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gh-155152: Fix quadratic processing of concatenated zstd frames in zipimport - #155154
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lpyu001
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brettcannon,
ericsnowcurrently,
ncoghlan and
warsaw
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August 4, 2026 08:48
lpyu001
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brettcannon
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October 15, 2026 20:44
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needs backport to 3.14
emmatyping
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Oct 23, 2026
…N1EEN.rst Co-authored-by: Emma Smith <emma@emmatyping.dev>
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Thanks @lpyu001 for the PR, and @emmatyping for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14, 3.15. |
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Sorry, @lpyu001 and @emmatyping, I could not cleanly backport this to Please backport manually with cherry_picker, see the devguide for more information. |
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GH-160565 is a backport of this pull request to the 3.15 branch. |
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Python 3.14's zipimport does not support Zstandard, so a backport should not be necessary |
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The implementation uses _zstd.get_frame_size() to determine the compressed size of each Zstandard frame and passes only that frame to the decompressor. A memoryview enables zero-copy slicing while advancing through the input. This ensures each compressed byte is processed once, reducing cumulative input handling from O(N²) to O(N).
zipimport._zstd_decompress()repeatedly processes remaining input for concatenated frames #155152