/*!
@mainpage
These pages contain the API documentation of JSON for Modern C++, a C++11
header-only JSON class.
Class @ref nlohmann::basic_json is a good entry point for the documentation.
@copyright The code is licensed under the MIT License
<http://opensource.org/licenses/MIT>,
Copyright (c) 2013-2015 Niels Lohmann.
@author Niels Lohmann <http://nlohmann.me>
@see https://github.com/nlohmann/json to download the source code
*/
#ifndef NLOHMANN_JSON_HPP
#define NLOHMANN_JSON_HPP
#include <algorithm>
#include <array>
#include <ciso646>
#include <cmath>
#include <cstdio>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <map>
#include <memory>
#include <sstream>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>
// enable ssize_t on MinGW
#ifdef __GNUC__
#ifdef __MINGW32__
#include <sys/types.h>
#endif
#endif
// enable ssize_t for MSVC
#ifdef _MSC_VER
#include <basetsd.h>
using ssize_t = SSIZE_T;
#endif
/*!
@brief namespace for Niels Lohmann
@see https://github.com/nlohmann
*/
namespace nlohmann
{
/// namespace with internal helper functions
namespace internals
{
// Helper to determine whether there's a key_type for T.
// http://stackoverflow.com/a/7728728/266378
template<typename T>
struct has_mapped_type
{
private:
template<typename C> static char test(typename C::mapped_type*);
template<typename C> static int test(...);
public:
enum { value = sizeof(test<T>(0)) == sizeof(char) };
};
}
/*!
@brief a class to store JSON values
@tparam ObjectType type for JSON objects
(@c std::map by default)
@tparam ArrayType type for JSON arrays
(@c std::vector by default)
@tparam StringType type for JSON strings and object keys
(@c std::string by default)
@tparam BooleanType type for JSON booleans
(@c bool by default)
@tparam NumberIntegerType type for JSON integer numbers
(@c int64_t by default)
@tparam NumberFloatType type for JSON floating-point numbers
(@c double by default)
@tparam AllocatorType type of the allocator to use
(@c std::allocator by default)
@requirement This class satisfies the Container requirements (see
http://en.cppreference.com/w/cpp/concept/Container):
- basic_json()
- basic_json(const basic_json&)
- reference& operator=(basic_json)
- ~basic_json()
- iterator begin(), const_iterator begin(), const_iterator cbegin()
- iterator end(), const_iterator end(), const_iterator cend()
- bool operator==(const_reference, const_reference), bool operator!=(const_reference, const_reference)
- void swap(reference other)
- size_type size(), size_type max_size()
- bool empty()
@note ObjectType trick from http://stackoverflow.com/a/9860911
@see RFC 7159 <http://rfc7159.net/rfc7159>
@see ECMA 404 <http://www.ecma-international.org/publications/standards/Ecma-404.htm>
*/
template <
template<typename U, typename V, typename... Args> class ObjectType = std::map,
template<typename U, typename... Args> class ArrayType = std::vector,
class StringType = std::string,
class BooleanType = bool,
class NumberIntegerType = int64_t,
class NumberFloatType = double,
template<typename U> class AllocatorType = std::allocator
>
class basic_json
{
public:
/////////////////////
// container types //
/////////////////////
/// @name container types
/// @{
using __basic_json =
basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberFloatType, AllocatorType>;
/// 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
class iterator;
/// a const iterator for a basic_json container
class const_iterator;
/// a reverse iterator for a basic_json container
class reverse_iterator;
/// a const reverse iterator for a basic_json container
class const_reverse_iterator;
/// @}
/*!
@brief returns the allocator associated with the container
*/
static allocator_type get_allocator()
{
return allocator_type();
}
///////////////////////////
// JSON value data types //
///////////////////////////
/// @name JSON value data types
/// @{
/// a type for an object
using object_t =
ObjectType<StringType, basic_json, std::less<StringType>, AllocatorType<std::pair<const StringType, basic_json>>>;
/// a type for an array
using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
/// a type for a string
using string_t = StringType;
/// a type for a boolean
using boolean_t = BooleanType;
/// a type for a number (integer)
using number_integer_t = NumberIntegerType;
/// a type for a number (floating-point)
using number_float_t = NumberFloatType;
/// a type for list initialization
using list_init_t = std::initializer_list<basic_json>;
/// @}
/////////////////////////////////
// JSON value type enumeration //
/////////////////////////////////
/*!
@brief the JSON value type enumeration
This enumeration collects the different JSON value types. It is used to
distinguish the stored values in the union @ref json_value.
*/
enum class value_t : uint8_t
{
null, ///< null value
object, ///< object (unordered set of name/value pairs)
array, ///< array (ordered collection of values)
string, ///< string value
boolean, ///< boolean value
number_integer, ///< number value (integer)
number_float, ///< number value (floating-point)
discarded ///< (internal) indicates the parser callback chose not to keep the value
};
////////////////////////
// JSON value storage //
////////////////////////
/// a JSON value
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 (floating-point)
number_float_t number_float;
/// default constructor (for null values)
json_value() noexcept = 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 (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::null):
case (value_t::discarded):
{
break;
}
case (value_t::object):
{
AllocatorType<object_t> alloc;
object = alloc.allocate(1);
alloc.construct(object);
break;
}
case (value_t::array):
{
AllocatorType<array_t> alloc;
array = alloc.allocate(1);
alloc.construct(array);
break;
}
case (value_t::string):
{
AllocatorType<string_t> alloc;
string = alloc.allocate(1);
alloc.construct(string, "");
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_float):
{
number_float = number_float_t(0.0);
break;
}
}
}
/// constructor for strings
json_value(const string_t& value)
{
AllocatorType<string_t> alloc;
string = alloc.allocate(1);
alloc.construct(string, value);
}
/// constructor for objects
json_value(const object_t& value)
{
AllocatorType<object_t> alloc;
object = alloc.allocate(1);
alloc.construct(object, value);
}
/// constructor for arrays
json_value(const array_t& value)
{
AllocatorType<array_t> alloc;
array = alloc.allocate(1);
alloc.construct(array, value);
}
};
//////////////////////////
// JSON parser callback //
//////////////////////////
/*!
@brief JSON callback events
This enumeration lists the parser events that can trigger calling a
callback function of type @ref parser_callback_t during parsing.
*/
enum class parse_event_t : uint8_t
{
/// the parser read `{` and started to process a JSON object
object_start,
/// the parser read `}` and finished processing a JSON object
object_end,
/// the parser read `[` and started to process a JSON array
array_start,
/// the parser read `]` and finished processing a JSON array
array_end,
/// the parser read a key of a value in an object
key,
/// the parser finished reading a JSON value
value
};
/*!
@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(std::istream&, parser_callback_t) or
@ref parse(const string_t&, parser_callback_t), 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
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(std::istream&, parser_callback_t) or
@ref parse(const string_t&, parser_callback_t) for examples
*/
using parser_callback_t = std::function<bool(
int depth, parse_event_t event, basic_json& parsed)>;
/*!
@brief comparison operator for JSON value types
Returns an ordering that is similar to Python:
- order: null < boolean < number < object < array < string
- furthermore, each type is not smaller than itself
*/
friend bool operator<(const value_t lhs, const value_t rhs)
{
static constexpr std::array<uint8_t, 7> order = {{
0, // null
3, // object
4, // array
5, // string
1, // boolean
2, // integer
2 // float
}
};
// discarded values are not comparable
if (lhs == value_t::discarded or rhs == value_t::discarded)
{
return false;
}
return order[static_cast<std::size_t>(lhs)] < order[static_cast<std::size_t>(rhs)];
}
//////////////////
// constructors //
//////////////////
/*!
@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] value the type of the value to create
@complexity Constant.
@throw std::bad_alloc if allocation for object, array, or string value
fails (thrown by the constructors of @ref json_value)
@liveexample{The following code shows the constructor for different @ref
value_t values,basic_json__value_t}
*/
basic_json(const value_t value)
: m_type(value), m_value(value)
{}
/*!
@brief create a null object (implicitly)
Create a `null` JSON value. This is the implicit version of the `null`
value constructor as it takes no parameters.
@complexity Constant.
@requirement This function satisfies the Container requirements:
- The complexity is constant.
- As postcondition, it holds: `basic_json().empty() == true`.
@liveexample{The following code shows the constructor for a `null` JSON
value.,basic_json}
@sa basic_json(std::nullptr_t)
@ingroup container
*/
basic_json() noexcept = default;
/*!
@brief create a null object (explicitly)
Create a `null` JSON value. This is the explicitly version of the `null`
value constructor as it takes a null pointer as parameter. It allows to
create `null` values by explicitly assigning a @c nullptr to a JSON value.
The passed null pointer itself is not read - it is only used to choose the
right constructor.
@complexity Constant.
@liveexample{The following code shows the constructor with null pointer
parameter.,basic_json__nullptr_t}
@sa basic_json()
*/
basic_json(std::nullptr_t) noexcept
: basic_json(value_t::null)
{}
/*!
@brief create an object (explicit)
Create an object JSON value with a given content.
@param[in] value a value for the object
@complexity Linear in the size of the passed @a value.
@throw std::bad_alloc if allocation for object value fails (thrown by
the constructor of @ref json_value)
@liveexample{The following code shows the constructor with an @ref object_t
parameter.,basic_json__object_t}
@sa basic_json(const CompatibleObjectType&)
*/
basic_json(const object_t& value)
: m_type(value_t::object), m_value(value)
{}
/*!
@brief create an object (implicit)
Create an object JSON value with a given content. This constructor allows
any type that can be used to construct values of type @ref object_t.
Examples include the types `std::map` and `std::unordered_map`.
@tparam CompatibleObjectType an object type whose `key_type` and
`value_type` is compatible to @ref object_t
@param[in] value a value for the object
@complexity Linear in the size of the passed @a value.
@throw std::bad_alloc if allocation for object value fails (thrown by
the constructor of @ref json_value)
@liveexample{The following code shows the constructor with several
compatible object type parameters.,basic_json__CompatibleObjectType}
@sa basic_json(const object_t&)
*/
template <class CompatibleObjectType, typename
std::enable_if<
std::is_constructible<typename object_t::key_type, typename CompatibleObjectType::key_type>::value and
std::is_constructible<basic_json, typename CompatibleObjectType::mapped_type>::value, int>::type
= 0>
basic_json(const CompatibleObjectType& value)
: m_type(value_t::object)
{
AllocatorType<object_t> alloc;
m_value.object = alloc.allocate(1);
using std::begin;
using std::end;
alloc.construct(m_value.object, begin(value), end(value));
}
/*!
@brief create an array (explicit)
Create an array JSON value with a given content.
@param[in] value a value for the array
@complexity Linear in the size of the passed @a value.
@throw std::bad_alloc if allocation for array value fails (thrown by
the constructor of @ref json_value)
@liveexample{The following code shows the constructor with an @ref array_t
parameter.,basic_json__array_t}
@sa basic_json(const CompatibleArrayType&)
*/
basic_json(const array_t& value)
: m_type(value_t::array), m_value(value)
{}
/*!
@brief create an array (implicit)
Create an array JSON value with a given content. This constructor allows
any type that can be used to construct values of type @ref array_t.
Examples include the types `std::vector`, `std::list`, and `std::set`.
@tparam CompatibleArrayType an object type whose `value_type` is compatible
to @ref array_t
@param[in] value a value for the array
@complexity Linear in the size of the passed @a value.
@throw std::bad_alloc if allocation for array value fails (thrown by
the constructor of @ref json_value)
@liveexample{The following code shows the constructor with several
compatible array type parameters.,basic_json__CompatibleArrayType}
@sa basic_json(const array_t&)
*/
template <class CompatibleArrayType, typename
std::enable_if<
not std::is_same<CompatibleArrayType, typename __basic_json::iterator>::value and
not std::is_same<CompatibleArrayType, typename __basic_json::const_iterator>::value and
not std::is_same<CompatibleArrayType, typename __basic_json::reverse_iterator>::value and
not std::is_same<CompatibleArrayType, typename __basic_json::const_reverse_iterator>::value and
not std::is_same<CompatibleArrayType, typename array_t::iterator>::value and
not std::is_same<CompatibleArrayType, typename array_t::const_iterator>::value and
std::is_constructible<basic_json, typename CompatibleArrayType::value_type>::value, int>::type
= 0>
basic_json(const CompatibleArrayType& value)
: m_type(value_t::array)
{
AllocatorType<array_t> alloc;
m_value.array = alloc.allocate(1);
using std::begin;
using std::end;
alloc.construct(m_value.array, begin(value), end(value));
}
/*!
@brief create a string (explicit)
Create an string JSON value with a given content.
@param[in] value a value for the string
@complexity Linear in the size of the passed @a value.
