* /*unused*/) noexcept
{
return is_object() ? m_value.object : nullptr;
}
/// get a pointer to the value (object)
constexpr const object_t* get_impl_ptr(const object_t* /*unused*/) const noexcept
{
return is_object() ? m_value.object : nullptr;
}
/// get a pointer to the value (array)
array_t* get_impl_ptr(array_t* /*unused*/) noexcept
{
return is_array() ? m_value.array : nullptr;
}
/// get a pointer to the value (array)
constexpr const array_t* get_impl_ptr(const array_t* /*unused*/) const noexcept
{
return is_array() ? m_value.array : nullptr;
}
/// get a pointer to the value (string)
string_t* get_impl_ptr(string_t* /*unused*/) noexcept
{
return is_string() ? m_value.string : nullptr;
}
/// get a pointer to the value (string)
constexpr const string_t* get_impl_ptr(const string_t* /*unused*/) const noexcept
{
return is_string() ? m_value.string : nullptr;
}
/// get a pointer to the value (boolean)
boolean_t* get_impl_ptr(boolean_t* /*unused*/) noexcept
{
return is_boolean() ? &m_value.boolean : nullptr;
}
/// get a pointer to the value (boolean)
constexpr const boolean_t* get_impl_ptr(const boolean_t* /*unused*/) const noexcept
{
return is_boolean() ? &m_value.boolean : nullptr;
}
/// get a pointer to the value (integer number)
number_integer_t* get_impl_ptr(number_integer_t* /*unused*/) noexcept
{
return is_number_integer() ? &m_value.number_integer : nullptr;
}
/// get a pointer to the value (integer number)
constexpr const number_integer_t* get_impl_ptr(const number_integer_t* /*unused*/) const noexcept
{
return is_number_integer() ? &m_value.number_integer : nullptr;
}
/// get a pointer to the value (unsigned number)
number_unsigned_t* get_impl_ptr(number_unsigned_t* /*unused*/) noexcept
{
return is_number_unsigned() ? &m_value.number_unsigned : nullptr;
}
/// get a pointer to the value (unsigned number)
constexpr const number_unsigned_t* get_impl_ptr(const number_unsigned_t* /*unused*/) const noexcept
{
return is_number_unsigned() ? &m_value.number_unsigned : nullptr;
}
/// get a pointer to the value (floating-point number)
number_float_t* get_impl_ptr(number_float_t* /*unused*/) noexcept
{
return is_number_float() ? &m_value.number_float : nullptr;
}
/// get a pointer to the value (floating-point number)
constexpr const number_float_t* get_impl_ptr(const number_float_t* /*unused*/) const noexcept
{
return is_number_float() ? &m_value.number_float : nullptr;
}
/*!
@brief helper function to implement get_ref()
This function helps to implement get_ref() without code duplication for
const and non-const overloads
@tparam ThisType will be deduced as `basic_json` or `const basic_json`
@throw type_error.303 if ReferenceType does not match underlying value
type of the current JSON
*/
template<typename ReferenceType, typename ThisType>
static ReferenceType get_ref_impl(ThisType& obj)
{
// delegate the call to get_ptr<>()
auto ptr = obj.template get_ptr<typename std::add_pointer<ReferenceType>::type>();
if (JSON_LIKELY(ptr != nullptr))
{
return *ptr;
}
JSON_THROW(type_error::create(303, "incompatible ReferenceType for get_ref, actual type is " + std::string(obj.type_name())));
}
public:
/// @name value access
/// Direct access to the stored value of a JSON value.
/// @{
/*!
@brief get special-case overload
This overloads avoids a lot of template boilerplate, it can be seen as the
identity method
@tparam BasicJsonType == @ref basic_json
@return a copy of *this
@complexity Constant.
@since version 2.1.0
*/
template<typename BasicJsonType, detail::enable_if_t<
std::is_same<typename std::remove_const<BasicJsonType>::type, basic_json_t>::value,
int> = 0>
basic_json get() const
{
return *this;
}
/*!
@brief get special-case overload
This overloads converts the current @ref basic_json in a different
@ref basic_json type
@tparam BasicJsonType == @ref basic_json
@return a copy of *this, converted into @tparam BasicJsonType
@complexity Depending on the implementation of the called `from_json()`
method.
@since version 3.1.2
*/
template<typename BasicJsonType, detail::enable_if_t<
not std::is_same<BasicJsonType, basic_json>::value and
detail::is_basic_json<BasicJsonType>::value, int> = 0>
BasicJsonType get() const
{
return *this;
}
/*!
@brief get a value (explicit)
Explicit type conversion between the JSON value and a compatible value
which is [CopyConstructible](http://en.cppreference.com/w/cpp/concept/CopyConstructible)
and [DefaultConstructible](http://en.cppreference.com/w/cpp/concept/DefaultConstructible).
The value is converted by calling the @ref json_serializer<ValueType>
`from_json()` method.
The function is equivalent to executing
@code {.cpp}
ValueType ret;
JSONSerializer<ValueType>::from_json(*this, ret);
return ret;
@endcode
This overloads is chosen if:
- @a ValueType is not @ref basic_json,
- @ref json_serializer<ValueType> has a `from_json()` method of the form
`void from_json(const basic_json&, ValueType&)`, and
- @ref json_serializer<ValueType> does not have a `from_json()` method of
the form `ValueType from_json(const basic_json&)`
@tparam ValueTypeCV the provided value type
@tparam ValueType the returned value type
@return copy of the JSON value, converted to @a ValueType
@throw what @ref json_serializer<ValueType> `from_json()` method throws
@liveexample{The example below shows several conversions from JSON values
to other types. There a few things to note: (1) Floating-point numbers can
be converted to integers\, (2) A JSON array can be converted to a standard
`std::vector<short>`\, (3) A JSON object can be converted to C++
associative containers such as `std::unordered_map<std::string\,
json>`.,get__ValueType_const}
@since version 2.1.0
*/
template<typename ValueTypeCV, typename ValueType = detail::uncvref_t<ValueTypeCV>,
detail::enable_if_t <
not detail::is_basic_json<ValueType>::value and
detail::has_from_json<basic_json_t, ValueType>::value and
not detail::has_non_default_from_json<basic_json_t, ValueType>::value,
int> = 0>
ValueType get() const noexcept(noexcept(
JSONSerializer<ValueType>::from_json(std::declval<const basic_json_t&>(), std::declval<ValueType&>())))
{
// we cannot static_assert on ValueTypeCV being non-const, because
// there is support for get<const basic_json_t>(), which is why we
// still need the uncvref
static_assert(not std::is_reference<ValueTypeCV>::value,
"get() cannot be used with reference types, you might want to use get_ref()");
static_assert(std::is_default_constructible<ValueType>::value,
"types must be DefaultConstructible when used with get()");
ValueType ret;
JSONSerializer<ValueType>::from_json(*this, ret);
return ret;
}
/*!
@brief get a value (explicit); special case
Explicit type conversion between the JSON value and a compatible value
which is **not** [CopyConstructible](http://en.cppreference.com/w/cpp/concept/CopyConstructible)
and **not** [DefaultConstructible](http://en.cppreference.com/w/cpp/concept/DefaultConstructible).
The value is converted by calling the @ref json_serializer<ValueType>
`from_json()` method.
The function is equivalent to executing
@code {.cpp}
return JSONSerializer<ValueTypeCV>::from_json(*this);
@endcode
This overloads is chosen if:
- @a ValueType is not @ref basic_json and
- @ref json_serializer<ValueType> has a `from_json()` method of the form
`ValueType from_json(const basic_json&)`
@note If @ref json_serializer<ValueType> has both overloads of
`from_json()`, this one is chosen.
@tparam ValueTypeCV the provided value type
@tparam ValueType the returned value type
@return copy of the JSON value, converted to @a ValueType
@throw what @ref json_serializer<ValueType> `from_json()` method throws
@since version 2.1.0
*/
template<typename ValueTypeCV, typename ValueType = detail::uncvref_t<ValueTypeCV>,
detail::enable_if_t<not std::is_same<basic_json_t, ValueType>::value and
detail::has_non_default_from_json<basic_json_t, ValueType>::value,
int> = 0>
ValueType get() const noexcept(noexcept(
JSONSerializer<ValueTypeCV>::from_json(std::declval<const basic_json_t&>())))
{
static_assert(not std::is_reference<ValueTypeCV>::value,
"get() cannot be used with reference types, you might want to use get_ref()");
return JSONSerializer<ValueTypeCV>::from_json(*this);
}
/*!
@brief get a pointer value (explicit)
Explicit pointer access to the internally stored JSON value. No copies are
made.
@warning The pointer becomes invalid if the underlying JSON object
changes.
@tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
@ref number_unsigned_t, or @ref number_float_t.
@return pointer to the internally stored JSON value if the requested
pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
@complexity Constant.
@liveexample{The example below shows how pointers to internal values of a
JSON value can be requested. Note that no type conversions are made and a
`nullptr` is returned if the value and the requested pointer type does not
match.,get__PointerType}
@sa @ref get_ptr() for explicit pointer-member access
@since version 1.0.0
*/
template<typename PointerType, typename std::enable_if<
std::is_pointer<PointerType>::value, int>::type = 0>
PointerType get() noexcept
{
// delegate the call to get_ptr
return get_ptr<PointerType>();
}
/*!
@brief get a pointer value (explicit)
@copydoc get()
*/
template<typename PointerType, typename std::enable_if<
std::is_pointer<PointerType>::value, int>::type = 0>
constexpr const PointerType get() const noexcept
{
// delegate the call to get_ptr
return get_ptr<PointerType>();
}
/*!
@brief get a pointer value (implicit)
Implicit pointer access to the internally stored JSON value. No copies are
made.
@warning Writing data to the pointee of the result yields an undefined
state.
@tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
@ref number_unsigned_t, or @ref number_float_t. Enforced by a static
assertion.
@return pointer to the internally stored JSON value if the requested
pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
@complexity Constant.
@liveexample{The example below shows how pointers to internal values of a
JSON value can be requested. Note that no type conversions are made and a
`nullptr` is returned if the value and the requested pointer type does not
match.,get_ptr}
@since version 1.0.0
*/
template<typename PointerType, typename std::enable_if<
std::is_pointer<PointerType>::value, int>::type = 0>
PointerType get_ptr() noexcept
{
// get the type of the PointerType (remove pointer and const)
using pointee_t = typename std::remove_const<typename
std::remove_pointer<typename
std::remove_const<PointerType>::type>::type>::type;
// make sure the type matches the allowed types
static_assert(
std::is_same<object_t, pointee_t>::value
or std::is_same<array_t, pointee_t>::value
or std::is_same<string_t, pointee_t>::value
or std::is_same<boolean_t, pointee_t>::value
or std::is_same<number_integer_t, pointee_t>::value
or std::is_same<number_unsigned_t, pointee_t>::value
or std::is_same<number_float_t, pointee_t>::value
, "incompatible pointer type");
// delegate the call to get_impl_ptr<>()
return get_impl_ptr(static_cast<PointerType>(nullptr));
}
/*!
@brief get a pointer value (implicit)
@copydoc get_ptr()
*/
template<typename PointerType, typename std::enable_if<
std::is_pointer<PointerType>::value and
std::is_const<typename std::remove_pointer<PointerType>::type>::value, int>::type = 0>
constexpr const PointerType get_ptr() const noexcept
{
// get the type of the PointerType (remove pointer and const)
using pointee_t = typename std::remove_const<typename
std::remove_pointer<typename
std::remove_const<PointerType>::type>::type>::type;
// make sure the type matches the allowed types
static_assert(
std::is_same<object_t, pointee_t>::value
or std::is_same<array_t, pointee_t>::value
or std::is_same<string_t, pointee_t>::value
or std::is_same<boolean_t, pointee_t>::value
or std::is_same<number_integer_t, pointee_t>::value
or std::is_same<number_unsigned_t, pointee_t>::value
or std::is_same<number_float_t, pointee_t>::value
, "incompatible pointer type");
// delegate the call to get_impl_ptr<>() const
return get_impl_ptr(static_cast<PointerType>(nullptr));
}
/*!
@brief get a reference value (implicit)
Implicit reference access to the internally stored JSON value. No copies
are made.
@warning Writing data to the referee of the result yields an undefined
state.
@tparam ReferenceType reference type; must be a reference to @ref array_t,
@ref object_t, @ref string_t, @ref boolean_t, @ref number_integer_t, or
@ref number_float_t. Enforced by static assertion.
@return reference to the internally stored JSON value if the requested
reference type @a ReferenceType fits to the JSON value; throws
type_error.303 otherwise
@throw type_error.303 in case passed type @a ReferenceType is incompatible
with the stored JSON value; see example below
@complexity Constant.
@liveexample{The example shows several calls to `get_ref()`.,get_ref}
@since version 1.1.0
*/
template<typename ReferenceType, typename std::enable_if<
std::is_reference<ReferenceType>::value, int>::type = 0>
ReferenceType get_ref()
{
// delegate call to get_ref_impl
return get_ref_impl<ReferenceType>(*this);
}
/*!
@brief get a reference value (implicit)
@copydoc get_ref()
*/
template<typename ReferenceType, typename std::enable_if<
std::is_reference<ReferenceType>::value and
std::is_const<typename std::remove_reference<ReferenceType>::type>::value, int>::type = 0>
ReferenceType get_ref() const
{
// delegate call to get_ref_impl
return get_ref_impl<ReferenceType>(*this);
}
/*!
@brief get a value (implicit)
Implicit type conversion between the JSON value and a compatible value.
The call is realized by calling @ref get() const.
@tparam ValueType non-pointer type compatible to the JSON value, for
instance `int` for JSON integer numbers, `bool` for JSON booleans, or
`std::vector` types for JSON arrays. The character type of @ref string_t
as well as an initializer list of this type is excluded to avoid
ambiguities as these types implicitly convert to `std::string`.
@return copy of the JSON value, converted to type @a ValueType
@throw type_error.302 in case passed type @a ValueType is incompatible
to the JSON value type (e.g., the JSON value is of type boolean, but a
string is requested); see example below
@complexity Linear in the size of the JSON value.
@liveexample{The example below shows several conversions from JSON values
to other types. There a few things to note: (1) Floating-point numbers can
be converted to integers\, (2) A JSON array can be converted to a standard
`std::vector<short>`\, (3) A JSON object can be converted to C++
associative containers such as `std::unordered_map<std::string\,
json>`.,operator__ValueType}
@since version 1.0.0
*/
template < typename ValueType, typename std::enable_if <
not std::is_pointer<ValueType>::value and
not std::is_same<ValueType, detail::json_ref<basic_json>>::value and
not std::is_same<ValueType, typename string_t::value_type>::value and
not detail::is_basic_json<ValueType>::value
#ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
#endif
#if defined(JSON_HAS_CPP_17)
and not std::is_same<ValueType, typename std::string_view>::value
#endif
, int >::type = 0 >
operator ValueType() const
{
// delegate the call to get<>() const
return get<ValueType>();
}
/// @}
////////////////////
// element access //
////////////////////
/// @name element access
/// Access to the JSON value.
/// @{
/*!
@brief access specified array element with bounds checking
Returns a reference to the element at specified location @a idx, with
bounds checking.
@param[in] idx index of the element to access
@return reference to the element at index @a idx
@throw type_error.304 if the JSON value is not an array; in this case,
calling `at` with an index makes no sense. See example below.
@throw out_of_range.401 if the index @a idx is out of range of the array;
that is, `idx >= size()`. See example below.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Constant.
@since version 1.0.0
@liveexample{The example below shows how array elements can be read and
written using `at()`. It also demonstrates the different exceptions that
can be thrown.,at__size_type}
*/
reference at(size_type idx)
{
// at only works for arrays
if (JSON_LIKELY(is_array()))
{
JSON_TRY
{
return m_value.array->at(idx);
}
JSON_CATCH (std::out_of_range&)
{
// create better exception explanation
JSON_THROW(out_of_range::create(401, "array index " + std::to_string(idx) + " is out of range"));
}
}
else
{
JSON_THROW(type_error::create(304, "cannot use at() with " + std::string(type_name())));
}
}
/*!
@brief access specified array element with bounds checking
Returns a const reference to the element at specified location @a idx,
with bounds checking.
@param[in] idx index of the element to access
@return const reference to the element at index @a idx
@throw type_error.304 if the JSON value is not an array; in this case,
calling `at` with an index makes no sense. See example below.
@throw out_of_range.401 if the index @a idx is out of range of the array;
that is, `idx >= size()`. See example below.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Constant.
@since version 1.0.0
@liveexample{The example below shows how array elements can be read using
`at()`. It also demonstrates the different exceptions that can be thrown.,
at__size_type_const}
*/
const_reference at(size_type idx) const
{
// at only works for arrays
if (JSON_LIKELY(is_array()))
{
JSON_TRY
{
return m_value.array->at(idx);
}
JSON_CATCH (std::out_of_range&)
{
// create better exception explanation
JSON_THROW(out_of_range::create(401, "array index " + std::to_string(idx) + " is out of range"));
}
}
else
{
JSON_THROW(type_error::create(304, "cannot use at() with " + std::string(type_name())));
}
}
/*!
@brief access specified object element with bounds checking
Returns a reference to the element at with specified key @a key, with
bounds checking.
