Imported Upstream version 1.1~hg20130304upstream/1.1_hg20130304

11 files changed, 489 insertions, 112 deletions

diff --git a/src/pkg/bytes/asm_386.s b/src/pkg/bytes/asm_386.s
index e7833de0c..c444b55e1 100644
--- a/src/pkg/bytes/asm_386.s
+++ b/src/pkg/bytes/asm_386.s
@@ -3,31 +3,31 @@
 // license that can be found in the LICENSE file.
 
 TEXT ·IndexByte(SB),7,$0
-	MOVL	p+0(FP), SI
-	MOVL	len+4(FP), CX
-	MOVB	b+12(FP), AL
+	MOVL	s+0(FP), SI
+	MOVL	s+4(FP), CX
+	MOVB	c+12(FP), AL
 	MOVL	SI, DI
 	CLD; REPN; SCASB
 	JZ 3(PC)
-	MOVL	$-1, ret+16(FP)
+	MOVL	$-1, r+16(FP)
 	RET
 	SUBL	SI, DI
 	SUBL	$1, DI
-	MOVL	DI, ret+16(FP)
+	MOVL	DI, r+16(FP)
 	RET
 
 TEXT ·Equal(SB),7,$0
-	MOVL	len+4(FP), BX
-	MOVL	len1+16(FP), CX
+	MOVL	a+4(FP), BX
+	MOVL	b+16(FP), CX
 	MOVL	$0, AX
 	CMPL	BX, CX
 	JNE	eqret
-	MOVL	p+0(FP), SI
-	MOVL	q+12(FP), DI
+	MOVL	a+0(FP), SI
+	MOVL	b+12(FP), DI
 	CLD
 	REP; CMPSB
 	JNE eqret
 	MOVL	$1, AX
 eqret:
-	MOVB	AX, ret+24(FP)
+	MOVB	AX, r+24(FP)
 	RET
diff --git a/src/pkg/bytes/asm_amd64.s b/src/pkg/bytes/asm_amd64.s
index 5caea5c52..482422642 100644
--- a/src/pkg/bytes/asm_amd64.s
+++ b/src/pkg/bytes/asm_amd64.s
@@ -3,12 +3,12 @@
 // license that can be found in the LICENSE file.
 
 TEXT ·IndexByte(SB),7,$0
-	MOVQ p+0(FP), SI
-	MOVL len+8(FP), BX
-	MOVB b+16(FP), AL
+	MOVQ s+0(FP), SI
+	MOVQ s+8(FP), BX
+	MOVB c+24(FP), AL
 	MOVQ SI, DI
 
-	CMPL BX, $16
+	CMPQ BX, $16
 	JLT small
 
 	// round up to first 16-byte boundary
@@ -63,15 +63,15 @@ condition:
 	JZ success
 
 failure:
-	MOVL $-1, ret+24(FP)
+	MOVQ $-1, r+32(FP)
 	RET
 
 // handle for lengths < 16
 small:
-	MOVL BX, CX
+	MOVQ BX, CX
 	REPN; SCASB
 	JZ success
-	MOVL $-1, ret+24(FP)
+	MOVQ $-1, r+32(FP)
 	RET
 
 // we've found the chunk containing the byte
@@ -81,28 +81,28 @@ ssesuccess:
 	BSFW DX, DX
 	SUBQ SI, DI
 	ADDQ DI, DX
-	MOVL DX, ret+24(FP)
+	MOVQ DX, r+32(FP)
 	RET
 
 success:
 	SUBQ SI, DI
 	SUBL $1, DI
-	MOVL DI, ret+24(FP)
+	MOVQ DI, r+32(FP)
 	RET
 
 TEXT ·Equal(SB),7,$0
-	MOVL	len+8(FP), BX
-	MOVL	len1+24(FP), CX
+	MOVQ	a+8(FP), BX
+	MOVQ	b+32(FP), CX
 	MOVL	$0, AX
-	CMPL	BX, CX
+	CMPQ	BX, CX
 	JNE	eqret
-	MOVQ	p+0(FP), SI
-	MOVQ	q+16(FP), DI
+	MOVQ	a+0(FP), SI
+	MOVQ	b+24(FP), DI
 	CLD
 	REP; CMPSB
 	MOVL	$1, DX
 	CMOVLEQ	DX, AX
 eqret:
-	MOVB	AX, ret+32(FP)
+	MOVB	AX, r+48(FP)
 	RET
 