@throw std::bad_alloc if allocation for string value fails (thrown by
the constructor of @ref json_value)
@liveexample{The following code shows the constructor with an @ref string_t
parameter.,basic_json__string_t}
@sa basic_json(const typename string_t::value_type*)
@sa basic_json(const CompatibleStringType&)
*/
basic_json(const string_t& value)
: m_type(value_t::string), m_value(value)
{}
/*!
@brief create a string (explicit)
Create a string JSON value with a given content.
@param[in] value a literal value for the string
@complexity Linear in the size of the passed @a value.
@throw std::bad_alloc if allocation for string value fails (thrown by
the constructor of @ref json_value)
@liveexample{The following code shows the constructor with string literal
parameter.,basic_json__string_t_value_type}
@sa basic_json(const string_t&)
@sa basic_json(const CompatibleStringType&)
*/
basic_json(const typename string_t::value_type* value)
: basic_json(string_t(value))
{}
/*!
@brief create a string (implicit)
Create a string JSON value with a given content.
@param[in] value a value for the string
@tparam CompatibleStringType an string type which is compatible to @ref
string_t
@complexity Linear in the size of the passed @a value.
@throw std::bad_alloc if allocation for string value fails (thrown by
the constructor of @ref json_value)
@liveexample{The following code shows the construction of a string value
from a compatible type.,basic_json__CompatibleStringType}
@sa basic_json(const string_t&)
*/
template <class CompatibleStringType, typename
std::enable_if<
std::is_constructible<string_t, CompatibleStringType>::value, int>::type
= 0>
basic_json(const CompatibleStringType& value)
: basic_json(string_t(value))
{}
/*!
@brief create a boolean (explicit)
Creates a JSON boolean type from a given value.
@param[in] value a boolean value to store
@complexity Constant.
@liveexample{The example below demonstrates boolean
values.,basic_json__boolean_t}
*/
basic_json(boolean_t value)
: m_type(value_t::boolean), m_value(value)
{}
/*!
@brief create an integer number (explicit)
Create an interger number JSON value with a given content.
@tparam T helper type to compare number_integer_t and int (not visible in)
the interface.
@param[in] value an integer to create a JSON number from
@note This constructor would have the same signature as @ref
basic_json(const int value), so we need to switch this one off in case
number_integer_t is the same as int. This is done via the helper type @a T.
@complexity Constant.
@liveexample{The example below shows the construction of a JSON integer
number value.,basic_json__number_integer_t}
@sa basic_json(const int)
*/
template<typename T,
typename std::enable_if<
not (std::is_same<T, int>::value)
and std::is_same<T, number_integer_t>::value
, int>::type = 0>
basic_json(const number_integer_t value)
: m_type(value_t::number_integer), m_value(value)
{}
/*!
@brief create an integer number from an enum type (explicit)
Create an integer number JSON value with a given content.
@param[in] value an integer to create a JSON number from
@note This constructor allows to pass enums directly to a constructor. As
C++ has no way of specifying the type of an anonymous enum explicitly, we
can only rely on the fact that such values implicitly convert to int. As
int may already be the same type of number_integer_t, we may need to switch
off the constructor @ref basic_json(const number_integer_t).
@complexity Constant.
@liveexample{The example below shows the construction of a JSON integer
number value from an anonymous enum.,basic_json__const_int}
@sa basic_json(const number_integer_t)
*/
basic_json(const int value)
: m_type(value_t::number_integer),
m_value(static_cast<number_integer_t>(value))
{}
/*!
@brief create an integer number (implicit)
Create an integer number JSON value with a given content. This constructor
allows any type that can be used to construct values of type @ref
number_integer_t. Examples may include the types `int`, `int32_t`, or
`short`.
@tparam CompatibleNumberIntegerType an integer type which is compatible to
@ref number_integer_t.
@param[in] value an integer to create a JSON number from
@complexity Constant.
@liveexample{The example below shows the construction of several JSON
integer number values from compatible
types.,basic_json__CompatibleIntegerNumberType}
@sa basic_json(const number_integer_t)
*/
template<typename CompatibleNumberIntegerType, typename
std::enable_if<
std::is_constructible<number_integer_t, CompatibleNumberIntegerType>::value and
std::numeric_limits<CompatibleNumberIntegerType>::is_integer, CompatibleNumberIntegerType>::type
= 0>
basic_json(const CompatibleNumberIntegerType value) noexcept
: m_type(value_t::number_integer),
m_value(static_cast<number_integer_t>(value))
{}
/*!
@brief create a floating-point number (explicit)
Create a floating-point number JSON value with a given content.
@param[in] value a floating-point value to create a JSON number from
@note RFC 7159 <http://www.rfc-editor.org/rfc/rfc7159.txt>, section 6
disallows NaN values:
> Numeric values that cannot be represented in the grammar below (such
> as Infinity and NaN) are not permitted.
In case the parameter @a value is not a number, a JSON null value is
created instead.
@complexity Constant.
@liveexample{The following example creates several floating-point
values.,basic_json__number_float_t}
*/
basic_json(const number_float_t value)
: m_type(value_t::number_float), m_value(value)
{
// replace infinity and NAN by null
if (not std::isfinite(value))
{
m_type = value_t::null;
m_value = json_value();
}
}
/*!
@brief create an floating-point number (implicit)
Create an floating-point number JSON value with a given content. This
constructor allows any type that can be used to construct values of type
@ref number_float_t. Examples may include the types `float`.
@tparam CompatibleNumberFloatType a floating-point type which is compatible
to @ref number_float_t.
@param[in] value a floating-point to create a JSON number from
@note RFC 7159 <http://www.rfc-editor.org/rfc/rfc7159.txt>, section 6
disallows NaN values:
> Numeric values that cannot be represented in the grammar below (such
> as Infinity and NaN) are not permitted.
In case the parameter @a value is not a number, a JSON null value is
created instead.
@complexity Constant.
@liveexample{The example below shows the construction of several JSON
floating-point number values from compatible
types.,basic_json__CompatibleNumberFloatType}
@sa basic_json(const number_float_t)
*/
template<typename CompatibleNumberFloatType, typename = typename
std::enable_if<
std::is_constructible<number_float_t, CompatibleNumberFloatType>::value and
std::is_floating_point<CompatibleNumberFloatType>::value>::type
>
basic_json(const CompatibleNumberFloatType value) noexcept
: basic_json(number_float_t(value))
{}
/*!
@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 ratioinale is as follows:
1. The empty initializer list is written as `{}` which is exactly an empty
JSON object.
2. C++ has now 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(list_init_t) with an empty
initializer list in this case
- arrays whose elements satisfy rule 2: use @ref array(list_init_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(list_init_t) and @ref object(list_init_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 std::domain_error 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
@complexity Linear in the size of the initializer list @a init.
@liveexample{The example below shows how JSON values are created from
initializer lists,basic_json__list_init_t}
@sa basic_json array(list_init_t) - create a JSON array value from an
initializer list
@sa basic_json object(list_init_t) - create a JSON object value from an
initializer list
*/
basic_json(list_init_t init, bool type_deduction = true,
value_t manual_type = value_t::array)
{
// the initializer list could describe an object
bool is_object = true;
// check if each element is an array with two elements whose first element
// is a string
for (const auto& element : init)
{
if (element.m_type != value_t::array or element.size() != 2
or element[0].m_type != value_t::string)
{
// we found an element that makes it impossible to use the
// initializer list as object
is_object = false;
break;
}
}
// 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_object = false;
}
// if object is wanted but impossible, throw an exception
if (manual_type == value_t::object and not is_object)
{
throw std::domain_error("cannot create object from initializer list");
}
}
if (is_object)
{
// the initializer list is a list of pairs -> create object
m_type = value_t::object;
m_value = value_t::object;
for (auto& element : init)
{
m_value.object->emplace(std::move(*(element[0].m_value.string)), std::move(element[1]));
}
}
else
{
// the initializer list describes an array -> create array
m_type = value_t::array;
AllocatorType<array_t> alloc;
m_value.array = alloc.allocate(1);
alloc.construct(m_value.array, std::move(init));
}
}
/*!
@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(list_init_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.
@liveexample{The following code shows an example for the @ref array
function.,array}
@sa basic_json(list_init_t, bool, value_t) - create a JSON value from an
initializer list
@sa basic_json object(list_init_t) - create a JSON object value from an
initializer list
*/
static basic_json array(list_init_t init = list_init_t())
{
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 elments 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 basic_json array(list_init_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(list_init_t, bool, value_t).
@param[in] init initializer list to create an object from (optional)
@return JSON object value
@throw std::domain_error if @a init is not a pair whose first elements are
strings; thrown by @ref basic_json(list_init_t, bool, value_t)
@complexity Linear in the size of @a init.
@liveexample{The following code shows an example for the @ref object
function.,object}
@sa basic_json(list_init_t, bool, value_t) - create a JSON value from an
initializer list
@sa basic_json array(list_init_t) - create a JSON array value from an
initializer list
*/
static basic_json object(list_init_t init = list_init_t())
{
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 count copies of a passed
value. In case @a count is `0`, an empty array is created. As postcondition,
`std::distance(begin(),end()) == count` holds.
@param[in] count the number of JSON copies of @a value to create
@param[in] value the JSON value to copy
@complexity Linear in @a count.
@liveexample{The following code shows examples for the @ref
basic_json(size_type\, const basic_json&)
constructor.,basic_json__size_type_basic_json}
*/
basic_json(size_type count, const basic_json& value)
: m_type(value_t::array)
{
AllocatorType<array_t> alloc;
m_value.array = alloc.allocate(1);
alloc.construct(m_value.array, count, value);
}
/*!
@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 atomic value types (number, boolean, or string), @a first must
be `begin()` and @a last must be `end()`. In this case, the value is
copied. Otherwise, std::out_of_range is thrown.
- In case of compound value types (array, object), the constructor behaves
as similar versions for `std::vector`.
- In case of a null value type, std::domain_error is thrown.
@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)
@throw std::domain_error if iterators are not compatible; that is, do not
belong to the same JSON value
@throw std::out_of_range if iterators are for an atomic value type (number,
boolean, or string) where an out of range error can be detected easily
@throw std::bad_alloc if allocation for object, array, or string fails
@throw std::domain_error if called with a null value
@complexity Linear in distance between @a first and @a last.
@liveexample{The example below shows several ways to create JSON values by
specifying a subrange with iterators.,basic_json__InputIt_InputIt}
*/
template <class InputIT, typename
std::enable_if<
std::is_same<InputIT, typename __basic_json::iterator>::value or
std::is_same<InputIT, typename __basic_json::const_iterator>::value
, int>::type
= 0>
basic_json(InputIT first, InputIT last) : m_type(first.m_object->m_type)
{
// make sure iterator fits the current value
if (first.m_object != last.m_object)
{
throw std::domain_error("iterators are not compatible");
}
// check if iterator range is complete for atomic values
switch (m_type)
{
case value_t::number_integer:
case value_t::number_float:
case value_t::boolean:
case value_t::string:
{
if (first.m_it.generic_iterator != 0 or last.m_it.generic_iterator != 1)
{
throw std::out_of_range("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_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:
{
AllocatorType<object_t> alloc;
m_value.object = alloc.allocate(1);
alloc.construct(m_value.object, first.m_it.object_iterator, last.m_it.object_iterator);
break;
}
case value_t::array:
{
AllocatorType<array_t> alloc;
m_value.array = alloc.allocate(1);
alloc.construct(m_value.array, first.m_it.array_iterator, last.m_it.array_iterator);
break;
}
default:
{
throw std::domain_error("cannot use construct with iterators from " + first.m_object->type_name());
}
}
}
///////////////////////////////////////
// other constructors and destructor //
///////////////////////////////////////
/*!
@brief copy constructor
Creates a copy of a given JSON value.
@param[in] other the JSON value to copy
@complexity Linear in the size of @a other.
@requirement This function satisfies the Container requirements:
- The complexity is linear.
- As postcondition, it holds: `other == basic_json(other)`.
@throw std::bad_alloc if allocation for object, array, or string fails.
@liveexample{The following code shows an example for the copy
constructor.,basic_json__basic_json}
@ingroup container
*/
basic_json(const basic_json& other)
: m_type(other.m_type)
{
switch (m_type)
{
case (value_t::null):
case (value_t::discarded):
{
break;
}
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_float):
{
m_value = other.m_value.number_float;
break;
}
}
}
/*!
@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 @a other is a JSON null value
@complexity Constant.
@liveexample{The code below shows the move constructor explicitly called
via std::move.,basic_json__moveconstructor}
*/
basic_json(basic_json&& other) noexcept
: m_type(std::move(other.m_type)),
m_value(std::move(other.m_value))
{
// invalidate payload
other.m_type = value_t::null;
other.m_value = {};
}
/*!
@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 satisfies the 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}
@ingroup container
*/
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
)
{
using std::swap;
std::swap(m_type, other.m_type);
std::swap(m_value, other.m_value);
return *this;
}
/*!
@brief destructor
Destroys the JSON value and frees all allocated memory.