@param[in] key key of the element to access
@return reference to the element at key @a key
@throw type_error.304 if the JSON value is not an object; in this case,
calling `at` with a key makes no sense. See example below.
@throw out_of_range.403 if the key @a key is is not stored in the object;
that is, `find(key) == end()`. See example below.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Logarithmic in the size of the container.
@sa @ref operator[](const typename object_t::key_type&) for unchecked
access by reference
@sa @ref value() for access by value with a default value
@since version 1.0.0
@liveexample{The example below shows how object elements can be read and
written using `at()`. It also demonstrates the different exceptions that
can be thrown.,at__object_t_key_type}
*/
reference at(const typename object_t::key_type& key)
{
// at only works for objects
if (JSON_LIKELY(is_object()))
{
JSON_TRY
{
return m_value.object->at(key);
}
JSON_CATCH (std::out_of_range&)
{
// create better exception explanation
JSON_THROW(out_of_range::create(403, "key '" + key + "' not found"));
}
}
else
{
JSON_THROW(type_error::create(304, "cannot use at() with " + std::string(type_name())));
}
}
/*!
@brief access specified object element with bounds checking
Returns a const reference to the element at with specified key @a key,
with bounds checking.
@param[in] key key of the element to access
@return const reference to the element at key @a key
@throw type_error.304 if the JSON value is not an object; in this case,
calling `at` with a key makes no sense. See example below.
@throw out_of_range.403 if the key @a key is is not stored in the object;
that is, `find(key) == end()`. See example below.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Logarithmic in the size of the container.
@sa @ref operator[](const typename object_t::key_type&) for unchecked
access by reference
@sa @ref value() for access by value with a default value
@since version 1.0.0
@liveexample{The example below shows how object elements can be read using
`at()`. It also demonstrates the different exceptions that can be thrown.,
at__object_t_key_type_const}
*/
const_reference at(const typename object_t::key_type& key) const
{
// at only works for objects
if (JSON_LIKELY(is_object()))
{
JSON_TRY
{
return m_value.object->at(key);
}
JSON_CATCH (std::out_of_range&)
{
// create better exception explanation
JSON_THROW(out_of_range::create(403, "key '" + key + "' not found"));
}
}
else
{
JSON_THROW(type_error::create(304, "cannot use at() with " + std::string(type_name())));
}
}
/*!
@brief access specified array element
Returns a reference to the element at specified location @a idx.
@note If @a idx is beyond the range of the array (i.e., `idx >= size()`),
then the array is silently filled up with `null` values to make `idx` a
valid reference to the last stored element.
@param[in] idx index of the element to access
@return reference to the element at index @a idx
@throw type_error.305 if the JSON value is not an array or null; in that
cases, using the [] operator with an index makes no sense.
@complexity Constant if @a idx is in the range of the array. Otherwise
linear in `idx - size()`.
@liveexample{The example below shows how array elements can be read and
written using `[]` operator. Note the addition of `null`
values.,operatorarray__size_type}
@since version 1.0.0
*/
reference operator[](size_type idx)
{
// implicitly convert null value to an empty array
if (is_null())
{
m_type = value_t::array;
m_value.array = create<array_t>();
assert_invariant();
}
// operator[] only works for arrays
if (JSON_LIKELY(is_array()))
{
// fill up array with null values if given idx is outside range
if (idx >= m_value.array->size())
{
m_value.array->insert(m_value.array->end(),
idx - m_value.array->size() + 1,
basic_json());
}
return m_value.array->operator[](idx);
}
JSON_THROW(type_error::create(305, "cannot use operator[] with " + std::string(type_name())));
}
/*!
@brief access specified array element
Returns a const reference to the element at specified location @a idx.
@param[in] idx index of the element to access
@return const reference to the element at index @a idx
@throw type_error.305 if the JSON value is not an array; in that case,
using the [] operator with an index makes no sense.
@complexity Constant.
@liveexample{The example below shows how array elements can be read using
the `[]` operator.,operatorarray__size_type_const}
@since version 1.0.0
*/
const_reference operator[](size_type idx) const
{
// const operator[] only works for arrays
if (JSON_LIKELY(is_array()))
{
return m_value.array->operator[](idx);
}
JSON_THROW(type_error::create(305, "cannot use operator[] with " + std::string(type_name())));
}
/*!
@brief access specified object element
Returns a reference to the element at with specified key @a key.
@note If @a key is not found in the object, then it is silently added to
the object and filled with a `null` value to make `key` a valid reference.
In case the value was `null` before, it is converted to an object.
@param[in] key key of the element to access
@return reference to the element at key @a key
@throw type_error.305 if the JSON value is not an object or null; in that
cases, using the [] operator with a key makes no sense.
@complexity Logarithmic in the size of the container.
@liveexample{The example below shows how object elements can be read and
written using the `[]` operator.,operatorarray__key_type}
@sa @ref at(const typename object_t::key_type&) for access by reference
with range checking
@sa @ref value() for access by value with a default value
@since version 1.0.0
*/
reference operator[](const typename object_t::key_type& key)
{
// implicitly convert null value to an empty object
if (is_null())
{
m_type = value_t::object;
m_value.object = create<object_t>();
assert_invariant();
}
// operator[] only works for objects
if (JSON_LIKELY(is_object()))
{
return m_value.object->operator[](key);
}
JSON_THROW(type_error::create(305, "cannot use operator[] with " + std::string(type_name())));
}
/*!
@brief read-only access specified object element
Returns a const reference to the element at with specified key @a key. No
bounds checking is performed.
@warning If the element with key @a key does not exist, the behavior is
undefined.
@param[in] key key of the element to access
@return const reference to the element at key @a key
@pre The element with key @a key must exist. **This precondition is
enforced with an assertion.**
@throw type_error.305 if the JSON value is not an object; in that case,
using the [] operator with a key makes no sense.
@complexity Logarithmic in the size of the container.
@liveexample{The example below shows how object elements can be read using
the `[]` operator.,operatorarray__key_type_const}
@sa @ref at(const typename object_t::key_type&) for access by reference
with range checking
@sa @ref value() for access by value with a default value
@since version 1.0.0
*/
const_reference operator[](const typename object_t::key_type& key) const
{
// const operator[] only works for objects
if (JSON_LIKELY(is_object()))
{
assert(m_value.object->find(key) != m_value.object->end());
return m_value.object->find(key)->second;
}
JSON_THROW(type_error::create(305, "cannot use operator[] with " + std::string(type_name())));
}
/*!
@brief access specified object element
Returns a reference to the element at with specified key @a key.
@note If @a key is not found in the object, then it is silently added to
the object and filled with a `null` value to make `key` a valid reference.
In case the value was `null` before, it is converted to an object.
@param[in] key key of the element to access
@return reference to the element at key @a key
@throw type_error.305 if the JSON value is not an object or null; in that
cases, using the [] operator with a key makes no sense.
@complexity Logarithmic in the size of the container.
@liveexample{The example below shows how object elements can be read and
written using the `[]` operator.,operatorarray__key_type}
@sa @ref at(const typename object_t::key_type&) for access by reference
with range checking
@sa @ref value() for access by value with a default value
@since version 1.1.0
*/
template<typename T>
reference operator[](T* key)
{
// implicitly convert null to object
if (is_null())
{
m_type = value_t::object;
m_value = value_t::object;
assert_invariant();
}
// at only works for objects
if (JSON_LIKELY(is_object()))
{
return m_value.object->operator[](key);
}
JSON_THROW(type_error::create(305, "cannot use operator[] with " + std::string(type_name())));
}
/*!
@brief read-only access specified object element
Returns a const reference to the element at with specified key @a key. No
bounds checking is performed.
@warning If the element with key @a key does not exist, the behavior is
undefined.
@param[in] key key of the element to access
@return const reference to the element at key @a key
@pre The element with key @a key must exist. **This precondition is
enforced with an assertion.**
@throw type_error.305 if the JSON value is not an object; in that case,
using the [] operator with a key makes no sense.
@complexity Logarithmic in the size of the container.
@liveexample{The example below shows how object elements can be read using
the `[]` operator.,operatorarray__key_type_const}
@sa @ref at(const typename object_t::key_type&) for access by reference
with range checking
@sa @ref value() for access by value with a default value
@since version 1.1.0
*/
template<typename T>
const_reference operator[](T* key) const
{
// at only works for objects
if (JSON_LIKELY(is_object()))
{
assert(m_value.object->find(key) != m_value.object->end());
return m_value.object->find(key)->second;
}
JSON_THROW(type_error::create(305, "cannot use operator[] with " + std::string(type_name())));
}
/*!
@brief access specified object element with default value
Returns either a copy of an object's element at the specified key @a key
or a given default value if no element with key @a key exists.
The function is basically equivalent to executing
@code {.cpp}
try {
return at(key);
} catch(out_of_range) {
return default_value;
}
@endcode
@note Unlike @ref at(const typename object_t::key_type&), this function
does not throw if the given key @a key was not found.
@note Unlike @ref operator[](const typename object_t::key_type& key), this
function does not implicitly add an element to the position defined by @a
key. This function is furthermore also applicable to const objects.
@param[in] key key of the element to access
@param[in] default_value the value to return if @a key is not found
@tparam ValueType type compatible to JSON values, for instance `int` for
JSON integer numbers, `bool` for JSON booleans, or `std::vector` types for
JSON arrays. Note the type of the expected value at @a key and the default
value @a default_value must be compatible.
@return copy of the element at key @a key or @a default_value if @a key
is not found
@throw type_error.306 if the JSON value is not an object; in that case,
using `value()` with a key makes no sense.
@complexity Logarithmic in the size of the container.
@liveexample{The example below shows how object elements can be queried
with a default value.,basic_json__value}
@sa @ref at(const typename object_t::key_type&) for access by reference
with range checking
@sa @ref operator[](const typename object_t::key_type&) for unchecked
access by reference
@since version 1.0.0
*/
template<class ValueType, typename std::enable_if<
std::is_convertible<basic_json_t, ValueType>::value, int>::type = 0>
ValueType value(const typename object_t::key_type& key, const ValueType& default_value) const
{
// at only works for objects
if (JSON_LIKELY(is_object()))
{
// if key is found, return value and given default value otherwise
const auto it = find(key);
if (it != end())
{
return *it;
}
return default_value;
}
JSON_THROW(type_error::create(306, "cannot use value() with " + std::string(type_name())));
}
/*!
@brief overload for a default value of type const char*
@copydoc basic_json::value(const typename object_t::key_type&, ValueType) const
*/
string_t value(const typename object_t::key_type& key, const char* default_value) const
{
return value(key, string_t(default_value));
}
/*!
@brief access specified object element via JSON Pointer with default value
Returns either a copy of an object's element at the specified key @a key
or a given default value if no element with key @a key exists.
The function is basically equivalent to executing
@code {.cpp}
try {
return at(ptr);
} catch(out_of_range) {
return default_value;
}
@endcode
@note Unlike @ref at(const json_pointer&), this function does not throw
if the given key @a key was not found.
@param[in] ptr a JSON pointer to the element to access
@param[in] default_value the value to return if @a ptr found no value
@tparam ValueType type compatible to JSON values, for instance `int` for
JSON integer numbers, `bool` for JSON booleans, or `std::vector` types for
JSON arrays. Note the type of the expected value at @a key and the default
value @a default_value must be compatible.
@return copy of the element at key @a key or @a default_value if @a key
is not found
@throw type_error.306 if the JSON value is not an objec; in that case,
using `value()` with a key makes no sense.
@complexity Logarithmic in the size of the container.
@liveexample{The example below shows how object elements can be queried
with a default value.,basic_json__value_ptr}
@sa @ref operator[](const json_pointer&) for unchecked access by reference
@since version 2.0.2
*/
template<class ValueType, typename std::enable_if<
std::is_convertible<basic_json_t, ValueType>::value, int>::type = 0>
ValueType value(const json_pointer& ptr, const ValueType& default_value) const
{
// at only works for objects
if (JSON_LIKELY(is_object()))
{
// if pointer resolves a value, return it or use default value
JSON_TRY
{
return ptr.get_checked(this);
}
JSON_CATCH (out_of_range&)
{
return default_value;
}
}
JSON_THROW(type_error::create(306, "cannot use value() with " + std::string(type_name())));
}
/*!
@brief overload for a default value of type const char*
@copydoc basic_json::value(const json_pointer&, ValueType) const
*/
string_t value(const json_pointer& ptr, const char* default_value) const
{
return value(ptr, string_t(default_value));
}
/*!
@brief access the first element
Returns a reference to the first element in the container. For a JSON
container `c`, the expression `c.front()` is equivalent to `*c.begin()`.
@return In case of a structured type (array or object), a reference to the
first element is returned. In case of number, string, or boolean values, a
reference to the value is returned.
@complexity Constant.
@pre The JSON value must not be `null` (would throw `std::out_of_range`)
or an empty array or object (undefined behavior, **guarded by
assertions**).
@post The JSON value remains unchanged.
@throw invalid_iterator.214 when called on `null` value
@liveexample{The following code shows an example for `front()`.,front}
@sa @ref back() -- access the last element
@since version 1.0.0
*/
reference front()
{
return *begin();
}
/*!
@copydoc basic_json::front()
*/
const_reference front() const
{
return *cbegin();
}
/*!
@brief access the last element
Returns a reference to the last element in the container. For a JSON
container `c`, the expression `c.back()` is equivalent to
@code {.cpp}
auto tmp = c.end();
--tmp;
return *tmp;
@endcode
@return In case of a structured type (array or object), a reference to the
last element is returned. In case of number, string, or boolean values, a
reference to the value is returned.
@complexity Constant.
@pre The JSON value must not be `null` (would throw `std::out_of_range`)
or an empty array or object (undefined behavior, **guarded by
assertions**).
@post The JSON value remains unchanged.
@throw invalid_iterator.214 when called on a `null` value. See example
below.
@liveexample{The following code shows an example for `back()`.,back}
@sa @ref front() -- access the first element
@since version 1.0.0
*/
reference back()
{
auto tmp = end();
--tmp;
return *tmp;
}
/*!
@copydoc basic_json::back()
*/
const_reference back() const
{
auto tmp = cend();
--tmp;
return *tmp;
}
/*!
@brief remove element given an iterator
Removes the element specified by iterator @a pos. The iterator @a pos must
be valid and dereferenceable. Thus the `end()` iterator (which is valid,
but is not dereferenceable) cannot be used as a value for @a pos.
If called on a primitive type other than `null`, the resulting JSON value
will be `null`.
@param[in] pos iterator to the element to remove
@return Iterator following the last removed element. If the iterator @a
pos refers to the last element, the `end()` iterator is returned.
@tparam IteratorType an @ref iterator or @ref const_iterator
@post Invalidates iterators and references at or after the point of the
erase, including the `end()` iterator.
@throw type_error.307 if called on a `null` value; example: `"cannot use
erase() with null"`
@throw invalid_iterator.202 if called on an iterator which does not belong
to the current JSON value; example: `"iterator does not fit current
value"`
@throw invalid_iterator.205 if called on a primitive type with invalid
iterator (i.e., any iterator which is not `begin()`); example: `"iterator
out of range"`
@complexity The complexity depends on the type:
- objects: amortized constant
- arrays: linear in distance between @a pos and the end of the container
- strings: linear in the length of the string
- other types: constant
@liveexample{The example shows the result of `erase()` for different JSON
types.,erase__IteratorType}
@sa @ref erase(IteratorType, IteratorType) -- removes the elements in
the given range
@sa @ref erase(const typename object_t::key_type&) -- removes the element
from an object at the given key
@sa @ref erase(const size_type) -- removes the element from an array at
the given index
@since version 1.0.0
*/
template<class IteratorType, typename std::enable_if<
std::is_same<IteratorType, typename basic_json_t::iterator>::value or
std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int>::type
= 0>
IteratorType erase(IteratorType pos)
{
// make sure iterator fits the current value
if (JSON_UNLIKELY(this != pos.m_object))
{
JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
}
IteratorType result = end();
switch (m_type)
{
case value_t::boolean:
case value_t::number_float:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::string:
{
if (JSON_UNLIKELY(not pos.m_it.primitive_iterator.is_begin()))
{
JSON_THROW(invalid_iterator::create(205, "iterator out of range"));
}
if (is_string())
{
AllocatorType<string_t> alloc;
std::allocator_traits<decltype(alloc)>::destroy(alloc, m_value.string);
std::allocator_traits<decltype(alloc)>::deallocate(alloc, m_value.string, 1);
m_value.string = nullptr;
}
m_type = value_t::null;
assert_invariant();
break;
}
case value_t::object:
{
result.m_it.object_iterator = m_value.object->erase(pos.m_it.object_iterator);
break;
}
case value_t::array:
{
result.m_it.array_iterator = m_value.array->erase(pos.m_it.array_iterator);
break;
}
default:
JSON_THROW(type_error::create(307, "cannot use erase() with " + std::string(type_name())));
}
return result;
}
/*!
@brief remove elements given an iterator range
Removes the element specified by the range `[first; last)`. The iterator
@a first does not need to be dereferenceable if `first == last`: erasing
an empty range is a no-op.
If called on a primitive type other than `null`, the resulting JSON value
will be `null`.
