deploy: 7c9208bfb3

2026-07-09 12:05:10 +00:00 · 2026-07-08 18:19:46 +00:00
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+# nlohmann::basic_json::to_bson
+
+```
+// (1)
+static std::vector<std::uint8_t> to_bson(const basic_json& j);
+
+// (2)
+static void to_bson(const basic_json& j, detail::output_adapter<std::uint8_t> o);
+static void to_bson(const basic_json& j, detail::output_adapter<char> o);
+```
+
+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).
+
+1. Returns a byte vector containing the BSON serialization.
+1. Writes the BSON serialization to an output adapter.
+
+The exact mapping and its limitations are described on a [dedicated page](https://json.nlohmann.me/features/binary_formats/bson/index.md).
+
+## Parameters
+
+`j` (in) : JSON value to serialize
+
+`o` (in) : output adapter to write serialization to
+
+## Return value
+
+1. BSON serialization as a byte vector
+1. (none)
+
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+
+## Exceptions
+
+- 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"`
+- 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)"`
+
+## Complexity
+
+Linear in the size of the JSON value `j`.
+
+## Examples
+
+Example
+
+The example shows the serialization of a JSON value to a byte vector in BSON format.
+
+```
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using namespace nlohmann::literals;
+
+int main()
+{
+    // create a JSON value
+    json j = R"({"compact": true, "schema": 0})"_json;
+
+    // serialize it to BSON
+    std::vector<std::uint8_t> v = json::to_bson(j);
+
+    // print the vector content
+    for (auto& byte : v)
+    {
+        std::cout << "0x" << std::hex << std::setw(2) << std::setfill('0') << (int)byte << " ";
+    }
+    std::cout << std::endl;
+}
+```
+
+Output:
+
+```
+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
+```
+
+## See also
+
+- [from_bson](https://json.nlohmann.me/api/basic_json/from_bson/index.md) create a JSON value from an input in BSON format
+- [to_cbor](https://json.nlohmann.me/api/basic_json/to_cbor/index.md) create a CBOR serialization of a JSON value
+- [to_msgpack](https://json.nlohmann.me/api/basic_json/to_msgpack/index.md) create a MessagePack serialization of a JSON value
+- [to_ubjson](https://json.nlohmann.me/api/basic_json/to_ubjson/index.md) create a UBJSON serialization of a JSON value
+- [to_bjdata](https://json.nlohmann.me/api/basic_json/to_bjdata/index.md) create a BJData serialization of a JSON value
+
+## Version history
+
+- Added in version 3.4.0.