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78 lines
2.4 KiB
Markdown
78 lines
2.4 KiB
Markdown
# <small>nlohmann::basic_json::</small>to_msgpack
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```cpp
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// (1)
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static std::vector<std::uint8_t> to_msgpack(const basic_json& j);
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// (2)
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static void to_msgpack(const basic_json& j, detail::output_adapter<std::uint8_t> o);
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static void to_msgpack(const basic_json& j, detail::output_adapter<char> o);
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```
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Serializes a given JSON value `j` to a byte vector using the MessagePack serialization format. MessagePack is a binary
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serialization format that aims to be more compact than JSON itself, yet more efficient to parse.
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1. Returns a byte vector containing the MessagePack serialization.
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2. Writes the MessagePack serialization to an output adapter.
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The exact mapping and its limitations are described on a [dedicated page](../../features/binary_formats/messagepack.md).
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## Parameters
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`j` (in)
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: JSON value to serialize
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`o` (in)
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: output adapter to write serialization to
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## Return value
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1. MessagePack serialization as a byte vector
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2. (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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## Exceptions
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- Throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412) if the length of a string, binary
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value, array, or object exceeds 4294967295, the maximum MessagePack can store; example:
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`"MessagePack length 4294967296 exceeds maximum of 4294967295"`
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- Throws [`out_of_range.415`](../../home/exceptions.md#jsonexceptionout_of_range415) if the subtype of a binary value
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exceeds 255, the maximum of the MessagePack ext type; example:
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`"subtype 70000 is too large for the MessagePack ext type (max 255)"`
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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 MessagePack format.
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```cpp
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--8<-- "examples/to_msgpack.cpp"
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```
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Output:
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```json
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--8<-- "examples/to_msgpack.output"
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```
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## See also
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- [from_msgpack](from_msgpack.md) create a JSON value from an input in MessagePack format
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- [to_cbor](to_cbor.md) create a CBOR serialization of a JSON value
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- [to_bson](to_bson.md) create a BSON serialization of a JSON value
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- [to_ubjson](to_ubjson.md) create a UBJSON serialization of a JSON value
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- [to_bjdata](to_bjdata.md) create a BJData serialization of a JSON value
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## Version history
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- Added in version 2.0.9.
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- Throws `out_of_range.412` and `out_of_range.415` since version 3.13.0.
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