@param[in] first iterator to the beginning of the range to remove
@param[in] last iterator past the end of the range to remove
@return Iterator following the last removed element. If the iterator @a
second refers to the last element, the `end()` iterator is returned.
@tparam IteratorType an @ref iterator or @ref const_iterator
@post Invalidates iterators and references at or after the point of the
erase, including the `end()` iterator.
@throw type_error.307 if called on a `null` value; example: `"cannot use
erase() with null"`
@throw invalid_iterator.203 if called on iterators which does not belong
to the current JSON value; example: `"iterators do not fit current value"`
@throw invalid_iterator.204 if called on a primitive type with invalid
iterators (i.e., if `first != begin()` and `last != end()`); example:
`"iterators out of range"`
@complexity The complexity depends on the type:
- objects: `log(size()) + std::distance(first, last)`
- arrays: linear in the distance between @a first and @a last, plus linear
in the distance between @a last and end of the container
- strings: linear in the length of the string
- other types: constant
@liveexample{The example shows the result of `erase()` for different JSON
types.,erase__IteratorType_IteratorType}
@sa @ref erase(IteratorType) -- removes the element at a given position
@sa @ref erase(const typename object_t::key_type&) -- removes the element
from an object at the given key
@sa @ref erase(const size_type) -- removes the element from an array at
the given index
@since version 1.0.0
*/
template<class IteratorType, typename std::enable_if<
std::is_same<IteratorType, typename basic_json_t::iterator>::value or
std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int>::type
= 0>
IteratorType erase(IteratorType first, IteratorType last)
{
// make sure iterator fits the current value
if (JSON_UNLIKELY(this != first.m_object or this != last.m_object))
{
JSON_THROW(invalid_iterator::create(203, "iterators do not fit current value"));
}
IteratorType result = end();
switch (m_type)
{
case value_t::boolean:
case value_t::number_float:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::string:
{
if (JSON_LIKELY(not first.m_it.primitive_iterator.is_begin()
or not last.m_it.primitive_iterator.is_end()))
{
JSON_THROW(invalid_iterator::create(204, "iterators out of range"));
}
if (is_string())
{
AllocatorType<string_t> alloc;
std::allocator_traits<decltype(alloc)>::destroy(alloc, m_value.string);
std::allocator_traits<decltype(alloc)>::deallocate(alloc, m_value.string, 1);
m_value.string = nullptr;
}
m_type = value_t::null;
assert_invariant();
break;
}
case value_t::object:
{
result.m_it.object_iterator = m_value.object->erase(first.m_it.object_iterator,
last.m_it.object_iterator);
break;
}
case value_t::array:
{
result.m_it.array_iterator = m_value.array->erase(first.m_it.array_iterator,
last.m_it.array_iterator);
break;
}
default:
JSON_THROW(type_error::create(307, "cannot use erase() with " + std::string(type_name())));
}
return result;
}
/*!
@brief remove element from a JSON object given a key
Removes elements from a JSON object with the key value @a key.
@param[in] key value of the elements to remove
@return Number of elements removed. If @a ObjectType is the default
`std::map` type, the return value will always be `0` (@a key was not
found) or `1` (@a key was found).
@post References and iterators to the erased elements are invalidated.
Other references and iterators are not affected.
@throw type_error.307 when called on a type other than JSON object;
example: `"cannot use erase() with null"`
@complexity `log(size()) + count(key)`
@liveexample{The example shows the effect of `erase()`.,erase__key_type}
@sa @ref erase(IteratorType) -- removes the element at a given position
@sa @ref erase(IteratorType, IteratorType) -- removes the elements in
the given range
@sa @ref erase(const size_type) -- removes the element from an array at
the given index
@since version 1.0.0
*/
size_type erase(const typename object_t::key_type& key)
{
// this erase only works for objects
if (JSON_LIKELY(is_object()))
{
return m_value.object->erase(key);
}
JSON_THROW(type_error::create(307, "cannot use erase() with " + std::string(type_name())));
}
/*!
@brief remove element from a JSON array given an index
Removes element from a JSON array at the index @a idx.
@param[in] idx index of the element to remove
@throw type_error.307 when called on a type other than JSON object;
example: `"cannot use erase() with null"`
@throw out_of_range.401 when `idx >= size()`; example: `"array index 17
is out of range"`
@complexity Linear in distance between @a idx and the end of the container.
@liveexample{The example shows the effect of `erase()`.,erase__size_type}
@sa @ref erase(IteratorType) -- removes the element at a given position
@sa @ref erase(IteratorType, IteratorType) -- removes the elements in
the given range
@sa @ref erase(const typename object_t::key_type&) -- removes the element
from an object at the given key
@since version 1.0.0
*/
void erase(const size_type idx)
{
// this erase only works for arrays
if (JSON_LIKELY(is_array()))
{
if (JSON_UNLIKELY(idx >= size()))
{
JSON_THROW(out_of_range::create(401, "array index " + std::to_string(idx) + " is out of range"));
}
m_value.array->erase(m_value.array->begin() + static_cast<difference_type>(idx));
}
else
{
JSON_THROW(type_error::create(307, "cannot use erase() with " + std::string(type_name())));
}
}
/// @}
////////////
// lookup //
////////////
/// @name lookup
/// @{
/*!
@brief find an element in a JSON object
Finds an element in a JSON object with key equivalent to @a key. If the
element is not found or the JSON value is not an object, end() is
returned.
@note This method always returns @ref end() when executed on a JSON type
that is not an object.
@param[in] key key value of the element to search for.
@return Iterator to an element with key equivalent to @a key. If no such
element is found or the JSON value is not an object, past-the-end (see
@ref end()) iterator is returned.
@complexity Logarithmic in the size of the JSON object.
@liveexample{The example shows how `find()` is used.,find__key_type}
@since version 1.0.0
*/
template<typename KeyT>
iterator find(KeyT&& key)
{
auto result = end();
if (is_object())
{
result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
}
return result;
}
/*!
@brief find an element in a JSON object
@copydoc find(KeyT&&)
*/
template<typename KeyT>
const_iterator find(KeyT&& key) const
{
auto result = cend();
if (is_object())
{
result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
}
return result;
}
/*!
@brief returns the number of occurrences of a key in a JSON object
Returns the number of elements with key @a key. If ObjectType is the
default `std::map` type, the return value will always be `0` (@a key was
not found) or `1` (@a key was found).
@note This method always returns `0` when executed on a JSON type that is
not an object.
@param[in] key key value of the element to count
@return Number of elements with key @a key. If the JSON value is not an
object, the return value will be `0`.
@complexity Logarithmic in the size of the JSON object.
@liveexample{The example shows how `count()` is used.,count}
@since version 1.0.0
*/
template<typename KeyT>
size_type count(KeyT&& key) const
{
// return 0 for all nonobject types
return is_object() ? m_value.object->count(std::forward<KeyT>(key)) : 0;
}
/// @}
///////////////
// iterators //
///////////////
/// @name iterators
/// @{
/*!
@brief returns an iterator to the first element
Returns an iterator to the first element.
@image html range-begin-end.svg "Illustration from cppreference.com"
@return iterator to the first element
@complexity Constant.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is constant.
@liveexample{The following code shows an example for `begin()`.,begin}
@sa @ref cbegin() -- returns a const iterator to the beginning
@sa @ref end() -- returns an iterator to the end
@sa @ref cend() -- returns a const iterator to the end
@since version 1.0.0
*/
iterator begin() noexcept
{
iterator result(this);
result.set_begin();
return result;
}
/*!
@copydoc basic_json::cbegin()
*/
const_iterator begin() const noexcept
{
return cbegin();
}
/*!
@brief returns a const iterator to the first element
Returns a const iterator to the first element.
@image html range-begin-end.svg "Illustration from cppreference.com"
@return const iterator to the first element
@complexity Constant.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is constant.
- Has the semantics of `const_cast<const basic_json&>(*this).begin()`.
@liveexample{The following code shows an example for `cbegin()`.,cbegin}
@sa @ref begin() -- returns an iterator to the beginning
@sa @ref end() -- returns an iterator to the end
@sa @ref cend() -- returns a const iterator to the end
@since version 1.0.0
*/
const_iterator cbegin() const noexcept
{
const_iterator result(this);
result.set_begin();
return result;
}
/*!
@brief returns an iterator to one past the last element
Returns an iterator to one past the last element.
@image html range-begin-end.svg "Illustration from cppreference.com"
@return iterator one past the last element
@complexity Constant.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is constant.
@liveexample{The following code shows an example for `end()`.,end}
@sa @ref cend() -- returns a const iterator to the end
@sa @ref begin() -- returns an iterator to the beginning
@sa @ref cbegin() -- returns a const iterator to the beginning
@since version 1.0.0
*/
iterator end() noexcept
{
iterator result(this);
result.set_end();
return result;
}
/*!
@copydoc basic_json::cend()
*/
const_iterator end() const noexcept
{
return cend();
}
/*!
@brief returns a const iterator to one past the last element
Returns a const iterator to one past the last element.
@image html range-begin-end.svg "Illustration from cppreference.com"
@return const iterator one past the last element
@complexity Constant.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is constant.
- Has the semantics of `const_cast<const basic_json&>(*this).end()`.
@liveexample{The following code shows an example for `cend()`.,cend}
@sa @ref end() -- returns an iterator to the end
@sa @ref begin() -- returns an iterator to the beginning
@sa @ref cbegin() -- returns a const iterator to the beginning
@since version 1.0.0
*/
const_iterator cend() const noexcept
{
const_iterator result(this);
result.set_end();
return result;
}
/*!
@brief returns an iterator to the reverse-beginning
Returns an iterator to the reverse-beginning; that is, the last element.
@image html range-rbegin-rend.svg "Illustration from cppreference.com"
@complexity Constant.
@requirement This function helps `basic_json` satisfying the
[ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer)
requirements:
- The complexity is constant.
- Has the semantics of `reverse_iterator(end())`.
@liveexample{The following code shows an example for `rbegin()`.,rbegin}
@sa @ref crbegin() -- returns a const reverse iterator to the beginning
@sa @ref rend() -- returns a reverse iterator to the end
@sa @ref crend() -- returns a const reverse iterator to the end
@since version 1.0.0
*/
reverse_iterator rbegin() noexcept
{
return reverse_iterator(end());
}
/*!
@copydoc basic_json::crbegin()
*/
const_reverse_iterator rbegin() const noexcept
{
return crbegin();
}
/*!
@brief returns an iterator to the reverse-end
Returns an iterator to the reverse-end; that is, one before the first
element.
@image html range-rbegin-rend.svg "Illustration from cppreference.com"
@complexity Constant.
@requirement This function helps `basic_json` satisfying the
[ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer)
requirements:
- The complexity is constant.
- Has the semantics of `reverse_iterator(begin())`.
@liveexample{The following code shows an example for `rend()`.,rend}
@sa @ref crend() -- returns a const reverse iterator to the end
@sa @ref rbegin() -- returns a reverse iterator to the beginning
@sa @ref crbegin() -- returns a const reverse iterator to the beginning
@since version 1.0.0
*/
reverse_iterator rend() noexcept
{
return reverse_iterator(begin());
}
/*!
@copydoc basic_json::crend()
*/
const_reverse_iterator rend() const noexcept
{
return crend();
}
/*!
@brief returns a const reverse iterator to the last element
Returns a const iterator to the reverse-beginning; that is, the last
element.
@image html range-rbegin-rend.svg "Illustration from cppreference.com"
@complexity Constant.
@requirement This function helps `basic_json` satisfying the
[ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer)
requirements:
- The complexity is constant.
- Has the semantics of `const_cast<const basic_json&>(*this).rbegin()`.
@liveexample{The following code shows an example for `crbegin()`.,crbegin}
@sa @ref rbegin() -- returns a reverse iterator to the beginning
@sa @ref rend() -- returns a reverse iterator to the end
@sa @ref crend() -- returns a const reverse iterator to the end
@since version 1.0.0
*/
const_reverse_iterator crbegin() const noexcept
{
return const_reverse_iterator(cend());
}
/*!
@brief returns a const reverse iterator to one before the first
Returns a const reverse iterator to the reverse-end; that is, one before
the first element.
@image html range-rbegin-rend.svg "Illustration from cppreference.com"
@complexity Constant.
@requirement This function helps `basic_json` satisfying the
[ReversibleContainer](http://en.cppreference.com/w/cpp/concept/ReversibleContainer)
requirements:
- The complexity is constant.
- Has the semantics of `const_cast<const basic_json&>(*this).rend()`.
@liveexample{The following code shows an example for `crend()`.,crend}
@sa @ref rend() -- returns a reverse iterator to the end
@sa @ref rbegin() -- returns a reverse iterator to the beginning
@sa @ref crbegin() -- returns a const reverse iterator to the beginning
@since version 1.0.0
*/
const_reverse_iterator crend() const noexcept
{
return const_reverse_iterator(cbegin());
}
public:
/*!
@brief wrapper to access iterator member functions in range-based for
This function allows to access @ref iterator::key() and @ref
iterator::value() during range-based for loops. In these loops, a
reference to the JSON values is returned, so there is no access to the
underlying iterator.
For loop without iterator_wrapper:
@code{cpp}
for (auto it = j_object.begin(); it != j_object.end(); ++it)
{
std::cout << "key: " << it.key() << ", value:" << it.value() << '\n';
}
@endcode
Range-based for loop without iterator proxy:
@code{cpp}
for (auto it : j_object)
{
// "it" is of type json::reference and has no key() member
std::cout << "value: " << it << '\n';
}
@endcode
Range-based for loop with iterator proxy:
@code{cpp}
for (auto it : json::iterator_wrapper(j_object))
{
std::cout << "key: " << it.key() << ", value:" << it.value() << '\n';
}
@endcode
@note When iterating over an array, `key()` will return the index of the
element as string (see example).
@param[in] ref reference to a JSON value
@return iteration proxy object wrapping @a ref with an interface to use in
range-based for loops
@liveexample{The following code shows how the wrapper is used,iterator_wrapper}
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Constant.
@note The name of this function is not yet final and may change in the
future.
@deprecated This stream operator is deprecated and will be removed in
future 4.0.0 of the library. Please use @ref items() instead;
that is, replace `json::iterator_wrapper(j)` with `j.items()`.
*/
JSON_DEPRECATED
static iteration_proxy<iterator> iterator_wrapper(reference ref) noexcept
{
return ref.items();
}
/*!
@copydoc iterator_wrapper(reference)
*/
JSON_DEPRECATED
static iteration_proxy<const_iterator> iterator_wrapper(const_reference ref) noexcept
{
return ref.items();
}
/*!
@brief helper to access iterator member functions in range-based for
This function allows to access @ref iterator::key() and @ref
iterator::value() during range-based for loops. In these loops, a
reference to the JSON values is returned, so there is no access to the
underlying iterator.
For loop without `items()` function:
@code{cpp}
for (auto it = j_object.begin(); it != j_object.end(); ++it)
{
std::cout << "key: " << it.key() << ", value:" << it.value() << '\n';
}
@endcode
Range-based for loop without `items()` function:
@code{cpp}
for (auto it : j_object)
{
// "it" is of type json::reference and has no key() member
std::cout << "value: " << it << '\n';
}
@endcode
Range-based for loop with `items()` function:
@code{cpp}
for (auto it : j_object.items())
{
std::cout << "key: " << it.key() << ", value:" << it.value() << '\n';
}
@endcode
@note When iterating over an array, `key()` will return the index of the
element as string (see example). For primitive types (e.g., numbers),
`key()` returns an empty string.
@return iteration proxy object wrapping @a ref with an interface to use in
range-based for loops
@liveexample{The following code shows how the function is used.,items}
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Constant.
@since version 3.x.x.
*/
iteration_proxy<iterator> items() noexcept
{
return iteration_proxy<iterator>(*this);
}
/*!
@copydoc items()
*/
iteration_proxy<const_iterator> items() const noexcept
{
return iteration_proxy<const_iterator>(*this);
}
/// @}
//////////////
// capacity //
//////////////
/// @name capacity
/// @{
/*!
@brief checks whether the container is empty.
Checks if a JSON value has no elements (i.e. whether its @ref size is `0`).
@return The return value depends on the different types and is
defined as follows:
Value type | return value
----------- | -------------
null | `true`
boolean | `false`
string | `false`
number | `false`
object | result of function `object_t::empty()`
array | result of function `array_t::empty()`
@liveexample{The following code uses `empty()` to check if a JSON
object contains any elements.,empty}
@complexity Constant, as long as @ref array_t and @ref object_t satisfy
the Container concept; that is, their `empty()` functions have constant
complexity.
@iterators No changes.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@note This function does not return whether a string stored as JSON value
is empty - it returns whether the JSON container itself is empty which is
false in the case of a string.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is constant.
- Has the semantics of `begin() == end()`.
@sa @ref size() -- returns the number of elements
@since version 1.0.0
*/
bool empty() const noexcept
{
switch (m_type)
{
case value_t::null:
{
// null values are empty
return true;
}
case value_t::array:
{
// delegate call to array_t::empty()
return m_value.array->empty();
}
case value_t::object:
{
// delegate call to object_t::empty()
return m_value.object->empty();
}
default:
{
// all other types are nonempty
return false;
}
}
}
/*!
@brief returns the number of elements
Returns the number of elements in a JSON value.
