fix comment on strings.LastIndex.

add bytes.LastIndex.
add strings.Reader.

R=r
DELTA=59  (56 added, 0 deleted, 3 changed)
OCL=35585
CL=35601

src/pkg/Make.deps

@@ -41,7 +41,7 @@ hash/adler32.install: hash.install os.install
 hash/crc32.install: hash.install os.install
 http.install: bufio.install bytes.install container/vector.install fmt.install io.install log.install net.install os.install path.install strconv.install strings.install utf8.install
 image.install:
-image/png.install: compress/zlib.install hash.install hash/crc32.install image.install io.install os.install
+image/png.install: bufio.install compress/zlib.install hash.install hash/crc32.install image.install io.install os.install strconv.install
 io.install: bytes.install os.install strings.install sync.install
 json.install: bytes.install container/vector.install fmt.install math.install reflect.install strconv.install strings.install utf8.install
 log.install: fmt.install io.install os.install runtime.install time.install
@@ -58,7 +58,7 @@ rpc.install: bufio.install fmt.install gob.install http.install io.install log.i
 runtime.install:
 sort.install:
 strconv.install: bytes.install math.install os.install unicode.install utf8.install
-strings.install: unicode.install utf8.install
+strings.install: os.install unicode.install utf8.install
 sync.install:
 syscall.install: sync.install
 tabwriter.install: bytes.install container/vector.install io.install os.install utf8.install

src/pkg/bytes/bytes.go

@@ -112,6 +112,21 @@ func Index(s, sep []byte) int {
 	return -1;
 }
 
+// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
+func LastIndex(s, sep []byte) int {
+	n := len(sep);
+	if n == 0 {
+		return len(s);
+	}
+	c := sep[0];
+	for i := len(s)-n; i >= 0; i-- {
+		if s[i] == c && (n == 1 || Equal(s[i : i+n], sep)) {
+			return i;
+		}
+	}
+	return -1;
+}
+
 // Split splits the array s around each instance of sep, returning an array of subarrays of s.
 // If sep is empty, Split splits s after each UTF-8 sequence.
 // If n > 0, split Splits s into at most n subarrays; the last subarray will contain an unsplit remainder.

src/pkg/strings/Makefile

@@ -6,6 +6,7 @@ include $(GOROOT)/src/Make.$(GOARCH)
 
 TARG=strings
 GOFILES=\
+	reader.go\
 	strings.go\
 
 include $(GOROOT)/src/Make.pkg

src/pkg/strings/reader.go

@@ -0,0 +1,40 @@
+// Copyright 2009 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
+
+import "os"
+
+// A Reader satisfies calls to Read and ReadByte by
+// reading from a string.
+type Reader string
+
+func (r *Reader) Read(b []byte) (n int, err os.Error) {
+	s := *r;
+	if len(s) == 0 {
+		return 0, os.EOF;
+	}
+	for n < len(s) && n < len(b) {
+		b[n] = s[n];
+		n++;
+	}
+	*r = s[n:len(s)];
+	return;
+}
+
+func (r *Reader) ReadByte() (b byte, err os.Error) {
+	s := *r;
+	if len(s) == 0 {
+		return 0, os.EOF;
+	}
+	b = s[0];
+	*r = s[1:len(s)];
+	return;
+}
+
+// NewReader returns a new Reader reading from s.
+// It is similar to bytes.NewBufferString but more efficient and read-only.
+func NewReader(s string) *Reader {
+	return (*Reader)(&s);
+}

src/pkg/strings/strings.go

@@ -64,7 +64,7 @@ func Index(s, sep string) int {
 	return -1
 }
 
-// Index returns the index of the last instance of sep in s, or -1 if sep is not present in s.
+// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
 func LastIndex(s, sep string) int {
 	n := len(sep);
 	if n == 0 {