6 files changed, 210 insertions, 13 deletions

diff --git a/libgo/go/strings/compare.go b/libgo/go/strings/compare.go
new file mode 100644
index 00000000000..b84dddea74e
--- /dev/null
+++ b/libgo/go/strings/compare.go
@@ -0,0 +1,28 @@
+// Copyright 2015 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strings
+
+// Compare returns an integer comparing two strings lexicographically.
+// The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
+//
+// Compare is included only for symmetry with package bytes.
+// It is usually clearer and always faster to use the built-in
+// string comparison operators ==, <, >, and so on.
+func Compare(a, b string) int {
+	// NOTE(rsc): This function does NOT call the runtime cmpstring function,
+	// because we do not want to provide any performance justification for
+	// using strings.Compare. Basically no one should use strings.Compare.
+	// As the comment above says, it is here only for symmetry with package bytes.
+	// If performance is important, the compiler should be changed to recognize
+	// the pattern so that all code doing three-way comparisons, not just code
+	// using strings.Compare, can benefit.
+	if a == b {
+		return 0
+	}
+	if a < b {
+		return -1
+	}
+	return +1
+}
diff --git a/libgo/go/strings/compare_test.go b/libgo/go/strings/compare_test.go
new file mode 100644
index 00000000000..68fc88e1431
--- /dev/null
+++ b/libgo/go/strings/compare_test.go
@@ -0,0 +1,98 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strings_test
+
+// Derived from bytes/compare_test.go.
+// Benchmarks omitted since the underlying implementation is identical.
+
+import (
+	. "strings"
+	"testing"
+)
+
+var compareTests = []struct {
+	a, b string
+	i    int
+}{
+	{"", "", 0},
+	{"a", "", 1},
+	{"", "a", -1},
+	{"abc", "abc", 0},
+	{"ab", "abc", -1},
+	{"abc", "ab", 1},
+	{"x", "ab", 1},
+	{"ab", "x", -1},
+	{"x", "a", 1},
+	{"b", "x", -1},
+	// test runtime·memeq's chunked implementation
+	{"abcdefgh", "abcdefgh", 0},
+	{"abcdefghi", "abcdefghi", 0},
+	{"abcdefghi", "abcdefghj", -1},
+}
+
+func TestCompare(t *testing.T) {
+	for _, tt := range compareTests {
+		cmp := Compare(tt.a, tt.b)
+		if cmp != tt.i {
+			t.Errorf(`Compare(%q, %q) = %v`, tt.a, tt.b, cmp)
+		}
+	}
+}
+
+func TestCompareIdenticalString(t *testing.T) {
+	var s = "Hello Gophers!"
+	if Compare(s, s) != 0 {
+		t.Error("s != s")
+	}
+	if Compare(s, s[:1]) != 1 {
+		t.Error("s > s[:1] failed")
+	}
+}
+
+func TestCompareStrings(t *testing.T) {
+	n := 128
+	a := make([]byte, n+1)
+	b := make([]byte, n+1)
+	for len := 0; len < 128; len++ {
+		// randomish but deterministic data.  No 0 or 255.
+		for i := 0; i < len; i++ {
+			a[i] = byte(1 + 31*i%254)
+			b[i] = byte(1 + 31*i%254)
+		}
+		// data past the end is different
+		for i := len; i <= n; i++ {
+			a[i] = 8
+			b[i] = 9
+		}
+
+		cmp := Compare(string(a[:len]), string(b[:len]))
+		if cmp != 0 {
+			t.Errorf(`CompareIdentical(%d) = %d`, len, cmp)
+		}
+		if len > 0 {
+			cmp = Compare(string(a[:len-1]), string(b[:len]))
+			if cmp != -1 {
+				t.Errorf(`CompareAshorter(%d) = %d`, len, cmp)
+			}
+			cmp = Compare(string(a[:len]), string(b[:len-1]))
+			if cmp != 1 {
+				t.Errorf(`CompareBshorter(%d) = %d`, len, cmp)
+			}
+		}
+		for k := 0; k < len; k++ {
+			b[k] = a[k] - 1
+			cmp = Compare(string(a[:len]), string(b[:len]))
+			if cmp != 1 {
+				t.Errorf(`CompareAbigger(%d,%d) = %d`, len, k, cmp)
+			}
+			b[k] = a[k] + 1
+			cmp = Compare(string(a[:len]), string(b[:len]))
+			if cmp != -1 {
+				t.Errorf(`CompareBbigger(%d,%d) = %d`, len, k, cmp)
+			}
+			b[k] = a[k]
+		}
+	}
+}
diff --git a/libgo/go/strings/reader.go b/libgo/go/strings/reader.go
index 82df974398c..7a872fbcb08 100644
--- a/libgo/go/strings/reader.go
+++ b/libgo/go/strings/reader.go
@@ -28,6 +28,12 @@ func (r *Reader) Len() int {
 	return int(int64(len(r.s)) - r.i)
 }
 