@return The return value depends on the different types and is
defined as follows:
Value type | return value
----------- | -------------
null | `0`
boolean | `1`
string | `1`
number | `1`
object | result of function object_t::size()
array | result of function array_t::size()
@liveexample{The following code calls `size()` on the different value
types.,size}
@complexity Constant, as long as @ref array_t and @ref object_t satisfy
the Container concept; that is, their size() functions have constant
complexity.
@iterators No changes.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@note This function does not return the length of a string stored as JSON
value - it returns the number of elements in the JSON value which is 1 in
the case of a string.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is constant.
- Has the semantics of `std::distance(begin(), end())`.
@sa @ref empty() -- checks whether the container is empty
@sa @ref max_size() -- returns the maximal number of elements
@since version 1.0.0
*/
size_type size() const noexcept
{
switch (m_type)
{
case value_t::null:
{
// null values are empty
return 0;
}
case value_t::array:
{
// delegate call to array_t::size()
return m_value.array->size();
}
case value_t::object:
{
// delegate call to object_t::size()
return m_value.object->size();
}
default:
{
// all other types have size 1
return 1;
}
}
}
/*!
@brief returns the maximum possible number of elements
Returns the maximum number of elements a JSON value is able to hold due to
system or library implementation limitations, i.e. `std::distance(begin(),
end())` for the JSON value.
@return The return value depends on the different types and is
defined as follows:
Value type | return value
----------- | -------------
null | `0` (same as `size()`)
boolean | `1` (same as `size()`)
string | `1` (same as `size()`)
number | `1` (same as `size()`)
object | result of function `object_t::max_size()`
array | result of function `array_t::max_size()`
@liveexample{The following code calls `max_size()` on the different value
types. Note the output is implementation specific.,max_size}
@complexity Constant, as long as @ref array_t and @ref object_t satisfy
the Container concept; that is, their `max_size()` functions have constant
complexity.
@iterators No changes.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@requirement This function helps `basic_json` satisfying the
[Container](http://en.cppreference.com/w/cpp/concept/Container)
requirements:
- The complexity is constant.
- Has the semantics of returning `b.size()` where `b` is the largest
possible JSON value.
@sa @ref size() -- returns the number of elements
@since version 1.0.0
*/
size_type max_size() const noexcept
{
switch (m_type)
{
case value_t::array:
{
// delegate call to array_t::max_size()
return m_value.array->max_size();
}
case value_t::object:
{
// delegate call to object_t::max_size()
return m_value.object->max_size();
}
default:
{
// all other types have max_size() == size()
return size();
}
}
}
/// @}
///////////////
// modifiers //
///////////////
/// @name modifiers
/// @{
/*!
@brief clears the contents
Clears the content of a JSON value and resets it to the default value as
if @ref basic_json(value_t) would have been called with the current value
type from @ref type():
Value type | initial value
----------- | -------------
null | `null`
boolean | `false`
string | `""`
number | `0`
object | `{}`
array | `[]`
@post Has the same effect as calling
@code {.cpp}
*this = basic_json(type());
@endcode
@liveexample{The example below shows the effect of `clear()` to different
JSON types.,clear}
@complexity Linear in the size of the JSON value.
@iterators All iterators, pointers and references related to this container
are invalidated.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@sa @ref basic_json(value_t) -- constructor that creates an object with the
same value than calling `clear()`
@since version 1.0.0
*/
void clear() noexcept
{
switch (m_type)
{
case value_t::number_integer:
{
m_value.number_integer = 0;
break;
}
case value_t::number_unsigned:
{
m_value.number_unsigned = 0;
break;
}
case value_t::number_float:
{
m_value.number_float = 0.0;
break;
}
case value_t::boolean:
{
m_value.boolean = false;
break;
}
case value_t::string:
{
m_value.string->clear();
break;
}
case value_t::array:
{
m_value.array->clear();
break;
}
case value_t::object:
{
m_value.object->clear();
break;
}
default:
break;
}
}
/*!
@brief add an object to an array
Appends the given element @a val to the end of the JSON value. If the
function is called on a JSON null value, an empty array is created before
appending @a val.
@param[in] val the value to add to the JSON array
@throw type_error.308 when called on a type other than JSON array or
null; example: `"cannot use push_back() with number"`
@complexity Amortized constant.
@liveexample{The example shows how `push_back()` and `+=` can be used to
add elements to a JSON array. Note how the `null` value was silently
converted to a JSON array.,push_back}
@since version 1.0.0
*/
void push_back(basic_json&& val)
{
// push_back only works for null objects or arrays
if (JSON_UNLIKELY(not(is_null() or is_array())))
{
JSON_THROW(type_error::create(308, "cannot use push_back() with " + std::string(type_name())));
}
// transform null object into an array
if (is_null())
{
m_type = value_t::array;
m_value = value_t::array;
assert_invariant();
}
// add element to array (move semantics)
m_value.array->push_back(std::move(val));
// invalidate object
val.m_type = value_t::null;
}
/*!
@brief add an object to an array
@copydoc push_back(basic_json&&)
*/
reference operator+=(basic_json&& val)
{
push_back(std::move(val));
return *this;
}
/*!
@brief add an object to an array
@copydoc push_back(basic_json&&)
*/
void push_back(const basic_json& val)
{
// push_back only works for null objects or arrays
if (JSON_UNLIKELY(not(is_null() or is_array())))
{
JSON_THROW(type_error::create(308, "cannot use push_back() with " + std::string(type_name())));
}
// transform null object into an array
if (is_null())
{
m_type = value_t::array;
m_value = value_t::array;
assert_invariant();
}
// add element to array
m_value.array->push_back(val);
}
/*!
@brief add an object to an array
@copydoc push_back(basic_json&&)
*/
reference operator+=(const basic_json& val)
{
push_back(val);
return *this;
}
/*!
@brief add an object to an object
Inserts the given element @a val to the JSON object. If the function is
called on a JSON null value, an empty object is created before inserting
@a val.
@param[in] val the value to add to the JSON object
@throw type_error.308 when called on a type other than JSON object or
null; example: `"cannot use push_back() with number"`
@complexity Logarithmic in the size of the container, O(log(`size()`)).
@liveexample{The example shows how `push_back()` and `+=` can be used to
add elements to a JSON object. Note how the `null` value was silently
converted to a JSON object.,push_back__object_t__value}
@since version 1.0.0
*/
void push_back(const typename object_t::value_type& val)
{
// push_back only works for null objects or objects
if (JSON_UNLIKELY(not(is_null() or is_object())))
{
JSON_THROW(type_error::create(308, "cannot use push_back() with " + std::string(type_name())));
}
// transform null object into an object
if (is_null())
{
m_type = value_t::object;
m_value = value_t::object;
assert_invariant();
}
// add element to array
m_value.object->insert(val);
}
/*!
@brief add an object to an object
@copydoc push_back(const typename object_t::value_type&)
*/
reference operator+=(const typename object_t::value_type& val)
{
push_back(val);
return *this;
}
/*!
@brief add an object to an object
This function allows to use `push_back` with an initializer list. In case
1. the current value is an object,
2. the initializer list @a init contains only two elements, and
3. the first element of @a init is a string,
@a init is converted into an object element and added using
@ref push_back(const typename object_t::value_type&). Otherwise, @a init
is converted to a JSON value and added using @ref push_back(basic_json&&).
@param[in] init an initializer list
@complexity Linear in the size of the initializer list @a init.
@note This function is required to resolve an ambiguous overload error,
because pairs like `{"key", "value"}` can be both interpreted as
`object_t::value_type` or `std::initializer_list<basic_json>`, see
https://github.com/nlohmann/json/issues/235 for more information.
@liveexample{The example shows how initializer lists are treated as
objects when possible.,push_back__initializer_list}
*/
void push_back(initializer_list_t init)
{
if (is_object() and init.size() == 2 and (*init.begin())->is_string())
{
basic_json&& key = init.begin()->moved_or_copied();
push_back(typename object_t::value_type(
std::move(key.get_ref<string_t&>()), (init.begin() + 1)->moved_or_copied()));
}
else
{
push_back(basic_json(init));
}
}
/*!
@brief add an object to an object
@copydoc push_back(initializer_list_t)
*/
reference operator+=(initializer_list_t init)
{
push_back(init);
return *this;
}
/*!
@brief add an object to an array
Creates a JSON value from the passed parameters @a args to the end of the
JSON value. If the function is called on a JSON null value, an empty array
is created before appending the value created from @a args.
@param[in] args arguments to forward to a constructor of @ref basic_json
@tparam Args compatible types to create a @ref basic_json object
@throw type_error.311 when called on a type other than JSON array or
null; example: `"cannot use emplace_back() with number"`
@complexity Amortized constant.
@liveexample{The example shows how `push_back()` can be used to add
elements to a JSON array. Note how the `null` value was silently converted
to a JSON array.,emplace_back}
@since version 2.0.8
*/
template<class... Args>
void emplace_back(Args&& ... args)
{
// emplace_back only works for null objects or arrays
if (JSON_UNLIKELY(not(is_null() or is_array())))
{
JSON_THROW(type_error::create(311, "cannot use emplace_back() with " + std::string(type_name())));
}
// transform null object into an array
if (is_null())
{
m_type = value_t::array;
m_value = value_t::array;
assert_invariant();
}
// add element to array (perfect forwarding)
m_value.array->emplace_back(std::forward<Args>(args)...);
}
/*!
@brief add an object to an object if key does not exist
Inserts a new element into a JSON object constructed in-place with the
given @a args if there is no element with the key in the container. If the
function is called on a JSON null value, an empty object is created before
appending the value created from @a args.
@param[in] args arguments to forward to a constructor of @ref basic_json
@tparam Args compatible types to create a @ref basic_json object
@return a pair consisting of an iterator to the inserted element, or the
already-existing element if no insertion happened, and a bool
denoting whether the insertion took place.
@throw type_error.311 when called on a type other than JSON object or
null; example: `"cannot use emplace() with number"`
@complexity Logarithmic in the size of the container, O(log(`size()`)).
@liveexample{The example shows how `emplace()` can be used to add elements
to a JSON object. Note how the `null` value was silently converted to a
JSON object. Further note how no value is added if there was already one
value stored with the same key.,emplace}
@since version 2.0.8
*/
template<class... Args>
std::pair<iterator, bool> emplace(Args&& ... args)
{
// emplace only works for null objects or arrays
if (JSON_UNLIKELY(not(is_null() or is_object())))
{
JSON_THROW(type_error::create(311, "cannot use emplace() with " + std::string(type_name())));
}
// transform null object into an object
if (is_null())
{
m_type = value_t::object;
m_value = value_t::object;
assert_invariant();
}
// add element to array (perfect forwarding)
auto res = m_value.object->emplace(std::forward<Args>(args)...);
// create result iterator and set iterator to the result of emplace
auto it = begin();
it.m_it.object_iterator = res.first;
// return pair of iterator and boolean
return {it, res.second};
}
/*!
@brief inserts element
Inserts element @a val before iterator @a pos.
@param[in] pos iterator before which the content will be inserted; may be
the end() iterator
@param[in] val element to insert
@return iterator pointing to the inserted @a val.
@throw type_error.309 if called on JSON values other than arrays;
example: `"cannot use insert() with string"`
@throw invalid_iterator.202 if @a pos is not an iterator of *this;
example: `"iterator does not fit current value"`
@complexity Constant plus linear in the distance between @a pos and end of
the container.
@liveexample{The example shows how `insert()` is used.,insert}
@since version 1.0.0
*/
iterator insert(const_iterator pos, const basic_json& val)
{
// insert only works for arrays
if (JSON_LIKELY(is_array()))
{
// check if iterator pos fits to this JSON value
if (JSON_UNLIKELY(pos.m_object != this))
{
JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
}
// insert to array and return iterator
iterator result(this);
result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, val);
return result;
}
JSON_THROW(type_error::create(309, "cannot use insert() with " + std::string(type_name())));
}
/*!
@brief inserts element
@copydoc insert(const_iterator, const basic_json&)
*/
iterator insert(const_iterator pos, basic_json&& val)
{
return insert(pos, val);
}
/*!
@brief inserts elements
Inserts @a cnt copies of @a val before iterator @a pos.
@param[in] pos iterator before which the content will be inserted; may be
the end() iterator
@param[in] cnt number of copies of @a val to insert
@param[in] val element to insert
@return iterator pointing to the first element inserted, or @a pos if
`cnt==0`
@throw type_error.309 if called on JSON values other than arrays; example:
`"cannot use insert() with string"`
@throw invalid_iterator.202 if @a pos is not an iterator of *this;
example: `"iterator does not fit current value"`
@complexity Linear in @a cnt plus linear in the distance between @a pos
and end of the container.
@liveexample{The example shows how `insert()` is used.,insert__count}
@since version 1.0.0
*/
iterator insert(const_iterator pos, size_type cnt, const basic_json& val)
{
// insert only works for arrays
if (JSON_LIKELY(is_array()))
{
// check if iterator pos fits to this JSON value
if (JSON_UNLIKELY(pos.m_object != this))
{
JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
}
// insert to array and return iterator
iterator result(this);
result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, cnt, val);
return result;
}
JSON_THROW(type_error::create(309, "cannot use insert() with " + std::string(type_name())));
}
/*!
@brief inserts elements
Inserts elements from range `[first, last)` before iterator @a pos.
@param[in] pos iterator before which the content will be inserted; may be
the end() iterator
@param[in] first begin of the range of elements to insert
@param[in] last end of the range of elements to insert
@throw type_error.309 if called on JSON values other than arrays; example:
`"cannot use insert() with string"`
@throw invalid_iterator.202 if @a pos is not an iterator of *this;
example: `"iterator does not fit current value"`
@throw invalid_iterator.210 if @a first and @a last do not belong to the
same JSON value; example: `"iterators do not fit"`
@throw invalid_iterator.211 if @a first or @a last are iterators into
container for which insert is called; example: `"passed iterators may not
belong to container"`
@return iterator pointing to the first element inserted, or @a pos if
`first==last`
@complexity Linear in `std::distance(first, last)` plus linear in the
distance between @a pos and end of the container.
@liveexample{The example shows how `insert()` is used.,insert__range}
@since version 1.0.0
*/
iterator insert(const_iterator pos, const_iterator first, const_iterator last)
{
// insert only works for arrays
if (JSON_UNLIKELY(not is_array()))
{
JSON_THROW(type_error::create(309, "cannot use insert() with " + std::string(type_name())));
}
// check if iterator pos fits to this JSON value
if (JSON_UNLIKELY(pos.m_object != this))
{
JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
}
// check if range iterators belong to the same JSON object
if (JSON_UNLIKELY(first.m_object != last.m_object))
{
JSON_THROW(invalid_iterator::create(210, "iterators do not fit"));
}
if (JSON_UNLIKELY(first.m_object == this))
{
JSON_THROW(invalid_iterator::create(211, "passed iterators may not belong to container"));
}
// insert to array and return iterator
iterator result(this);
result.m_it.array_iterator = m_value.array->insert(
pos.m_it.array_iterator,
first.m_it.array_iterator,
last.m_it.array_iterator);
return result;
}
/*!
@brief inserts elements
Inserts elements from initializer list @a ilist before iterator @a pos.
@param[in] pos iterator before which the content will be inserted; may be
the end() iterator
@param[in] ilist initializer list to insert the values from
@throw type_error.309 if called on JSON values other than arrays; example:
`"cannot use insert() with string"`
@throw invalid_iterator.202 if @a pos is not an iterator of *this;
example: `"iterator does not fit current value"`
@return iterator pointing to the first element inserted, or @a pos if
`ilist` is empty
@complexity Linear in `ilist.size()` plus linear in the distance between
@a pos and end of the container.
@liveexample{The example shows how `insert()` is used.,insert__ilist}
@since version 1.0.0
*/
iterator insert(const_iterator pos, initializer_list_t ilist)
{
// insert only works for arrays
if (JSON_UNLIKELY(not is_array()))
{
JSON_THROW(type_error::create(309, "cannot use insert() with " + std::string(type_name())));
}
// check if iterator pos fits to this JSON value
if (JSON_UNLIKELY(pos.m_object != this))
{
JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
}
// insert to array and return iterator
iterator result(this);
result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, ilist.begin(), ilist.end());
return result;
}
/*!
@brief inserts elements
Inserts elements from range `[first, last)`.
@param[in] first begin of the range of elements to insert
@param[in] last end of the range of elements to insert
@throw type_error.309 if called on JSON values other than objects; example:
`"cannot use insert() with string"`
@throw invalid_iterator.202 if iterator @a first or @a last does does not
point to an object; example: `"iterators first and last must point to
objects"`
@throw invalid_iterator.210 if @a first and @a last do not belong to the
same JSON value; example: `"iterators do not fit"`
@complexity Logarithmic: `O(N*log(size() + N))`, where `N` is the number
of elements to insert.
@liveexample{The example shows how `insert()` is used.,insert__range_object}
@since version 3.0.0
*/
void insert(const_iterator first, const_iterator last)
{
// insert only works for objects
if (JSON_UNLIKELY(not is_object()))
{
JSON_THROW(type_error::create(309, "cannot use insert() with " + std::string(type_name())));
}
// check if range iterators belong to the same JSON object
if (JSON_UNLIKELY(first.m_object != last.m_object))
{
JSON_THROW(invalid_iterator::create(210, "iterators do not fit"));
}
// passed iterators must belong to objects
if (JSON_UNLIKELY(not first.m_object->is_object()))
{
JSON_THROW(invalid_iterator::create(202, "iterators first and last must point to objects"));
}
m_value.object->insert(first.m_it.object_iterator, last.m_it.object_iterator);
}
/*!
