Skip to content

nlohmann::basic_json::to_cbor

// (1)
static std::vector<std::uint8_t> to_cbor(const basic_json& j,
                                          const error_handler_t error_handler = error_handler_t::keep);

// (2)
static void to_cbor(const basic_json& j, detail::output_adapter<std::uint8_t> o,
                     const error_handler_t error_handler = error_handler_t::keep);
static void to_cbor(const basic_json& j, detail::output_adapter<char> o,
                     const error_handler_t error_handler = error_handler_t::keep);

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 that aims to be more compact than JSON itself, yet more efficient to parse.

  1. Returns a byte vector containing the CBOR serialization.
  2. Writes the CBOR serialization to an output adapter.

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

Parameters

j (in)
JSON value to serialize
o (in)
output adapter to write serialization to
error_handler (in)
how to treat a string or object key in j that is not valid UTF-8; see error_handler_t. The default, keep, writes the ill-formed bytes to the output as is, as every version of to_cbor did before this parameter was added; strict throws; replace/ignore sanitize it the same way dump would. If JSON_STRICT_BINARY_UTF8 is enabled, the default is strict instead.

Return value

  1. CBOR serialization as a byte vector
  2. (none)

Exception safety

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

Exceptions

Complexity

Linear in the size of the JSON value j.

Examples

Example

The example shows the serialization of a JSON value to a byte vector in CBOR format.

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

using json = nlohmann::json;
using namespace nlohmann::literals;

int main()
{
    // create a JSON value
    json j = R"({"compact": true, "schema": 0})"_json;

    // serialize it to CBOR
    std::vector<std::uint8_t> v = json::to_cbor(j);

    // print the vector content
    for (auto& byte : v)
    {
        std::cout << "0x" << std::hex << std::setw(2) << std::setfill('0') << (int)byte << " ";
    }
    std::cout << std::endl;
}

Output:

0xa2 0x67 0x63 0x6f 0x6d 0x70 0x61 0x63 0x74 0xf5 0x66 0x73 0x63 0x68 0x65 0x6d 0x61 0x00

See also

  • from_cbor create a JSON value from an input in CBOR format
  • to_msgpack create a MessagePack serialization of a JSON value
  • to_bson create a BSON serialization of a JSON value
  • to_ubjson create a UBJSON serialization of a JSON value
  • to_bjdata create a BJData serialization of a JSON value
  • to_bon8 create a BON8 serialization of a JSON value

Version history

  • Added in version 2.0.9.
  • Compact representation of floating-point numbers added in version 3.8.0.
  • Added error_handler parameter in version 3.13.0 unreleased. Its default, keep, writes the bytes of a string or object key that is not valid UTF-8 unchanged, as before; strict (the default if JSON_STRICT_BINARY_UTF8 is enabled) throws type_error.316.