diff --git a/src/pkg/bytes/asm_arm.s b/src/pkg/bytes/asm_arm.s
index 4ed0c1580..c7685f041 100644
--- a/src/pkg/bytes/asm_arm.s
+++ b/src/pkg/bytes/asm_arm.s
@@ -2,10 +2,55 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// no memchr implementation on arm yet
 TEXT ·IndexByte(SB),7,$0
-	B	·indexBytePortable(SB)
+	MOVW	s+0(FP), R0
+	MOVW	s+4(FP), R1
+	MOVBU	c+12(FP), R2	// byte to find
+	MOVW	R0, R4		// store base for later
+	ADD	R0, R1		// end 
+
+_loop:
+	CMP	R0, R1
+	B.EQ	_notfound
+	MOVBU.P	1(R0), R3
+	CMP	R2, R3
+	B.NE	_loop
+
+	SUB	$1, R0		// R0 will be one beyond the position we want
+	SUB	R4, R0		// remove base
+	MOVW    R0, r+16(FP) 
+	RET
+
+_notfound:
+	MOVW	$-1, R0
+	MOVW	R0, r+16(FP)
+	RET
 
-// no memcmp implementation on arm yet
 TEXT ·Equal(SB),7,$0
-	B	·equalPortable(SB)
+	MOVW	a+4(FP), R1
+	MOVW	b+16(FP), R3
+	
+	CMP	R1, R3		// unequal lengths are not equal
+	B.NE	_notequal
+
+	MOVW	a+0(FP), R0
+	MOVW	b+12(FP), R2
+	ADD	R0, R1		// end
+
+_next:
+	CMP	R0, R1
+	B.EQ	_equal		// reached the end
+	MOVBU.P	1(R0), R4
+	MOVBU.P	1(R2), R5
+	CMP	R4, R5
+	B.EQ	_next
+
+_notequal:
+	MOVW	$0, R0
+	MOVBU	R0, r+24(FP)
+	RET
+
+_equal:
+	MOVW	$1, R0
+	MOVBU	R0, r+24(FP)
+	RET
diff --git a/src/pkg/bytes/buffer.go b/src/pkg/bytes/buffer.go
index afdf22055..85c157798 100644
--- a/src/pkg/bytes/buffer.go
+++ b/src/pkg/bytes/buffer.go
@@ -99,6 +99,19 @@ func (b *Buffer) grow(n int) int {
 	return b.off + m
 }
 
+// Grow grows the buffer's capacity, if necessary, to guarantee space for
+// another n bytes. After Grow(n), at least n bytes can be written to the
+// buffer without another allocation.
+// If n is negative, Grow will panic.
+// If the buffer can't grow it will panic with ErrTooLarge.
+func (b *Buffer) Grow(n int) {
+	if n < 0 {
+		panic("bytes.Buffer.Grow: negative count")
+	}
+	m := b.grow(n)
+	b.buf = b.buf[0:m]
+}
+
 // Write appends the contents of p to the buffer.  The return
 // value n is the length of p; err is always nil.
 // If the buffer becomes too large, Write will panic with
@@ -347,16 +360,25 @@ func (b *Buffer) UnreadByte() error {
 // ReadBytes returns err != nil if and only if the returned data does not end in
 // delim.
 func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
+	slice, err := b.readSlice(delim)
+	// return a copy of slice. The buffer's backing array may
+	// be overwritten by later calls.
+	line = append(line, slice...)
+	return
+}
+
+// readSlice is like ReadBytes but returns a reference to internal buffer data.
+func (b *Buffer) readSlice(delim byte) (line []byte, err error) {
 	i := IndexByte(b.buf[b.off:], delim)
-	size := i + 1
+	end := b.off + i + 1
 	if i < 0 {
-		size = len(b.buf) - b.off
+		end = len(b.buf)
 		err = io.EOF
 	}
-	line = make([]byte, size)
-	copy(line, b.buf[b.off:])
-	b.off += size
-	return
+	line = b.buf[b.off:end]
+	b.off = end
+	b.lastRead = opRead
+	return line, err
 }
 
 // ReadString reads until the first occurrence of delim in the input,
@@ -366,8 +388,8 @@ func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
 // ReadString returns err != nil if and only if the returned data does not end
 // in delim.
 func (b *Buffer) ReadString(delim byte) (line string, err error) {
-	bytes, err := b.ReadBytes(delim)
-	return string(bytes), err
+	slice, err := b.readSlice(delim)
+	return string(slice), err
 }
 
 // NewBuffer creates and initializes a new Buffer using buf as its initial
diff --git a/src/pkg/bytes/buffer_test.go b/src/pkg/bytes/buffer_test.go
index d0af11f10..f9fb2625a 100644
--- a/src/pkg/bytes/buffer_test.go
+++ b/src/pkg/bytes/buffer_test.go
@@ -8,20 +8,21 @@ import (
 	. "bytes"
 	"io"
 	"math/rand"
+	"runtime"
 	"testing"
 	"unicode/utf8"
 )
 