@brief updates a JSON object from another object, overwriting existing keys
Inserts all values from JSON object @a j and overwrites existing keys.
@param[in] j JSON object to read values from
@throw type_error.312 if called on JSON values other than objects; example:
`"cannot use update() with string"`
@complexity O(N*log(size() + N)), where N is the number of elements to
insert.
@liveexample{The example shows how `update()` is used.,update}
@sa https://docs.python.org/3.6/library/stdtypes.html#dict.update
@since version 3.0.0
*/
void update(const_reference j)
{
// implicitly convert null value to an empty object
if (is_null())
{
m_type = value_t::object;
m_value.object = create<object_t>();
assert_invariant();
}
if (JSON_UNLIKELY(not is_object()))
{
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(type_name())));
}
if (JSON_UNLIKELY(not j.is_object()))
{
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(j.type_name())));
}
for (auto it = j.cbegin(); it != j.cend(); ++it)
{
m_value.object->operator[](it.key()) = it.value();
}
}
/*!
@brief updates a JSON object from another object, overwriting existing keys
Inserts all values from from range `[first, last)` and overwrites existing
keys.
@param[in] first begin of the range of elements to insert
@param[in] last end of the range of elements to insert
@throw type_error.312 if called on JSON values other than objects; example:
`"cannot use update() with string"`
@throw invalid_iterator.202 if iterator @a first or @a last does does not
point to an object; example: `"iterators first and last must point to
objects"`
@throw invalid_iterator.210 if @a first and @a last do not belong to the
same JSON value; example: `"iterators do not fit"`
@complexity O(N*log(size() + N)), where N is the number of elements to
insert.
@liveexample{The example shows how `update()` is used__range.,update}
@sa https://docs.python.org/3.6/library/stdtypes.html#dict.update
@since version 3.0.0
*/
void update(const_iterator first, const_iterator last)
{
// implicitly convert null value to an empty object
if (is_null())
{
m_type = value_t::object;
m_value.object = create<object_t>();
assert_invariant();
}
if (JSON_UNLIKELY(not is_object()))
{
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(type_name())));
}
// check if range iterators belong to the same JSON object
if (JSON_UNLIKELY(first.m_object != last.m_object))
{
JSON_THROW(invalid_iterator::create(210, "iterators do not fit"));
}
// passed iterators must belong to objects
if (JSON_UNLIKELY(not first.m_object->is_object()
or not last.m_object->is_object()))
{
JSON_THROW(invalid_iterator::create(202, "iterators first and last must point to objects"));
}
for (auto it = first; it != last; ++it)
{
m_value.object->operator[](it.key()) = it.value();
}
}
/*!
@brief exchanges the values
Exchanges the contents of the JSON value with those of @a other. Does not
invoke any move, copy, or swap operations on individual elements. All
iterators and references remain valid. The past-the-end iterator is
invalidated.
@param[in,out] other JSON value to exchange the contents with
@complexity Constant.
@liveexample{The example below shows how JSON values can be swapped with
`swap()`.,swap__reference}
@since version 1.0.0
*/
void swap(reference other) noexcept (
std::is_nothrow_move_constructible<value_t>::value and
std::is_nothrow_move_assignable<value_t>::value and
std::is_nothrow_move_constructible<json_value>::value and
std::is_nothrow_move_assignable<json_value>::value
)
{
std::swap(m_type, other.m_type);
std::swap(m_value, other.m_value);
assert_invariant();
}
/*!
@brief exchanges the values
Exchanges the contents of a JSON array with those of @a other. Does not
invoke any move, copy, or swap operations on individual elements. All
iterators and references remain valid. The past-the-end iterator is
invalidated.
@param[in,out] other array to exchange the contents with
@throw type_error.310 when JSON value is not an array; example: `"cannot
use swap() with string"`
@complexity Constant.
@liveexample{The example below shows how arrays can be swapped with
`swap()`.,swap__array_t}
@since version 1.0.0
*/
void swap(array_t& other)
{
// swap only works for arrays
if (JSON_LIKELY(is_array()))
{
std::swap(*(m_value.array), other);
}
else
{
JSON_THROW(type_error::create(310, "cannot use swap() with " + std::string(type_name())));
}
}
/*!
@brief exchanges the values
Exchanges the contents of a JSON object with those of @a other. Does not
invoke any move, copy, or swap operations on individual elements. All
iterators and references remain valid. The past-the-end iterator is
invalidated.
@param[in,out] other object to exchange the contents with
@throw type_error.310 when JSON value is not an object; example:
`"cannot use swap() with string"`
@complexity Constant.
@liveexample{The example below shows how objects can be swapped with
`swap()`.,swap__object_t}
@since version 1.0.0
*/
void swap(object_t& other)
{
// swap only works for objects
if (JSON_LIKELY(is_object()))
{
std::swap(*(m_value.object), other);
}
else
{
JSON_THROW(type_error::create(310, "cannot use swap() with " + std::string(type_name())));
}
}
/*!
@brief exchanges the values
Exchanges the contents of a JSON string with those of @a other. Does not
invoke any move, copy, or swap operations on individual elements. All
iterators and references remain valid. The past-the-end iterator is
invalidated.
@param[in,out] other string to exchange the contents with
@throw type_error.310 when JSON value is not a string; example: `"cannot
use swap() with boolean"`
@complexity Constant.
@liveexample{The example below shows how strings can be swapped with
`swap()`.,swap__string_t}
@since version 1.0.0
*/
void swap(string_t& other)
{
// swap only works for strings
if (JSON_LIKELY(is_string()))
{
std::swap(*(m_value.string), other);
}
else
{
JSON_THROW(type_error::create(310, "cannot use swap() with " + std::string(type_name())));
}
}
/// @}
public:
//////////////////////////////////////////
// lexicographical comparison operators //
//////////////////////////////////////////
/// @name lexicographical comparison operators
/// @{
/*!
@brief comparison: equal
Compares two JSON values for equality according to the following rules:
- Two JSON values are equal if (1) they are from the same type and (2)
their stored values are the same according to their respective
`operator==`.
- Integer and floating-point numbers are automatically converted before
comparison. Note than two NaN values are always treated as unequal.
- Two JSON null values are equal.
@note Floating-point inside JSON values numbers are compared with
`json::number_float_t::operator==` which is `double::operator==` by
default. To compare floating-point while respecting an epsilon, an alternative
[comparison function](https://github.com/mariokonrad/marnav/blob/master/src/marnav/math/floatingpoint.hpp#L34-#L39)
could be used, for instance
@code {.cpp}
template<typename T, typename = typename std::enable_if<std::is_floating_point<T>::value, T>::type>
inline bool is_same(T a, T b, T epsilon = std::numeric_limits<T>::epsilon()) noexcept
{
return std::abs(a - b) <= epsilon;
}
@endcode
@note NaN values never compare equal to themselves or to other NaN values.
@param[in] lhs first JSON value to consider
@param[in] rhs second JSON value to consider
@return whether the values @a lhs and @a rhs are equal
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@complexity Linear.
@liveexample{The example demonstrates comparing several JSON
types.,operator__equal}
@since version 1.0.0
*/
friend bool operator==(const_reference lhs, const_reference rhs) noexcept
{
const auto lhs_type = lhs.type();
const auto rhs_type = rhs.type();
if (lhs_type == rhs_type)
{
switch (lhs_type)
{
case value_t::array:
return (*lhs.m_value.array == *rhs.m_value.array);
case value_t::object:
return (*lhs.m_value.object == *rhs.m_value.object);
case value_t::null:
return true;
case value_t::string:
return (*lhs.m_value.string == *rhs.m_value.string);
case value_t::boolean:
return (lhs.m_value.boolean == rhs.m_value.boolean);
case value_t::number_integer:
return (lhs.m_value.number_integer == rhs.m_value.number_integer);
case value_t::number_unsigned:
return (lhs.m_value.number_unsigned == rhs.m_value.number_unsigned);
case value_t::number_float:
return (lhs.m_value.number_float == rhs.m_value.number_float);
default:
return false;
}
}
else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
{
return (static_cast<number_float_t>(lhs.m_value.number_integer) == rhs.m_value.number_float);
}
else if (lhs_type == value_t::number_float and rhs_type == value_t::number_integer)
{
return (lhs.m_value.number_float == static_cast<number_float_t>(rhs.m_value.number_integer));
}
else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_float)
{
return (static_cast<number_float_t>(lhs.m_value.number_unsigned) == rhs.m_value.number_float);
}
else if (lhs_type == value_t::number_float and rhs_type == value_t::number_unsigned)
{
return (lhs.m_value.number_float == static_cast<number_float_t>(rhs.m_value.number_unsigned));
}
else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_integer)
{
return (static_cast<number_integer_t>(lhs.m_value.number_unsigned) == rhs.m_value.number_integer);
}
else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_unsigned)
{
return (lhs.m_value.number_integer == static_cast<number_integer_t>(rhs.m_value.number_unsigned));
}
return false;
}
/*!
@brief comparison: equal
@copydoc operator==(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator==(const_reference lhs, const ScalarType rhs) noexcept
{
return (lhs == basic_json(rhs));
}
/*!
@brief comparison: equal
@copydoc operator==(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator==(const ScalarType lhs, const_reference rhs) noexcept
{
return (basic_json(lhs) == rhs);
}
/*!
@brief comparison: not equal
Compares two JSON values for inequality by calculating `not (lhs == rhs)`.
@param[in] lhs first JSON value to consider
@param[in] rhs second JSON value to consider
@return whether the values @a lhs and @a rhs are not equal
@complexity Linear.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@liveexample{The example demonstrates comparing several JSON
types.,operator__notequal}
@since version 1.0.0
*/
friend bool operator!=(const_reference lhs, const_reference rhs) noexcept
{
return not (lhs == rhs);
}
/*!
@brief comparison: not equal
@copydoc operator!=(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator!=(const_reference lhs, const ScalarType rhs) noexcept
{
return (lhs != basic_json(rhs));
}
/*!
@brief comparison: not equal
@copydoc operator!=(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator!=(const ScalarType lhs, const_reference rhs) noexcept
{
return (basic_json(lhs) != rhs);
}
/*!
@brief comparison: less than
Compares whether one JSON value @a lhs is less than another JSON value @a
rhs according to the following rules:
- If @a lhs and @a rhs have the same type, the values are compared using
the default `<` operator.
- Integer and floating-point numbers are automatically converted before
comparison
- In case @a lhs and @a rhs have different types, the values are ignored
and the order of the types is considered, see
@ref operator<(const value_t, const value_t).
@param[in] lhs first JSON value to consider
@param[in] rhs second JSON value to consider
@return whether @a lhs is less than @a rhs
@complexity Linear.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@liveexample{The example demonstrates comparing several JSON
types.,operator__less}
@since version 1.0.0
*/
friend bool operator<(const_reference lhs, const_reference rhs) noexcept
{
const auto lhs_type = lhs.type();
const auto rhs_type = rhs.type();
if (lhs_type == rhs_type)
{
switch (lhs_type)
{
case value_t::array:
return (*lhs.m_value.array) < (*rhs.m_value.array);
case value_t::object:
return *lhs.m_value.object < *rhs.m_value.object;
case value_t::null:
return false;
case value_t::string:
return *lhs.m_value.string < *rhs.m_value.string;
case value_t::boolean:
return lhs.m_value.boolean < rhs.m_value.boolean;
case value_t::number_integer:
return lhs.m_value.number_integer < rhs.m_value.number_integer;
case value_t::number_unsigned:
return lhs.m_value.number_unsigned < rhs.m_value.number_unsigned;
case value_t::number_float:
return lhs.m_value.number_float < rhs.m_value.number_float;
default:
return false;
}
}
else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
{
return static_cast<number_float_t>(lhs.m_value.number_integer) < rhs.m_value.number_float;
}
else if (lhs_type == value_t::number_float and rhs_type == value_t::number_integer)
{
return lhs.m_value.number_float < static_cast<number_float_t>(rhs.m_value.number_integer);
}
else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_float)
{
return static_cast<number_float_t>(lhs.m_value.number_unsigned) < rhs.m_value.number_float;
}
else if (lhs_type == value_t::number_float and rhs_type == value_t::number_unsigned)
{
return lhs.m_value.number_float < static_cast<number_float_t>(rhs.m_value.number_unsigned);
}
else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_unsigned)
{
return lhs.m_value.number_integer < static_cast<number_integer_t>(rhs.m_value.number_unsigned);
}
else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_integer)
{
return static_cast<number_integer_t>(lhs.m_value.number_unsigned) < rhs.m_value.number_integer;
}
// We only reach this line if we cannot compare values. In that case,
// we compare types. Note we have to call the operator explicitly,
// because MSVC has problems otherwise.
return operator<(lhs_type, rhs_type);
}
/*!
@brief comparison: less than
@copydoc operator<(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator<(const_reference lhs, const ScalarType rhs) noexcept
{
return (lhs < basic_json(rhs));
}
/*!
@brief comparison: less than
@copydoc operator<(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator<(const ScalarType lhs, const_reference rhs) noexcept
{
return (basic_json(lhs) < rhs);
}
/*!
@brief comparison: less than or equal
Compares whether one JSON value @a lhs is less than or equal to another
JSON value by calculating `not (rhs < lhs)`.
@param[in] lhs first JSON value to consider
@param[in] rhs second JSON value to consider
@return whether @a lhs is less than or equal to @a rhs
@complexity Linear.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@liveexample{The example demonstrates comparing several JSON
types.,operator__greater}
@since version 1.0.0
*/
friend bool operator<=(const_reference lhs, const_reference rhs) noexcept
{
return not (rhs < lhs);
}
/*!
@brief comparison: less than or equal
@copydoc operator<=(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator<=(const_reference lhs, const ScalarType rhs) noexcept
{
return (lhs <= basic_json(rhs));
}
/*!
@brief comparison: less than or equal
@copydoc operator<=(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator<=(const ScalarType lhs, const_reference rhs) noexcept
{
return (basic_json(lhs) <= rhs);
}
/*!
@brief comparison: greater than
Compares whether one JSON value @a lhs is greater than another
JSON value by calculating `not (lhs <= rhs)`.
@param[in] lhs first JSON value to consider
@param[in] rhs second JSON value to consider
@return whether @a lhs is greater than to @a rhs
@complexity Linear.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@liveexample{The example demonstrates comparing several JSON
types.,operator__lessequal}
@since version 1.0.0
*/
friend bool operator>(const_reference lhs, const_reference rhs) noexcept
{
return not (lhs <= rhs);
}
/*!
@brief comparison: greater than
@copydoc operator>(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator>(const_reference lhs, const ScalarType rhs) noexcept
{
return (lhs > basic_json(rhs));
}
/*!
@brief comparison: greater than
@copydoc operator>(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator>(const ScalarType lhs, const_reference rhs) noexcept
{
return (basic_json(lhs) > rhs);
}
/*!
@brief comparison: greater than or equal
Compares whether one JSON value @a lhs is greater than or equal to another
JSON value by calculating `not (lhs < rhs)`.
@param[in] lhs first JSON value to consider
@param[in] rhs second JSON value to consider
@return whether @a lhs is greater than or equal to @a rhs
@complexity Linear.
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@liveexample{The example demonstrates comparing several JSON
types.,operator__greaterequal}
@since version 1.0.0
*/
friend bool operator>=(const_reference lhs, const_reference rhs) noexcept
{
return not (lhs < rhs);
}
/*!
@brief comparison: greater than or equal
@copydoc operator>=(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator>=(const_reference lhs, const ScalarType rhs) noexcept
{
return (lhs >= basic_json(rhs));
}
/*!
@brief comparison: greater than or equal
@copydoc operator>=(const_reference, const_reference)
*/
template<typename ScalarType, typename std::enable_if<
std::is_scalar<ScalarType>::value, int>::type = 0>
friend bool operator>=(const ScalarType lhs, const_reference rhs) noexcept
{
return (basic_json(lhs) >= rhs);
}
/// @}
///////////////////
// serialization //
///////////////////
/// @name serialization
/// @{
/*!
@brief serialize to stream
Serialize the given JSON value @a j to the output stream @a o. The JSON
value will be serialized using the @ref dump member function.
- The indentation of the output can be controlled with the member variable
`width` of the output stream @a o. For instance, using the manipulator
`std::setw(4)` on @a o sets the indentation level to `4` and the
serialization result is the same as calling `dump(4)`.
- The indentation character can be controlled with the member variable
`fill` of the output stream @a o. For instance, the manipulator
`std::setfill('\\t')` sets indentation to use a tab character rather than
the default space character.
@param[in,out] o stream to serialize to
@param[in] j JSON value to serialize
@return the stream @a o
@throw type_error.316 if a string stored inside the JSON value is not
UTF-8 encoded
@complexity Linear.