@complexity Linear.
@requirement This function satisfies the Container requirements:
- The complexity is linear.
- All stored elements are destroyed and all memory is freed.
@ingroup container
*/
~basic_json() noexcept
{
switch (m_type)
{
case (value_t::object):
{
AllocatorType<object_t> alloc;
alloc.destroy(m_value.object);
alloc.deallocate(m_value.object, 1);
m_value.object = nullptr;
break;
}
case (value_t::array):
{
AllocatorType<array_t> alloc;
alloc.destroy(m_value.array);
alloc.deallocate(m_value.array, 1);
m_value.array = nullptr;
break;
}
case (value_t::string):
{
AllocatorType<string_t> alloc;
alloc.destroy(m_value.string);
alloc.deallocate(m_value.string, 1);
m_value.string = nullptr;
break;
}
default:
{
// all other types need no specific destructor
break;
}
}
}
public:
///////////////////////
// object inspection //
///////////////////////
/// @name object inspection
/// @{
/*!
@brief serialization
Serialization function for JSON values. The function tries to mimick
Python's @p json.dumps() function, and currently supports its @p indent
parameter.
@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
@return string containing the serialization of the JSON value
@complexity Linear.
@liveexample{The following example shows the effect of different @a indent
parameters to the result of the serializaion.,dump}
@see https://docs.python.org/2/library/json.html#json.dump
*/
string_t dump(const int indent = -1) const noexcept
{
std::stringstream ss;
if (indent >= 0)
{
dump(ss, true, static_cast<unsigned int>(indent));
}
else
{
dump(ss, false, 0);
}
return ss.str();
}
/// return the type of the object (explicit)
value_t type() const noexcept
{
return m_type;
}
/*!
@brief return whether value is null
This function returns true iff the JSON value is null.
@return `true` if value type is null, `false` otherwise.
@complexity Constant.
@liveexample{The following code exemplifies @ref is_null for all JSON
value types.,is_null}
*/
bool is_null() const noexcept
{
return m_type == value_t::null;
}
/*!
@brief return whether value is a boolean
This function returns true iff the JSON value is a boolean.
@return `true` if value type is boolean, `false` otherwise.
@complexity Constant.
@liveexample{The following code exemplifies @ref is_boolean for all JSON
value types.,is_boolean}
*/
bool is_boolean() const noexcept
{
return m_type == value_t::boolean;
}
/*!
@brief return whether value is a number
This function returns true iff the JSON value is a number. This includes
both integer and floating-point values.
@return `true` if value type is number, `false` otherwise.
@complexity Constant.
@liveexample{The following code exemplifies @ref is_number for all JSON
value types.,is_number}
*/
bool is_number() const noexcept
{
return (m_type == value_t::number_integer) or (m_type == value_t::number_float);
}
/*!
@brief return whether value is an integer number
This function returns true iff the JSON value is an integer number. This
excludes floating-point values.
@return `true` if value type is an integer number, `false` otherwise.
@complexity Constant.
@liveexample{The following code exemplifies @ref is_number_integer for all
JSON value types.,is_number_integer}
*/
bool is_number_integer() const noexcept
{
return m_type == value_t::number_integer;
}
/*!
@brief return whether value is a floating-point number
This function returns true iff the JSON value is a floating-point number.
This excludes integer values.
@return `true` if value type is a floating-point number, `false` otherwise.
@complexity Constant.
@liveexample{The following code exemplifies @ref is_number_float for all
JSON value types.,is_number_float}
*/
bool is_number_float() const noexcept
{
return m_type == value_t::number_float;
}
/*!
@brief return whether value is an object
This function returns true iff the JSON value is an object.
@return `true` if value type is object, `false` otherwise.
@complexity Constant.
@liveexample{The following code exemplifies @ref is_object for all JSON
value types.,is_object}
*/
bool is_object() const noexcept
{
return m_type == value_t::object;
}
/*!
@brief return whether value is an array
This function returns true iff the JSON value is an array.
@return `true` if value type is array, `false` otherwise.
@complexity Constant.
@liveexample{The following code exemplifies @ref is_array for all JSON
value types.,is_array}
*/
bool is_array() const noexcept
{
return m_type == value_t::array;
}
/*!
@brief return whether value is a string
This function returns true iff the JSON value is a string.
@return `true` if value type is string, `false` otherwise.
@complexity Constant.
@liveexample{The following code exemplifies @ref is_string for all JSON
value types.,is_string}
*/
bool is_string() const noexcept
{
return m_type == value_t::string;
}
// return whether value is discarded
bool is_discarded() const noexcept
{
return m_type == value_t::discarded;
}
/// return the type of the object (implicit)
operator value_t() const noexcept
{
return m_type;
}
/// @}
private:
//////////////////
// value access //
//////////////////
/// get an object (explicit)
template <class T, typename
std::enable_if<
std::is_convertible<typename object_t::key_type, typename T::key_type>::value and
std::is_convertible<__basic_json, typename T::mapped_type>::value
, int>::type = 0>
T get_impl(T*) const
{
switch (m_type)
{
case (value_t::object):
{
return T(m_value.object->begin(), m_value.object->end());
}
default:
{
throw std::domain_error("value type must be object, but is " + type_name());
}
}
}
/// get an object (explicit)
object_t get_impl(object_t*) const
{
switch (m_type)
{
case (value_t::object):
{
return *(m_value.object);
}
default:
{
throw std::domain_error("value type must be object, but is " + type_name());
}
}
}
/// get an array (explicit)
template <class T, typename
std::enable_if<
std::is_convertible<__basic_json, typename T::value_type>::value and
not std::is_same<__basic_json, typename T::value_type>::value and
not std::is_arithmetic<T>::value and
not std::is_convertible<std::string, T>::value and
not internals::has_mapped_type<T>::value
, int>::type = 0>
T get_impl(T*) const
{
switch (m_type)
{
case (value_t::array):
{
T to_vector;
std::transform(m_value.array->begin(), m_value.array->end(),
std::inserter(to_vector, to_vector.end()), [](basic_json i)
{
return i.get<typename T::value_type>();
});
return to_vector;
}
default:
{
throw std::domain_error("value type must be array, but is " + type_name());
}
}
}
/// get an array (explicit)
template <class T, typename
std::enable_if<
std::is_convertible<__basic_json, T>::value and
not std::is_same<__basic_json, T>::value
, int>::type = 0>
std::vector<T> get_impl(std::vector<T>*) const
{
switch (m_type)
{
case (value_t::array):
{
std::vector<T> to_vector;
to_vector.reserve(m_value.array->size());
std::transform(m_value.array->begin(), m_value.array->end(),
std::inserter(to_vector, to_vector.end()), [](basic_json i)
{
return i.get<T>();
});
return to_vector;
}
default:
{
throw std::domain_error("value type must be array, but is " + type_name());
}
}
}
/// get an array (explicit)
template <class T, typename
std::enable_if<
std::is_same<basic_json, typename T::value_type>::value and
not internals::has_mapped_type<T>::value
, int>::type = 0>
T get_impl(T*) const
{
switch (m_type)
{
case (value_t::array):
{
return T(m_value.array->begin(), m_value.array->end());
}
default:
{
throw std::domain_error("value type must be array, but is " + type_name());
}
}
}
array_t get_impl(array_t*) const
{
switch (m_type)
{
case (value_t::array):
{
return *(m_value.array);
}
default:
{
throw std::domain_error("value type must be array, but is " + type_name());
}
}
}
/// get a string (explicit)
template <typename T, typename
std::enable_if<
std::is_convertible<string_t, T>::value
, int>::type = 0>
T get_impl(T*) const
{
switch (m_type)
{
case (value_t::string):
{
return *m_value.string;
}
default:
{
throw std::domain_error("value type must be string, but is " + type_name());
}
}
}
/// get a number (explicit)
template<typename T, typename
std::enable_if<
std::is_arithmetic<T>::value
, int>::type = 0>
T get_impl(T*) const
{
switch (m_type)
{
case (value_t::number_integer):
{
return static_cast<T>(m_value.number_integer);
}
case (value_t::number_float):
{
return static_cast<T>(m_value.number_float);
}
default:
{
throw std::domain_error("value type must be number, but is " + type_name());
}
}
}
/// get a boolean (explicit)
boolean_t get_impl(boolean_t*) const
{
switch (m_type)
{
case (value_t::boolean):
{
return m_value.boolean;
}
default:
{
throw std::domain_error("value type must be boolean, but is " + type_name());
}
}
}
public:
/// @name value access
/// @{
/// get a value (explicit)
// <http://stackoverflow.com/a/8315197/266378>
template<typename T>
T get() const
{
return get_impl(static_cast<T*>(nullptr));
}
/// get a value (implicit)
template<typename T>
operator T() const
{
return get<T>();
}
/// @}
////////////////////
// element access //
////////////////////
/// @name element access
/// @{
/*!
@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 std::domain_error if JSON is not an array
@throw std::out_of_range if the index @a idx is out of range of the array;
that is, `idx >= size()`
@complexity Constant.
@liveexample{The example below shows how array elements can be read and
written using at.,at__size_type}
*/
reference at(size_type idx)
{
// at only works for arrays
if (m_type != value_t::array)
{
throw std::domain_error("cannot use at() with " + type_name());
}
return m_value.array->at(idx);
}
/*!
@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 std::domain_error if JSON is not an array
@throw std::out_of_range if the index @a idx is out of range of the array;
that is, `idx >= size()`
@complexity Constant.
@liveexample{The example below shows how array elements can be read using
at.,at__size_type_const}
*/
const_reference at(size_type idx) const
{
// at only works for arrays
if (m_type != value_t::array)
{
throw std::domain_error("cannot use at() with " + type_name());
}
return m_value.array->at(idx);
}
/*!
@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 std::domain_error if JSON is not an object
@throw std::out_of_range if the key @a key is is not stored in the object;
that is, `find(key) == end()`
@complexity Logarithmic in the size of the container.
@liveexample{The example below shows how object elements can be read and
written using at.,at__object_t_key_type}
*/
reference at(const typename object_t::key_type& key)
{
// at only works for objects
if (m_type != value_t::object)
{
throw std::domain_error("cannot use at() with " + type_name());
}
return m_value.object->at(key);
}
/*!
@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 std::domain_error if JSON is not an object
@throw std::out_of_range if the key @a key is is not stored in the object;
that is, `find(key) == end()`
@complexity Logarithmic in the size of the container.
@liveexample{The example below shows how object elements can be read using
at.,at__object_t_key_type_const}
*/
const_reference at(const typename object_t::key_type& key) const
{
// at only works for objects
if (m_type != value_t::object)
{
throw std::domain_error("cannot use at() with " + type_name());
}
return m_value.object->at(key);
}
/*!
@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 std::domain_error if JSON is not an array or null
@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}
*/
reference operator[](size_type idx)
{
// implicitly convert null to object
if (m_type == value_t::null)
{
m_type = value_t::array;
AllocatorType<array_t> alloc;
m_value.array = alloc.allocate(1);
alloc.construct(m_value.array);
}
// [] only works for arrays
if (m_type != value_t::array)
{
throw std::domain_error("cannot use operator[] with " + type_name());
}
for (size_t i = m_value.array->size(); i <= idx; ++i)
{
m_value.array->push_back(basic_json());
}
return m_value.array->operator[](idx);
}
/*!
@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 std::domain_error if JSON is not an array
@complexity Constant.
@liveexample{The example below shows how array elements can be read using
the [] operator.,operatorarray__size_type_const}
*/
const_reference operator[](size_type idx) const
{
// at only works for arrays
if (m_type != value_t::array)
{
throw std::domain_error("cannot use operator[] with " + type_name());
}
return m_value.array->operator[](idx);
}
/// access specified element
reference operator[](const typename object_t::key_type& key)
{
// implicitly convert null to object
if (m_type == value_t::null)
{
m_type = value_t::object;
AllocatorType<object_t> alloc;
m_value.object = alloc.allocate(1);
alloc.construct(m_value.object);
}
// [] only works for objects
if (m_type != value_t::object)
{
throw std::domain_error("cannot use operator[] with " + type_name());
}
return m_value.object->operator[](key);
}
/// access specified element
const_reference operator[](const typename object_t::key_type& key) const
{
// at only works for objects
if (m_type != value_t::object)
{
throw std::domain_error("cannot use operator[] with " + type_name());
}
return m_value.object->operator[](key);
}
/// access specified element (needed for clang)
template<typename T, std::size_t n>
reference operator[](const T (&key)[n])
{
// implicitly convert null to object
if (m_type == value_t::null)
{
m_type = value_t::object;
m_value = value_t::object;
}
// at only works for objects
if (m_type != value_t::object)
{
throw std::domain_error("cannot use operator[] with " + type_name());
}
return m_value.object->operator[](key);
}
/// access specified element (needed for clang)
template<typename T, std::size_t n>
const_reference operator[](const T (&key)[n]) const
{
// at only works for objects
if (m_type != value_t::object)
{
throw std::domain_error("cannot use operator[] with " + type_name());
}
return m_value.object->operator[](key);
}
/*!
