code review 6495114: bytes, strings: faster Fields

src/pkg/strings/strings_test.go

Index: src/pkg/strings/strings_test.go 
=================================================================== 
--- a/src/pkg/strings/strings_test.go 
+++ b/src/pkg/strings/strings_test.go 
@@ -7,6 +7,7 @@ 
 import ( 
	"bytes" 
	"io" 
+	"math/rand" 
	"reflect" 
	. "strings" 
	"testing" 
@@ -311,6 +312,13 @@ 
 } 
 
 func TestFieldsFunc(t *testing.T) { 
+	for _, tt := range fieldstests { 
+	a := FieldsFunc(tt.s, unicode.IsSpace) 
+	if !eq(a, tt.a) { 
+	t.Errorf("FieldsFunc(%q, unicode.IsSpace) = %v; want %v", tt.s, a, tt.a) 
+	continue 
+	} 
+	} 
	pred := func(c rune) bool { return c == 'X' } 
	for _, tt := range FieldsFuncTests { 
	a := FieldsFunc(tt.s, pred) 
@@ -984,3 +992,39 @@ 
	} 
	} 
 } 
+ 
+var makeFieldsInput = func() string { 
+	x := make([]byte, 1<<20) 
+	// Input is ~10% space, ~10% 2-byte UTF-8, rest ASCII non-space. 
+	for i := range x { 
+	switch rand.Intn(10) { 
+	case 0: 
+	x[i] = ' ' 
+	case 1: 
+	if i > 0 && x[i-1] == 'x' { 
+	copy(x[i-1:], "χ") 
+	break 
+	} 
+	fallthrough 
+	default: 
+	x[i] = 'x' 
+	} 
+	} 
+	return string(x) 
+} 
+ 
+var fieldsInput = makeFieldsInput() 
+ 
+func BenchmarkFields(b *testing.B) { 
+	b.SetBytes(int64(len(fieldsInput))) 
+	for i := 0; i < b.N; i++ { 
+	Fields(fieldsInput) 
+	} 
+} 
+ 
+func BenchmarkFieldsFunc(b *testing.B) { 
+	b.SetBytes(int64(len(fieldsInput))) 
+	for i := 0; i < b.N; i++ { 
+	FieldsFunc(fieldsInput, unicode.IsSpace) 
+	} 
+}