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Niels Lohmann
1e101ecac1
* Add BON8 support Add to_bon8/from_bon8 and input_format_t::bon8 for BON8, a binary format that uses the byte values that cannot begin a UTF-8 character as type markers, so strings need no length prefix. It is the most compact of the supported binary formats on the benchmark files. The reader is non-recursive like the other binary readers. A string ends at the first byte that cannot continue it, so the reader hands the one or two bytes it reads past a string back to the value that follows. The writer produces the canonical representation of the specification, except for NFC normalization; its output is identical to that of the reference implementation (HikoGUI) on all files of the test data. The round-trip tests need the .bon8 files of json_test_data 3.2.0. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Address review comments - Reuse detail::validate_one_utf8 to check strings in to_bon8; the error now names the first byte of the invalid sequence. - Document that to_bon8 leaves bytes in the output adapter on an exception, and that string_open is only an output of write_bon8_marker. - Explain why the pushback buffer of the BON8 reader cannot overflow. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Select the BON8 float prefix by type get_bon8_float_prefix only depends on the type of its argument, so make the type a template parameter instead of passing an unused value. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Rename a test variable that Flawfinder mistakes for read() Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Fix the BON8 CI failures - compare the float in write_bon8_float with number_float_t constants, so GCC does not warn about a float-to-double conversion - mark check_bon8_utf8's context as used when exceptions are disabled - choose the compact float prefix in a helper rather than with nested conditional operators (clang-tidy) - use auto for the cast in the BON8 integer reader (clang-tidy) - write the int32 minimum test values as long long literals (MSVC C4146) Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Amalgamate Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Read BON8 strings in bulk from contiguous input - copy the valid UTF-8 of a string in one step when the input is contiguous (twitter.json is read in 1.68 instead of 2.52 ms, jeopardy.json in 196 instead of 297 ms, close to CBOR and MessagePack) - share the new valid_utf8_prefix() with the writer's UTF-8 check, which now skips ASCII 8 bytes at a time - let the fuzzer check that contiguous and stream input give the same value or error, and test both paths in the unit tests - clarify that a second 0xFF after a string is an empty string Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Link the BON8 functions from the other binary format pages Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Name the bulk scan flag after the input, not BON8 Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Read BSON keys in bulk from contiguous input BSON keys (and array indices) are C-style strings, which were read byte by byte. For contiguous input they are now read up to their \x00-byte in one step, using the same bulk_scan flag as BON8 strings: twitter.json is read in 1.46 instead of 2.01 ms, citm_catalog.json in 2.93 instead of 3.33 ms, jeopardy.json in 182 instead of 207 ms. canada.json, whose keys are almost all one-digit array indices, takes 2 % longer. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Fix the BON8 CI failures of the bulk-read tests - skip the contiguous-versus-stream tests of BON8 strings and BSON keys when exceptions are disabled: they catch the parse errors of invalid input, and without exceptions the library aborts instead - use static_cast for the int64 test value (google-readability-casting) Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Move the explicit basic_json instantiation into its own test file Linking test-regression3_cpp20 with clang and MinGW failed with "relocation truncated to fit: IMAGE_REL_AMD64_REL32 against `.rdata'", as test-regression2 did before #5511. The explicit instantiation of basic_json<> for #4825 compiles every member function, including the BON8 reader and writer, into that object, and it was already close to the limit (2,226,104 bytes on develop, 2,234,960 with BON8; clang -O1, C++20). Give the instantiation a file of its own: unit-regression3 is now 1,594,736 bytes and unit-explicit_instantiation 1,095,064. The new file mentions JSON_HAS_CPP_17 and JSON_HAS_CPP_20 so it keeps being built for the C++17 standard the regression was about. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Convert the bytes of the BON8 test strings explicitly The str() helper constructed a std::string from a byte range, which converts each unsigned char implicitly; -fsanitize=integer reports that for bytes of 0x80 and above (ci_test_clang_sanitizer). Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2.6 KiB
2.6 KiB
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).
- Returns a byte vector containing the BSON serialization.
- Writes the BSON serialization to an output adapter.
The exact mapping and its limitations are described on a dedicated page.
Parameters
j(in)- JSON value to serialize
o(in)- output adapter to write serialization to
Return value
- BSON serialization as a byte vector
- (none)
Exception safety
Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
Exceptions
- Throws
type_error.317if 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.409if 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)" - Throws
out_of_range.412if the length of a document, array, string, or binary value exceeds the range of the 32-bit BSON length field; example:"BSON length 2147483661 exceeds maximum of 2147483647"
Complexity
Linear in the size of the JSON value j. The length prefixes of all nested documents and arrays are computed in one
pass before anything is written.
Examples
??? example
The example shows the serialization of a JSON value to a byte vector in BSON format.
```cpp
--8<-- "examples/to_bson.cpp"
```
Output:
```json
--8<-- "examples/to_bson.output"
```
See also
- from_bson create a JSON value from an input in BSON format
- to_cbor create a CBOR serialization of a JSON value
- to_msgpack create a MessagePack serialization of a JSON value
- to_ubjson create a UBJSON serialization of a JSON value
- to_bjdata create a BJData serialization of a JSON value
- to_bon8 create a BON8 serialization of a JSON value
Version history
- Added in version 3.4.0.
- Linear in the size of
j, and no longer limited by the call stack for deeply nested values, since version 3.13.0.