@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 compound value (array or object), a reference to the
first element is returned. In cast of number, string, or boolean values, a
reference to the value is returned.
@complexity Constant.
@note Calling `front` on an empty container is undefined.
@throw std::out_of_range when called on null value
@liveexample{The following code shows an example for @ref front.,front}
*/
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 `{ auto tmp =
c.end(); --tmp; return *tmp; }`.
@return In case of a compound value (array or object), a reference to the
last element is returned. In cast of number, string, or boolean values, a
reference to the value is returned.
@complexity Constant.
@note Calling `back` on an empty container is undefined.
@throw std::out_of_range when called on null value.
@liveexample{The following code shows an example for @ref back.,back}
*/
reference back()
{
auto tmp = end();
--tmp;
return *tmp;
}
/*!
@copydoc basic_json::back()
*/
const_reference back() const
{
auto tmp = cend();
--tmp;
return *tmp;
}
/// remove element given an iterator
template <class T, typename
std::enable_if<
std::is_same<T, typename __basic_json::iterator>::value or
std::is_same<T, typename __basic_json::const_iterator>::value
, int>::type
= 0>
T erase(T pos)
{
// make sure iterator fits the current value
if (this != pos.m_object or m_type != pos.m_object->m_type)
{
throw std::domain_error("iterator does not fit current value");
}
T result = end();
switch (m_type)
{
case value_t::number_integer:
case value_t::number_float:
case value_t::boolean:
case value_t::string:
{
if (pos.m_it.generic_iterator != 0)
{
throw std::out_of_range("iterator out of range");
}
if (m_type == value_t::string)
{
delete m_value.string;
m_value.string = nullptr;
}
m_type = value_t::null;
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:
{
throw std::domain_error("cannot use erase() with " + type_name());
}
}
return result;
}
/// remove elements given an iterator range
template <class T, typename
std::enable_if<
std::is_same<T, typename basic_json::iterator>::value or
std::is_same<T, typename basic_json::const_iterator>::value
, int>::type
= 0>
T erase(T first, T last)
{
// make sure iterator fits the current value
if (this != first.m_object or this != last.m_object or
m_type != first.m_object->m_type or m_type != last.m_object->m_type)
{
throw std::domain_error("iterators do not fit current value");
}
T result = end();
switch (m_type)
{
case value_t::number_integer:
case value_t::number_float:
case value_t::boolean:
case value_t::string:
{
if (first.m_it.generic_iterator != 0 or last.m_it.generic_iterator != 1)
{
throw std::out_of_range("iterators out of range");
}
if (m_type == value_t::string)
{
delete m_value.string;
m_value.string = nullptr;
}
m_type = value_t::null;
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:
{
throw std::domain_error("cannot use erase with " + type_name());
}
}
return result;
}
/// remove element from an object given a key
size_type erase(const typename object_t::key_type& key)
{
// this erase only works for objects
if (m_type != value_t::object)
{
throw std::domain_error("cannot use erase() with " + type_name());
}
return m_value.object->erase(key);
}
/// remove element from an array given an index
void erase(const size_type idx)
{
// this erase only works for arrays
if (m_type != value_t::array)
{
throw std::domain_error("cannot use erase() with " + type_name());
}
if (idx >= size())
{
throw std::out_of_range("index out of range");
}
m_value.array->erase(m_value.array->begin() + static_cast<difference_type>(idx));
}
/// find an element in an object
iterator find(typename object_t::key_type key)
{
auto result = end();
if (m_type == value_t::object)
{
result.m_it.object_iterator = m_value.object->find(key);
}
return result;
}
/// find an element in an object
const_iterator find(typename object_t::key_type key) const
{
auto result = cend();
if (m_type == value_t::object)
{
result.m_it.object_iterator = m_value.object->find(key);
}
return result;
}
/// returns the number of occurrences of a key in an object
size_type count(typename object_t::key_type key) const
{
// return 0 for all nonobject types
return (m_type == value_t::object) ? m_value.object->count(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 satisfies the Container requirements:
- The complexity is constant.
@liveexample{The following code shows an example for @ref begin.,begin}
@ingroup container
*/
iterator begin() noexcept
{
iterator result(this);
result.set_begin();
return result;
}
/*!
@copydoc basic_json::cbegin()
@ingroup container
*/
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 satisfies the 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 @ref cbegin.,cbegin}
@ingroup container
*/
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 satisfies the Container requirements:
- The complexity is constant.
@liveexample{The following code shows an example for @ref end.,end}
@ingroup container
*/
iterator end() noexcept
{
iterator result(this);
result.set_end();
return result;
}
/*!
@copydoc basic_json::cend()
@ingroup container
*/
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 satisfies the 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 @ref cend.,cend}
@ingroup container
*/
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 satisfies the ReversibleContainer requirements:
- The complexity is constant.
- Has the semantics of `reverse_iterator(end())`.
@liveexample{The following code shows an example for @ref rbegin.,rbegin}
@ingroup reversiblecontainer
*/
reverse_iterator rbegin() noexcept
{
return reverse_iterator(end());
}
/*!
@copydoc basic_json::crbegin()
@ingroup reversiblecontainer
*/
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 satisfies the ReversibleContainer requirements:
- The complexity is constant.
- Has the semantics of `reverse_iterator(begin())`.
@liveexample{The following code shows an example for @ref rend.,rend}
@ingroup reversiblecontainer
*/
reverse_iterator rend() noexcept
{
return reverse_iterator(begin());
}
/*!
@copydoc basic_json::crend()
@ingroup reversiblecontainer
*/
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 satisfies the 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 @ref crbegin.,crbegin}
@ingroup reversiblecontainer
*/
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 satisfies the 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 @ref crend.,crend}
@ingroup reversiblecontainer
*/
const_reverse_iterator crend() const noexcept
{
return const_reverse_iterator(cbegin());
}
/// @}
//////////////
// capacity //
//////////////
/// @name capacity
/// @{
/*!
@brief checks whether the container is empty
Checks if a JSON value has no elements.
@return The return value depends on the different value types and is
defined as follows:
Value type | return value
----------- | -------------
null | @c true
boolean | @c false
string | @c false
number | @c false
object | result of function object_t::empty()
array | result of function array_t::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.
@requirement This function satisfies the Container requirements:
- The complexity is constant.
- Has the semantics of `begin() == end()`.
@liveexample{The following code uses @ref empty to check if a @ref json
object contains any elements.,empty}
@ingroup container
*/
bool empty() const noexcept
{
switch (m_type)
{
case (value_t::null):
{
return true;
}
case (value_t::array):
{
return m_value.array->empty();
}
case (value_t::object):
{
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 value types and is
defined as follows:
Value type | return value
----------- | -------------
null | @c 0
boolean | @c 1
string | @c 1
number | @c 1
object | result of function object_t::size()
array | result of function array_t::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.
@requirement This function satisfies the Container requirements:
- The complexity is constant.
- Has the semantics of `std::distance(begin(), end())`.
@liveexample{The following code calls @ref size on the different value
types.,size}
@ingroup container
*/
size_type size() const noexcept
{
switch (m_type)
{
case (value_t::null):
{
return 0;
}
case (value_t::array):
{
return m_value.array->size();
}
case (value_t::object):
{
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 value types and is
defined as follows:
Value type | return value
----------- | -------------
null | @c 0
boolean | @c 1
string | @c 1
number | @c 1
object | result of function object_t::max_size()
array | result of function array_t::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.
@requirement This function satisfies the Container requirements:
- The complexity is constant.
- Has the semantics of returning `b.size()` where `b` is the largest
possible JSON value.
@liveexample{The following code calls @ref max_size on the different value
types. Note the output is implementation specific.,max_size}
@ingroup container
*/
size_type max_size() const noexcept
{
switch (m_type)
{
case (value_t::null):
{
return 0;
}
case (value_t::array):
{
return m_value.array->max_size();
}
case (value_t::object):
{
return m_value.object->max_size();
}
default:
{
// all other types have max_size 1
return 1;
}
}
}
/// @}
///////////////
// 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:
Value type | initial value
----------- | -------------
null | `null`
boolean | `false`
string | `""`
number | `0`
object | `{}`
array | `[]`
@note Floating-point numbers are set to `0.0` which will be serialized to
`0`. The vale type remains @ref number_float_t.
@complexity Linear in the size of the JSON value.
@liveexample{The example below shows the effect of @ref clear to different
JSON value types.,clear}
*/
void clear() noexcept
{
switch (m_type)
{
case (value_t::null):
case (value_t::discarded):
{
break;
}
case (value_t::number_integer):
{
m_value.number_integer = 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;
}
}
}
/// add an object to an array
void push_back(basic_json&& value)
{
// push_back only works for null objects or arrays
if (not(m_type == value_t::null or m_type == value_t::array))
{
throw std::domain_error("cannot use push_back() with " + type_name());
}
// transform null object into an array
if (m_type == value_t::null)
{
m_type = value_t::array;
m_value = value_t::array;
}
// add element to array (move semantics)
m_value.array->push_back(std::move(value));
// invalidate object
value.m_type = value_t::null;
}
/// add an object to an array
reference operator+=(basic_json&& value)
{
push_back(std::move(value));
return *this;
}
/// add an object to an array
void push_back(const basic_json& value)
{
// push_back only works for null objects or arrays
if (not(m_type == value_t::null or m_type == value_t::array))
{
throw std::domain_error("cannot use push_back() with " + type_name());
}
// transform null object into an array
if (m_type == value_t::null)
{
m_type = value_t::array;
m_value = value_t::array;
}
// add element to array
m_value.array->push_back(value);
}
/// add an object to an array
reference operator+=(const basic_json& value)
{
push_back(value);
return *this;
}
/// add an object to an object
void push_back(const typename object_t::value_type& value)
{
// push_back only works for null objects or objects
if (not(m_type == value_t::null or m_type == value_t::object))
{
throw std::domain_error("cannot use push_back() with " + type_name());
}
// transform null object into an object
if (m_type == value_t::null)
{
m_type = value_t::object;
m_value = value_t::object;
}
// add element to array
m_value.object->insert(value);
}
/// add an object to an object
reference operator+=(const typename object_t::value_type& value)
{
push_back(value);
return operator[](value.first);
}
/*!
@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 arrays can be
swapped.,swap__reference}
@ingroup container
*/
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);
}
/*!
@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 std::domain_error when JSON value is not an array
@complexity Constant.
@liveexample{The example below shows how JSON values can be
swapped.,swap__array_t}
@ingroup container
*/
void swap(array_t& other)
{
// swap only works for arrays
if (m_type != value_t::array)
{
throw std::domain_error("cannot use swap() with " + type_name());
}
// swap arrays
std::swap(*(m_value.array), other);
}
/// swaps the contents
void swap(object_t& other)
{
// swap only works for objects
if (m_type != value_t::object)
{
throw std::domain_error("cannot use swap() with " + type_name());
}
// swap arrays
std::swap(*(m_value.object), other);
}
/// swaps the contents
void swap(string_t& other)
{
// swap only works for strings
if (m_type != value_t::string)
{
throw std::domain_error("cannot use swap() with " + type_name());
}
// swap arrays
std::swap(*(m_value.string), other);
}
/// @}
//////////////////////////////////////////
// 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.
- Integer and floating-point numbers are automatically converted before
comparison. Floating-point numbers are compared indirectly: two
floating-point numbers `f1` and `f2` are considered equal if neither
`f1 > f2` nor `f2 > f1` holds.
- Two JSON null values are equal.
@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
@complexity Linear.
@todo Add example.
@ingroup container
*/
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_float):
return approx(lhs.m_value.number_float, rhs.m_value.number_float);
case (value_t::discarded):
return false;
}
}
else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
{
return approx(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 approx(lhs.m_value.number_float,
static_cast<number_float_t>(rhs.m_value.number_integer));
}
return false;
}
/*!
@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.
@todo Add example.
@ingroup container
*/
friend bool operator!=(const_reference lhs, const_reference rhs) noexcept
{
return not (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.
@todo Add example.
*/
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_float):
return lhs.m_value.number_float < rhs.m_value.number_float;
case (value_t::discarded):
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);
}
// We only reach this line if we cannot compare values. In that case,
// we compare types.
return lhs_type < rhs_type;
}
/*!
@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.
@todo Add example.
*/
friend bool operator<=(const_reference lhs, const_reference rhs) noexcept
{
return not (rhs < lhs);
}
/*!
@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.
@todo Add example.
*/
friend bool operator>(const_reference lhs, const_reference rhs) noexcept
{
return not (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.
@todo Add example.
*/
friend bool operator>=(const_reference lhs, const_reference rhs) noexcept
{
return not (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)`.