@liveexample{The example below shows the serialization with different
parameters to `width` to adjust the indentation level.,operator_serialize}
@since version 1.0.0; indentation character added in version 3.0.0
*/
friend std::ostream& operator<<(std::ostream& o, const basic_json& j)
{
// read width member and use it as indentation parameter if nonzero
const bool pretty_print = (o.width() > 0);
const auto indentation = (pretty_print ? o.width() : 0);
// reset width to 0 for subsequent calls to this stream
o.width(0);
// do the actual serialization
serializer s(detail::output_adapter<char>(o), o.fill());
s.dump(j, pretty_print, false, static_cast<unsigned int>(indentation));
return o;
}
/*!
@brief serialize to stream
@deprecated This stream operator is deprecated and will be removed in
future 4.0.0 of the library. Please use
@ref operator<<(std::ostream&, const basic_json&)
instead; that is, replace calls like `j >> o;` with `o << j;`.
@since version 1.0.0; deprecated since version 3.0.0
*/
JSON_DEPRECATED
friend std::ostream& operator>>(const basic_json& j, std::ostream& o)
{
return o << j;
}
/// @}
/////////////////////
// deserialization //
/////////////////////
/// @name deserialization
/// @{
/*!
@brief deserialize from a compatible input
This function reads from a compatible input. Examples are:
- an array of 1-byte values
- strings with character/literal type with size of 1 byte
- input streams
- container with contiguous storage of 1-byte values. Compatible container
types include `std::vector`, `std::string`, `std::array`,
`std::valarray`, and `std::initializer_list`. Furthermore, C-style
arrays can be used with `std::begin()`/`std::end()`. User-defined
containers can be used as long as they implement random-access iterators
and a contiguous storage.
@pre Each element of the container has a size of 1 byte. Violating this
precondition yields undefined behavior. **This precondition is enforced
with a static assertion.**
@pre The container storage is contiguous. Violating this precondition
yields undefined behavior. **This precondition is enforced with an
assertion.**
@pre Each element of the container has a size of 1 byte. Violating this
precondition yields undefined behavior. **This precondition is enforced
with a static assertion.**
@warning There is no way to enforce all preconditions at compile-time. If
the function is called with a noncompliant container and with
assertions switched off, the behavior is undefined and will most
likely yield segmentation violation.
@param[in] i input to read from
@param[in] cb a parser callback function of type @ref parser_callback_t
which is used to control the deserialization by filtering unwanted values
(optional)
@return result of the deserialization
@throw parse_error.101 if a parse error occurs; example: `""unexpected end
of input; expected string literal""`
@throw parse_error.102 if to_unicode fails or surrogate error
@throw parse_error.103 if to_unicode fails
@complexity Linear in the length of the input. The parser is a predictive
LL(1) parser. The complexity can be higher if the parser callback function
@a cb has a super-linear complexity.
@note A UTF-8 byte order mark is silently ignored.
@liveexample{The example below demonstrates the `parse()` function reading
from an array.,parse__array__parser_callback_t}
@liveexample{The example below demonstrates the `parse()` function with
and without callback function.,parse__string__parser_callback_t}
@liveexample{The example below demonstrates the `parse()` function with
and without callback function.,parse__istream__parser_callback_t}
@liveexample{The example below demonstrates the `parse()` function reading
from a contiguous container.,parse__contiguouscontainer__parser_callback_t}
@since version 2.0.3 (contiguous containers)
*/
static basic_json parse(detail::input_adapter i,
const parser_callback_t cb = nullptr,
const bool allow_exceptions = true)
{
basic_json result;
parser(i, cb, allow_exceptions).parse(true, result);
return result;
}
/*!
@copydoc basic_json parse(detail::input_adapter, const parser_callback_t)
*/
static basic_json parse(detail::input_adapter& i,
const parser_callback_t cb = nullptr,
const bool allow_exceptions = true)
{
basic_json result;
parser(i, cb, allow_exceptions).parse(true, result);
return result;
}
static bool accept(detail::input_adapter i)
{
return parser(i).accept(true);
}
static bool accept(detail::input_adapter& i)
{
return parser(i).accept(true);
}
/*!
@brief deserialize from an iterator range with contiguous storage
This function reads from an iterator range of a container with contiguous
storage of 1-byte values. Compatible container types include
`std::vector`, `std::string`, `std::array`, `std::valarray`, and
`std::initializer_list`. Furthermore, C-style arrays can be used with
`std::begin()`/`std::end()`. User-defined containers can be used as long
as they implement random-access iterators and a contiguous storage.
@pre The iterator range is contiguous. Violating this precondition yields
undefined behavior. **This precondition is enforced with an assertion.**
@pre Each element in the range has a size of 1 byte. Violating this
precondition yields undefined behavior. **This precondition is enforced
with a static assertion.**
@warning There is no way to enforce all preconditions at compile-time. If
the function is called with noncompliant iterators and with
assertions switched off, the behavior is undefined and will most
likely yield segmentation violation.
@tparam IteratorType iterator of container with contiguous storage
@param[in] first begin of the range to parse (included)
@param[in] last end of the range to parse (excluded)
@param[in] cb a parser callback function of type @ref parser_callback_t
which is used to control the deserialization by filtering unwanted values
(optional)
@param[in] allow_exceptions whether to throw exceptions in case of a
parse error (optional, true by default)
@return result of the deserialization
@throw parse_error.101 in case of an unexpected token
@throw parse_error.102 if to_unicode fails or surrogate error
@throw parse_error.103 if to_unicode fails
@complexity Linear in the length of the input. The parser is a predictive
LL(1) parser. The complexity can be higher if the parser callback function
@a cb has a super-linear complexity.
@note A UTF-8 byte order mark is silently ignored.
@liveexample{The example below demonstrates the `parse()` function reading
from an iterator range.,parse__iteratortype__parser_callback_t}
@since version 2.0.3
*/
template<class IteratorType, typename std::enable_if<
std::is_base_of<
std::random_access_iterator_tag,
typename std::iterator_traits<IteratorType>::iterator_category>::value, int>::type = 0>
static basic_json parse(IteratorType first, IteratorType last,
const parser_callback_t cb = nullptr,
const bool allow_exceptions = true)
{
basic_json result;
parser(detail::input_adapter(first, last), cb, allow_exceptions).parse(true, result);
return result;
}
template<class IteratorType, typename std::enable_if<
std::is_base_of<
std::random_access_iterator_tag,
typename std::iterator_traits<IteratorType>::iterator_category>::value, int>::type = 0>
static bool accept(IteratorType first, IteratorType last)
{
return parser(detail::input_adapter(first, last)).accept(true);
}
/*!
@brief deserialize from stream
@deprecated This stream operator is deprecated and will be removed in
version 4.0.0 of the library. Please use
@ref operator>>(std::istream&, basic_json&)
instead; that is, replace calls like `j << i;` with `i >> j;`.
@since version 1.0.0; deprecated since version 3.0.0
*/
JSON_DEPRECATED
friend std::istream& operator<<(basic_json& j, std::istream& i)
{
return operator>>(i, j);
}
/*!
@brief deserialize from stream
Deserializes an input stream to a JSON value.
@param[in,out] i input stream to read a serialized JSON value from
@param[in,out] j JSON value to write the deserialized input to
@throw parse_error.101 in case of an unexpected token
@throw parse_error.102 if to_unicode fails or surrogate error
@throw parse_error.103 if to_unicode fails
@complexity Linear in the length of the input. The parser is a predictive
LL(1) parser.
@note A UTF-8 byte order mark is silently ignored.
@liveexample{The example below shows how a JSON value is constructed by
reading a serialization from a stream.,operator_deserialize}
@sa parse(std::istream&, const parser_callback_t) for a variant with a
parser callback function to filter values while parsing
@since version 1.0.0
*/
friend std::istream& operator>>(std::istream& i, basic_json& j)
{
parser(detail::input_adapter(i)).parse(false, j);
return i;
}
/// @}
///////////////////////////
// convenience functions //
///////////////////////////
/*!
@brief return the type as string
Returns the type name as string to be used in error messages - usually to
indicate that a function was called on a wrong JSON type.
@return a string representation of a the @a m_type member:
Value type | return value
----------- | -------------
null | `"null"`
boolean | `"boolean"`
string | `"string"`
number | `"number"` (for all number types)
object | `"object"`
array | `"array"`
discarded | `"discarded"`
@exceptionsafety No-throw guarantee: this function never throws exceptions.
@complexity Constant.
@liveexample{The following code exemplifies `type_name()` for all JSON
types.,type_name}
@sa @ref type() -- return the type of the JSON value
@sa @ref operator value_t() -- return the type of the JSON value (implicit)
@since version 1.0.0, public since 2.1.0, `const char*` and `noexcept`
since 3.0.0
*/
const char* type_name() const noexcept
{
{
switch (m_type)
{
case value_t::null:
return "null";
case value_t::object:
return "object";
case value_t::array:
return "array";
case value_t::string:
return "string";
case value_t::boolean:
return "boolean";
case value_t::discarded:
return "discarded";
default:
return "number";
}
}
}
private:
//////////////////////
// member variables //
//////////////////////
/// the type of the current element
value_t m_type = value_t::null;
/// the value of the current element
json_value m_value = {};
//////////////////////////////////////////
// binary serialization/deserialization //
//////////////////////////////////////////
/// @name binary serialization/deserialization support
/// @{
public:
/*!
@brief create a CBOR serialization of a given JSON value
Serializes a given JSON value @a j to a byte vector using the CBOR (Concise
Binary Object Representation) serialization format. CBOR is a binary
serialization format which aims to be more compact than JSON itself, yet
more efficient to parse.
The library uses the following mapping from JSON values types to
CBOR types according to the CBOR specification (RFC 7049):
JSON value type | value/range | CBOR type | first byte
--------------- | ------------------------------------------ | ---------------------------------- | ---------------
null | `null` | Null | 0xF6
boolean | `true` | True | 0xF5
boolean | `false` | False | 0xF4
number_integer | -9223372036854775808..-2147483649 | Negative integer (8 bytes follow) | 0x3B
number_integer | -2147483648..-32769 | Negative integer (4 bytes follow) | 0x3A
number_integer | -32768..-129 | Negative integer (2 bytes follow) | 0x39
number_integer | -128..-25 | Negative integer (1 byte follow) | 0x38
number_integer | -24..-1 | Negative integer | 0x20..0x37
number_integer | 0..23 | Integer | 0x00..0x17
number_integer | 24..255 | Unsigned integer (1 byte follow) | 0x18
number_integer | 256..65535 | Unsigned integer (2 bytes follow) | 0x19
number_integer | 65536..4294967295 | Unsigned integer (4 bytes follow) | 0x1A
number_integer | 4294967296..18446744073709551615 | Unsigned integer (8 bytes follow) | 0x1B
number_unsigned | 0..23 | Integer | 0x00..0x17
number_unsigned | 24..255 | Unsigned integer (1 byte follow) | 0x18
number_unsigned | 256..65535 | Unsigned integer (2 bytes follow) | 0x19
number_unsigned | 65536..4294967295 | Unsigned integer (4 bytes follow) | 0x1A
number_unsigned | 4294967296..18446744073709551615 | Unsigned integer (8 bytes follow) | 0x1B
number_float | *any value* | Double-Precision Float | 0xFB
string | *length*: 0..23 | UTF-8 string | 0x60..0x77
string | *length*: 23..255 | UTF-8 string (1 byte follow) | 0x78
string | *length*: 256..65535 | UTF-8 string (2 bytes follow) | 0x79
string | *length*: 65536..4294967295 | UTF-8 string (4 bytes follow) | 0x7A
string | *length*: 4294967296..18446744073709551615 | UTF-8 string (8 bytes follow) | 0x7B
array | *size*: 0..23 | array | 0x80..0x97
array | *size*: 23..255 | array (1 byte follow) | 0x98
array | *size*: 256..65535 | array (2 bytes follow) | 0x99
array | *size*: 65536..4294967295 | array (4 bytes follow) | 0x9A
array | *size*: 4294967296..18446744073709551615 | array (8 bytes follow) | 0x9B
object | *size*: 0..23 | map | 0xA0..0xB7
object | *size*: 23..255 | map (1 byte follow) | 0xB8
object | *size*: 256..65535 | map (2 bytes follow) | 0xB9
object | *size*: 65536..4294967295 | map (4 bytes follow) | 0xBA
object | *size*: 4294967296..18446744073709551615 | map (8 bytes follow) | 0xBB
@note The mapping is **complete** in the sense that any JSON value type
can be converted to a CBOR value.
@note If NaN or Infinity are stored inside a JSON number, they are
serialized properly. This behavior differs from the @ref dump()
function which serializes NaN or Infinity to `null`.
@note The following CBOR types are not used in the conversion:
- byte strings (0x40..0x5F)
- UTF-8 strings terminated by "break" (0x7F)
- arrays terminated by "break" (0x9F)
- maps terminated by "break" (0xBF)
- date/time (0xC0..0xC1)
- bignum (0xC2..0xC3)
- decimal fraction (0xC4)
- bigfloat (0xC5)
- tagged items (0xC6..0xD4, 0xD8..0xDB)
- expected conversions (0xD5..0xD7)
- simple values (0xE0..0xF3, 0xF8)
- undefined (0xF7)
- half and single-precision floats (0xF9-0xFA)
- break (0xFF)
@param[in] j JSON value to serialize
@return MessagePack serialization as byte vector
@complexity Linear in the size of the JSON value @a j.
@liveexample{The example shows the serialization of a JSON value to a byte
vector in CBOR format.,to_cbor}
@sa http://cbor.io
@sa @ref from_cbor(detail::input_adapter, const bool strict) for the
analogous deserialization
@sa @ref to_msgpack(const basic_json&) for the related MessagePack format
@sa @ref to_ubjson(const basic_json&, const bool, const bool) for the
related UBJSON format
@since version 2.0.9
*/
static std::vector<uint8_t> to_cbor(const basic_json& j)
{
std::vector<uint8_t> result;
to_cbor(j, result);
return result;
}
static void to_cbor(const basic_json& j, detail::output_adapter<uint8_t> o)
{
binary_writer<uint8_t>(o).write_cbor(j);
}
static void to_cbor(const basic_json& j, detail::output_adapter<char> o)
{
binary_writer<char>(o).write_cbor(j);
}
/*!
@brief create a MessagePack serialization of a given JSON value
Serializes a given JSON value @a j to a byte vector using the MessagePack
serialization format. MessagePack is a binary serialization format which
aims to be more compact than JSON itself, yet more efficient to parse.
The library uses the following mapping from JSON values types to
MessagePack types according to the MessagePack specification:
JSON value type | value/range | MessagePack type | first byte
--------------- | --------------------------------- | ---------------- | ----------
null | `null` | nil | 0xC0
boolean | `true` | true | 0xC3
boolean | `false` | false | 0xC2
number_integer | -9223372036854775808..-2147483649 | int64 | 0xD3
number_integer | -2147483648..-32769 | int32 | 0xD2
number_integer | -32768..-129 | int16 | 0xD1
number_integer | -128..-33 | int8 | 0xD0
number_integer | -32..-1 | negative fixint | 0xE0..0xFF
number_integer | 0..127 | positive fixint | 0x00..0x7F
number_integer | 128..255 | uint 8 | 0xCC
number_integer | 256..65535 | uint 16 | 0xCD
number_integer | 65536..4294967295 | uint 32 | 0xCE
number_integer | 4294967296..18446744073709551615 | uint 64 | 0xCF
number_unsigned | 0..127 | positive fixint | 0x00..0x7F
number_unsigned | 128..255 | uint 8 | 0xCC
number_unsigned | 256..65535 | uint 16 | 0xCD
number_unsigned | 65536..4294967295 | uint 32 | 0xCE
number_unsigned | 4294967296..18446744073709551615 | uint 64 | 0xCF
number_float | *any value* | float 64 | 0xCB
string | *length*: 0..31 | fixstr | 0xA0..0xBF
string | *length*: 32..255 | str 8 | 0xD9
string | *length*: 256..65535 | str 16 | 0xDA
string | *length*: 65536..4294967295 | str 32 | 0xDB
array | *size*: 0..15 | fixarray | 0x90..0x9F
array | *size*: 16..65535 | array 16 | 0xDC
array | *size*: 65536..4294967295 | array 32 | 0xDD
object | *size*: 0..15 | fix map | 0x80..0x8F
object | *size*: 16..65535 | map 16 | 0xDE
object | *size*: 65536..4294967295 | map 32 | 0xDF
@note The mapping is **complete** in the sense that any JSON value type
can be converted to a MessagePack value.
@note The following values can **not** be converted to a MessagePack value:
- strings with more than 4294967295 bytes
- arrays with more than 4294967295 elements
- objects with more than 4294967295 elements
@note The following MessagePack types are not used in the conversion:
- bin 8 - bin 32 (0xC4..0xC6)
- ext 8 - ext 32 (0xC7..0xC9)
- float 32 (0xCA)
- fixext 1 - fixext 16 (0xD4..0xD8)
@note Any MessagePack output created @ref to_msgpack can be successfully
parsed by @ref from_msgpack.
@note If NaN or Infinity are stored inside a JSON number, they are
serialized properly. This behavior differs from the @ref dump()
function which serializes NaN or Infinity to `null`.
@param[in] j JSON value to serialize
@return MessagePack serialization as byte vector
@complexity Linear in the size of the JSON value @a j.