+// Size returns the original length of the underlying string.
+// Size is the number of bytes available for reading via ReadAt.
+// The returned value is always the same and is not affected by calls
+// to any other method.
+func (r *Reader) Size() int64 { return int64(len(r.s)) }
+
 func (r *Reader) Read(b []byte) (n int, err error) {
 	if len(b) == 0 {
 		return 0, nil
diff --git a/libgo/go/strings/reader_test.go b/libgo/go/strings/reader_test.go
index bee90eb2585..5003a37be48 100644
--- a/libgo/go/strings/reader_test.go
+++ b/libgo/go/strings/reader_test.go
@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"strings"
 	"sync"
@@ -157,3 +158,15 @@ func TestWriteTo(t *testing.T) {
 		}
 	}
 }
+
+// tests that Len is affected by reads, but Size is not.
+func TestReaderLenSize(t *testing.T) {
+	r := strings.NewReader("abc")
+	io.CopyN(ioutil.Discard, r, 1)
+	if r.Len() != 2 {
+		t.Errorf("Len = %d; want 2", r.Len())
+	}
+	if r.Size() != 3 {
+		t.Errorf("Size = %d; want 3", r.Size())
+	}
+}
diff --git a/libgo/go/strings/strings.go b/libgo/go/strings/strings.go
index 27d384983ef..dd51dabb322 100644
--- a/libgo/go/strings/strings.go
+++ b/libgo/go/strings/strings.go
@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package strings implements simple functions to manipulate strings.
+// Package strings implements simple functions to manipulate UTF-8 encoded strings.
+//
+// For information about UTF-8 strings in Go, see https://blog.golang.org/strings.
 package strings
 
 import (
@@ -78,6 +80,7 @@ func hashStrRev(sep string) (uint32, uint32) {
 }
 
 // Count counts the number of non-overlapping instances of sep in s.
+// If sep is an empty string, Count returns 1 + the number of Unicode code points in s.
 func Count(s, sep string) int {
 	n := 0
 	// special cases
@@ -125,17 +128,17 @@ func Count(s, sep string) int {
 	return n
 }
 
-// Contains returns true if substr is within s.
+// Contains reports whether substr is within s.
 func Contains(s, substr string) bool {
 	return Index(s, substr) >= 0
 }
 
-// ContainsAny returns true if any Unicode code points in chars are within s.
+// ContainsAny reports whether any Unicode code points in chars are within s.
 func ContainsAny(s, chars string) bool {
 	return IndexAny(s, chars) >= 0
 }
 
