queson 0.2.0

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queson

An experimental JSON encoder/decoder Python module written in Rust.

Goals:

• Faster than Python's built-in json module, with at least comparable RAM usage.
• Only Rust code.
• Transparent support for arbitrary-precision integers, without encoding them as strings.
• During encoding and decoding, support for a custom "object hook" function.
  • When encoding, the object hook is called on any value that is unsupported by the encoder. If the hook returns a value that is supported, encoding proceeds with that value instead.
  • When decoding, the object hook is called with each produced dict value. The value returned by the function takes the place of the dict in the decoded object graph.
• During encoding, support for "fragment" values, which represent already-JSON-encoded strings that should be dumped verbatim in the output.

Benchmark

The following results were collected using the benchmarks directory in this repository. The documents tested are real-world messages collected from the Archipelago client.

Benchmark environment:

• Debian Trixie (Linux kernel 6.19.6)
• AMD Ryzen 9 3900X with 32GB RAM
• Python 3.11.11
  • orjson 3.9.5

Benchmark	json	queson	orjson
testfiles/jsonmsg-1.json loads	177 us	86.7 us: 2.04x faster	52.8 us: 3.34x faster
testfiles/jsonmsg-1.json dumps	213 us	67.2 us: 3.16x faster	21.1 us: 10.07x faster
testfiles/jsonmsg-23.json loads	2.29 ms	1.53 ms: 1.50x faster	785 us: 2.92x faster
testfiles/jsonmsg-23.json dumps	2.66 ms	575 us: 4.61x faster	236 us: 11.26x faster
testfiles/jsonmsg-5.json loads	897 us	879 us: 1.02x faster	522 us: 1.72x faster
testfiles/jsonmsg-5.json dumps	1.24 ms	395 us: 3.13x faster	225 us: 5.51x faster
testfiles/jsonmsg-7.json loads	664 us	523 us: 1.27x faster	295 us: 2.25x faster
testfiles/jsonmsg-7.json dumps	865 us	180 us: 4.81x faster	73.7 us: 11.73x faster
testfiles/oops-all-ints.json loads	168 us	80.5 us: 2.09x faster	45.6 us: 3.69x faster
testfiles/oops-all-ints.json dumps	203 us	65.2 us: 3.11x faster	20.1 us: 10.10x faster
Geometric mean	(ref)	2.37x faster	5.03x faster

Running the same benchmarks but monitoring memory usage concludes that queson has a 2% higher RSS peak than json, and orjson has a 13% higher RSS peak than json.

Differences from Python's json module

This list may not be exhaustive.

• There is currently no streaming support (load and dump are absent). This may be added in the future.
• Non-finite float values (NaN, Infinity, -Infinity) are rejected during encoding and decoding as they are not valid JSON.
• dumpb/dumps does not support float dict keys. The JSON specification does not guarantee a particular method of formatting float values, nor does it guarantee any specific level of precision. The lack of a canonical float representation means float keys are of dubious value.
• loads does not support bytearray objects. This is because they are mutable, and object hook support would allow Python code to mutate the contents while the decoder is running. As this can invalidate the data pointer, it would be necessary to re-obtain the data pointer after every object hook invocation for soundness.

Compliance

Passes the following test suites:

• https://github.com/nst/JSONTestSuite