Avoiding extra allocation in zlib.reader.Reset #1086

travelpolicy · 2025-07-21T06:02:54Z

Without change in this PR line 182 ( z.digest.Reset() ) never works and we always have an extra allocation.

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Bug Fixes
- Improved handling of internal state when resetting, ensuring certain data is preserved as expected.

coderabbitai · 2025-07-21T06:03:00Z

📝 Walkthrough

Walkthrough

The Reset method of the reader struct in zlib/reader.go was updated to preserve both the decompressor and digest fields during reset, instead of only keeping the decompressor. No changes were made to the method's signature or to any exported entities.

Changes

File(s)	Change Summary
zlib/reader.go	Modified `reader.Reset` to preserve both `decompressor` and `digest`.

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Reviewing files that changed from the base of the PR and between d140606 and be31b8c.

📒 Files selected for processing (1)

zlib/reader.go (1 hunks)

🔇 Additional comments (1)

zlib/reader.go (1)

135-135: LGTM! Excellent fix for the memory allocation issue.

This change correctly preserves the digest field during reset, allowing it to be reused via z.digest.Reset() on line 182 instead of allocating a new digest every time. This aligns perfectly with the PR objective of avoiding unnecessary allocations while maintaining the correct reset behavior.

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klauspost

Good spot!

This PR contains the following updates: | Package | Change | Age | Confidence | |---|---|---|---| | [github.com/klauspost/compress](https://github.com/klauspost/compress) | `v1.18.0` -> `v1.18.1` | [![age](https://developer.mend.io/api/mc/badges/age/go/github.com%2fklauspost%2fcompress/v1.18.1?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://developer.mend.io/api/mc/badges/confidence/go/github.com%2fklauspost%2fcompress/v1.18.0/v1.18.1?slim=true)](https://docs.renovatebot.com/merge-confidence/) | --- ### Release Notes <details> <summary>klauspost/compress (github.com/klauspost/compress)</summary> ### [`v1.18.1`](https://github.com/klauspost/compress/releases/tag/v1.18.1) [Compare Source](klauspost/compress@v1.18.0...v1.18.1) #### What's Changed - zstd: Fix incorrect buffer size in dictionary encodes by [@klauspost](https://github.com/klauspost) in [#1059](klauspost/compress#1059) - s2: check for cap, not len of buffer in EncodeBetter/Best by [@vdarulis](https://github.com/vdarulis) in [#1080](klauspost/compress#1080) - zstd: Add simple zstd EncodeTo/DecodeTo functions by [@klauspost](https://github.com/klauspost) in [#1079](klauspost/compress#1079) - zlib: Avoiding extra allocation in zlib.reader.Reset by [@travelpolicy](https://github.com/travelpolicy) in [#1086](klauspost/compress#1086) - gzhttp: remove redundant err check in zstdReader by [@ryanfowler](https://github.com/ryanfowler) in [#1090](klauspost/compress#1090) - Run modernize. Deprecate Go 1.22 by [@klauspost](https://github.com/klauspost) in [#1095](klauspost/compress#1095) - flate: Simplify matchlen by [@klauspost](https://github.com/klauspost) in [#1101](klauspost/compress#1101) - flate: Add examples by [@klauspost](https://github.com/klauspost) in [#1102](klauspost/compress#1102) - flate: Use exact sizes for huffman tables by [@klauspost](https://github.com/klauspost) in [#1103](klauspost/compress#1103) - flate: Faster load+store by [@klauspost](https://github.com/klauspost) in [#1104](klauspost/compress#1104) - Add notice to S2 about MinLZ by [@klauspost](https://github.com/klauspost) in [#1065](klauspost/compress#1065) #### New Contributors - [@wooffie](https://github.com/wooffie) made their first contribution in [#1069](klauspost/compress#1069) - [@vdarulis](https://github.com/vdarulis) made their first contribution in [#1080](klauspost/compress#1080) - [@travelpolicy](https://github.com/travelpolicy) made their first contribution in [#1086](klauspost/compress#1086) - [@ryanfowler](https://github.com/ryanfowler) made their first contribution in [#1090](klauspost/compress#1090) **Full Changelog**: <klauspost/compress@v1.18.0...v1.18.1> </details> --- ### Configuration 📅 **Schedule**: Branch creation - Between 12:00 AM and 03:59 AM ( * 0-3 * * * ) (UTC), Automerge - Between 12:00 AM and 03:59 AM ( * 0-3 * * * ) (UTC). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/9786 Reviewed-by: Earl Warren <[email protected]> Co-authored-by: Renovate Bot <[email protected]> Co-committed-by: Renovate Bot <[email protected]>

Avoiding extra allocation in Reset

be31b8c

travelpolicy changed the title ~~Avoiding extra allocation in Reset~~ Avoiding extra allocation in zlib.reader.Reset Jul 21, 2025

klauspost approved these changes Jul 21, 2025

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klauspost merged commit 1a8c0e4 into klauspost:master Jul 21, 2025
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m90 mentioned this pull request Oct 21, 2025

Bump github.com/klauspost/compress from 1.18.0 to 1.18.1 offen/docker-volume-backup#656

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Avoiding extra allocation in zlib.reader.Reset #1086

Avoiding extra allocation in zlib.reader.Reset #1086

travelpolicy commented Jul 21, 2025 •

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