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89 lines
3.2 KiB
Markdown
89 lines
3.2 KiB
Markdown
# <small>nlohmann::basic_json::</small>to_cbor
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```cpp
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// (1)
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static std::vector<std::uint8_t> to_cbor(const basic_json& j,
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const error_handler_t error_handler = error_handler_t::keep);
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// (2)
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static void to_cbor(const basic_json& j, detail::output_adapter<std::uint8_t> o,
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const error_handler_t error_handler = error_handler_t::keep);
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static void to_cbor(const basic_json& j, detail::output_adapter<char> o,
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const error_handler_t error_handler = error_handler_t::keep);
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```
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Serializes a given JSON value `j` to a byte vector using the CBOR (Concise Binary Object Representation) serialization
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format. CBOR is a binary serialization format that aims to be more compact than JSON itself, yet more efficient to
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parse.
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1. Returns a byte vector containing the CBOR serialization.
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2. Writes the CBOR serialization to an output adapter.
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The exact mapping and its limitations are described on a [dedicated page](../../features/binary_formats/cbor.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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`error_handler` (in)
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: how to treat a string or object key in `j` that is not valid UTF-8; see [`error_handler_t`](error_handler_t.md).
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The default, `keep`, writes the ill-formed bytes to the output as is, as every version of `to_cbor` did before
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this parameter was added; `strict` throws; `replace`/`ignore` sanitize it the same way [`dump`](dump.md) would.
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If [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled, the default is `strict` instead.
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## Return value
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1. CBOR 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 [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if a string or object key in `j` is
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not valid UTF-8 and `error_handler` is `strict` (the default only if
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[`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled)
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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 CBOR format.
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```cpp
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--8<-- "examples/to_cbor.cpp"
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```
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Output:
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```json
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--8<-- "examples/to_cbor.output"
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```
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## See also
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- [from_cbor](from_cbor.md) create a JSON value from an input in CBOR format
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- [to_msgpack](to_msgpack.md) create a MessagePack 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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- [to_bon8](to_bon8.md) create a BON8 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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- Compact representation of floating-point numbers added in version 3.8.0.
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- Added `error_handler` parameter in version 3.13.0. Its default, `keep`, writes the bytes of a string or object key
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that is not valid UTF-8 unchanged, as before; `strict` (the default if
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[`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316`.
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