[go] archive/tar: check for non-ASCII bytes without decoding runes

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Aug 10, 2026, 12:44:47 PM (17 hours ago) Aug 10

to David Teather, Gerrit Bot, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, Dmitri Shuralyov, Dmitri Shuralyov, Mark Freeman, golang...@luci-project-accounts.iam.gserviceaccount.com, qiu laidongfeng, Joseph Tsai, golang-co...@googlegroups.com

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Change information

Commit message:

archive/tar: check for non-ASCII bytes without decoding runes

readHeader used bytes.IndexFunc with a rune predicate to reject USTAR
and PAX headers containing non-ASCII bytes, making an uninlinable
indirect call for every byte of the 512-byte block. Scanning the
bytes directly rejects exactly the same blocks: ASCII bytes decode
one at a time, so the old scan always reached the first byte >= 0x80,
where DecodeRune returns a rune >= 0x80 (possibly RuneError).

goos: darwin
goarch: arm64
pkg: archive/tar
cpu: Apple M2 Pro
                 │     old     │             new                     │
                 │   sec/op    │   sec/op     vs base                │
/Reader/USTAR-10   1.955µ ± 1%   1.098µ ± 1%  -43.84% (p=0.000 n=25)
/Reader/GNU-10     909.5n ± 1%   904.9n ± 1%        ~ (p=0.211 n=25)
/Reader/PAX-10     4.331µ ± 1%   2.569µ ± 1%  -40.68% (p=0.000 n=25)
geomean            1.975µ        1.367µ       -30.79%

Fixes #80633

Change-Id: I47dd7490e06d2096fad1fa90b0fc9cabaaeb3cc3

GitHub-Last-Rev: 05dd37d6007e85fec8d489ff4df25271b5eb7005

GitHub-Pull-Request: golang/go#80634

Reviewed-on: https://go-review.googlesource.com/c/go/+/807800

Auto-Submit: Sean Liao <se...@liao.dev>

Reviewed-by: Mark Freeman <markf...@google.com>

Reviewed-by: Dmitri Shuralyov <dmit...@google.com>

Reviewed-by: Sean Liao <se...@liao.dev>

LUCI-TryBot-Result: golang...@luci-project-accounts.iam.gserviceaccount.com <golang...@luci-project-accounts.iam.gserviceaccount.com>

Files:

M src/archive/tar/reader.go

Change size: XS

Delta: 1 file changed, 5 insertions(+), 3 deletions(-)

Branch: refs/heads/master

Submit Requirements:

Code-Review: +2 by Sean Liao, +1 by Mark Freeman, +1 by Dmitri Shuralyov
TryBots-Pass: LUCI-TryBot-Result+1 by golang...@luci-project-accounts.iam.gserviceaccount.com

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