-const N = 10000  // make this bigger for a larger (and slower) test
-var data string  // test data for write tests
-var bytes []byte // test data; same as data but as a slice.
+const N = 10000      // make this bigger for a larger (and slower) test
+var data string      // test data for write tests
+var testBytes []byte // test data; same as data but as a slice.
 
 func init() {
-	bytes = make([]byte, N)
+	testBytes = make([]byte, N)
 	for i := 0; i < N; i++ {
-		bytes[i] = 'a' + byte(i%26)
+		testBytes[i] = 'a' + byte(i%26)
 	}
-	data = string(bytes)
+	data = string(testBytes)
 }
 
 // Verify that contents of buf match the string s.
@@ -84,7 +85,7 @@ func fillBytes(t *testing.T, testname string, buf *Buffer, s string, n int, fub
 }
 
 func TestNewBuffer(t *testing.T) {
-	buf := NewBuffer(bytes)
+	buf := NewBuffer(testBytes)
 	check(t, "NewBuffer", buf, data)
 }
 
@@ -187,7 +188,7 @@ func TestLargeByteWrites(t *testing.T) {
 		limit = 9
 	}
 	for i := 3; i < limit; i += 3 {
-		s := fillBytes(t, "TestLargeWrites (1)", &buf, "", 5, bytes)
+		s := fillBytes(t, "TestLargeWrites (1)", &buf, "", 5, testBytes)
 		empty(t, "TestLargeByteWrites (2)", &buf, s, make([]byte, len(data)/i))
 	}
 	check(t, "TestLargeByteWrites (3)", &buf, "")
@@ -205,7 +206,7 @@ func TestLargeStringReads(t *testing.T) {
 func TestLargeByteReads(t *testing.T) {
 	var buf Buffer
 	for i := 3; i < 30; i += 3 {
-		s := fillBytes(t, "TestLargeReads (1)", &buf, "", 5, bytes[0:len(bytes)/i])
+		s := fillBytes(t, "TestLargeReads (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
 		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(data)))
 	}
 	check(t, "TestLargeByteReads (3)", &buf, "")
@@ -219,7 +220,7 @@ func TestMixedReadsAndWrites(t *testing.T) {
 		if i%2 == 0 {
 			s = fillString(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, data[0:wlen])
 		} else {
-			s = fillBytes(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, bytes[0:wlen])
+			s = fillBytes(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, testBytes[0:wlen])
 		}
 
 		rlen := rand.Intn(len(data))
@@ -240,7 +241,7 @@ func TestNil(t *testing.T) {
 func TestReadFrom(t *testing.T) {
 	var buf Buffer
 	for i := 3; i < 30; i += 3 {
-		s := fillBytes(t, "TestReadFrom (1)", &buf, "", 5, bytes[0:len(bytes)/i])
+		s := fillBytes(t, "TestReadFrom (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
 		var b Buffer
 		b.ReadFrom(&buf)
 		empty(t, "TestReadFrom (2)", &b, s, make([]byte, len(data)))
@@ -250,16 +251,16 @@ func TestReadFrom(t *testing.T) {
 func TestWriteTo(t *testing.T) {
 	var buf Buffer
 	for i := 3; i < 30; i += 3 {
-		s := fillBytes(t, "TestReadFrom (1)", &buf, "", 5, bytes[0:len(bytes)/i])
+		s := fillBytes(t, "TestWriteTo (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
 		var b Buffer
 		buf.WriteTo(&b)
-		empty(t, "TestReadFrom (2)", &b, s, make([]byte, len(data)))
+		empty(t, "TestWriteTo (2)", &b, s, make([]byte, len(data)))
 	}
 }
 
 func TestRuneIO(t *testing.T) {
 	const NRune = 1000
-	// Built a test array while we write the data
+	// Built a test slice while we write the data
 	b := make([]byte, utf8.UTFMax*NRune)
 	var buf Buffer
 	n := 0
@@ -374,6 +375,72 @@ func TestReadBytes(t *testing.T) {
 	}
 }
 
