Remove consumed frames in place - #1321
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Deleting the consumed prefix preserves the bytearray's amortized left-delete behavior instead of copying the entire remaining buffer after every frame. Closes python-hyper#474
Kriechi
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Jul 27, 2026
| # At this point, as we know we'll use or discard the entire frame, we | ||
| # can update the data. | ||
| self._data = self._data[9+length:] | ||
| del self._data[:9+length] |
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Please add a comment here about the behaviour with in-place update without copy, ideally referencing CPython docs.
Kriechi
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Jul 27, 2026
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| next(buffer) | ||
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| assert buffer._data is data |
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please add a comment to clearly call out that this checks if the object is still the same (internally checked with the id(...) function.
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Thanks - this looks like an amazing and unexpectedly simple change 🎉 |
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Closes #474.
FrameBuffernow stores incoming bytes in abytearray, but consuming a frame still assignsself._data[9 + length:]back to the attribute. That creates and copies a new buffer for every frame, so parsing many buffered frames remains quadratic.Delete the consumed prefix in place instead. CPython's optimized left deletion can then advance the bytearray start offset without copying the full remaining suffix. A regression test verifies both that the same bytearray object is retained and that the next frame remains buffered.
Benchmark
I buffered repeated valid, empty SETTINGS frames and then iterated the
FrameBufferon CPython 3.11 / Windows:The post-change throughput stays near 312,000 frames/s across the three input sizes.
Validation
python -m pytest— 1,654 passedpython -m mypy --strict-bytes src tests/typing/strict_bytes.pytest_basic_logic.py)git diff --check