nlohmann::basic_json::to_bon8

// (1)
static std::vector<std::uint8_t> to_bon8(const basic_json& j);

// (2)
static void to_bon8(const basic_json& j, detail::output_adapter<std::uint8_t> o);
static void to_bon8(const basic_json& j, detail::output_adapter<char> o);

Serializes a given JSON value j to a byte vector using the BON8 (Binary Object Notation 8) serialization format. BON8 is a compact binary serialization format that stores strings as UTF-8 without a length prefix.

Returns a byte vector containing the BON8 serialization.
Writes the BON8 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

Return value

BON8 serialization as a byte vector
(none)

Exception safety

Strong guarantee: if an exception is thrown, there are no changes in the JSON value j, which is never modified. With (2), the bytes written before the exception remain in the output adapter.

Exceptions

Throws out_of_range.407 if j contains an integer outside the range of int64 (an unsigned integer above 9223372036854775807, or, with a number type wider than 64 bits, any integer beyond int64), which BON8 cannot represent
Throws type_error.316 if j contains a string that is not valid UTF-8
Throws type_error.321 if j or a value nested in it is discarded; example: "cannot serialize discarded value to BON8"

Complexity

Linear in the size of the JSON value j.

Examples

Example: serialize a JSON value to BON8

The example shows the serialization of a JSON value to a byte vector in BON8 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, "format": "BON8", "schema": 0})"_json;

    // serialize it to BON8
    std::vector<std::uint8_t> v = json::to_bon8(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:

0x89 0x63 0x6f 0x6d 0x70 0x61 0x63 0x74 0xf9 0x66 0x6f 0x72 0x6d 0x61 0x74 0xff 0x42 0x4f 0x4e 0x38 0xff 0x73 0x63 0x68 0x65 0x6d 0x61 0x90

Example: type_error.316 exception

The example shows how serializing a string that is not valid UTF-8 throws an exception, because BON8 stores strings as UTF-8.

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

using json = nlohmann::json;

int main()
{
    // create a JSON string that is not valid UTF-8
    std::string invalid_utf8;
    invalid_utf8.push_back(static_cast<char>(0xFF));
    json j = invalid_utf8;

    // exception type_error.316
    try
    {
        json::to_bon8(j);
    }
    catch (const json::type_error& e)
    {
        std::cout << e.what() << '\n';
    }
}