@liveexample{The example shows the serialization of a JSON value to a byte
vector in MessagePack format.,to_msgpack}
@sa http://msgpack.org
@sa @ref from_msgpack(const std::vector<uint8_t>&, const size_t) for the
analogous deserialization
@sa @ref to_cbor(const basic_json& for the related CBOR format
@sa @ref to_ubjson(const basic_json&, const bool, const bool) for the
related UBJSON format
@since version 2.0.9
*/
static std::vector<uint8_t> to_msgpack(const basic_json& j)
{
std::vector<uint8_t> result;
to_msgpack(j, result);
return result;
}
static void to_msgpack(const basic_json& j, detail::output_adapter<uint8_t> o)
{
binary_writer<uint8_t>(o).write_msgpack(j);
}
static void to_msgpack(const basic_json& j, detail::output_adapter<char> o)
{
binary_writer<char>(o).write_msgpack(j);
}
/*!
@brief create a UBJSON serialization of a given JSON value
Serializes a given JSON value @a j to a byte vector using the UBJSON
(Universal Binary JSON) serialization format. UBJSON aims to be more compact
than JSON itself, yet more efficient to parse.
The library uses the following mapping from JSON values types to
UBJSON types according to the UBJSON specification:
JSON value type | value/range | UBJSON type | marker
--------------- | --------------------------------- | ----------- | ------
null | `null` | null | `Z`
boolean | `true` | true | `T`
boolean | `false` | false | `F`
number_integer | -9223372036854775808..-2147483649 | int64 | `L`
number_integer | -2147483648..-32769 | int32 | `l`
number_integer | -32768..-129 | int16 | `I`
number_integer | -128..127 | int8 | `i`
number_integer | 128..255 | uint8 | `U`
number_integer | 256..32767 | int16 | `I`
number_integer | 32768..2147483647 | int32 | `l`
number_integer | 2147483648..9223372036854775807 | int64 | `L`
number_unsigned | 0..127 | int8 | `i`
number_unsigned | 128..255 | uint8 | `U`
number_unsigned | 256..32767 | int16 | `I`
number_unsigned | 32768..2147483647 | int32 | `l`
number_unsigned | 2147483648..9223372036854775807 | int64 | `L`
number_float | *any value* | float64 | `D`
string | *with shortest length indicator* | string | `S`
array | *see notes on optimized format* | array | `[`
object | *see notes on optimized format* | map | `{`
@note The mapping is **complete** in the sense that any JSON value type
can be converted to a UBJSON value.
@note The following values can **not** be converted to a UBJSON value:
- strings with more than 9223372036854775807 bytes (theoretical)
- unsigned integer numbers above 9223372036854775807
@note The following markers are not used in the conversion:
- `Z`: no-op values are not created.
- `C`: single-byte strings are serialized with `S` markers.
@note Any UBJSON output created @ref to_ubjson can be successfully parsed
by @ref from_ubjson.
@note If NaN or Infinity are stored inside a JSON number, they are
serialized properly. This behavior differs from the @ref dump()
function which serializes NaN or Infinity to `null`.
@note The optimized formats for containers are supported: Parameter
@a use_size adds size information to the beginning of a container and
removes the closing marker. Parameter @a use_type further checks
whether all elements of a container have the same type and adds the
type marker to the beginning of the container. The @a use_type
parameter must only be used together with @a use_size = true. Note
that @a use_size = true alone may result in larger representations -
the benefit of this parameter is that the receiving side is
immediately informed on the number of elements of the container.
@param[in] j JSON value to serialize
@param[in] use_size whether to add size annotations to container types
@param[in] use_type whether to add type annotations to container types
(must be combined with @a use_size = true)
@return UBJSON serialization as byte vector
@complexity Linear in the size of the JSON value @a j.
@liveexample{The example shows the serialization of a JSON value to a byte
vector in UBJSON format.,to_ubjson}
@sa http://ubjson.org
@sa @ref from_ubjson(detail::input_adapter, const bool strict) for the
analogous deserialization
@sa @ref to_cbor(const basic_json& for the related CBOR format
@sa @ref to_msgpack(const basic_json&) for the related MessagePack format
@since version 3.1.0
*/
static std::vector<uint8_t> to_ubjson(const basic_json& j,
const bool use_size = false,
const bool use_type = false)
{
std::vector<uint8_t> result;
to_ubjson(j, result, use_size, use_type);
return result;
}
static void to_ubjson(const basic_json& j, detail::output_adapter<uint8_t> o,
const bool use_size = false, const bool use_type = false)
{
binary_writer<uint8_t>(o).write_ubjson(j, use_size, use_type);
}
static void to_ubjson(const basic_json& j, detail::output_adapter<char> o,
const bool use_size = false, const bool use_type = false)
{
binary_writer<char>(o).write_ubjson(j, use_size, use_type);
}
/*!
@brief create a JSON value from an input in CBOR format
Deserializes a given input @a i to a JSON value using the CBOR (Concise
Binary Object Representation) serialization format.
The library maps CBOR types to JSON value types as follows:
CBOR type | JSON value type | first byte
---------------------- | --------------- | ----------
Integer | number_unsigned | 0x00..0x17
Unsigned integer | number_unsigned | 0x18
Unsigned integer | number_unsigned | 0x19
Unsigned integer | number_unsigned | 0x1A
Unsigned integer | number_unsigned | 0x1B
Negative integer | number_integer | 0x20..0x37
Negative integer | number_integer | 0x38
Negative integer | number_integer | 0x39
Negative integer | number_integer | 0x3A
Negative integer | number_integer | 0x3B
Negative integer | number_integer | 0x40..0x57
UTF-8 string | string | 0x60..0x77
UTF-8 string | string | 0x78
UTF-8 string | string | 0x79
UTF-8 string | string | 0x7A
UTF-8 string | string | 0x7B
UTF-8 string | string | 0x7F
array | array | 0x80..0x97
array | array | 0x98
array | array | 0x99
array | array | 0x9A
array | array | 0x9B
array | array | 0x9F
map | object | 0xA0..0xB7
map | object | 0xB8
map | object | 0xB9
map | object | 0xBA
map | object | 0xBB
map | object | 0xBF
False | `false` | 0xF4
True | `true` | 0xF5
Nill | `null` | 0xF6
Half-Precision Float | number_float | 0xF9
Single-Precision Float | number_float | 0xFA
Double-Precision Float | number_float | 0xFB
@warning The mapping is **incomplete** in the sense that not all CBOR
types can be converted to a JSON value. The following CBOR types
are not supported and will yield parse errors (parse_error.112):
- byte strings (0x40..0x5F)
- date/time (0xC0..0xC1)
- bignum (0xC2..0xC3)
- decimal fraction (0xC4)
- bigfloat (0xC5)
- tagged items (0xC6..0xD4, 0xD8..0xDB)
- expected conversions (0xD5..0xD7)
- simple values (0xE0..0xF3, 0xF8)
- undefined (0xF7)
@warning CBOR allows map keys of any type, whereas JSON only allows
strings as keys in object values. Therefore, CBOR maps with keys
other than UTF-8 strings are rejected (parse_error.113).
@note Any CBOR output created @ref to_cbor can be successfully parsed by
@ref from_cbor.
@param[in] i an input in CBOR format convertible to an input adapter
@param[in] strict whether to expect the input to be consumed until EOF
(true by default)
@return deserialized JSON value
@throw parse_error.110 if the given input ends prematurely or the end of
file was not reached when @a strict was set to true
@throw parse_error.112 if unsupported features from CBOR were
used in the given input @a v or if the input is not valid CBOR
@throw parse_error.113 if a string was expected as map key, but not found
@complexity Linear in the size of the input @a i.
@liveexample{The example shows the deserialization of a byte vector in CBOR
format to a JSON value.,from_cbor}
@sa http://cbor.io
@sa @ref to_cbor(const basic_json&) for the analogous serialization
@sa @ref from_msgpack(detail::input_adapter, const bool) for the
related MessagePack format
@sa @ref from_ubjson(detail::input_adapter, const bool) for the related
UBJSON format
@since version 2.0.9; parameter @a start_index since 2.1.1; changed to
consume input adapters, removed start_index parameter, and added
@a strict parameter since 3.0.0
*/
static basic_json from_cbor(detail::input_adapter i,
const bool strict = true)
{
return binary_reader(i).parse_cbor(strict);
}
/*!
@copydoc from_cbor(detail::input_adapter, const bool)
*/
template<typename A1, typename A2,
detail::enable_if_t<std::is_constructible<detail::input_adapter, A1, A2>::value, int> = 0>
static basic_json from_cbor(A1 && a1, A2 && a2, const bool strict = true)
{
return binary_reader(detail::input_adapter(std::forward<A1>(a1), std::forward<A2>(a2))).parse_cbor(strict);
}
/*!
@brief create a JSON value from an input in MessagePack format
Deserializes a given input @a i to a JSON value using the MessagePack
serialization format.
The library maps MessagePack types to JSON value types as follows:
MessagePack type | JSON value type | first byte
---------------- | --------------- | ----------
positive fixint | number_unsigned | 0x00..0x7F
fixmap | object | 0x80..0x8F
fixarray | array | 0x90..0x9F
fixstr | string | 0xA0..0xBF
nil | `null` | 0xC0
false | `false` | 0xC2
true | `true` | 0xC3
float 32 | number_float | 0xCA
float 64 | number_float | 0xCB
uint 8 | number_unsigned | 0xCC
uint 16 | number_unsigned | 0xCD
uint 32 | number_unsigned | 0xCE
uint 64 | number_unsigned | 0xCF
int 8 | number_integer | 0xD0
int 16 | number_integer | 0xD1
int 32 | number_integer | 0xD2
int 64 | number_integer | 0xD3
str 8 | string | 0xD9
str 16 | string | 0xDA
str 32 | string | 0xDB
array 16 | array | 0xDC
array 32 | array | 0xDD
map 16 | object | 0xDE
map 32 | object | 0xDF
negative fixint | number_integer | 0xE0-0xFF
@warning The mapping is **incomplete** in the sense that not all
MessagePack types can be converted to a JSON value. The following
MessagePack types are not supported and will yield parse errors:
- bin 8 - bin 32 (0xC4..0xC6)
- ext 8 - ext 32 (0xC7..0xC9)
- fixext 1 - fixext 16 (0xD4..0xD8)
@note Any MessagePack output created @ref to_msgpack can be successfully
parsed by @ref from_msgpack.
@param[in] i an input in MessagePack format convertible to an input
adapter
@param[in] strict whether to expect the input to be consumed until EOF
(true by default)
@throw parse_error.110 if the given input ends prematurely or the end of
file was not reached when @a strict was set to true
@throw parse_error.112 if unsupported features from MessagePack were
used in the given input @a i or if the input is not valid MessagePack
@throw parse_error.113 if a string was expected as map key, but not found
@complexity Linear in the size of the input @a i.
@liveexample{The example shows the deserialization of a byte vector in
MessagePack format to a JSON value.,from_msgpack}
@sa http://msgpack.org
@sa @ref to_msgpack(const basic_json&) for the analogous serialization
@sa @ref from_cbor(detail::input_adapter, const bool) for the related CBOR
format
@sa @ref from_ubjson(detail::input_adapter, const bool) for the related
UBJSON format
@since version 2.0.9; parameter @a start_index since 2.1.1; changed to
consume input adapters, removed start_index parameter, and added
@a strict parameter since 3.0.0
*/
static basic_json from_msgpack(detail::input_adapter i,
const bool strict = true)
{
return binary_reader(i).parse_msgpack(strict);
}
/*!
@copydoc from_msgpack(detail::input_adapter, const bool)
*/
template<typename A1, typename A2,
detail::enable_if_t<std::is_constructible<detail::input_adapter, A1, A2>::value, int> = 0>
static basic_json from_msgpack(A1 && a1, A2 && a2, const bool strict = true)
{
return binary_reader(detail::input_adapter(std::forward<A1>(a1), std::forward<A2>(a2))).parse_msgpack(strict);
}
/*!
@brief create a JSON value from an input in UBJSON format
Deserializes a given input @a i to a JSON value using the UBJSON (Universal
Binary JSON) serialization format.
The library maps UBJSON types to JSON value types as follows:
UBJSON type | JSON value type | marker
----------- | --------------------------------------- | ------
no-op | *no value, next value is read* | `N`
null | `null` | `Z`
false | `false` | `F`
true | `true` | `T`
float32 | number_float | `d`
float64 | number_float | `D`
uint8 | number_unsigned | `U`
int8 | number_integer | `i`
int16 | number_integer | `I`
int32 | number_integer | `l`
int64 | number_integer | `L`
string | string | `S`
char | string | `C`
array | array (optimized values are supported) | `[`
object | object (optimized values are supported) | `{`
@note The mapping is **complete** in the sense that any UBJSON value can
be converted to a JSON value.
@param[in] i an input in UBJSON format convertible to an input adapter
@param[in] strict whether to expect the input to be consumed until EOF
(true by default)
@throw parse_error.110 if the given input ends prematurely or the end of
file was not reached when @a strict was set to true
@throw parse_error.112 if a parse error occurs
@throw parse_error.113 if a string could not be parsed successfully
@complexity Linear in the size of the input @a i.
@liveexample{The example shows the deserialization of a byte vector in
UBJSON format to a JSON value.,from_ubjson}
@sa http://ubjson.org
@sa @ref to_ubjson(const basic_json&, const bool, const bool) for the
analogous serialization
@sa @ref from_cbor(detail::input_adapter, const bool) for the related CBOR
format
@sa @ref from_msgpack(detail::input_adapter, const bool) for the related
MessagePack format
@since version 3.1.0
*/
static basic_json from_ubjson(detail::input_adapter i,
const bool strict = true)
{
return binary_reader(i).parse_ubjson(strict);
}
template<typename A1, typename A2,
detail::enable_if_t<std::is_constructible<detail::input_adapter, A1, A2>::value, int> = 0>
static basic_json from_ubjson(A1 && a1, A2 && a2, const bool strict = true)
{
return binary_reader(detail::input_adapter(std::forward<A1>(a1), std::forward<A2>(a2))).parse_ubjson(strict);
}
/// @}
//////////////////////////
// JSON Pointer support //
//////////////////////////
/// @name JSON Pointer functions
/// @{
/*!
@brief access specified element via JSON Pointer
Uses a JSON pointer to retrieve a reference to the respective JSON value.
No bound checking is performed. Similar to @ref operator[](const typename
object_t::key_type&), `null` values are created in arrays and objects if
necessary.
In particular:
- If the JSON pointer points to an object key that does not exist, it
is created an filled with a `null` value before a reference to it
is returned.
- If the JSON pointer points to an array index that does not exist, it
is created an filled with a `null` value before a reference to it
is returned. All indices between the current maximum and the given
index are also filled with `null`.
- The special value `-` is treated as a synonym for the index past the
end.
@param[in] ptr a JSON pointer
@return reference to the element pointed to by @a ptr
@complexity Constant.
@throw parse_error.106 if an array index begins with '0'
@throw parse_error.109 if an array index was not a number
@throw out_of_range.404 if the JSON pointer can not be resolved
@liveexample{The behavior is shown in the example.,operatorjson_pointer}
@since version 2.0.0
*/
reference operator[](const json_pointer& ptr)
{
return ptr.get_unchecked(this);
}
/*!
@brief access specified element via JSON Pointer
Uses a JSON pointer to retrieve a reference to the respective JSON value.
No bound checking is performed. The function does not change the JSON
value; no `null` values are created. In particular, the the special value
`-` yields an exception.
@param[in] ptr JSON pointer to the desired element
@return const reference to the element pointed to by @a ptr
@complexity Constant.
@throw parse_error.106 if an array index begins with '0'
@throw parse_error.109 if an array index was not a number
@throw out_of_range.402 if the array index '-' is used
@throw out_of_range.404 if the JSON pointer can not be resolved
@liveexample{The behavior is shown in the example.,operatorjson_pointer_const}
@since version 2.0.0
*/
const_reference operator[](const json_pointer& ptr) const
{
return ptr.get_unchecked(this);
}
/*!
@brief access specified element via JSON Pointer
Returns a reference to the element at with specified JSON pointer @a ptr,
with bounds checking.
@param[in] ptr JSON pointer to the desired element
@return reference to the element pointed to by @a ptr
@throw parse_error.106 if an array index in the passed JSON pointer @a ptr
begins with '0'. See example below.
@throw parse_error.109 if an array index in the passed JSON pointer @a ptr
is not a number. See example below.
@throw out_of_range.401 if an array index in the passed JSON pointer @a ptr
is out of range. See example below.
@throw out_of_range.402 if the array index '-' is used in the passed JSON
pointer @a ptr. As `at` provides checked access (and no elements are
implicitly inserted), the index '-' is always invalid. See example below.
@throw out_of_range.403 if the JSON pointer describes a key of an object
which cannot be found. See example below.
@throw out_of_range.404 if the JSON pointer @a ptr can not be resolved.
See example below.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Constant.
@since version 2.0.0
@liveexample{The behavior is shown in the example.,at_json_pointer}
*/
reference at(const json_pointer& ptr)
{
return ptr.get_checked(this);
}
/*!
@brief access specified element via JSON Pointer
Returns a const reference to the element at with specified JSON pointer @a
ptr, with bounds checking.
