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bytes: minor optimization to lastIndexFunc

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Before and after:
BenchmarkTrimSpace  20000000   81.3 ns/op
BenchmarkTrimSpace  50000000   58.0 ns/op

(most whitespace trimming is ASCII whitespace)

Same optimization appeared a handful of other places
in this file, but not here.

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/7305063
This commit is contained in:
Brad Fitzpatrick 2013-02-07 16:00:06 -08:00
parent 7594440ef1
commit 30a9957aac
2 changed files with 11 additions and 1 deletions
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5
src/pkg/bytes/bytes.go
View File

@ -571,7 +571,10 @@ func indexFunc(s []byte, f func(r rune) bool, truth bool) int {
// inverted.
func lastIndexFunc(s []byte, f func(r rune) bool, truth bool) int {
for i := len(s); i > 0; {
r, size := utf8.DecodeLastRune(s[0:i])
r, size := rune(s[i-1]), 1
if r >= utf8.RuneSelf {
r, size = utf8.DecodeLastRune(s[0:i])
}
i -= size
if f(r) == truth {
return i

7
src/pkg/bytes/bytes_test.go
View File

@ -1073,3 +1073,10 @@ func BenchmarkFieldsFunc(b *testing.B) {
FieldsFunc(fieldsInput, unicode.IsSpace)
}
}
func BenchmarkTrimSpace(b *testing.B) {
s := []byte(" Some text. \n")
for i := 0; i < b.N; i++ {
TrimSpace(s)
}
}