+func TestReadString(t *testing.T) {
+	for _, test := range readBytesTests {
+		buf := NewBufferString(test.buffer)
+		var err error
+		for _, expected := range test.expected {
+			var s string
+			s, err = buf.ReadString(test.delim)
+			if s != expected {
+				t.Errorf("expected %q, got %q", expected, s)
+			}
+			if err != nil {
+				break
+			}
+		}
+		if err != test.err {
+			t.Errorf("expected error %v, got %v", test.err, err)
+		}
+	}
+}
+
+func BenchmarkReadString(b *testing.B) {
+	const n = 32 << 10
+
+	data := make([]byte, n)
+	data[n-1] = 'x'
+	b.SetBytes(int64(n))
+	for i := 0; i < b.N; i++ {
+		buf := NewBuffer(data)
+		_, err := buf.ReadString('x')
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func TestGrow(t *testing.T) {
+	x := []byte{'x'}
+	y := []byte{'y'}
+	tmp := make([]byte, 72)
+	for _, startLen := range []int{0, 100, 1000, 10000, 100000} {
+		xBytes := Repeat(x, startLen)
+		for _, growLen := range []int{0, 100, 1000, 10000, 100000} {
+			buf := NewBuffer(xBytes)
+			// If we read, this affects buf.off, which is good to test.
+			readBytes, _ := buf.Read(tmp)
+			buf.Grow(growLen)
+			yBytes := Repeat(y, growLen)
+			// Check no allocation occurs in write, as long as we're single-threaded.
+			var m1, m2 runtime.MemStats
+			runtime.ReadMemStats(&m1)
+			buf.Write(yBytes)
+			runtime.ReadMemStats(&m2)
+			if runtime.GOMAXPROCS(-1) == 1 && m1.Mallocs != m2.Mallocs {
+				t.Errorf("allocation occurred during write")
+			}
+			// Check that buffer has correct data.
+			if !Equal(buf.Bytes()[0:startLen-readBytes], xBytes[readBytes:]) {
+				t.Errorf("bad initial data at %d %d", startLen, growLen)
+			}
+			if !Equal(buf.Bytes()[startLen-readBytes:startLen-readBytes+growLen], yBytes) {
+				t.Errorf("bad written data at %d %d", startLen, growLen)
+			}
+		}
+	}
+}
+
 // Was a bug: used to give EOF reading empty slice at EOF.
 func TestReadEmptyAtEOF(t *testing.T) {
 	b := new(Buffer)
@@ -386,3 +453,25 @@ func TestReadEmptyAtEOF(t *testing.T) {
 		t.Errorf("wrong count; got %d want 0", n)
 	}
 }
+
+func TestUnreadByte(t *testing.T) {
+	b := new(Buffer)
+	b.WriteString("abcdefghijklmnopqrstuvwxyz")
+
+	_, err := b.ReadBytes('m')
+	if err != nil {
+		t.Fatalf("ReadBytes: %v", err)
+	}
+
+	err = b.UnreadByte()
+	if err != nil {
+		t.Fatalf("UnreadByte: %v", err)
+	}
+	c, err := b.ReadByte()
+	if err != nil {
+		t.Fatalf("ReadByte: %v", err)
+	}
+	if c != 'm' {
+		t.Errorf("ReadByte = %q; want %q", c, 'm')
+	}
+}
diff --git a/src/pkg/bytes/bytes.go b/src/pkg/bytes/bytes.go
index 7d1426fb4..3bab65ef9 100644
--- a/src/pkg/bytes/bytes.go
+++ b/src/pkg/bytes/bytes.go
@@ -11,8 +11,8 @@ import (
 	"unicode/utf8"
 )
 
-// Compare returns an integer comparing the two byte arrays lexicographically.
-// The result will be 0 if a==b, -1 if a < b, and +1 if a > b
+// Compare returns an integer comparing two byte slices lexicographically.
+// The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
 // A nil argument is equivalent to an empty slice.
 func Compare(a, b []byte) int {
 	m := len(a)
@@ -37,10 +37,6 @@ func Compare(a, b []byte) int {
 	return 0
 }
 
-// Equal returns a boolean reporting whether a == b.
-// A nil argument is equivalent to an empty slice.
-func Equal(a, b []byte) bool
-
 func equalPortable(a, b []byte) bool {
 	if len(a) != len(b) {
 		return false
@@ -53,8 +49,8 @@ func equalPortable(a, b []byte) bool {
 	return true
 }
 
-// explode splits s into an array of UTF-8 sequences, one per Unicode character (still arrays of bytes),
-// up to a maximum of n byte arrays. Invalid UTF-8 sequences are chopped into individual bytes.
+// explode splits s into a slice of UTF-8 sequences, one per Unicode character (still slices of bytes),
+// up to a maximum of n byte slices. Invalid UTF-8 sequences are chopped into individual bytes.
 func explode(s []byte, n int) [][]byte {
 	if n <= 0 {
 		n = len(s)
@@ -226,7 +222,7 @@ func LastIndexAny(s []byte, chars string) int {
 }
 