@param[in] ptr JSON pointer to the desired element
@return reference to the element pointed to by @a ptr
@throw parse_error.106 if an array index in the passed JSON pointer @a ptr
begins with '0'. See example below.
@throw parse_error.109 if an array index in the passed JSON pointer @a ptr
is not a number. See example below.
@throw out_of_range.401 if an array index in the passed JSON pointer @a ptr
is out of range. See example below.
@throw out_of_range.402 if the array index '-' is used in the passed JSON
pointer @a ptr. As `at` provides checked access (and no elements are
implicitly inserted), the index '-' is always invalid. See example below.
@throw out_of_range.403 if the JSON pointer describes a key of an object
which cannot be found. See example below.
@throw out_of_range.404 if the JSON pointer @a ptr can not be resolved.
See example below.
@exceptionsafety Strong guarantee: if an exception is thrown, there are no
changes in the JSON value.
@complexity Constant.
@since version 2.0.0
@liveexample{The behavior is shown in the example.,at_json_pointer_const}
*/
const_reference at(const json_pointer& ptr) const
{
return ptr.get_checked(this);
}
/*!
@brief return flattened JSON value
The function creates a JSON object whose keys are JSON pointers (see [RFC
6901](https://tools.ietf.org/html/rfc6901)) and whose values are all
primitive. The original JSON value can be restored using the @ref
unflatten() function.
@return an object that maps JSON pointers to primitive values
@note Empty objects and arrays are flattened to `null` and will not be
reconstructed correctly by the @ref unflatten() function.
@complexity Linear in the size the JSON value.
@liveexample{The following code shows how a JSON object is flattened to an
object whose keys consist of JSON pointers.,flatten}
@sa @ref unflatten() for the reverse function
@since version 2.0.0
*/
basic_json flatten() const
{
basic_json result(value_t::object);
json_pointer::flatten("", *this, result);
return result;
}
/*!
@brief unflatten a previously flattened JSON value
The function restores the arbitrary nesting of a JSON value that has been
flattened before using the @ref flatten() function. The JSON value must
meet certain constraints:
1. The value must be an object.
2. The keys must be JSON pointers (see
[RFC 6901](https://tools.ietf.org/html/rfc6901))
3. The mapped values must be primitive JSON types.
@return the original JSON from a flattened version
@note Empty objects and arrays are flattened by @ref flatten() to `null`
values and can not unflattened to their original type. Apart from
this example, for a JSON value `j`, the following is always true:
`j == j.flatten().unflatten()`.
@complexity Linear in the size the JSON value.
@throw type_error.314 if value is not an object
@throw type_error.315 if object values are not primitive
@liveexample{The following code shows how a flattened JSON object is
unflattened into the original nested JSON object.,unflatten}
@sa @ref flatten() for the reverse function
@since version 2.0.0
*/
basic_json unflatten() const
{
return json_pointer::unflatten(*this);
}
/// @}
//////////////////////////
// JSON Patch functions //
//////////////////////////
/// @name JSON Patch functions
/// @{
/*!
@brief applies a JSON patch
[JSON Patch](http://jsonpatch.com) defines a JSON document structure for
expressing a sequence of operations to apply to a JSON) document. With
this function, a JSON Patch is applied to the current JSON value by
executing all operations from the patch.
@param[in] json_patch JSON patch document
@return patched document
@note The application of a patch is atomic: Either all operations succeed
and the patched document is returned or an exception is thrown. In
any case, the original value is not changed: the patch is applied
to a copy of the value.
@throw parse_error.104 if the JSON patch does not consist of an array of
objects
@throw parse_error.105 if the JSON patch is malformed (e.g., mandatory
attributes are missing); example: `"operation add must have member path"`
@throw out_of_range.401 if an array index is out of range.
@throw out_of_range.403 if a JSON pointer inside the patch could not be
resolved successfully in the current JSON value; example: `"key baz not
found"`
@throw out_of_range.405 if JSON pointer has no parent ("add", "remove",
"move")
@throw other_error.501 if "test" operation was unsuccessful
@complexity Linear in the size of the JSON value and the length of the
JSON patch. As usually only a fraction of the JSON value is affected by
the patch, the complexity can usually be neglected.
@liveexample{The following code shows how a JSON patch is applied to a
value.,patch}
@sa @ref diff -- create a JSON patch by comparing two JSON values
@sa [RFC 6902 (JSON Patch)](https://tools.ietf.org/html/rfc6902)
@sa [RFC 6901 (JSON Pointer)](https://tools.ietf.org/html/rfc6901)
@since version 2.0.0
*/
basic_json patch(const basic_json& json_patch) const
{
// make a working copy to apply the patch to
basic_json result = *this;
// the valid JSON Patch operations
enum class patch_operations {add, remove, replace, move, copy, test, invalid};
const auto get_op = [](const std::string & op)
{
if (op == "add")
{
return patch_operations::add;
}
if (op == "remove")
{
return patch_operations::remove;
}
if (op == "replace")
{
return patch_operations::replace;
}
if (op == "move")
{
return patch_operations::move;
}
if (op == "copy")
{
return patch_operations::copy;
}
if (op == "test")
{
return patch_operations::test;
}
return patch_operations::invalid;
};
// wrapper for "add" operation; add value at ptr
const auto operation_add = [&result](json_pointer & ptr, basic_json val)
{
// adding to the root of the target document means replacing it
if (ptr.is_root())
{
result = val;
}
else
{
// make sure the top element of the pointer exists
json_pointer top_pointer = ptr.top();
if (top_pointer != ptr)
{
result.at(top_pointer);
}
// get reference to parent of JSON pointer ptr
const auto last_path = ptr.pop_back();
basic_json& parent = result[ptr];
switch (parent.m_type)
{
case value_t::null:
case value_t::object:
{
// use operator[] to add value
parent[last_path] = val;
break;
}
case value_t::array:
{
if (last_path == "-")
{
// special case: append to back
parent.push_back(val);
}
else
{
const auto idx = json_pointer::array_index(last_path);
if (JSON_UNLIKELY(static_cast<size_type>(idx) > parent.size()))
{
// avoid undefined behavior
JSON_THROW(out_of_range::create(401, "array index " + std::to_string(idx) + " is out of range"));
}
else
{
// default case: insert add offset
parent.insert(parent.begin() + static_cast<difference_type>(idx), val);
}
}
break;
}
default:
{
// if there exists a parent it cannot be primitive
assert(false); // LCOV_EXCL_LINE
}
}
}
};
// wrapper for "remove" operation; remove value at ptr
const auto operation_remove = [&result](json_pointer & ptr)
{
// get reference to parent of JSON pointer ptr
const auto last_path = ptr.pop_back();
basic_json& parent = result.at(ptr);
// remove child
if (parent.is_object())
{
// perform range check
auto it = parent.find(last_path);
if (JSON_LIKELY(it != parent.end()))
{
parent.erase(it);
}
else
{
JSON_THROW(out_of_range::create(403, "key '" + last_path + "' not found"));
}
}
else if (parent.is_array())
{
// note erase performs range check
parent.erase(static_cast<size_type>(json_pointer::array_index(last_path)));
}
};
// type check: top level value must be an array
if (JSON_UNLIKELY(not json_patch.is_array()))
{
JSON_THROW(parse_error::create(104, 0, "JSON patch must be an array of objects"));
}
// iterate and apply the operations
for (const auto& val : json_patch)
{
// wrapper to get a value for an operation
const auto get_value = [&val](const std::string & op,
const std::string & member,
bool string_type) -> basic_json &
{
// find value
auto it = val.m_value.object->find(member);
// context-sensitive error message
const auto error_msg = (op == "op") ? "operation" : "operation '" + op + "'";
// check if desired value is present
if (JSON_UNLIKELY(it == val.m_value.object->end()))
{
JSON_THROW(parse_error::create(105, 0, error_msg + " must have member '" + member + "'"));
}
// check if result is of type string
if (JSON_UNLIKELY(string_type and not it->second.is_string()))
{
JSON_THROW(parse_error::create(105, 0, error_msg + " must have string member '" + member + "'"));
}
// no error: return value
return it->second;
};
// type check: every element of the array must be an object
if (JSON_UNLIKELY(not val.is_object()))
{
JSON_THROW(parse_error::create(104, 0, "JSON patch must be an array of objects"));
}
// collect mandatory members
const std::string op = get_value("op", "op", true);
const std::string path = get_value(op, "path", true);
json_pointer ptr(path);
switch (get_op(op))
{
case patch_operations::add:
{
operation_add(ptr, get_value("add", "value", false));
break;
}
case patch_operations::remove:
{
operation_remove(ptr);
break;
}
case patch_operations::replace:
{
// the "path" location must exist - use at()
result.at(ptr) = get_value("replace", "value", false);
break;
}
case patch_operations::move:
{
const std::string from_path = get_value("move", "from", true);
json_pointer from_ptr(from_path);
// the "from" location must exist - use at()
basic_json v = result.at(from_ptr);
// The move operation is functionally identical to a
// "remove" operation on the "from" location, followed
// immediately by an "add" operation at the target
// location with the value that was just removed.
operation_remove(from_ptr);
operation_add(ptr, v);
break;
}
case patch_operations::copy:
{
const std::string from_path = get_value("copy", "from", true);
const json_pointer from_ptr(from_path);
// the "from" location must exist - use at()
basic_json v = result.at(from_ptr);
// The copy is functionally identical to an "add"
// operation at the target location using the value
// specified in the "from" member.
operation_add(ptr, v);
break;
}
case patch_operations::test:
{
bool success = false;
JSON_TRY
{
// check if "value" matches the one at "path"
// the "path" location must exist - use at()
success = (result.at(ptr) == get_value("test", "value", false));
}
JSON_CATCH (out_of_range&)
{
// ignore out of range errors: success remains false
}
// throw an exception if test fails
if (JSON_UNLIKELY(not success))
{
JSON_THROW(other_error::create(501, "unsuccessful: " + val.dump()));
}
break;
}
case patch_operations::invalid:
{
// op must be "add", "remove", "replace", "move", "copy", or
// "test"
JSON_THROW(parse_error::create(105, 0, "operation value '" + op + "' is invalid"));
}
}
}
return result;
}
/*!
@brief creates a diff as a JSON patch
Creates a [JSON Patch](http://jsonpatch.com) so that value @a source can
be changed into the value @a target by calling @ref patch function.
@invariant For two JSON values @a source and @a target, the following code
yields always `true`:
@code {.cpp}
source.patch(diff(source, target)) == target;
@endcode
@note Currently, only `remove`, `add`, and `replace` operations are
generated.
@param[in] source JSON value to compare from
@param[in] target JSON value to compare against
@param[in] path helper value to create JSON pointers
@return a JSON patch to convert the @a source to @a target
@complexity Linear in the lengths of @a source and @a target.
@liveexample{The following code shows how a JSON patch is created as a
diff for two JSON values.,diff}
@sa @ref patch -- apply a JSON patch
@sa @ref merge_patch -- apply a JSON Merge Patch
@sa [RFC 6902 (JSON Patch)](https://tools.ietf.org/html/rfc6902)
@since version 2.0.0
*/
static basic_json diff(const basic_json& source, const basic_json& target,
const std::string& path = "")
{
// the patch
basic_json result(value_t::array);
// if the values are the same, return empty patch
if (source == target)
{
return result;
}
if (source.type() != target.type())
{
// different types: replace value
result.push_back(
{
{"op", "replace"}, {"path", path}, {"value", target}
});
}
else
{
switch (source.type())
{
case value_t::array:
{
// first pass: traverse common elements
std::size_t i = 0;
while (i < source.size() and i < target.size())
{
// recursive call to compare array values at index i
auto temp_diff = diff(source[i], target[i], path + "/" + std::to_string(i));
result.insert(result.end(), temp_diff.begin(), temp_diff.end());
++i;
}
// i now reached the end of at least one array
// in a second pass, traverse the remaining elements
// remove my remaining elements
const auto end_index = static_cast<difference_type>(result.size());
while (i < source.size())
{
// add operations in reverse order to avoid invalid
// indices
result.insert(result.begin() + end_index, object(
{
{"op", "remove"},
{"path", path + "/" + std::to_string(i)}
}));
++i;
}
// add other remaining elements
while (i < target.size())
{
result.push_back(
{
{"op", "add"},
{"path", path + "/" + std::to_string(i)},
{"value", target[i]}
});
++i;
}
break;
}
case value_t::object:
{
// first pass: traverse this object's elements
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
// escape the key name to be used in a JSON patch
const auto key = json_pointer::escape(it.key());
if (target.find(it.key()) != target.end())
{
// recursive call to compare object values at key it
auto temp_diff = diff(it.value(), target[it.key()], path + "/" + key);
result.insert(result.end(), temp_diff.begin(), temp_diff.end());
}
else
{
// found a key that is not in o -> remove it
result.push_back(object(
{
{"op", "remove"}, {"path", path + "/" + key}
}));
}
}
// second pass: traverse other object's elements
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
if (source.find(it.key()) == source.end())
{
// found a key that is not in this -> add it
const auto key = json_pointer::escape(it.key());
result.push_back(
{
{"op", "add"}, {"path", path + "/" + key},
{"value", it.value()}
});
}
}
break;
}
default:
{
// both primitive type: replace value
result.push_back(
{
{"op", "replace"}, {"path", path}, {"value", target}
});
break;
}
}
}
return result;
}
/// @}
////////////////////////////////
// JSON Merge Patch functions //
////////////////////////////////
/// @name JSON Merge Patch functions
/// @{
/*!
@brief applies a JSON Merge Patch
The merge patch format is primarily intended for use with the HTTP PATCH
method as a means of describing a set of modifications to a target
resource's content. This function applies a merge patch to the current
JSON value.
The function implements the following algorithm from Section 2 of
[RFC 7396 (JSON Merge Patch)](https://tools.ietf.org/html/rfc7396):
```
define MergePatch(Target, Patch):
if Patch is an Object:
if Target is not an Object:
Target = {} // Ignore the contents and set it to an empty Object
for each Name/Value pair in Patch:
if Value is null:
if Name exists in Target:
remove the Name/Value pair from Target
else:
Target[Name] = MergePatch(Target[Name], Value)
return Target
else:
return Patch
```
Thereby, `Target` is the current object; that is, the patch is applied to
the current value.
@param[in] patch the patch to apply
@complexity Linear in the lengths of @a patch.
@liveexample{The following code shows how a JSON Merge Patch is applied to
a JSON document.,merge_patch}
@sa @ref patch -- apply a JSON patch
@sa [RFC 7396 (JSON Merge Patch)](https://tools.ietf.org/html/rfc7396)
@since version 3.0.0
*/
void merge_patch(const basic_json& patch)
{
if (patch.is_object())
{
if (not is_object())
{
*this = object();
}
for (auto it = patch.begin(); it != patch.end(); ++it)
{
if (it.value().is_null())
{
erase(it.key());
}
else
{
operator[](it.key()).merge_patch(it.value());
}
}
}
else
{
*this = patch;
}
}
/// @}
};
} // namespace nlohmann
///////////////////////
// nonmember support //
///////////////////////
// specialization of std::swap, and std::hash
namespace std
{
/*!
@brief exchanges the values of two JSON objects
@since version 1.0.0
*/
template<>
inline void swap(nlohmann::json& j1,
nlohmann::json& j2) noexcept(
is_nothrow_move_constructible<nlohmann::json>::value and
is_nothrow_move_assignable<nlohmann::json>::value
)
{
j1.swap(j2);
}
/// hash value for JSON objects
template<>
struct hash<nlohmann::json>
{
/*!
@brief return a hash value for a JSON object
@since version 1.0.0
*/
std::size_t operator()(const nlohmann::json& j) const
{
// a naive hashing via the string representation
const auto& h = hash<nlohmann::json::string_t>();
return h(j.dump());
}
};
/// specialization for std::less<value_t>
/// @note: do not remove the space after '<',
/// see https://github.com/nlohmann/json/pull/679
template<>
struct less< ::nlohmann::detail::value_t>
{
/*!
@brief compare two value_t enum values
@since version 3.0.0
*/
bool operator()(nlohmann::detail::value_t lhs,
nlohmann::detail::value_t rhs) const noexcept
{
return nlohmann::detail::operator<(lhs, rhs);
}
};
} // namespace std
/*!
@brief user-defined string literal for JSON values
This operator implements a user-defined string literal for JSON objects. It
can be used by adding `"_json"` to a string literal and returns a JSON object
if no parse error occurred.
@param[in] s a string representation of a JSON object
@param[in] n the length of string @a s
@return a JSON object
@since version 1.0.0
*/
inline nlohmann::json operator "" _json(const char* s, std::size_t n)
{
return nlohmann::json::parse(s, s + n);
}
/*!
@brief user-defined string literal for JSON pointer
This operator implements a user-defined string literal for JSON Pointers. It
can be used by adding `"_json_pointer"` to a string literal and returns a JSON pointer
object if no parse error occurred.
@param[in] s a string representation of a JSON Pointer
@param[in] n the length of string @a s
@return a JSON pointer object
@since version 2.0.0
*/
inline nlohmann::json::json_pointer operator "" _json_pointer(const char* s, std::size_t n)
{
return nlohmann::json::json_pointer(std::string(s, n));
}
#include <nlohmann/detail/macro_unscope.hpp>
#endif
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