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bytes, strings: speed up TrimSpace

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This change lifts bounds checks out of loops in the TrimSpace functions,
among other micro-optimizations. Here are some benchmark results
(no change to allocations):

goos: darwin
goarch: amd64
pkg: bytes
cpu: Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
                         │     old     │                 new                 │
                         │   sec/op    │   sec/op     vs base                │
TrimSpace/NoTrim-8         4.406n ± 0%   3.829n ± 1%  -13.11% (p=0.000 n=20)
TrimSpace/ASCII-8          7.688n ± 1%   5.872n ± 1%  -23.61% (p=0.000 n=20)
TrimSpace/SomeNonASCII-8   82.25n ± 1%   81.00n ± 1%   -1.51% (p=0.001 n=20)
TrimSpace/JustNonASCII-8   131.6n ± 8%   132.2n ± 1%        ~ (p=0.899 n=20)
geomean                    24.61n        22.15n        -9.99%

pkg: strings
                         │     old     │                 new                 │
                         │   sec/op    │   sec/op     vs base                │
TrimSpace/NoTrim-8         4.178n ± 0%   3.857n ± 2%   -7.68% (p=0.001 n=20)
TrimSpace/ASCII-8          7.708n ± 0%   5.585n ± 1%  -27.55% (p=0.000 n=20)
TrimSpace/SomeNonASCII-8   98.70n ± 1%   88.54n ± 1%  -10.30% (p=0.000 n=20)
TrimSpace/JustNonASCII-8   132.8n ± 2%   123.2n ± 0%   -7.16% (p=0.000 n=20)
geomean                    25.49n        22.02n       -13.61%

Change-Id: I523f03a909c82a51940b44c7b2634985b7447982
GitHub-Last-Rev: 35163f04c6
GitHub-Pull-Request: golang/go#75127
Reviewed-on: https://go-review.googlesource.com/c/go/+/698735
Reviewed-by: Sean Liao <sean@liao.dev>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Sean Liao <sean@liao.dev>
Reviewed-by: Keith Randall <khr@google.com>
This commit is contained in:
Julien Cretel 2025-08-25 20:38:20 +00:00 • committed by Gopher Robot
parent 38204e0872
commit 89d41d254a
2 changed files with 44 additions and 56 deletions
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53
src/bytes/bytes.go
View file

@ -1117,41 +1117,34 @@ func trimRightUnicode(s []byte, cutset string) []byte {
// TrimSpace returns a subslice of s by slicing off all leading and
// trailing white space, as defined by Unicode.
func TrimSpace(s []byte) []byte {
// Fast path for ASCII: look for the first ASCII non-space byte
start := 0
for ; start < len(s); start++ {
c := s[start]
// Fast path for ASCII: look for the first ASCII non-space byte.
for lo, c := range s {
if c >= utf8.RuneSelf {
// If we run into a non-ASCII byte, fall back to the
// slower unicode-aware method on the remaining bytes
return TrimFunc(s[start:], unicode.IsSpace)
// slower unicode-aware method on the remaining bytes.
return TrimFunc(s[lo:], unicode.IsSpace)
}
if asciiSpace[c] == 0 {
break
if asciiSpace[c] != 0 {
continue
}
s = s[lo:]
// Now look for the first ASCII non-space byte from the end.
for hi := len(s) - 1; hi >= 0; hi-- {
c := s[hi]
if c >= utf8.RuneSelf {
return TrimFunc(s[:hi+1], unicode.IsSpace)
}
if asciiSpace[c] == 0 {
// At this point, s[:hi+1] starts and ends with ASCII
// non-space bytes, so we're done. Non-ASCII cases have
// already been handled above.
return s[:hi+1]
}
}
}
// Now look for the first ASCII non-space byte from the end
stop := len(s)
for ; stop > start; stop-- {
c := s[stop-1]
if c >= utf8.RuneSelf {
return TrimFunc(s[start:stop], unicode.IsSpace)
}
if asciiSpace[c] == 0 {
break
}
}
// At this point s[start:stop] starts and ends with an ASCII
// non-space bytes, so we're done. Non-ASCII cases have already
// been handled above.
if start == stop {
// Special case to preserve previous TrimLeftFunc behavior,
// returning nil instead of empty slice if all spaces.
return nil
}
return s[start:stop]
// Special case to preserve previous TrimLeftFunc behavior,
// returning nil instead of empty slice if all spaces.
return nil
}
// Runes interprets s as a sequence of UTF-8-encoded code points.

47
src/strings/strings.go
View file

@ -1091,37 +1091,32 @@ func trimRightUnicode(s, cutset string) string {
// TrimSpace returns a slice of the string s, with all leading
// and trailing white space removed, as defined by Unicode.
func TrimSpace(s string) string {
// Fast path for ASCII: look for the first ASCII non-space byte
start := 0
for ; start < len(s); start++ {
c := s[start]
// Fast path for ASCII: look for the first ASCII non-space byte.
for lo, c := range []byte(s) {
if c >= utf8.RuneSelf {
// If we run into a non-ASCII byte, fall back to the
// slower unicode-aware method on the remaining bytes
return TrimFunc(s[start:], unicode.IsSpace)
// slower unicode-aware method on the remaining bytes.
return TrimFunc(s[lo:], unicode.IsSpace)
}
if asciiSpace[c] == 0 {
break
if asciiSpace[c] != 0 {
continue
}
s = s[lo:]
// Now look for the first ASCII non-space byte from the end.
for hi := len(s) - 1; hi >= 0; hi-- {
c := s[hi]
if c >= utf8.RuneSelf {
return TrimRightFunc(s[:hi+1], unicode.IsSpace)
}
if asciiSpace[c] == 0 {
// At this point, s[:hi+1] starts and ends with ASCII
// non-space bytes, so we're done. Non-ASCII cases have
// already been handled above.
return s[:hi+1]
}
}
}
// Now look for the first ASCII non-space byte from the end
stop := len(s)
for ; stop > start; stop-- {
c := s[stop-1]
if c >= utf8.RuneSelf {
// start has been already trimmed above, should trim end only
return TrimRightFunc(s[start:stop], unicode.IsSpace)
}
if asciiSpace[c] == 0 {
break
}
}
// At this point s[start:stop] starts and ends with an ASCII
// non-space bytes, so we're done. Non-ASCII cases have already
// been handled above.
return s[start:stop]
return ""
}
// TrimPrefix returns s without the provided leading prefix string.