@param[in,out] o stream to serialize to
@param[in] j JSON value to serialize
@return the stream @a o
@complexity Linear.
@liveexample{The example below shows the serialization with different
parameters to `width` to adjust the indentation level.,operator_serialize}
*/
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
j.dump(o, pretty_print, static_cast<unsigned int>(indentation));
return o;
}
/*!
@brief serialize to stream
@copydoc operator<<(std::ostream&, const basic_json&)
*/
friend std::ostream& operator>>(const basic_json& j, std::ostream& o)
{
return o << j;
}
/// @}
/////////////////////
// deserialization //
/////////////////////
/// @name deserialization
/// @{
/*!
@brief deserialize from string
@param[in] s string to read a serialized JSON value 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
@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.
@liveexample{The example below demonstrates the parse function with and
without callback function.,parse__string__parser_callback_t}
@sa parse(std::istream&, parser_callback_t) for a version that reads from
an input stream
*/
static basic_json parse(const string_t& s, parser_callback_t cb = nullptr)
{
return parser(s, cb).parse();
}
/*!
@brief deserialize from stream
@param[in,out] i stream to read a serialized JSON value 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
@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.
@liveexample{The example below demonstrates the parse function with and
without callback function.,parse__istream__parser_callback_t}
@sa parse(const string_t&, parser_callback_t) for a version that reads
from a string
*/
static basic_json parse(std::istream& i, parser_callback_t cb = nullptr)
{
return parser(i, cb).parse();
}
/*!
@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 std::invalid_argument in case of parse errors
@complexity Linear in the length of the input. The parser is a predictive
LL(1) parser.
@liveexample{The example below shows how a JSON value is constructed by
reading a serialization from a stream.,operator_deserialize}
@sa parse(std::istream&, parser_callback_t) for a variant with a parser
callback function to filter values while parsing
*/
friend std::istream& operator<<(basic_json& j, std::istream& i)
{
j = parser(i).parse();
return i;
}
/*!
@brief deserialize from stream
@copydoc operator<<(basic_json&, std::istream&)
*/
friend std::istream& operator>>(std::istream& i, basic_json& j)
{
j = parser(i).parse();
return i;
}
/// @}
private:
///////////////////////////
// convenience functions //
///////////////////////////
/// return the type as string
string_t 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";
}
}
}
/*!
@brief escape a string
Escape a string by replacing certain special characters by a sequence of an
escape character (backslash) and another character and other control
characters by a sequence of "\u" followed by a four-digit hex
representation.
@param[out] o the stream to write the escaped string to
@param[in] s the string to escape
*/
static void escape_string(std::ostream& o, const string_t& s) noexcept
{
for (const auto c : s)
{
switch (c)
{
// quotation mark (0x22)
case '"':
{
o << "\\\"";
break;
}
// reverse solidus (0x5c)
case '\\':
{
o << "\\\\";
break;
}
// backspace (0x08)
case '\b':
{
o << "\\b";
break;
}
// formfeed (0x0c)
case '\f':
{
o << "\\f";
break;
}
// newline (0x0a)
case '\n':
{
o << "\\n";
break;
}
// carriage return (0x0d)
case '\r':
{
o << "\\r";
break;
}
// horizontal tab (0x09)
case '\t':
{
o << "\\t";
break;
}
default:
{
if (c >= 0 and c <= 0x1f)
{
// control characters (everything between 0x00 and 0x1f)
// -> create four-digit hex representation
o << "\\u" << std::hex << std::setw(4) << std::setfill('0') << int(c);
}
else
{
// all other characters are added as-is
o << c;
}
break;
}
}
}
}
/*!
@brief internal implementation of the serialization function
This function is called by the public member function dump and organizes
the serializaion internally. The indentation level is propagated as
additional parameter. In case of arrays and objects, the function is called
recursively. Note that
- strings and object keys are escaped using escape_string()
- integer numbers are converted implictly via operator<<
- floating-point numbers are converted to a string using "%g" format
@param[out] o stream to write to
@param[in] pretty_print whether the output shall be pretty-printed
@param[in] indent_step the indent level
@param[in] current_indent the current indent level (only used internally)
*/
void dump(std::ostream& o, const bool pretty_print, const unsigned int indent_step,
const unsigned int current_indent = 0) const noexcept
{
// variable to hold indentation for recursive calls
unsigned int new_indent = current_indent;
switch (m_type)
{
case (value_t::object):
{
if (m_value.object->empty())
{
o << "{}";
return;
}
o << "{";
// increase indentation
if (pretty_print)
{
new_indent += indent_step;
o << "\n";
}
for (auto i = m_value.object->cbegin(); i != m_value.object->cend(); ++i)
{
if (i != m_value.object->cbegin())
{
o << (pretty_print ? ",\n" : ",");
}
o << string_t(new_indent, ' ') << "\"";
escape_string(o, i->first);
o << "\":" << (pretty_print ? " " : "");
i->second.dump(o, pretty_print, indent_step, new_indent);
}
// decrease indentation
if (pretty_print)
{
new_indent -= indent_step;
o << "\n";
}
o << string_t(new_indent, ' ') + "}";
return;
}
case (value_t::array):
{
if (m_value.array->empty())
{
o << "[]";
return;
}
o << "[";
// increase indentation
if (pretty_print)
{
new_indent += indent_step;
o << "\n";
}
for (auto i = m_value.array->cbegin(); i != m_value.array->cend(); ++i)
{
if (i != m_value.array->cbegin())
{
o << (pretty_print ? ",\n" : ",");
}
o << string_t(new_indent, ' ');
i->dump(o, pretty_print, indent_step, new_indent);
}
// decrease indentation
if (pretty_print)
{
new_indent -= indent_step;
o << "\n";
}
o << string_t(new_indent, ' ') << "]";
return;
}
case (value_t::string):
{
o << string_t("\"");
escape_string(o, *m_value.string);
o << "\"";
return;
}
case (value_t::boolean):
{
o << (m_value.boolean ? "true" : "false");
return;
}
case (value_t::number_integer):
{
o << m_value.number_integer;
return;
}
case (value_t::number_float):
{
// 15 digits of precision allows round-trip IEEE 754
// string->double->string; to be safe, we read this value from
// std::numeric_limits<number_float_t>::digits10
o << std::setprecision(std::numeric_limits<number_float_t>::digits10) << m_value.number_float;
return;
}
case (value_t::discarded):
{
o << "<discarded>";
return;
}
default:
{
o << "null";
return;
}
}
}
/// "equality" comparison for floating point numbers
template<typename T>
static bool approx(const T a, const T b)
{
return not (a > b or a < b);
}
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 = {};
private:
///////////////
// iterators //
///////////////
/// an iterator value
union internal_iterator
{
/// iterator for JSON objects
typename object_t::iterator object_iterator;
/// iterator for JSON arrays
typename array_t::iterator array_iterator;
/// generic iterator for all other value types
difference_type generic_iterator;
/// default constructor
internal_iterator() : generic_iterator(-1) {}
};
public:
/// a random access iterator for the basic_json class
class iterator : public std::iterator<std::random_access_iterator_tag, basic_json>
{
// allow basic_json class to access m_it
friend class basic_json;
public:
/// the type of the values when the iterator is dereferenced
using value_type = typename basic_json::value_type;
/// a type to represent differences between iterators
using difference_type = typename basic_json::difference_type;
/// defines a pointer to the type iterated over (value_type)
using pointer = typename basic_json::pointer;
/// defines a reference to the type iterated over (value_type)
using reference = typename basic_json::reference;
/// the category of the iterator
using iterator_category = std::bidirectional_iterator_tag;
/// default constructor
iterator() = default;
/// constructor for a given JSON instance
iterator(pointer object) noexcept : m_object(object)
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator = typename object_t::iterator();
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator = typename array_t::iterator();
break;
}
default:
{
m_it.generic_iterator = -1;
break;
}
}
}
/// copy constructor
iterator(const iterator& other) noexcept
: m_object(other.m_object), m_it(other.m_it)
{}
/// copy assignment
iterator& operator=(iterator other) noexcept (
std::is_nothrow_move_constructible<pointer>::value and
std::is_nothrow_move_assignable<pointer>::value and
std::is_nothrow_move_constructible<internal_iterator>::value and
std::is_nothrow_move_assignable<internal_iterator>::value
)
{
std::swap(m_object, other.m_object);
std::swap(m_it, other.m_it);
return *this;
}
private:
/// set the iterator to the first value
void set_begin() noexcept
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator = m_object->m_value.object->begin();
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator = m_object->m_value.array->begin();
break;
}
case (basic_json::value_t::null):
{
// set to end so begin()==end() is true: null is empty
m_it.generic_iterator = 1;
break;
}
default:
{
m_it.generic_iterator = 0;
break;
}
}
}
/// set the iterator past the last value
void set_end() noexcept
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator = m_object->m_value.object->end();
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator = m_object->m_value.array->end();
break;
}
default:
{
m_it.generic_iterator = 1;
break;
}
}
}
public:
/// return a reference to the value pointed to by the iterator
reference operator*()
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
return m_it.object_iterator->second;
}
case (basic_json::value_t::array):
{
return *m_it.array_iterator;
}
case (basic_json::value_t::null):
{
throw std::out_of_range("cannot get value");
}
default:
{
if (m_it.generic_iterator == 0)
{
return *m_object;
}
else
{
throw std::out_of_range("cannot get value");
}
}
}
}
/// dereference the iterator
pointer operator->()
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
return &(m_it.object_iterator->second);
}
case (basic_json::value_t::array):
{
return &*m_it.array_iterator;
}
case (basic_json::value_t::null):
{
throw std::out_of_range("cannot get value");
}
default:
{
if (m_it.generic_iterator == 0)
{
return m_object;
}
else
{
throw std::out_of_range("cannot get value");
}
}
}
}
/// post-increment (it++)
iterator operator++(int)
{
auto result = *this;
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator++;
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator++;
break;
}
default:
{
m_it.generic_iterator++;
break;
}
}
return result;
}
/// pre-increment (++it)
iterator& operator++()
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
++m_it.object_iterator;
break;
}
case (basic_json::value_t::array):
{
++m_it.array_iterator;
break;
}
default:
{
++m_it.generic_iterator;
break;
}
}
return *this;
}
/// post-decrement (it--)
iterator operator--(int)
{
auto result = *this;
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator--;
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator--;
break;
}
default:
{
m_it.generic_iterator--;
break;
}
}
return result;
}
/// pre-decrement (--it)
iterator& operator--()
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
--m_it.object_iterator;
break;
}
case (basic_json::value_t::array):
{
--m_it.array_iterator;
break;
}
default:
{
--m_it.generic_iterator;
break;
}
}
return *this;
}
/// comparison: equal
bool operator==(const iterator& other) const
{
// if objects are not the same, the comparison is undefined
if (m_object != other.m_object)
{
throw std::domain_error("cannot compare iterators of different containers");
}
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
return (m_it.object_iterator == other.m_it.object_iterator);
}
case (basic_json::value_t::array):
{
return (m_it.array_iterator == other.m_it.array_iterator);
}
default:
{
return (m_it.generic_iterator == other.m_it.generic_iterator);
}
}
}
/// comparison: not equal
bool operator!=(const iterator& other) const
{
return not operator==(other);
}
/// comparison: smaller
bool operator<(const iterator& other) const
{
// if objects are not the same, the comparison is undefined
if (m_object != other.m_object)
{
throw std::domain_error("cannot compare iterators of different containers");
}
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
throw std::domain_error("cannot use operator< for object iterators");
}
case (basic_json::value_t::array):
{
return (m_it.array_iterator < other.m_it.array_iterator);
}
default:
{
return (m_it.generic_iterator < other.m_it.generic_iterator);
}
}
}
/// comparison: less than or equal
bool operator<=(const iterator& other) const
{
return not other.operator < (*this);
}
/// comparison: greater than
bool operator>(const iterator& other) const
{
return not operator<=(other);
}
/// comparison: greater than or equal
bool operator>=(const iterator& other) const
{
return not operator<(other);
}
/// add to iterator
iterator& operator+=(difference_type i)
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
throw std::domain_error("cannot use operator+= for object iterators");
}
case (basic_json::value_t::array):
{
m_it.array_iterator += i;
break;
}
default:
{
m_it.generic_iterator += i;
break;
}
}
return *this;
}
/// subtract from iterator
iterator& operator-=(difference_type i)
{
return operator+=(-i);
}
/// add to iterator
iterator operator+(difference_type i)
{
auto result = *this;
result += i;
return result;
}
/// subtract from iterator
iterator operator-(difference_type i)
{
auto result = *this;
result -= i;
return result;
}
/// return difference
difference_type operator-(const iterator& other) const
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
throw std::domain_error("cannot use operator- for object iterators");
return 0;
}
case (basic_json::value_t::array):
{
return m_it.array_iterator - other.m_it.array_iterator;
}
default:
{
return m_it.generic_iterator - other.m_it.generic_iterator;
}
}
}
/// access to successor
reference operator[](difference_type n)
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
throw std::domain_error("cannot use operator[] for object iterators");
}
case (basic_json::value_t::array):
{
return *(m_it.array_iterator + n);
}
case (basic_json::value_t::null):
{
throw std::out_of_range("cannot get value");
}
default:
{
if (m_it.generic_iterator == -n)
{
return *m_object;
}
else
{
throw std::out_of_range("cannot get value");
}
}
}
}
/// return the key of an object iterator
typename object_t::key_type key() const
