to_cbor() [1/3]

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 = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer, class BinaryType = std::vector<std::uint8_t>>

static std::vector< std::uint8_t > nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::to_cbor ( const basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType > &  j )

inlinestatic

create a CBOR serialization of a given JSON value

Serializes a given JSON value j to a byte vector using the CBOR (Concise Binary Object Representation) serialization format. CBOR is a binary serialization format which aims to be more compact than JSON itself, yet more efficient to parse.

The library uses the following mapping from JSON values types to CBOR types according to the CBOR specification (RFC 7049):

JSON value type	value/range	CBOR type	first byte
null	null	Null	0xF6
boolean	true	True	0xF5
boolean	false	False	0xF4
number_integer	-9223372036854775808..-2147483649	Negative integer (8 bytes follow)	0x3B
number_integer	-2147483648..-32769	Negative integer (4 bytes follow)	0x3A
number_integer	-32768..-129	Negative integer (2 bytes follow)	0x39
number_integer	-128..-25	Negative integer (1 byte follow)	0x38
number_integer	-24..-1	Negative integer	0x20..0x37
number_integer	0..23	Integer	0x00..0x17
number_integer	24..255	Unsigned integer (1 byte follow)	0x18
number_integer	256..65535	Unsigned integer (2 bytes follow)	0x19
number_integer	65536..4294967295	Unsigned integer (4 bytes follow)	0x1A
number_integer	4294967296..18446744073709551615	Unsigned integer (8 bytes follow)	0x1B
number_unsigned	0..23	Integer	0x00..0x17
number_unsigned	24..255	Unsigned integer (1 byte follow)	0x18
number_unsigned	256..65535	Unsigned integer (2 bytes follow)	0x19
number_unsigned	65536..4294967295	Unsigned integer (4 bytes follow)	0x1A
number_unsigned	4294967296..18446744073709551615	Unsigned integer (8 bytes follow)	0x1B
number_float	any value representable by a float	Single-Precision Float	0xFA
number_float	any value NOT representable by a float	Double-Precision Float	0xFB
string	length: 0..23	UTF-8 string	0x60..0x77
string	length: 23..255	UTF-8 string (1 byte follow)	0x78
string	length: 256..65535	UTF-8 string (2 bytes follow)	0x79
string	length: 65536..4294967295	UTF-8 string (4 bytes follow)	0x7A
string	length: 4294967296..18446744073709551615	UTF-8 string (8 bytes follow)	0x7B
array	size: 0..23	array	0x80..0x97
array	size: 23..255	array (1 byte follow)	0x98
array	size: 256..65535	array (2 bytes follow)	0x99
array	size: 65536..4294967295	array (4 bytes follow)	0x9A
array	size: 4294967296..18446744073709551615	array (8 bytes follow)	0x9B
object	size: 0..23	map	0xA0..0xB7
object	size: 23..255	map (1 byte follow)	0xB8
object	size: 256..65535	map (2 bytes follow)	0xB9
object	size: 65536..4294967295	map (4 bytes follow)	0xBA
object	size: 4294967296..18446744073709551615	map (8 bytes follow)	0xBB
binary	size: 0..23	byte string	0x40..0x57
binary	size: 23..255	byte string (1 byte follow)	0x58
binary	size: 256..65535	byte string (2 bytes follow)	0x59
binary	size: 65536..4294967295	byte string (4 bytes follow)	0x5A
binary	size: 4294967296..18446744073709551615	byte string (8 bytes follow)	0x5B

Binary values with subtype are mapped to tagged values (0xD8..0xDB) depending on the subtype, followed by a byte string, see "binary" cells in the table above.

Note

The mapping is complete in the sense that any JSON value type can be converted to a CBOR value.

If NaN or Infinity are stored inside a JSON number, they are serialized properly. This behavior differs from the dump() function which serializes NaN or Infinity to null.

The following CBOR types are not used in the conversion:

• UTF-8 strings terminated by "break" (0x7F)
• arrays terminated by "break" (0x9F)
• maps terminated by "break" (0xBF)
• byte strings terminated by "break" (0x5F)
• date/time (0xC0..0xC1)
• bignum (0xC2..0xC3)
• decimal fraction (0xC4)
• bigfloat (0xC5)
• expected conversions (0xD5..0xD7)
• simple values (0xE0..0xF3, 0xF8)
• undefined (0xF7)
• half-precision floats (0xF9)
• break (0xFF)

Parameters

[in]

j

JSON value to serialize

Returns

CBOR serialization as byte vector

@complexity Linear in the size of the JSON value j.

@liveexample{The example shows the serialization of a JSON value to a byte vector in CBOR format.,to_cbor}

See also

http://cbor.io

see from_cbor(InputType&&, const bool, const bool, const cbor_tag_handler_t) for the analogous deserialization

see to_msgpack(const basic_json&) for the related MessagePack format

see to_ubjson(const basic_json&, const bool, const bool) for the related UBJSON format

Since

version 2.0.9; compact representation of floating-point numbers since version 3.8.0

Definition at line 25041 of file json.hpp.

    {
        std::vector<std::uint8_t> result;
        to_cbor(j, result);
        return result;
    }