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nlohmann
139 lines
3.9 KiB
Markdown
139 lines
3.9 KiB
Markdown
# nlohmann::basic_json::to_ubjson
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```
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// (1)
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static std::vector<std::uint8_t> to_ubjson(const basic_json& j,
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const bool use_size = false,
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const bool use_type = false);
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// (2)
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static void to_ubjson(const basic_json& j, detail::output_adapter<std::uint8_t> o,
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const bool use_size = false, const bool use_type = false);
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static void to_ubjson(const basic_json& j, detail::output_adapter<char> o,
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const bool use_size = false, const bool use_type = false);
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```
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Serializes a given JSON value `j` to a byte vector using the UBJSON (Universal Binary JSON) serialization format. UBJSON aims to be more compact than JSON itself, yet more efficient to parse.
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1. Returns a byte vector containing the UBJSON serialization.
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1. Writes the UBJSON serialization to an output adapter.
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The exact mapping and its limitations are described on a [dedicated page](https://json.nlohmann.me/features/binary_formats/ubjson/index.md).
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## Parameters
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`j` (in) : JSON value to serialize
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`o` (in) : output adapter to write serialization to
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`use_size` (in) : whether to add size annotations to container types; optional, `false` by default.
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`use_type` (in) : whether to add type annotations to container types (must be combined with `use_size = true`); optional, `false` by default.
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## Return value
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1. UBJSON serialization as a byte vector
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1. (none)
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## Exception safety
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Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
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## Complexity
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Linear in the size of the JSON value `j`.
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## Examples
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Example
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The example shows the serialization of a JSON value to a byte vector in UBJSON format.
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```
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#include <iostream>
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#include <iomanip>
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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using namespace nlohmann::literals;
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// function to print UBJSON's diagnostic format
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void print_byte(uint8_t byte)
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{
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if (32 < byte and byte < 128)
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{
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std::cout << (char)byte;
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}
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else
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{
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std::cout << (int)byte;
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}
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}
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int main()
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{
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// create a JSON value
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json j = R"({"compact": true, "schema": false})"_json;
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// serialize it to UBJSON
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std::vector<std::uint8_t> v = json::to_ubjson(j);
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// print the vector content
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for (auto& byte : v)
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{
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print_byte(byte);
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}
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std::cout << std::endl;
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// create an array of numbers
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json array = {1, 2, 3, 4, 5, 6, 7, 8};
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// serialize it to UBJSON using default representation
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std::vector<std::uint8_t> v_array = json::to_ubjson(array);
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// serialize it to UBJSON using size optimization
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std::vector<std::uint8_t> v_array_size = json::to_ubjson(array, true);
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// serialize it to UBJSON using type optimization
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std::vector<std::uint8_t> v_array_size_and_type = json::to_ubjson(array, true, true);
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// print the vector contents
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for (auto& byte : v_array)
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{
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print_byte(byte);
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}
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std::cout << std::endl;
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for (auto& byte : v_array_size)
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{
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print_byte(byte);
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}
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std::cout << std::endl;
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for (auto& byte : v_array_size_and_type)
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{
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print_byte(byte);
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}
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std::cout << std::endl;
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}
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```
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Output:
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```
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{i7compactTi6schemaF}
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[i1i2i3i4i5i6i7i8]
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[#i8i1i2i3i4i5i6i7i8
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[$i#i812345678
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```
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## See also
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- [from_ubjson](https://json.nlohmann.me/api/basic_json/from_ubjson/index.md) create a JSON value from an input in UBJSON format
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- [to_cbor](https://json.nlohmann.me/api/basic_json/to_cbor/index.md) create a CBOR serialization of a JSON value
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- [to_msgpack](https://json.nlohmann.me/api/basic_json/to_msgpack/index.md) create a MessagePack serialization of a JSON value
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- [to_bson](https://json.nlohmann.me/api/basic_json/to_bson/index.md) create a BSON serialization of a JSON value
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- [to_bjdata](https://json.nlohmann.me/api/basic_json/to_bjdata/index.md) create a BJData serialization of a JSON value
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## Version history
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- Added in version 3.1.0.
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