nlohmann::detail Namespace Reference

detail namespace with internal helper functions More...

Namespaces
	dtoa_impl
	implements the Grisu2 algorithm for binary to decimal floating-point conversion.

Classes
class	binary_reader
	deserialization of CBOR, MessagePack, and UBJSON values More...
class	binary_writer
	serialization to CBOR and MessagePack values More...
class	exception
	general exception of the basic_json class More...
class	file_input_adapter
class	input_stream_adapter
struct	internal_iterator
	an iterator value More...
class	invalid_iterator
	exception indicating errors with iterators More...
class	iter_impl
	a template for a bidirectional iterator for the basic_json class This class implements a both iterators (iterator and const_iterator) for the basic_json class. More...
class	iteration_proxy
	proxy class for the items() function More...
class	json_reverse_iterator
	a template for a reverse iterator class More...
class	json_sax_dom_parser
	SAX implementation to create a JSON value from SAX events. More...
class	lexer
	lexical analysis More...
class	other_error
	exception indicating other library errors More...
class	out_of_range
	exception indicating access out of the defined range More...
struct	output_adapter_protocol
	abstract output adapter interface More...
class	output_stream_adapter
	output adapter for output streams More...
class	output_string_adapter
	output adapter for basic_string More...
class	output_vector_adapter
	output adapter for byte vectors More...
class	parse_error
	exception indicating a parse error More...
class	parser
	syntax analysis More...
struct	position_t
	struct to capture the start position of the current token More...
class	type_error
	exception indicating executing a member function with a wrong type More...

Typedefs
template<typename CharType >
using	output_adapter_t = std::shared_ptr< output_adapter_protocol< CharType > >
	a type to simplify interfaces

Enumerations
enum	value_t : std::uint8_t {   value_t::null, value_t::object, value_t::array, value_t::string,   value_t::boolean, value_t::number_integer, value_t::number_unsigned, value_t::number_float,   value_t::binary, value_t::discarded }
	the JSON type enumeration More...
enum	input_format_t
	the supported input formats
enum	cbor_tag_handler_t { cbor_tag_handler_t::error, cbor_tag_handler_t::ignore }
	how to treat CBOR tags More...
enum	parse_event_t : uint8_t {   parse_event_t::object_start, parse_event_t::object_end, parse_event_t::array_start, parse_event_t::array_end,   parse_event_t::key, parse_event_t::value }
enum	error_handler_t { error_handler_t::strict, error_handler_t::replace, error_handler_t::ignore }
	how to treat decoding errors More...

Functions
bool	operator< (const value_t lhs, const value_t rhs) noexcept
	comparison operator for JSON types More...
template<typename BasicJsonType >
std::size_t	hash (const BasicJsonType &j)
	hash a JSON value More...
template<typename FloatType >
JSON_HEDLEY_RETURNS_NON_NULL char *	to_chars (char *first, const char *last, FloatType value)
	generates a decimal representation of the floating-point number value in [first, last). More...

Detailed Description

detail namespace with internal helper functions

This namespace collects functions that should not be exposed, implementations of some basic_json methods, and meta-programming helpers.

Since

version 2.1.0

Enumeration Type Documentation

value_t

enum nlohmann::detail::value_t : std::uint8_t

strong

the JSON type enumeration

This enumeration collects the different JSON types. It is internally used to distinguish the stored values, and the functions basic_json::is_null(), basic_json::is_object(), basic_json::is_array(), basic_json::is_string(), basic_json::is_boolean(), basic_json::is_number() (with basic_json::is_number_integer(), basic_json::is_number_unsigned(), and basic_json::is_number_float()), basic_json::is_discarded(), basic_json::is_primitive(), and basic_json::is_structured() rely on it.

Note

There are three enumeration entries (number_integer, number_unsigned, and number_float), because the library distinguishes these three types for numbers: basic_json::number_unsigned_t is used for unsigned integers, basic_json::number_integer_t is used for signed integers, and basic_json::number_float_t is used for floating-point numbers or to approximate integers which do not fit in the limits of their respective type.

See also

basic_json::basic_json(const value_t value_type) – create a JSON value with the default value for a given type

Since

version 1.0.0

Enumerator
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 (signed integer)
number_unsigned	number value (unsigned integer)
number_float	number value (floating-point)
binary	binary array (ordered collection of bytes)
discarded	discarded by the parser callback function

cbor_tag_handler_t

enum nlohmann::detail::cbor_tag_handler_t

strong

how to treat CBOR tags

Enumerator
error	throw a parse_error exception in case of a tag
ignore	ignore tags

parse_event_t

enum nlohmann::detail::parse_event_t : uint8_t

strong

Enumerator
object_start	the parser read { and started to process a JSON object
object_end	the parser read } and finished processing a JSON object
array_start	the parser read [ and started to process a JSON array
array_end	the parser read ] and finished processing a JSON array
key	the parser read a key of a value in an object
value	the parser finished reading a JSON value

error_handler_t

enum nlohmann::detail::error_handler_t

strong

how to treat decoding errors

Enumerator
strict	throw a type_error exception in case of invalid UTF-8
replace	replace invalid UTF-8 sequences with U+FFFD
ignore	ignore invalid UTF-8 sequences

Function Documentation

operator<()

bool nlohmann::detail::operator< ( const value_t  lhs, const value_t  rhs  )

inlinenoexcept

comparison operator for JSON types

Returns an ordering that is similar to Python:

• order: null < boolean < number < object < array < string < binary
• furthermore, each type is not smaller than itself
• discarded values are not comparable
• binary is represented as a b"" string in python and directly comparable to a string; however, making a binary array directly comparable with a string would be surprising behavior in a JSON file.

Since

version 1.0.0

hash()

template<typename BasicJsonType >

std::size_t nlohmann::detail::hash

(

const BasicJsonType &

j

)

hash a JSON value

The hash function tries to rely on std::hash where possible. Furthermore, the type of the JSON value is taken into account to have different hash values for null, 0, 0U, and false, etc.

Template Parameters

BasicJsonType

basic_json specialization

Parameters

j	JSON value to hash

Returns

hash value of j

to_chars()

template<typename FloatType >

JSON_HEDLEY_RETURNS_NON_NULL char* nlohmann::detail::to_chars	(	char *	first,
		const char *	last,
		FloatType	value
	)

generates a decimal representation of the floating-point number value in [first, last).

The format of the resulting decimal representation is similar to printf's g format. Returns an iterator pointing past-the-end of the decimal representation.

Note

The input number must be finite, i.e. NaN's and Inf's are not supported.

The buffer must be large enough.

The result is NOT null-terminated.