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author | Marcel van Lohuizen <mpvl@golang.org> | 2015-11-05 17:52:53 +0100 |
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committer | Marcel van Lohuizen <mpvl@golang.org> | 2015-11-16 11:29:13 +0000 |
commit | 9b299c1efd902842b788d7dc103512b6b2568ea9 (patch) | |
tree | 17b3d2e273385f06f0b866e931ef9ac88e8e8e97 /src/unicode | |
parent | 25a28da0807f3fa85588fb219f6fa40314bde675 (diff) | |
download | go-9b299c1efd902842b788d7dc103512b6b2568ea9.tar.gz go-9b299c1efd902842b788d7dc103512b6b2568ea9.zip |
unicode/utf8: removed uses of ranging over string
Ranging over string is much slower than using DecodeRuneInString.
See golang.org/issue/13162.
Replacing ranging over a string with the implementation of the Bytes
counterpart results in the following performance improvements:
RuneCountInStringTenASCIIChars-8 43.0ns ± 1% 16.4ns ± 2% -61.80% (p=0.000 n=7+8)
RuneCountInStringTenJapaneseChars-8 161ns ± 2% 154ns ± 2% -4.58% (p=0.000 n=8+8)
ValidStringTenASCIIChars-8 52.2ns ± 1% 13.2ns ± 1% -74.62% (p=0.001 n=7+7)
ValidStringTenJapaneseChars-8 173ns ± 2% 153ns ± 2% -11.78% (p=0.000 n=7+8)
Update golang/go#13162
Change-Id: Ifc40a6a94bb3317f1f2d929d310bd2694645e9f6
Reviewed-on: https://go-review.googlesource.com/16695
Reviewed-by: Russ Cox <rsc@golang.org>
Diffstat (limited to 'src/unicode')
-rw-r--r-- | src/unicode/utf8/utf8.go | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/src/unicode/utf8/utf8.go b/src/unicode/utf8/utf8.go index 9ac37184d6..5d29ec080e 100644 --- a/src/unicode/utf8/utf8.go +++ b/src/unicode/utf8/utf8.go @@ -382,10 +382,16 @@ func RuneCount(p []byte) int { // RuneCountInString is like RuneCount but its input is a string. func RuneCountInString(s string) (n int) { - for range s { + for i := 0; i < len(s); { n++ + if s[i] < RuneSelf { + i++ + } else { + _, size := DecodeRuneInString(s[i:]) + i += size + } } - return + return n } // RuneStart reports whether the byte could be the first byte of @@ -415,16 +421,18 @@ func Valid(p []byte) bool { // ValidString reports whether s consists entirely of valid UTF-8-encoded runes. func ValidString(s string) bool { - for i, r := range s { - if r == RuneError { - // The RuneError value can be an error - // sentinel value (if it's size 1) or the same - // value encoded properly. Decode it to see if - // it's the 1 byte sentinel value. + for i := 0; i < len(s); { + if s[i] < RuneSelf { + i++ + } else { _, size := DecodeRuneInString(s[i:]) if size == 1 { + // All valid runes of size 1 (those + // below RuneSelf) were handled above. + // This must be a RuneError. return false } + i += size } } return true |