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nlohmann::basic_json::from_ubjson

// (1)
template<typename InputType>
static basic_json from_ubjson(InputType&& i,
                              const bool strict = true,
                              const bool allow_exceptions = true);
// (2)
template<typename IteratorType>
static basic_json from_ubjson(IteratorType first, IteratorType last,
                              const bool strict = true,
                              const bool allow_exceptions = true);

Deserializes a given input to a JSON value using the UBJSON (Universal Binary JSON) serialization format.

  1. Reads from a compatible input.
  2. Reads from an iterator range.

The exact mapping and its limitations is described on a dedicated page.

Template parameters

InputType

A compatible input, for instance:

  • an std::istream object
  • a FILE pointer
  • a C-style array of characters
  • a pointer to a null-terminated string of single byte characters
  • an object obj for which begin(obj) and end(obj) produces a valid pair of iterators.
IteratorType
a compatible iterator type

Parameters

i (in)
an input in UBJSON format convertible to an input adapter
first (in)
iterator to start of the input
last (in)
iterator to end of the input
strict (in)
whether to expect the input to be consumed until EOF (true by default)
allow_exceptions (in)
whether to throw exceptions in case of a parse error (optional, true by default)

Return value

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

Exception safety

Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

Exceptions

  • Throws parse_error.110 if the given input ends prematurely or the end of file was not reached when strict was set to true
  • Throws parse_error.112 if a parse error occurs
  • Throws parse_error.113 if a string could not be parsed successfully

Complexity

Linear in the size of the input.

Examples

Example

The example shows the deserialization of a byte vector in UBJSON format to a JSON value.

#include <iostream>
#include <iomanip>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
{
    // create byte vector
    std::vector<std::uint8_t> v = {0x7B, 0x69, 0x07, 0x63, 0x6F, 0x6D, 0x70, 0x61,
                                   0x63, 0x74, 0x54, 0x69, 0x06, 0x73, 0x63, 0x68,
                                   0x65, 0x6D, 0x61, 0x69, 0x00, 0x7D
                                  };

    // deserialize it with UBJSON
    json j = json::from_ubjson(v);

    // print the deserialized JSON value
    std::cout << std::setw(2) << j << std::endl;
}

Output:

{
  "compact": true,
  "schema": 0
}

Version history

  • Added in version 3.1.0.
  • Added allow_exceptions parameter in version 3.2.0.

Deprecation

  • Overload (2) replaces calls to from_ubjson with a pointer and a length as first two parameters, which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like from_ubjson(ptr, len, ...); with from_ubjson(ptr, ptr+len, ...);.
  • Overload (2) replaces calls to from_ubjson with a pair of iterators as their first parameter, which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like from_ubjson({ptr, ptr+len}, ...); with from_ubjson(ptr, ptr+len, ...);.

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.


Last update: May 1, 2022
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