Update to current Go library.

From-SVN: r171732

2 files changed, 48 insertions, 19 deletions

diff --git a/libgo/go/strings/strings.go b/libgo/go/strings/strings.go
index 5f009e5..93c7c46 100644
--- a/libgo/go/strings/strings.go
+++ b/libgo/go/strings/strings.go
@@ -275,20 +275,10 @@ func Join(a []string, sep string) string {
 	}
 
 	b := make([]byte, n)
-	bp := 0
-	for i := 0; i < len(a); i++ {
-		s := a[i]
-		for j := 0; j < len(s); j++ {
-			b[bp] = s[j]
-			bp++
-		}
-		if i+1 < len(a) {
-			s = sep
-			for j := 0; j < len(s); j++ {
-				b[bp] = s[j]
-				bp++
-			}
-		}
+	bp := copy(b, a[0])
+	for _, s := range a[1:] {
+		bp += copy(b[bp:], sep)
+		bp += copy(b[bp:], s)
 	}
 	return string(b)
 }
@@ -312,9 +302,19 @@ func Map(mapping func(rune int) int, s string) string {
 	// fine.  It could also shrink but that falls out naturally.
 	maxbytes := len(s) // length of b
 	nbytes := 0        // number of bytes encoded in b
-	b := make([]byte, maxbytes)
-	for _, c := range s {
+	// The output buffer b is initialized on demand, the first
+	// time a character differs.
+	var b []byte
+
+	for i, c := range s {
 		rune := mapping(c)
+		if b == nil {
+			if rune == c {
+				continue
+			}
+			b = make([]byte, maxbytes)
+			nbytes = copy(b, s[:i])
+		}
 		if rune >= 0 {
 			wid := 1
 			if rune >= utf8.RuneSelf {
@@ -330,6 +330,9 @@ func Map(mapping func(rune int) int, s string) string {
 			nbytes += utf8.EncodeRune(b[nbytes:maxbytes], rune)
 		}
 	}
+	if b == nil {
+		return s
+	}
 	return string(b[0:nbytes])
 }
 
diff --git a/libgo/go/strings/strings_test.go b/libgo/go/strings/strings_test.go
index 41e3987..c45b148 100644
--- a/libgo/go/strings/strings_test.go
+++ b/libgo/go/strings/strings_test.go
@@ -6,10 +6,12 @@ package strings_test
 
 import (
 	"os"
+	"reflect"
 	"strconv"
 	. "strings"
 	"testing"
 	"unicode"
+	"unsafe"
 	"utf8"
 )
 
@@ -429,12 +431,32 @@ func TestMap(t *testing.T) {
 	if m != expect {
 		t.Errorf("drop: expected %q got %q", expect, m)
 	}
+
+	// 6. Identity
+	identity := func(rune int) int {
+		return rune
+	}
+	orig := "Input string that we expect not to be copied."
+	m = Map(identity, orig)
+	if (*reflect.StringHeader)(unsafe.Pointer(&orig)).Data !=
+		(*reflect.StringHeader)(unsafe.Pointer(&m)).Data {
+		t.Error("unexpected copy during identity map")
+	}
 }
 
 func TestToUpper(t *testing.T) { runStringTests(t, ToUpper, "ToUpper", upperTests) }
 
 func TestToLower(t *testing.T) { runStringTests(t, ToLower, "ToLower", lowerTests) }
 
+func BenchmarkMapNoChanges(b *testing.B) {
+	identity := func(rune int) int {
+		return rune
+	}
+	for i := 0; i < b.N; i++ {
+		Map(identity, "Some string that won't be modified.")
+	}
+}
+
 func TestSpecialCase(t *testing.T) {
 	lower := "abcçdefgğhıijklmnoöprsştuüvyz"
 	upper := "ABCÇDEFGĞHIİJKLMNOÖPRSŞTUÜVYZ"
@@ -617,7 +639,11 @@ func equal(m string, s1, s2 string, t *testing.T) bool {
 
 func TestCaseConsistency(t *testing.T) {
 	// Make a string of all the runes.
-	a := make([]int, unicode.MaxRune+1)
+	numRunes := unicode.MaxRune + 1
+	if testing.Short() {
+		numRunes = 1000
+	}
+	a := make([]int, numRunes)
 	for i := range a {
 		a[i] = i
 	}
@@ -627,10 +653,10 @@ func TestCaseConsistency(t *testing.T) {
 	lower := ToLower(s)
 
 	// Consistency checks
-	if n := utf8.RuneCountInString(upper); n != unicode.MaxRune+1 {
+	if n := utf8.RuneCountInString(upper); n != numRunes {
 		t.Error("rune count wrong in upper:", n)
 	}
-	if n := utf8.RuneCountInString(lower); n != unicode.MaxRune+1 {
+	if n := utf8.RuneCountInString(lower); n != numRunes {
 		t.Error("rune count wrong in lower:", n)
 	}
 	if !equal("ToUpper(upper)", ToUpper(upper), upper, t) {