From 65fbf0e834e85997f137c46cc1677ed3e2c8ff4e Mon Sep 17 00:00:00 2001 From: Agniva De Sarker Date: Wed, 8 Nov 2017 09:15:53 +0530 Subject: strings: optimize ToLower MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Handling the ASCII case inline and call unicode.ToLower only for non-ASCII cases. Gives good improvements for the ASCII case and minor perf degrade for non-ASCII case name old time/op new time/op delta ToLower/#00 10.8ns ± 1% 9.0ns ± 1% -16.83% (p=0.008 n=5+5) ToLower/abc 23.3ns ± 4% 12.6ns ± 1% -46.01% (p=0.008 n=5+5) ToLower/AbC123 91.0ns ± 2% 70.4ns ± 0% -22.59% (p=0.008 n=5+5) ToLower/azAZ09_ 104ns ± 3% 75ns ± 1% -28.35% (p=0.008 n=5+5) ToLower/longStrinGwitHmixofsmaLLandcAps 254ns ± 4% 157ns ± 0% -38.19% (p=0.016 n=5+4) ToLower/LONGⱯSTRINGⱯWITHⱯNONASCIIⱯCHARS 446ns ± 1% 451ns ± 1% ~ (p=0.056 n=5+5) ToLower/ⱭⱭⱭⱭⱭ 345ns ± 1% 348ns ± 0% +0.93% (p=0.016 n=5+5) name old alloc/op new alloc/op delta ToLower/#00 0.00B 0.00B ~ (all equal) ToLower/abc 0.00B 0.00B ~ (all equal) ToLower/AbC123 16.0B ± 0% 16.0B ± 0% ~ (all equal) ToLower/azAZ09_ 24.0B ± 0% 16.0B ± 0% -33.33% (p=0.008 n=5+5) ToLower/longStrinGwitHmixofsmaLLandcAps 80.0B ± 0% 64.0B ± 0% -20.00% (p=0.008 n=5+5) ToLower/LONGⱯSTRINGⱯWITHⱯNONASCIIⱯCHARS 96.0B ± 0% 96.0B ± 0% ~ (all equal) ToLower/ⱭⱭⱭⱭⱭ 48.0B ± 0% 48.0B ± 0% ~ (all equal) Ran on a machine with Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz Fixes #17859 Change-Id: Iacc1e6b77e1aedba9447a6e94352606f131ea597 Reviewed-on: https://go-review.googlesource.com/76470 Reviewed-by: Marvin Stenger Reviewed-by: Joe Tsai --- src/strings/strings.go | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) (limited to 'src/strings/strings.go') diff --git a/src/strings/strings.go b/src/strings/strings.go index 73bba9278c..8520f8a732 100644 --- a/src/strings/strings.go +++ b/src/strings/strings.go @@ -571,7 +571,33 @@ func ToUpper(s string) string { } // ToLower returns a copy of the string s with all Unicode letters mapped to their lower case. -func ToLower(s string) string { return Map(unicode.ToLower, s) } +func ToLower(s string) string { + isASCII, hasUpper := true, false + for i := 0; i < len(s); i++ { + c := s[i] + if c >= utf8.RuneSelf { + isASCII = false + break + } + hasUpper = hasUpper || (c >= 'A' && c <= 'Z') + } + + if isASCII { // optimize for ASCII-only strings. + if !hasUpper { + return s + } + b := make([]byte, len(s)) + for i := 0; i < len(s); i++ { + c := s[i] + if c >= 'A' && c <= 'Z' { + c += 'a' - 'A' + } + b[i] = c + } + return string(b) + } + return Map(unicode.ToLower, s) +} // ToTitle returns a copy of the string s with all Unicode letters mapped to their title case. func ToTitle(s string) string { return Map(unicode.ToTitle, s) } -- cgit v1.3