 // Generic split: splits after each instance of sep,
-// including sepSave bytes of sep in the subarrays.
+// including sepSave bytes of sep in the subslices.
 func genSplit(s, sep []byte, sepSave, n int) [][]byte {
 	if n == 0 {
 		return nil
@@ -287,15 +283,15 @@ func SplitAfter(s, sep []byte) [][]byte {
 	return genSplit(s, sep, len(sep), -1)
 }
 
-// Fields splits the array s around each instance of one or more consecutive white space
-// characters, returning a slice of subarrays of s or an empty list if s contains only white space.
+// Fields splits the slice s around each instance of one or more consecutive white space
+// characters, returning a slice of subslices of s or an empty list if s contains only white space.
 func Fields(s []byte) [][]byte {
 	return FieldsFunc(s, unicode.IsSpace)
 }
 
 // FieldsFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
-// It splits the array s at each run of code points c satisfying f(c) and
-// returns a slice of subarrays of s.  If no code points in s satisfy f(c), an
+// It splits the slice s at each run of code points c satisfying f(c) and
+// returns a slice of subslices of s.  If no code points in s satisfy f(c), an
 // empty slice is returned.
 func FieldsFunc(s []byte, f func(rune) bool) [][]byte {
 	n := 0
@@ -333,45 +329,46 @@ func FieldsFunc(s []byte, f func(rune) bool) [][]byte {
 	return a[0:na]
 }
 
-// Join concatenates the elements of a to create a single byte array.   The separator
-// sep is placed between elements in the resulting array.
-func Join(a [][]byte, sep []byte) []byte {
-	if len(a) == 0 {
+// Join concatenates the elements of s to create a new byte slice. The separator
+// sep is placed between elements in the resulting slice.
+func Join(s [][]byte, sep []byte) []byte {
+	if len(s) == 0 {
 		return []byte{}
 	}
-	if len(a) == 1 {
-		return a[0]
+	if len(s) == 1 {
+		// Just return a copy.
+		return append([]byte(nil), s[0]...)
 	}
-	n := len(sep) * (len(a) - 1)
-	for i := 0; i < len(a); i++ {
-		n += len(a[i])
+	n := len(sep) * (len(s) - 1)
+	for _, v := range s {
+		n += len(v)
 	}
 
 	b := make([]byte, n)
-	bp := copy(b, a[0])
-	for _, s := range a[1:] {
+	bp := copy(b, s[0])
+	for _, v := range s[1:] {
 		bp += copy(b[bp:], sep)
-		bp += copy(b[bp:], s)
+		bp += copy(b[bp:], v)
 	}
 	return b
 }
 
-// HasPrefix tests whether the byte array s begins with prefix.
+// HasPrefix tests whether the byte slice s begins with prefix.
 func HasPrefix(s, prefix []byte) bool {
 	return len(s) >= len(prefix) && Equal(s[0:len(prefix)], prefix)
 }
 
-// HasSuffix tests whether the byte array s ends with suffix.
+// HasSuffix tests whether the byte slice s ends with suffix.
 func HasSuffix(s, suffix []byte) bool {
 	return len(s) >= len(suffix) && Equal(s[len(s)-len(suffix):], suffix)
 }
 
-// Map returns a copy of the byte array s with all its characters modified
+// Map returns a copy of the byte slice s with all its characters modified
 // according to the mapping function. If mapping returns a negative value, the character is
 // dropped from the string with no replacement.  The characters in s and the
 // output are interpreted as UTF-8-encoded Unicode code points.
 func Map(mapping func(r rune) rune, s []byte) []byte {
-	// In the worst case, the array can grow when mapped, making
+	// In the worst case, the slice can grow when mapped, making
 	// things unpleasant.  But it's so rare we barge in assuming it's
 	// fine.  It could also shrink but that falls out naturally.
 	maxbytes := len(s) // length of b
@@ -412,28 +409,28 @@ func Repeat(b []byte, count int) []byte {
 	return nb
 }
 
-// ToUpper returns a copy of the byte array s with all Unicode letters mapped to their upper case.
+// ToUpper returns a copy of the byte slice s with all Unicode letters mapped to their upper case.
 func ToUpper(s []byte) []byte { return Map(unicode.ToUpper, s) }
 
-// ToUpper returns a copy of the byte array s with all Unicode letters mapped to their lower case.
+// ToLower returns a copy of the byte slice s with all Unicode letters mapped to their lower case.
 func ToLower(s []byte) []byte { return Map(unicode.ToLower, s) }
 
-// ToTitle returns a copy of the byte array s with all Unicode letters mapped to their title case.
+// ToTitle returns a copy of the byte slice s with all Unicode letters mapped to their title case.
 func ToTitle(s []byte) []byte { return Map(unicode.ToTitle, s) }
 
