json/api/basic_json/to_bon8/index.md

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.

1. Returns a byte vector containing the BON8 serialization.
2. 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

1. BON8 serialization as a byte vector
2. (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 unsigned integer above 9223372036854775807, which BON8 cannot represent
• Throws type_error.316 if j contains a string that is not valid UTF-8

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';
    }
}

Output:

[json.exception.type_error.316] invalid UTF-8 byte at index 0: 0xFF

See also

• from_bon8 create a JSON value from an input in BON8 format
• to_cbor create a CBOR serialization of a JSON value
• 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

Version history

• Added in version 3.13.0 unreleased.