From 30a9957aacb21fef5195a43dba99669465a789e7 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@golang.org>
Date: Thu, 7 Feb 2013 16:00:06 -0800
Subject: [PATCH] bytes: minor optimization to lastIndexFunc
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
---
src/pkg/bytes/bytes.go | 5 ++++-
src/pkg/bytes/bytes_test.go | 7 +++++++
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/src/pkg/bytes/bytes.go b/src/pkg/bytes/bytes.go
index 31cf89ea87c..6d40af4436c 100644
--- a/src/pkg/bytes/bytes.go
+++ b/src/pkg/bytes/bytes.go
@@ -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
diff --git a/src/pkg/bytes/bytes_test.go b/src/pkg/bytes/bytes_test.go
index 1d073b143bd..1d6274c33d1 100644
--- a/src/pkg/bytes/bytes_test.go
+++ b/src/pkg/bytes/bytes_test.go
@@ -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)
+ }
+}
--
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