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
return m_it.object_iterator->first;
}
default:
{
throw std::domain_error("cannot use key() for non-object iterators");
}
}
}
/// return the key of an iterator
reference value()
{
return operator*();
}
private:
/// associated JSON instance
pointer m_object = nullptr;
/// the actual iterator of the associated instance
internal_iterator m_it = internal_iterator();
};
/// a const random access iterator for the basic_json class
class const_iterator : public std::iterator<std::random_access_iterator_tag, const basic_json>
{
// allow basic_json class to access m_it
friend class basic_json;
public:
/// the type of the values when the iterator is dereferenced
using value_type = typename basic_json::value_type;
/// a type to represent differences between iterators
using difference_type = typename basic_json::difference_type;
/// defines a pointer to the type iterated over (value_type)
using pointer = typename basic_json::const_pointer;
/// defines a reference to the type iterated over (value_type)
using reference = typename basic_json::const_reference;
/// the category of the iterator
using iterator_category = std::bidirectional_iterator_tag;
/// default constructor
const_iterator() = default;
/// constructor for a given JSON instance
const_iterator(pointer object) noexcept : m_object(object)
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator = typename object_t::iterator();
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator = typename array_t::iterator();
break;
}
default:
{
m_it.generic_iterator = -1;
break;
}
}
}
/// copy constructor given a nonconst iterator
const_iterator(const iterator& other) noexcept : m_object(other.m_object)
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator = other.m_it.object_iterator;
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator = other.m_it.array_iterator;
break;
}
default:
{
m_it.generic_iterator = other.m_it.generic_iterator;
break;
}
}
}
/// copy constructor
const_iterator(const const_iterator& other) noexcept
: m_object(other.m_object), m_it(other.m_it)
{}
/// copy assignment
const_iterator& operator=(const_iterator other) noexcept(
std::is_nothrow_move_constructible<pointer>::value and
std::is_nothrow_move_assignable<pointer>::value and
std::is_nothrow_move_constructible<internal_iterator>::value and
std::is_nothrow_move_assignable<internal_iterator>::value
)
{
std::swap(m_object, other.m_object);
std::swap(m_it, other.m_it);
return *this;
}
private:
/// set the iterator to the first value
void set_begin() noexcept
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator = m_object->m_value.object->begin();
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator = m_object->m_value.array->begin();
break;
}
case (basic_json::value_t::null):
{
// set to end so begin()==end() is true: null is empty
m_it.generic_iterator = 1;
break;
}
default:
{
m_it.generic_iterator = 0;
break;
}
}
}
/// set the iterator past the last value
void set_end() noexcept
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
m_it.object_iterator = m_object->m_value.object->end();
break;
}
case (basic_json::value_t::array):
{
m_it.array_iterator = m_object->m_value.array->end();
break;
}
default:
{
m_it.generic_iterator = 1;
break;
}
}
}
public:
/// return a reference to the value pointed to by the iterator
reference operator*() const
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
return m_it.object_iterator->second;
}
case (basic_json::value_t::array):
{
return *m_it.array_iterator;
}
case (basic_json::value_t::null):
{
throw std::out_of_range("cannot get value");
}
default:
{
if (m_it.generic_iterator == 0)
{
return *m_object;
}
else
{
throw std::out_of_range("cannot get value");
}
}
}
}
/// dereference the iterator
pointer operator->() const
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
return &(m_it.object_iterator->second);
}
case (basic_json::value_t::array):
{
return &*m_it.array_iterator;
}
default:
{
if (m_it.generic_iterator == 0)
{
return m_object;
}
else
{
throw std::out_of_range("cannot get value");
}
}
}
}
/// post-increment (it++)
const_iterator operator++(int)
{
auto result = *this;
++(*this);
return result;
}
/// pre-increment (++it)
const_iterator& operator++()
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
++m_it.object_iterator;
break;
}
case (basic_json::value_t::array):
{
++m_it.array_iterator;
break;
}
default:
{
++m_it.generic_iterator;
break;
}
}
return *this;
}
/// post-decrement (it--)
const_iterator operator--(int)
{
auto result = *this;
--(*this);
return result;
}
/// pre-decrement (--it)
const_iterator& operator--()
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
--m_it.object_iterator;
break;
}
case (basic_json::value_t::array):
{
--m_it.array_iterator;
break;
}
default:
{
--m_it.generic_iterator;
break;
}
}
return *this;
}
/// comparison: equal
bool operator==(const const_iterator& other) const
{
// if objects are not the same, the comparison is undefined
if (m_object != other.m_object)
{
throw std::domain_error("cannot compare iterators of different containers");
}
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
return (m_it.object_iterator == other.m_it.object_iterator);
}
case (basic_json::value_t::array):
{
return (m_it.array_iterator == other.m_it.array_iterator);
}
default:
{
return (m_it.generic_iterator == other.m_it.generic_iterator);
}
}
}
/// comparison: not equal
bool operator!=(const const_iterator& other) const
{
return not operator==(other);
}
/// comparison: smaller
bool operator<(const const_iterator& other) const
{
// if objects are not the same, the comparison is undefined
if (m_object != other.m_object)
{
throw std::domain_error("cannot compare iterators of different containers");
}
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
throw std::domain_error("cannot use operator< for object iterators");
}
case (basic_json::value_t::array):
{
return (m_it.array_iterator < other.m_it.array_iterator);
}
default:
{
return (m_it.generic_iterator < other.m_it.generic_iterator);
}
}
}
/// comparison: less than or equal
bool operator<=(const const_iterator& other) const
{
return not other.operator < (*this);
}
/// comparison: greater than
bool operator>(const const_iterator& other) const
{
return not operator<=(other);
}
/// comparison: greater than or equal
bool operator>=(const const_iterator& other) const
{
return not operator<(other);
}
/// add to iterator
const_iterator& operator+=(difference_type i)
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
throw std::domain_error("cannot use operator+= for object iterators");
}
case (basic_json::value_t::array):
{
m_it.array_iterator += i;
break;
}
default:
{
m_it.generic_iterator += i;
break;
}
}
return *this;
}
/// subtract from iterator
const_iterator& operator-=(difference_type i)
{
return operator+=(-i);
}
/// add to iterator
const_iterator operator+(difference_type i)
{
auto result = *this;
result += i;
return result;
}
/// subtract from iterator
const_iterator operator-(difference_type i)
{
auto result = *this;
result -= i;
return result;
}
/// return difference
difference_type operator-(const const_iterator& other) const
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
throw std::domain_error("cannot use operator- for object iterators");
}
case (basic_json::value_t::array):
{
return m_it.array_iterator - other.m_it.array_iterator;
}
default:
{
return m_it.generic_iterator - other.m_it.generic_iterator;
}
}
}
/// access to successor
reference operator[](difference_type n) const
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
throw std::domain_error("cannot use operator[] for object iterators");
}
case (basic_json::value_t::array):
{
return *(m_it.array_iterator + n);
}
case (basic_json::value_t::null):
{
throw std::out_of_range("cannot get value");
}
default:
{
if (m_it.generic_iterator == -n)
{
return *m_object;
}
else
{
throw std::out_of_range("cannot get value");
}
}
}
}
/// return the key of an object iterator
typename object_t::key_type key() const
{
switch (m_object->m_type)
{
case (basic_json::value_t::object):
{
return m_it.object_iterator->first;
}
default:
{
throw std::domain_error("cannot use key() for non-object iterators");
}
}
}
/// return the value of an iterator
reference value() const
{
return operator*();
}
private:
/// associated JSON instance
pointer m_object = nullptr;
/// the actual iterator of the associated instance
internal_iterator m_it = internal_iterator();
};
/// a reverse random access iterator for the basic_json class
class reverse_iterator : public std::reverse_iterator<typename basic_json::iterator>
{
public:
reverse_iterator(const typename
std::reverse_iterator<typename basic_json::iterator>::iterator_type&
it)
: std::reverse_iterator<basic_json::iterator>(it) {}
/// return the key of an object iterator
typename object_t::key_type key() const
{
return this->base().key();
}
/// return the value of an iterator
reference value() const
{
return this->base().operator * ();
}
};
/// a const reverse random access iterator for the basic_json class
class const_reverse_iterator : public std::reverse_iterator<typename basic_json::const_iterator>
{
public:
const_reverse_iterator(const typename
std::reverse_iterator<typename basic_json::const_iterator>::iterator_type& it)
: std::reverse_iterator<basic_json::const_iterator>(it) {}
/// return the key of an object iterator
typename object_t::key_type key() const
{
return this->base().key();
}
/// return the value of an iterator
const_reference value() const
{
return this->base().operator * ();
}
};
private:
//////////////////////
// lexer and parser //
//////////////////////
/*!
@brief lexical analysis
This class organizes the lexical analysis during JSON deserialization. The
core of it is a scanner generated by re2c <http://re2c.org> that processes
a buffer and recognizes tokens according to RFC 7159 and ECMA-404.
*/
class lexer
{
public:
/// token types for the parser
enum class token_type
{
uninitialized, ///< indicating the scanner is uninitialized
literal_true, ///< the "true" literal
literal_false, ///< the "false" literal
literal_null, ///< the "null" literal
value_string, ///< a string - use get_string() for actual value
value_number, ///< a number - use get_number() for actual value
begin_array, ///< the character for array begin "["
begin_object, ///< the character for object begin "{"
end_array, ///< the character for array end "]"
end_object, ///< the character for object end "}"
name_separator, ///< the name separator ":"
value_separator, ///< the value separator ","
parse_error, ///< indicating a parse error
end_of_input ///< indicating the end of the input buffer
};
/// the char type to use in the lexer
using lexer_char_t = unsigned char;
/// constructor with a given buffer
lexer(const string_t& s) noexcept
: m_stream(nullptr), m_buffer(s)
{
m_content = reinterpret_cast<const lexer_char_t*>(s.c_str());
m_start = m_cursor = m_content;
m_limit = m_content + s.size();
}
lexer(std::istream* s) noexcept
: m_stream(s), m_buffer()
{
getline(*m_stream, m_buffer);
m_content = reinterpret_cast<const lexer_char_t*>(m_buffer.c_str());
m_start = m_cursor = m_content;
m_limit = m_content + m_buffer.size();
}
/// default constructor
lexer() = default;
// switch of unwanted functions
lexer(const lexer&) = delete;
lexer operator=(const lexer&) = delete;
/*!
@brief create a string from a Unicode code point
@param[in] codepoint1 the code point (can be high surrogate)
@param[in] codepoint2 the code point (can be low surrogate or 0)
@return string representation of the code point
@throw std::out_of_range if code point is >0x10ffff
@throw std::invalid_argument if the low surrogate is invalid
@see <http://en.wikipedia.org/wiki/UTF-8#Sample_code>
*/
static string_t to_unicode(const std::size_t codepoint1,
const std::size_t codepoint2 = 0)
{
string_t result;
// calculate the codepoint from the given code points
std::size_t codepoint = codepoint1;
// check if codepoint1 is a high surrogate
if (codepoint1 >= 0xD800 and codepoint1 <= 0xDBFF)
{
// check if codepoint2 is a low surrogate
if (codepoint2 >= 0xDC00 and codepoint2 <= 0xDFFF)
{
codepoint =
// high surrogate occupies the most significant 22 bits
(codepoint1 << 10)
// low surrogate occupies the least significant 15 bits
+ codepoint2
// there is still the 0xD800, 0xDC00 and 0x10000 noise
// in the result so we have to substract with:
// (0xD800 << 10) + DC00 - 0x10000 = 0x35FDC00
- 0x35FDC00;
}
else
{
throw std::invalid_argument("missing or wrong low surrogate");
}
}
if (codepoint < 0x80)
{
// 1-byte characters: 0xxxxxxx (ASCII)
result.append(1, static_cast<typename string_t::value_type>(codepoint));
}
else if (codepoint <= 0x7ff)
{
// 2-byte characters: 110xxxxx 10xxxxxx
result.append(1, static_cast<typename string_t::value_type>(0xC0 | ((codepoint >> 6) & 0x1F)));
result.append(1, static_cast<typename string_t::value_type>(0x80 | (codepoint & 0x3F)));
}
else if (codepoint <= 0xffff)
{
// 3-byte characters: 1110xxxx 10xxxxxx 10xxxxxx
result.append(1, static_cast<typename string_t::value_type>(0xE0 | ((codepoint >> 12) & 0x0F)));
result.append(1, static_cast<typename string_t::value_type>(0x80 | ((codepoint >> 6) & 0x3F)));
result.append(1, static_cast<typename string_t::value_type>(0x80 | (codepoint & 0x3F)));
}
else if (codepoint <= 0x10ffff)
{
// 4-byte characters: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
result.append(1, static_cast<typename string_t::value_type>(0xF0 | ((codepoint >> 18) & 0x07)));
result.append(1, static_cast<typename string_t::value_type>(0x80 | ((codepoint >> 12) & 0x3F)));
result.append(1, static_cast<typename string_t::value_type>(0x80 | ((codepoint >> 6) & 0x3F)));
result.append(1, static_cast<typename string_t::value_type>(0x80 | (codepoint & 0x3F)));
}
else
{
throw std::out_of_range("code points above 0x10FFFF are invalid");
}
return result;
}
/// return name of values of type token_type
static std::string token_type_name(token_type t) noexcept
{
switch (t)
{
case (token_type::uninitialized):
return "<uninitialized>";
case (token_type::literal_true):
return "true literal";
case (token_type::literal_false):
return "false literal";
case (token_type::literal_null):
return "null literal";
case (token_type::value_string):
return "string literal";
case (token_type::value_number):
return "number literal";
case (token_type::begin_array):
return "[";
case (token_type::begin_object):
return "{";
case (token_type::end_array):
return "]";
case (token_type::end_object):
return "}";
case (token_type::name_separator):
return ":";
case (token_type::value_separator):
return ",";
case (token_type::end_of_input):
return "<end of input>";
default:
return "<parse error>";
}
}
/*!
