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nlohmann
91 lines
2.9 KiB
Markdown
91 lines
2.9 KiB
Markdown
# nlohmann::basic_json::to_bson
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```
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// (1)
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static std::vector<std::uint8_t> to_bson(const basic_json& j);
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// (2)
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static void to_bson(const basic_json& j, detail::output_adapter<std::uint8_t> o);
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static void to_bson(const basic_json& j, detail::output_adapter<char> o);
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```
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BSON (Binary JSON) is a binary format in which zero or more ordered key/value pairs are stored as a single entity (a so-called document).
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1. Returns a byte vector containing the BSON serialization.
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1. Writes the BSON 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/bson/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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## Return value
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1. BSON 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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## Exceptions
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- Throws [`type_error.317`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error317) if the top-level type of the JSON value is not an object; example: `"to serialize to BSON, top-level type must be object, but is string"`
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- Throws [`out_of_range.409`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range409) if a key in the JSON object contains a null byte (code point U+0000); example: `"BSON key cannot contain code point U+0000 (at byte 2)"`
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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 BSON 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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int main()
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{
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// create a JSON value
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json j = R"({"compact": true, "schema": 0})"_json;
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// serialize it to BSON
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std::vector<std::uint8_t> v = json::to_bson(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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std::cout << "0x" << std::hex << std::setw(2) << std::setfill('0') << (int)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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0x1b 0x00 0x00 0x00 0x08 0x63 0x6f 0x6d 0x70 0x61 0x63 0x74 0x00 0x01 0x10 0x73 0x63 0x68 0x65 0x6d 0x61 0x00 0x00 0x00 0x00 0x00 0x00
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```
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## See also
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- [from_bson](https://json.nlohmann.me/api/basic_json/from_bson/index.md) create a JSON value from an input in BSON 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_ubjson](https://json.nlohmann.me/api/basic_json/to_ubjson/index.md) create a UBJSON 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 3.4.0.
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