-// ToUpperSpecial returns a copy of the byte array s with all Unicode letters mapped to their
+// ToUpperSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
 // upper case, giving priority to the special casing rules.
 func ToUpperSpecial(_case unicode.SpecialCase, s []byte) []byte {
 	return Map(func(r rune) rune { return _case.ToUpper(r) }, s)
 }
 
-// ToLowerSpecial returns a copy of the byte array s with all Unicode letters mapped to their
+// ToLowerSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
 // lower case, giving priority to the special casing rules.
 func ToLowerSpecial(_case unicode.SpecialCase, s []byte) []byte {
 	return Map(func(r rune) rune { return _case.ToLower(r) }, s)
 }
 
-// ToTitleSpecial returns a copy of the byte array s with all Unicode letters mapped to their
+// ToTitleSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
 // title case, giving priority to the special casing rules.
 func ToTitleSpecial(_case unicode.SpecialCase, s []byte) []byte {
 	return Map(func(r rune) rune { return _case.ToTitle(r) }, s)
@@ -514,6 +511,24 @@ func TrimFunc(s []byte, f func(r rune) bool) []byte {
 	return TrimRightFunc(TrimLeftFunc(s, f), f)
 }
 
+// TrimPrefix returns s without the provided leading prefix string.
+// If s doesn't start with prefix, s is returned unchanged.
+func TrimPrefix(s, prefix []byte) []byte {
+	if HasPrefix(s, prefix) {
+		return s[len(prefix):]
+	}
+	return s
+}
+
+// TrimSuffix returns s without the provided trailing suffix string.
+// If s doesn't end with suffix, s is returned unchanged.
+func TrimSuffix(s, suffix []byte) []byte {
+	if HasSuffix(s, suffix) {
+		return s[:len(s)-len(suffix)]
+	}
+	return s
+}
+
 // IndexFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
 // It returns the byte index in s of the first Unicode
 // code point satisfying f(c), or -1 if none do.
@@ -552,7 +567,10 @@ 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
@@ -619,10 +637,8 @@ func Replace(s, old, new []byte, n int) []byte {
 		m = Count(s, old)
 	}
 	if m == 0 {
-		// Nothing to do. Just copy.
-		t := make([]byte, len(s))
-		copy(t, s)
-		return t
+		// Just return a copy.
+		return append([]byte(nil), s...)
 	}
 	if n < 0 || m < n {
 		n = m
diff --git a/src/pkg/bytes/bytes_decl.go b/src/pkg/bytes/bytes_decl.go
index 5d2b9e639..ce78be416 100644
--- a/src/pkg/bytes/bytes_decl.go
+++ b/src/pkg/bytes/bytes_decl.go
@@ -4,5 +4,13 @@
 
 package bytes
 
+//go:noescape
+
 // IndexByte returns the index of the first instance of c in s, or -1 if c is not present in s.
 func IndexByte(s []byte, c byte) int // asm_$GOARCH.s
+
+//go:noescape
+
+// Equal returns a boolean reporting whether a == b.
+// A nil argument is equivalent to an empty slice.
+func Equal(a, b []byte) bool // asm_$GOARCH.s
diff --git a/src/pkg/bytes/bytes_test.go b/src/pkg/bytes/bytes_test.go
index 000f23517..1d6274c33 100644
--- a/src/pkg/bytes/bytes_test.go
+++ b/src/pkg/bytes/bytes_test.go
@@ -6,6 +6,7 @@ package bytes_test
 
 import (
 	. "bytes"
+	"math/rand"
 	"reflect"
 	"testing"
 	"unicode"
@@ -24,16 +25,16 @@ func eq(a, b []string) bool {
 	return true
 }
 
-func arrayOfString(a [][]byte) []string {
-	result := make([]string, len(a))
-	for j := 0; j < len(a); j++ {
-		result[j] = string(a[j])
+func sliceOfString(s [][]byte) []string {
+	result := make([]string, len(s))
+	for i, v := range s {
+		result[i] = string(v)
 	}
 	return result
 }
 
 // For ease of reading, the test cases use strings that are converted to byte
-// arrays before invoking the functions.
+// slices before invoking the functions.
 
