from_cbor() [4/4]

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>>

template<typename IteratorType >

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::from_cbor ( IteratorType  first, IteratorType  last, const bool  strict = true, const bool  allow_exceptions = true, const cbor_tag_handler_t  tag_handler = cbor_tag_handler_t::error  )

inlinestatic

create a JSON value from an input in CBOR format

Deserializes a given input i to a JSON value using the CBOR (Concise Binary Object Representation) serialization format.

The library maps CBOR types to JSON value types as follows:

CBOR type	JSON value type	first byte
Integer	number_unsigned	0x00..0x17
Unsigned integer	number_unsigned	0x18
Unsigned integer	number_unsigned	0x19
Unsigned integer	number_unsigned	0x1A
Unsigned integer	number_unsigned	0x1B
Negative integer	number_integer	0x20..0x37
Negative integer	number_integer	0x38
Negative integer	number_integer	0x39
Negative integer	number_integer	0x3A
Negative integer	number_integer	0x3B
Byte string	binary	0x40..0x57
Byte string	binary	0x58
Byte string	binary	0x59
Byte string	binary	0x5A
Byte string	binary	0x5B
UTF-8 string	string	0x60..0x77
UTF-8 string	string	0x78
UTF-8 string	string	0x79
UTF-8 string	string	0x7A
UTF-8 string	string	0x7B
UTF-8 string	string	0x7F
array	array	0x80..0x97
array	array	0x98
array	array	0x99
array	array	0x9A
array	array	0x9B
array	array	0x9F
map	object	0xA0..0xB7
map	object	0xB8
map	object	0xB9
map	object	0xBA
map	object	0xBB
map	object	0xBF
False	false	0xF4
True	true	0xF5
Null	null	0xF6
Half-Precision Float	number_float	0xF9
Single-Precision Float	number_float	0xFA
Double-Precision Float	number_float	0xFB

Warning

The mapping is incomplete in the sense that not all CBOR types can be converted to a JSON value. The following CBOR types are not supported and will yield parse errors (parse_error.112):

• date/time (0xC0..0xC1)
• bignum (0xC2..0xC3)
• decimal fraction (0xC4)
• bigfloat (0xC5)
• expected conversions (0xD5..0xD7)
• simple values (0xE0..0xF3, 0xF8)
• undefined (0xF7)

CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps with keys other than UTF-8 strings are rejected (parse_error.113).

Note

Any CBOR output created to_cbor can be successfully parsed by from_cbor.

Parameters

[in]	i	an input in CBOR format convertible to an input adapter
[in]	strict	whether to expect the input to be consumed until EOF (true by default)
[in]	allow_exceptions	whether to throw exceptions in case of a parse error (optional, true by default)
[in]	tag_handler	how to treat CBOR tags (optional, error by default)

Returns

deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.

Exceptions

parse_error.110	if the given input ends prematurely or the end of file was not reached when strict was set to true
parse_error.112	if unsupported features from CBOR were used in the given input v or if the input is not valid CBOR
parse_error.113	if a string was expected as map key, but not found

@complexity Linear in the size of the input i.

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

See also

http://cbor.io

see to_cbor(const basic_json&) for the analogous serialization

see from_msgpack(InputType&&, const bool, const bool) for the related MessagePack format

see from_ubjson(InputType&&, const bool, const bool) for the related UBJSON format

Since

version 2.0.9; parameter start_index since 2.1.1; changed to consume input adapters, removed start_index parameter, and added strict parameter since 3.0.0; added allow_exceptions parameter since 3.2.0; added tag_handler parameter since 3.9.0.

Definition at line 25467 of file json.hpp.

    {
        basic_json result;
        detail::json_sax_dom_parser<basic_json> sdp(result, allow_exceptions);
        auto ia = detail::input_adapter(std::move(first), std::move(last));
        const bool res = binary_reader<decltype(ia)>(std::move(ia)).sax_parse(input_format_t::cbor, &sdp, strict, tag_handler);
        return res ? result : basic_json(value_t::discarded);
    }