-// ContainsRune returns true if the Unicode code point r is within s.
+// ContainsRune reports whether the Unicode code point r is within s.
 func ContainsRune(s string, r rune) bool {
 	return IndexRune(s, r) >= 0
 }
@@ -184,14 +187,7 @@ func LastIndex(s, sep string) int {
 	case n == 0:
 		return len(s)
 	case n == 1:
-		// special case worth making fast
-		c := sep[0]
-		for i := len(s) - 1; i >= 0; i-- {
-			if s[i] == c {
-				return i
-			}
-		}
-		return -1
+		return LastIndexByte(s, sep[0])
 	case n == len(s):
 		if sep == s {
 			return 0
@@ -270,6 +266,16 @@ func LastIndexAny(s, chars string) int {
 	return -1
 }
 
+// LastIndexByte returns the index of the last instance of c in s, or -1 if c is not present in s.
+func LastIndexByte(s string, c byte) int {
+	for i := len(s) - 1; i >= 0; i-- {
+		if s[i] == c {
+			return i
+		}
+	}
+	return -1
+}
+
 // Generic split: splits after each instance of sep,
 // including sepSave bytes of sep in the subarrays.
 func genSplit(s, sep string, sepSave, n int) []string {
@@ -519,7 +525,7 @@ func isSeparator(r rune) bool {
 // Title returns a copy of the string s with all Unicode letters that begin words
 // mapped to their title case.
 //
-// BUG: The rule Title uses for word boundaries does not handle Unicode punctuation properly.
+// BUG(rsc): The rule Title uses for word boundaries does not handle Unicode punctuation properly.
 func Title(s string) string {
 	// Use a closure here to remember state.
 	// Hackish but effective. Depends on Map scanning in order and calling
diff --git a/libgo/go/strings/strings_test.go b/libgo/go/strings/strings_test.go
index 7bb81ef3ca1..4e21deaecde 100644
--- a/libgo/go/strings/strings_test.go
+++ b/libgo/go/strings/strings_test.go
@@ -120,6 +120,23 @@ func TestLastIndex(t *testing.T)    { runIndexTests(t, LastIndex, "LastIndex", l
 func TestIndexAny(t *testing.T)     { runIndexTests(t, IndexAny, "IndexAny", indexAnyTests) }
 func TestLastIndexAny(t *testing.T) { runIndexTests(t, LastIndexAny, "LastIndexAny", lastIndexAnyTests) }
 
+func TestLastIndexByte(t *testing.T) {
+	testCases := []IndexTest{
+		{"", "q", -1},
+		{"abcdef", "q", -1},
+		{"abcdefabcdef", "a", len("abcdef")},      // something in the middle
+		{"abcdefabcdef", "f", len("abcdefabcde")}, // last byte
+		{"zabcdefabcdef", "z", 0},                 // first byte
+		{"a☺b☻c☹d", "b", len("a☺")},               // non-ascii
+	}
+	for _, test := range testCases {
+		actual := LastIndexByte(test.s, test.sep[0])
+		if actual != test.out {
+			t.Errorf("LastIndexByte(%q,%c) = %v; want %v", test.s, test.sep[0], actual, test.out)
+		}
+	}
+}
+
 var indexRuneTests = []struct {
 	s    string
 	rune rune
@@ -569,6 +586,35 @@ func TestTrim(t *testing.T) {
 	}
 }
 
+func BenchmarkTrim(b *testing.B) {
+	b.ReportAllocs()
+
+	for i := 0; i < b.N; i++ {
+		for _, tc := range trimTests {
+			name := tc.f
+			var f func(string, string) string
+			switch name {
+			case "Trim":
+				f = Trim
+			case "TrimLeft":
+				f = TrimLeft
+			case "TrimRight":
+				f = TrimRight
+			case "TrimPrefix":
+				f = TrimPrefix
+			case "TrimSuffix":
+				f = TrimSuffix
+			default:
+				b.Errorf("Undefined trim function %s", name)
+			}
+			actual := f(tc.in, tc.arg)
+			if actual != tc.out {
+				b.Errorf("%s(%q, %q) = %q; want %q", name, tc.in, tc.arg, actual, tc.out)
+			}
+		}
+	}
+}
+
 type predicate struct {
 	f    func(rune) bool
 	name string