 var abcd = "abcd"
 var faces = "☺☻☹"
@@ -434,7 +435,7 @@ var explodetests = []ExplodeTest{
 func TestExplode(t *testing.T) {
 	for _, tt := range explodetests {
 		a := SplitN([]byte(tt.s), nil, tt.n)
-		result := arrayOfString(a)
+		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf(`Explode("%s", %d) = %v; want %v`, tt.s, tt.n, result, tt.a)
 			continue
@@ -472,7 +473,7 @@ var splittests = []SplitTest{
 func TestSplit(t *testing.T) {
 	for _, tt := range splittests {
 		a := SplitN([]byte(tt.s), []byte(tt.sep), tt.n)
-		result := arrayOfString(a)
+		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, result, tt.a)
 			continue
@@ -490,6 +491,12 @@ func TestSplit(t *testing.T) {
 				t.Errorf("Split disagrees withSplitN(%q, %q, %d) = %v; want %v", tt.s, tt.sep, tt.n, b, a)
 			}
 		}
+		if len(a) > 0 {
+			in, out := a[0], s
+			if cap(in) == cap(out) && &in[:1][0] == &out[:1][0] {
+				t.Errorf("Join(%#v, %q) didn't copy", a, tt.sep)
+			}
+		}
 	}
 }
 
@@ -512,7 +519,7 @@ var splitaftertests = []SplitTest{
 func TestSplitAfter(t *testing.T) {
 	for _, tt := range splitaftertests {
 		a := SplitAfterN([]byte(tt.s), []byte(tt.sep), tt.n)
-		result := arrayOfString(a)
+		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, result, tt.a)
 			continue
@@ -552,7 +559,7 @@ var fieldstests = []FieldsTest{
 func TestFields(t *testing.T) {
 	for _, tt := range fieldstests {
 		a := Fields([]byte(tt.s))
-		result := arrayOfString(a)
+		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf("Fields(%q) = %v; want %v", tt.s, a, tt.a)
 			continue
@@ -561,6 +568,14 @@ func TestFields(t *testing.T) {
 }
 
 func TestFieldsFunc(t *testing.T) {
+	for _, tt := range fieldstests {
+		a := FieldsFunc([]byte(tt.s), unicode.IsSpace)
+		result := sliceOfString(a)
+		if !eq(result, 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' }
 	var fieldsFuncTests = []FieldsTest{
 		{"", []string{}},
@@ -570,15 +585,15 @@ func TestFieldsFunc(t *testing.T) {
 	}
 	for _, tt := range fieldsFuncTests {
 		a := FieldsFunc([]byte(tt.s), pred)
-		result := arrayOfString(a)
+		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf("FieldsFunc(%q) = %v, want %v", tt.s, a, tt.a)
 		}
 	}
 }
 
-// Test case for any function which accepts and returns a byte array.
-// For ease of creation, we write the byte arrays as strings.
+// Test case for any function which accepts and returns a byte slice.
+// For ease of creation, we write the byte slices as strings.
 type StringTest struct {
 	in, out string
 }
@@ -779,8 +794,8 @@ func TestRunes(t *testing.T) {
 }
 
 type TrimTest struct {
-	f               string
-	in, cutset, out string
+	f            string
+	in, arg, out string
 }
 
 var trimTests = []TrimTest{
@@ -805,12 +820,17 @@ var trimTests = []TrimTest{
 	{"TrimRight", "", "123", ""},
 	{"TrimRight", "", "", ""},
 	{"TrimRight", "☺\xc0", "☺", "☺\xc0"},
+	{"TrimPrefix", "aabb", "a", "abb"},
+	{"TrimPrefix", "aabb", "b", "aabb"},
+	{"TrimSuffix", "aabb", "a", "aabb"},
+	{"TrimSuffix", "aabb", "b", "aab"},
 }
 
 func TestTrim(t *testing.T) {
 	for _, tc := range trimTests {
 		name := tc.f
 		var f func([]byte, string) []byte
+		var fb func([]byte, []byte) []byte
 		switch name {
 		case "Trim":
 			f = Trim
@@ -818,12 +838,21 @@ func TestTrim(t *testing.T) {
 			f = TrimLeft
 		case "TrimRight":
 			f = TrimRight
+		case "TrimPrefix":
+			fb = TrimPrefix
+		case "TrimSuffix":
+			fb = TrimSuffix
 		default:
 			t.Errorf("Undefined trim function %s", name)
 		}
-		actual := string(f([]byte(tc.in), tc.cutset))
+		var actual string
+		if f != nil {
+			actual = string(f([]byte(tc.in), tc.arg))
+		} else {
+			actual = string(fb([]byte(tc.in), []byte(tc.arg)))
+		}
 		if actual != tc.out {
-			t.Errorf("%s(%q, %q) = %q; want %q", name, tc.in, tc.cutset, actual, tc.out)
+			t.Errorf("%s(%q, %q) = %q; want %q", name, tc.in, tc.arg, actual, tc.out)
 		}
 	}
 }
@@ -1008,3 +1037,46 @@ func TestEqualFold(t *testing.T) {
 		}
 	}
 }
+
+var makeFieldsInput = func() []byte {
+	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 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)
+	}
+}
+
+func BenchmarkTrimSpace(b *testing.B) {
+	s := []byte("  Some text.  \n")
+	for i := 0; i < b.N; i++ {
+		TrimSpace(s)
+	}
+}
diff --git a/src/pkg/bytes/example_test.go b/src/pkg/bytes/example_test.go
index 6fe8cd5a9..ad2dbc69b 100644
--- a/src/pkg/bytes/example_test.go
+++ b/src/pkg/bytes/example_test.go
@@ -5,24 +5,81 @@
 package bytes_test
 
