JSON for Modern C++  3.7.0

◆ from_msgpack() [1/2]

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>
static basic_json nlohmann::basic_json::from_msgpack ( detail::input_adapter &&  i,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

Deserializes a given input i to a JSON value using the MessagePack serialization format.

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

MessagePack type JSON value type first byte
positive fixint number_unsigned 0x00..0x7F
fixmap object 0x80..0x8F
fixarray array 0x90..0x9F
fixstr string 0xA0..0xBF
nil null 0xC0
false false 0xC2
true true 0xC3
float 32 number_float 0xCA
float 64 number_float 0xCB
uint 8 number_unsigned 0xCC
uint 16 number_unsigned 0xCD
uint 32 number_unsigned 0xCE
uint 64 number_unsigned 0xCF
int 8 number_integer 0xD0
int 16 number_integer 0xD1
int 32 number_integer 0xD2
int 64 number_integer 0xD3
str 8 string 0xD9
str 16 string 0xDA
str 32 string 0xDB
array 16 array 0xDC
array 32 array 0xDD
map 16 object 0xDE
map 32 object 0xDF
negative fixint number_integer 0xE0-0xFF
Warning
The mapping is incomplete in the sense that not all MessagePack types can be converted to a JSON value. The following MessagePack types are not supported and will yield parse errors:
  • bin 8 - bin 32 (0xC4..0xC6)
  • ext 8 - ext 32 (0xC7..0xC9)
  • fixext 1 - fixext 16 (0xD4..0xD8)
Note
Any MessagePack output created to_msgpack can be successfully parsed by from_msgpack.
Parameters
[in]ian input in MessagePack format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true 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.110if the given input ends prematurely or the end of file was not reached when strict was set to true
parse_error.112if unsupported features from MessagePack were used in the given input i or if the input is not valid MessagePack
parse_error.113if a string was expected as map key, but not found
Complexity
Linear in the size of the input i.
Example
The example shows the deserialization of a byte vector in MessagePack format to a JSON value.
1 #include <iostream>
2 #include <iomanip>
3 #include <nlohmann/json.hpp>
4 
5 using json = nlohmann::json;
6 
7 int main()
8 {
9  // create byte vector
10  std::vector<uint8_t> v = {0x82, 0xa7, 0x63, 0x6f, 0x6d, 0x70, 0x61, 0x63,
11  0x74, 0xc3, 0xa6, 0x73, 0x63, 0x68, 0x65, 0x6d,
12  0x61, 0x00
13  };
14 
15  // deserialize it with MessagePack
16  json j = json::from_msgpack(v);
17 
18  // print the deserialized JSON value
19  std::cout << std::setw(2) << j << std::endl;
20 }
basic_json<> json
default JSON class
Definition: json.hpp:2355
static basic_json from_msgpack(detail::input_adapter &&i, const bool strict=true, const bool allow_exceptions=true)
create a JSON value from an input in MessagePack format
Definition: json.hpp:21452

Output (play with this example online):
{
  "compact": true,
  "schema": 0
}
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/from_msgpack.cpp -o from_msgpack 
See also
http://msgpack.org
to_msgpack(const basic_json&) for the analogous serialization
from_cbor(detail::input_adapter&&, const bool, const bool) for the related CBOR format
from_ubjson(detail::input_adapter&&, const bool, const bool) for the related UBJSON format
from_bson(detail::input_adapter&&, const bool, const bool) for the related BSON 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

Definition at line 21452 of file json.hpp.