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nlohmann::basic_json::input_format_t

enum class input_format_t {
    json,
    cbor,
    msgpack,
    ubjson,
    bson,
    bjdata
};

This enumeration is used in the sax_parse function to choose the input format to parse:

json
JSON (JavaScript Object Notation)
cbor
CBOR (Concise Binary Object Representation)
msgpack
MessagePack
ubjson
UBJSON (Universal Binary JSON)
bson
BSON (Binary JSON)
bjdata
BJData (Binary JData)

Examples

Example

The example below shows how an input_format_t enum value is passed to sax_parse to set the input format to CBOR.

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

using json = nlohmann::json;

// a simple event consumer that collects string representations of the passed
// values; note inheriting from json::json_sax_t is not required, but can
// help not to forget a required function
class sax_event_consumer : public json::json_sax_t
{
  public:
    std::vector<std::string> events;

    bool null() override
    {
        events.push_back("null()");
        return true;
    }

    bool boolean(bool val) override
    {
        events.push_back("boolean(val=" + std::string(val ? "true" : "false") + ")");
        return true;
    }

    bool number_integer(number_integer_t val) override
    {
        events.push_back("number_integer(val=" + std::to_string(val) + ")");
        return true;
    }

    bool number_unsigned(number_unsigned_t val) override
    {
        events.push_back("number_unsigned(val=" + std::to_string(val) + ")");
        return true;
    }

    bool number_float(number_float_t val, const string_t& s) override
    {
        events.push_back("number_float(val=" + std::to_string(val) + ", s=" + s + ")");
        return true;
    }

    bool string(string_t& val) override
    {
        events.push_back("string(val=" + val + ")");
        return true;
    }

    bool start_object(std::size_t elements) override
    {
        events.push_back("start_object(elements=" + std::to_string(elements) + ")");
        return true;
    }

    bool end_object() override
    {
        events.push_back("end_object()");
        return true;
    }

    bool start_array(std::size_t elements) override
    {
        events.push_back("start_array(elements=" + std::to_string(elements) + ")");
        return true;
    }

    bool end_array() override
    {
        events.push_back("end_array()");
        return true;
    }

    bool key(string_t& val) override
    {
        events.push_back("key(val=" + val + ")");
        return true;
    }

    bool binary(json::binary_t& val) override
    {
        events.push_back("binary(val=[...])");
        return true;
    }

    bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex) override
    {
        events.push_back("parse_error(position=" + std::to_string(position) + ", last_token=" + last_token + ",\n            ex=" + std::string(ex.what()) + ")");
        return false;
    }
};

int main()
{
    // CBOR byte string
    std::vector<std::uint8_t> vec = {{0x44, 0xcA, 0xfe, 0xba, 0xbe}};

    // create a SAX event consumer object
    sax_event_consumer sec;

    // parse CBOR
    bool result = json::sax_parse(vec, &sec, json::input_format_t::cbor);

    // output the recorded events
    for (auto& event : sec.events)
    {
        std::cout << event << "\n";
    }

    // output the result of sax_parse
    std::cout << "\nresult: " << std::boolalpha << result << std::endl;
}

Output:

binary(val=[...])

result: true

Version history

  • Added in version 3.2.0.

Last update: May 17, 2022
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