This function implements a scanner for JSON. It is specified using
regular expressions that try to follow RFC 7159 and ECMA-404 as close
as possible. These regular expressions are then translated into a
deterministic finite automaton (DFA) by the tool re2c
<http://re2c.org>. As a result, the translated code for this function
consists of a large block of code with goto jumps.
@return the class of the next token read from the buffer
*/
token_type scan() noexcept
{
// pointer for backtracking information
m_marker = nullptr;
// remember the begin of the token
m_start = m_cursor;
{
lexer_char_t yych;
unsigned int yyaccept = 0;
static const unsigned char yybm[] =
{
0, 0, 0, 0, 0, 0, 0, 0,
0, 32, 32, 0, 0, 32, 0, 0,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
96, 64, 0, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
192, 192, 192, 192, 192, 192, 192, 192,
192, 192, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 0, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64,
};
if ((m_limit - m_cursor) < 5)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
if (yych <= '9')
{
if (yych <= ' ')
{
if (yych <= '\n')
{
if (yych <= 0x00)
{
goto basic_json_parser_27;
}
if (yych <= 0x08)
{
goto basic_json_parser_29;
}
if (yych >= '\n')
{
goto basic_json_parser_4;
}
}
else
{
if (yych == '\r')
{
goto basic_json_parser_2;
}
if (yych <= 0x1F)
{
goto basic_json_parser_29;
}
}
}
else
{
if (yych <= ',')
{
if (yych == '"')
{
goto basic_json_parser_26;
}
if (yych <= '+')
{
goto basic_json_parser_29;
}
goto basic_json_parser_14;
}
else
{
if (yych <= '-')
{
goto basic_json_parser_22;
}
if (yych <= '/')
{
goto basic_json_parser_29;
}
if (yych <= '0')
{
goto basic_json_parser_23;
}
goto basic_json_parser_25;
}
}
}
else
{
if (yych <= 'm')
{
if (yych <= '\\')
{
if (yych <= ':')
{
goto basic_json_parser_16;
}
if (yych == '[')
{
goto basic_json_parser_6;
}
goto basic_json_parser_29;
}
else
{
if (yych <= ']')
{
goto basic_json_parser_8;
}
if (yych == 'f')
{
goto basic_json_parser_21;
}
goto basic_json_parser_29;
}
}
else
{
if (yych <= 'z')
{
if (yych <= 'n')
{
goto basic_json_parser_18;
}
if (yych == 't')
{
goto basic_json_parser_20;
}
goto basic_json_parser_29;
}
else
{
if (yych <= '{')
{
goto basic_json_parser_10;
}
if (yych == '}')
{
goto basic_json_parser_12;
}
goto basic_json_parser_29;
}
}
}
basic_json_parser_2:
++m_cursor;
yych = *m_cursor;
goto basic_json_parser_5;
basic_json_parser_3:
{
return scan();
}
basic_json_parser_4:
++m_cursor;
if (m_limit <= m_cursor)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
basic_json_parser_5:
if (yybm[0 + yych] & 32)
{
goto basic_json_parser_4;
}
goto basic_json_parser_3;
basic_json_parser_6:
++m_cursor;
{
return token_type::begin_array;
}
basic_json_parser_8:
++m_cursor;
{
return token_type::end_array;
}
basic_json_parser_10:
++m_cursor;
{
return token_type::begin_object;
}
basic_json_parser_12:
++m_cursor;
{
return token_type::end_object;
}
basic_json_parser_14:
++m_cursor;
{
return token_type::value_separator;
}
basic_json_parser_16:
++m_cursor;
{
return token_type::name_separator;
}
basic_json_parser_18:
yyaccept = 0;
yych = *(m_marker = ++m_cursor);
if (yych == 'u')
{
goto basic_json_parser_59;
}
basic_json_parser_19:
{
return token_type::parse_error;
}
basic_json_parser_20:
yyaccept = 0;
yych = *(m_marker = ++m_cursor);
if (yych == 'r')
{
goto basic_json_parser_55;
}
goto basic_json_parser_19;
basic_json_parser_21:
yyaccept = 0;
yych = *(m_marker = ++m_cursor);
if (yych == 'a')
{
goto basic_json_parser_50;
}
goto basic_json_parser_19;
basic_json_parser_22:
yych = *++m_cursor;
if (yych <= '/')
{
goto basic_json_parser_19;
}
if (yych <= '0')
{
goto basic_json_parser_49;
}
if (yych <= '9')
{
goto basic_json_parser_40;
}
goto basic_json_parser_19;
basic_json_parser_23:
yyaccept = 1;
yych = *(m_marker = ++m_cursor);
if (yych <= 'D')
{
if (yych == '.')
{
goto basic_json_parser_42;
}
}
else
{
if (yych <= 'E')
{
goto basic_json_parser_43;
}
if (yych == 'e')
{
goto basic_json_parser_43;
}
}
basic_json_parser_24:
{
return token_type::value_number;
}
basic_json_parser_25:
yyaccept = 1;
yych = *(m_marker = ++m_cursor);
goto basic_json_parser_41;
basic_json_parser_26:
yyaccept = 0;
yych = *(m_marker = ++m_cursor);
if (yych <= 0x0F)
{
goto basic_json_parser_19;
}
goto basic_json_parser_31;
basic_json_parser_27:
++m_cursor;
{
return token_type::end_of_input;
}
basic_json_parser_29:
yych = *++m_cursor;
goto basic_json_parser_19;
basic_json_parser_30:
++m_cursor;
if (m_limit <= m_cursor)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
basic_json_parser_31:
if (yybm[0 + yych] & 64)
{
goto basic_json_parser_30;
}
if (yych <= 0x0F)
{
goto basic_json_parser_32;
}
if (yych <= '"')
{
goto basic_json_parser_34;
}
goto basic_json_parser_33;
basic_json_parser_32:
m_cursor = m_marker;
if (yyaccept == 0)
{
goto basic_json_parser_19;
}
else
{
goto basic_json_parser_24;
}
basic_json_parser_33:
++m_cursor;
if (m_limit <= m_cursor)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
if (yych <= 'e')
{
if (yych <= '/')
{
if (yych == '"')
{
goto basic_json_parser_30;
}
if (yych <= '.')
{
goto basic_json_parser_32;
}
goto basic_json_parser_30;
}
else
{
if (yych <= '\\')
{
if (yych <= '[')
{
goto basic_json_parser_32;
}
goto basic_json_parser_30;
}
else
{
if (yych == 'b')
{
goto basic_json_parser_30;
}
goto basic_json_parser_32;
}
}
}
else
{
if (yych <= 'q')
{
if (yych <= 'f')
{
goto basic_json_parser_30;
}
if (yych == 'n')
{
goto basic_json_parser_30;
}
goto basic_json_parser_32;
}
else
{
if (yych <= 's')
{
if (yych <= 'r')
{
goto basic_json_parser_30;
}
goto basic_json_parser_32;
}
else
{
if (yych <= 't')
{
goto basic_json_parser_30;
}
if (yych <= 'u')
{
goto basic_json_parser_36;
}
goto basic_json_parser_32;
}
}
}
basic_json_parser_34:
++m_cursor;
{
return token_type::value_string;
}
basic_json_parser_36:
++m_cursor;
if (m_limit <= m_cursor)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
if (yych <= '@')
{
if (yych <= '/')
{
goto basic_json_parser_32;
}
if (yych >= ':')
{
goto basic_json_parser_32;
}
}
else
{
if (yych <= 'F')
{
goto basic_json_parser_37;
}
if (yych <= '`')
{
goto basic_json_parser_32;
}
if (yych >= 'g')
{
goto basic_json_parser_32;
}
}
basic_json_parser_37:
++m_cursor;
if (m_limit <= m_cursor)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
if (yych <= '@')
{
if (yych <= '/')
{
goto basic_json_parser_32;
}
if (yych >= ':')
{
goto basic_json_parser_32;
}
}
else
{
if (yych <= 'F')
{
goto basic_json_parser_38;
}
if (yych <= '`')
{
goto basic_json_parser_32;
}
if (yych >= 'g')
{
goto basic_json_parser_32;
}
}
basic_json_parser_38:
++m_cursor;
if (m_limit <= m_cursor)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
if (yych <= '@')
{
if (yych <= '/')
{
goto basic_json_parser_32;
}
if (yych >= ':')
{
goto basic_json_parser_32;
}
}
else
{
if (yych <= 'F')
{
goto basic_json_parser_39;
}
if (yych <= '`')
{
goto basic_json_parser_32;
}
if (yych >= 'g')
{
goto basic_json_parser_32;
}
}
basic_json_parser_39:
++m_cursor;
if (m_limit <= m_cursor)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
if (yych <= '@')
{
if (yych <= '/')
{
goto basic_json_parser_32;
}
if (yych <= '9')
{
goto basic_json_parser_30;
}
goto basic_json_parser_32;
}
else
{
if (yych <= 'F')
{
goto basic_json_parser_30;
}
if (yych <= '`')
{
goto basic_json_parser_32;
}
if (yych <= 'f')
{
goto basic_json_parser_30;
}
goto basic_json_parser_32;
}
basic_json_parser_40:
yyaccept = 1;
m_marker = ++m_cursor;
if ((m_limit - m_cursor) < 3)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
basic_json_parser_41:
if (yybm[0 + yych] & 128)
{
goto basic_json_parser_40;
}
if (yych <= 'D')
{
if (yych != '.')
{
goto basic_json_parser_24;
}
}
else
{
if (yych <= 'E')
{
goto basic_json_parser_43;
}
if (yych == 'e')
{
goto basic_json_parser_43;
}
goto basic_json_parser_24;
}
basic_json_parser_42:
yych = *++m_cursor;
if (yych <= '/')
{
goto basic_json_parser_32;
}
if (yych <= '9')
{
goto basic_json_parser_47;
}
goto basic_json_parser_32;
basic_json_parser_43:
yych = *++m_cursor;
if (yych <= ',')
{
if (yych != '+')
{
goto basic_json_parser_32;
}
}
else
{
if (yych <= '-')
{
goto basic_json_parser_44;
}
if (yych <= '/')
{
goto basic_json_parser_32;
}
if (yych <= '9')
{
goto basic_json_parser_45;
}
goto basic_json_parser_32;
}
basic_json_parser_44:
yych = *++m_cursor;
if (yych <= '/')
{
goto basic_json_parser_32;
}
if (yych >= ':')
{
goto basic_json_parser_32;
}
basic_json_parser_45:
++m_cursor;
if (m_limit <= m_cursor)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
if (yych <= '/')
{
goto basic_json_parser_24;
}
if (yych <= '9')
{
goto basic_json_parser_45;
}
goto basic_json_parser_24;
basic_json_parser_47:
yyaccept = 1;
m_marker = ++m_cursor;
if ((m_limit - m_cursor) < 3)
{
yyfill(); // LCOV_EXCL_LINE;
}
yych = *m_cursor;
if (yych <= 'D')
{
if (yych <= '/')
{
goto basic_json_parser_24;
}
if (yych <= '9')
{
goto basic_json_parser_47;
}
goto basic_json_parser_24;
}
else
{
if (yych <= 'E')
{
goto basic_json_parser_43;
}
if (yych == 'e')
{
goto basic_json_parser_43;
}
goto basic_json_parser_24;
}
basic_json_parser_49:
yyaccept = 1;
yych = *(m_marker = ++m_cursor);
if (yych <= 'D')
{
if (yych == '.')
{
goto basic_json_parser_42;
}
goto basic_json_parser_24;
}
else
{
if (yych <= 'E')
{
goto basic_json_parser_43;
}
if (yych == 'e')
{
goto basic_json_parser_43;
}
goto basic_json_parser_24;
}
basic_json_parser_50:
yych = *++m_cursor;
if (yych != 'l')
{
goto basic_json_parser_32;
}
yych = *++m_cursor;
if (yych != 's')
{
goto basic_json_parser_32;
}
yych = *++m_cursor;
if (yych != 'e')
{
goto basic_json_parser_32;
}
++m_cursor;
{
return token_type::literal_false;
}
basic_json_parser_55:
yych = *++m_cursor;
if (yych != 'u')
{
goto basic_json_parser_32;
}
yych = *++m_cursor;
if (yych != 'e')
{
goto basic_json_parser_32;
}
++m_cursor;
{
return token_type::literal_true;
}
basic_json_parser_59:
yych = *++m_cursor;
if (yych != 'l')
{
goto basic_json_parser_32;
}
yych = *++m_cursor;
if (yych != 'l')
{
goto basic_json_parser_32;
}
++m_cursor;
{
return token_type::literal_null;
}
}
}
/// append data from the stream to the internal buffer
void yyfill() noexcept
{
if (not m_stream or not * m_stream)
{
return;
}
const ssize_t offset_start = m_start - m_content;
const ssize_t offset_marker = m_marker - m_start;
const ssize_t offset_cursor = m_cursor - m_start;
m_buffer.erase(0, static_cast<size_t>(offset_start));
std::string line;
std::getline(*m_stream, line);
m_buffer += "\n" + line; // add line with newline symbol
m_content = reinterpret_cast<const lexer_char_t*>(m_buffer.c_str());
m_start = m_content;
m_marker = m_start + offset_marker;
m_cursor = m_start + offset_cursor;
m_limit = m_start + m_buffer.size() - 1;
}
/// return string representation of last read token
string_t get_token() const noexcept
{
return string_t(reinterpret_cast<typename string_t::const_pointer>(m_start),
static_cast<size_t>(m_cursor - m_start));
}
/*!
@brief return string value for string tokens
The function iterates the characters between the opening and closing
quotes of the string value. The complete string is the range
[m_start,m_cursor). Consequently, we iterate from m_start+1 to
m_cursor-1.
We differentiate two cases:
1. Escaped characters. In this case, a new character is constructed
according to the nature of the escape. Some escapes create new
characters (e.g., @c "\\n" is replaced by @c "\n"), some are copied
as is (e.g., @c "\\\\"). Furthermore, Unicode escapes of the shape
@c "\\uxxxx" need special care. In this case, to_unicode takes care
of the construction of the values.
2. Unescaped characters are copied as is.
@return string value of current token without opening and closing quotes
@throw std::out_of_range if to_unicode fails
*/
string_t get_string() const
{
string_t result;
result.reserve(static_cast<size_t>(m_cursor - m_start - 2));
// iterate the result between the quotes
for (const lexer_char_t* i = m_start + 1; i < m_cursor - 1; ++i)
{
// process escaped characters
if (*i == '\\')
{
// read next character
++i;
switch (*i)
{
// the default escapes
case 't':
{
result += "\t";
break;
}
case 'b':
{
result += "\b";
break;
}
case 'f':
{
result += "\f";
break;
}
case 'n':
{
result += "\n";
break;
}
case 'r':
{
result += "\r";
break;
}
case '\\':
{
result += "\\";
break;
}
case '/':
{
result += "/";
break;
}
case '"':
{
result += "\"";
break;
}
// unicode
case 'u':
{
// get code xxxx from uxxxx
auto codepoint = std::strtoul(std::string(reinterpret_cast<typename string_t::const_pointer>(i + 1),
4).c_str(), nullptr, 16);
// check if codepoint is a high surrogate
if (codepoint >= 0xD800 and codepoint <= 0xDBFF)
{
// make sure there is a subsequent unicode
if ((i + 6 >= m_limit) or * (i + 5) != '\\' or * (i + 6) != 'u')
{
throw std::invalid_argument("missing low surrogate");
}
// get code yyyy from uxxxx\uyyyy
auto codepoint2 = std::strtoul(std::string(reinterpret_cast<typename string_t::const_pointer>
(i + 7), 4).c_str(), nullptr, 16);
result += to_unicode(codepoint, codepoint2);
// skip the next 11 characters (xxxx\uyyyy)
i += 11;
}
else
{
// add unicode character(s)
result += to_unicode(codepoint);
// skip the next four characters (xxxx)
i += 4;
}
break;
}
}
}
else
{
// all other characters are just copied to the end of the
// string
result.append(1, static_cast<typename string_t::value_type>(*i));
}
}
return result;
}
/*!
@brief return number value for number tokens
This function translates the last token into a floating point number.
The pointer m_begin points to the beginning of the parsed number. We
pass this pointer to std::strtod which sets endptr to the first
character past the converted number. If this pointer is not the same as
m_cursor, then either more or less characters have been used during the
comparison. This can happen for inputs like "01" which will be treated
like number 0 followed by number 1.
@return the result of the number conversion or NAN if the conversion
read past the current token. The latter case needs to be treated by the
caller function.
@throw std::range_error if passed value is out of range
*/
long double get_number() const
{
// conversion
typename string_t::value_type* endptr;
const auto float_val = std::strtold(reinterpret_cast<typename string_t::const_pointer>(m_start),
&endptr);
// return float_val if the whole number was translated and NAN
// otherwise
return (reinterpret_cast<lexer_char_t*>(endptr) == m_cursor) ? float_val : NAN;
}
private:
/// optional input stream
std::istream* m_stream;
/// the buffer
string_t m_buffer;
/// the buffer pointer
const lexer_char_t* m_content = nullptr;
/// pointer to the beginning of the current symbol
const lexer_char_t* m_start = nullptr;
/// pointer for backtracking information
const lexer_char_t* m_marker = nullptr;
/// pointer to the current symbol
const lexer_char_t* m_cursor = nullptr;
/// pointer to the end of the buffer
const lexer_char_t* m_limit = nullptr;
};
/*!
@brief syntax analysis
*/
class parser
{
public:
/// constructor for strings
parser(const string_t& s, parser_callback_t cb = nullptr) : callback(cb), m_lexer(s)
{
// read first token
get_token();
}
/// a parser reading from an input stream
parser(std::istream& _is, parser_callback_t cb = nullptr) : callback(cb),
m_lexer(&_is)
{
// read first token
get_token();
}
/// public parser interface
basic_json parse()
{
basic_json result = parse_internal(true);
expect(lexer::token_type::end_of_input);
// return parser result and replace it with null in case the
// top-level value was discarded by the callback function
return result.is_discarded() ? basic_json() : result;
}
private:
/// the actual parser
basic_json parse_internal(bool keep)
{
auto result = basic_json(value_t::discarded);
switch (last_token)
{
case (lexer::token_type::begin_object):
{
if (keep and (not callback or (keep = callback(depth++, parse_event_t::object_start, result))))
{
// explicitly set result to object to cope with {}
result.m_type = value_t::object;
result.m_value = json_value(value_t::object);
}
// read next token
get_token();
// closing } -> we are done
if (last_token == lexer::token_type::end_object)
{
get_token();
if (keep and callback and not callback(--depth, parse_event_t::object_end, result))
{
result = basic_json(value_t::discarded);
}
return result;
}
// no comma is expected here
unexpect(lexer::token_type::value_separator);
// otherwise: parse key-value pairs
do
{
// ugly, but could be fixed with loop reorganization
if (last_token == lexer::token_type::value_separator)
{
get_token();
}
// store key
expect(lexer::token_type::value_string);
const auto key = m_lexer.get_string();
bool keep_tag = false;
if (keep)
{
if (callback)
{
basic_json k(key);
keep_tag = callback(depth, parse_event_t::key, k);
}
else
{
keep_tag = true;
}
}
// parse separator (:)
get_token();
expect(lexer::token_type::name_separator);
// parse and add value
get_token();
auto value = parse_internal(keep);
if (keep and keep_tag and not value.is_discarded())
{
result[key] = std::move(value);
}
}
while (last_token == lexer::token_type::value_separator);
// closing }
expect(lexer::token_type::end_object);
get_token();
if (keep and callback and not callback(--depth, parse_event_t::object_end, result))
{
result = basic_json(value_t::discarded);
}
return result;
}
case (lexer::token_type::begin_array):
{
if (keep and (not callback or (keep = callback(depth++, parse_event_t::array_start, result))))
{
// explicitly set result to object to cope with []
result.m_type = value_t::array;
result.m_value = json_value(value_t::array);
}
// read next token
get_token();
// closing ] -> we are done
if (last_token == lexer::token_type::end_array)
{
get_token();
if (callback and not callback(--depth, parse_event_t::array_end, result))
{
result = basic_json(value_t::discarded);
}
return result;
}
// no comma is expected here
unexpect(lexer::token_type::value_separator);
// otherwise: parse values
do
{
// ugly, but could be fixed with loop reorganization
if (last_token == lexer::token_type::value_separator)
{
get_token();
}
// parse value
auto value = parse_internal(keep);
if (keep and not value.is_discarded())
{
result.push_back(std::move(value));
}
}
while (last_token == lexer::token_type::value_separator);
// closing ]
expect(lexer::token_type::end_array);
get_token();
if (keep and callback and not callback(--depth, parse_event_t::array_end, result))
{
result = basic_json(value_t::discarded);
}
return result;
}
case (lexer::token_type::literal_null):
{
get_token();
result.m_type = value_t::null;
break;
}
case (lexer::token_type::value_string):
{
const auto s = m_lexer.get_string();
get_token();
result = basic_json(s);
break;
}
case (lexer::token_type::literal_true):
{
get_token();
result.m_type = value_t::boolean;
result.m_value = true;
break;
}
case (lexer::token_type::literal_false):
{
get_token();
result.m_type = value_t::boolean;
result.m_value = false;
break;
}
case (lexer::token_type::value_number):
{
auto float_val = m_lexer.get_number();
// NAN is returned if token could not be translated
// completely
if (std::isnan(float_val))
{
throw std::invalid_argument(std::string("parse error - ") +
m_lexer.get_token() + " is not a number");
}
get_token();
// check if conversion loses precision
const auto int_val = static_cast<number_integer_t>(float_val);
if (approx(float_val, static_cast<long double>(int_val)))
{
// we basic_json not lose precision -> return int
result.m_type = value_t::number_integer;
result.m_value = int_val;
}
else
{
// we would lose precision -> returnfloat
result.m_type = value_t::number_float;
result.m_value = static_cast<number_float_t>(float_val);
}
break;
}
default:
{
// the last token was unexpected
unexpect(last_token);
}
}
if (keep and callback and not callback(depth, parse_event_t::value, result))
{
result = basic_json(value_t::discarded);
}
return result;
}
/// get next token from lexer
typename lexer::token_type get_token()
{
last_token = m_lexer.scan();
return last_token;
}
void expect(typename lexer::token_type t) const
{
if (t != last_token)
{
std::string error_msg = "parse error - unexpected \'";
error_msg += m_lexer.get_token();
error_msg += "\' (" + lexer::token_type_name(last_token);
error_msg += "); expected " + lexer::token_type_name(t);
throw std::invalid_argument(error_msg);
}
}
void unexpect(typename lexer::token_type t) const
{
if (t == last_token)
{
std::string error_msg = "parse error - unexpected \'";
error_msg += m_lexer.get_token();
error_msg += "\' (";
error_msg += lexer::token_type_name(last_token) + ")";
throw std::invalid_argument(error_msg);
}
}
private:
/// levels of recursion
int depth = 0;
/// callback function
parser_callback_t callback;
/// the type of the last read token
typename lexer::token_type last_token = lexer::token_type::uninitialized;
/// the lexer
lexer m_lexer;
};
};
/////////////
// presets //
/////////////
/*!
@brief default JSON class
This type is the default specialization of the @ref basic_json class which uses
the standard template types.
*/
using json = basic_json<>;
}
/////////////////////////
// nonmember functions //
/////////////////////////
// specialization of std::swap, and std::hash
namespace std
{
/*!
@brief exchanges the values of two JSON objects
@ingroup container
*/
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>
{
/// return a hash value for a JSON object
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());
}
};
}
/*!
@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 \p "_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
@return a JSON object
*/
inline nlohmann::json operator "" _json(const char* s, std::size_t)
{
return nlohmann::json::parse(reinterpret_cast<nlohmann::json::string_t::value_type*>
(const_cast<char*>(s)));
}
#endif