 import (
-	. "bytes"
+	"bytes"
 	"encoding/base64"
+	"fmt"
 	"io"
 	"os"
+	"sort"
 )
 
 func ExampleBuffer() {
-	var b Buffer // A Buffer needs no initialization.
+	var b bytes.Buffer // A Buffer needs no initialization.
 	b.Write([]byte("Hello "))
-	b.Write([]byte("world!"))
+	fmt.Fprintf(&b, "world!")
 	b.WriteTo(os.Stdout)
 	// Output: Hello world!
 }
 
 func ExampleBuffer_reader() {
 	// A Buffer can turn a string or a []byte into an io.Reader.
-	buf := NewBufferString("R29waGVycyBydWxlIQ==")
+	buf := bytes.NewBufferString("R29waGVycyBydWxlIQ==")
 	dec := base64.NewDecoder(base64.StdEncoding, buf)
 	io.Copy(os.Stdout, dec)
 	// Output: Gophers rule!
 }
+
+func ExampleCompare() {
+	// Interpret Compare's result by comparing it to zero.
+	var a, b []byte
+	if bytes.Compare(a, b) < 0 {
+		// a less b
+	}
+	if bytes.Compare(a, b) <= 0 {
+		// a less or equal b
+	}
+	if bytes.Compare(a, b) > 0 {
+		// a greater b
+	}
+	if bytes.Compare(a, b) >= 0 {
+		// a greater or equal b
+	}
+
+	// Prefer Equal to Compare for equality comparisons.
+	if bytes.Equal(a, b) {
+		// a equal b
+	}
+	if !bytes.Equal(a, b) {
+		// a not equal b
+	}
+}
+
+func ExampleCompare_search() {
+	// Binary search to find a matching byte slice.
+	var needle []byte
+	var haystack [][]byte // Assume sorted
+	i := sort.Search(len(haystack), func(i int) bool {
+		// Return haystack[i] >= needle.
+		return bytes.Compare(haystack[i], needle) >= 0
+	})
+	if i < len(haystack) && bytes.Equal(haystack[i], needle) {
+		// Found it!
+	}
+}
+
+func ExampleTrimSuffix() {
+	var b = []byte("Hello, goodbye, etc!")
+	b = bytes.TrimSuffix(b, []byte("goodbye, etc!"))
+	b = bytes.TrimSuffix(b, []byte("gopher"))
+	b = append(b, bytes.TrimSuffix([]byte("world!"), []byte("x!"))...)
+	os.Stdout.Write(b)
+	// Output: Hello, world!
+}
+
+func ExampleTrimPrefix() {
+	var b = []byte("Goodbye,, world!")
+	b = bytes.TrimPrefix(b, []byte("Goodbye,"))
+	b = bytes.TrimPrefix(b, []byte("See ya,"))
+	fmt.Printf("Hello%s", b)
+	// Output: Hello, world!
+}
diff --git a/src/pkg/bytes/reader.go b/src/pkg/bytes/reader.go
index a062e54ba..77511b945 100644
--- a/src/pkg/bytes/reader.go
+++ b/src/pkg/bytes/reader.go
@@ -10,7 +10,7 @@ import (
 	"unicode/utf8"
 )
 
-// A Reader implements the io.Reader, io.ReaderAt, io.Seeker,
+// A Reader implements the io.Reader, io.ReaderAt, io.WriterTo, io.Seeker,
 // io.ByteScanner, and io.RuneScanner interfaces by reading from
 // a byte slice.
 // Unlike a Buffer, a Reader is read-only and supports seeking.
@@ -121,5 +121,24 @@ func (r *Reader) Seek(offset int64, whence int) (int64, error) {
 	return abs, nil
 }
 
+// WriteTo implements the io.WriterTo interface.
+func (r *Reader) WriteTo(w io.Writer) (n int64, err error) {
+	r.prevRune = -1
+	if r.i >= len(r.s) {
+		return 0, nil
+	}
+	b := r.s[r.i:]
+	m, err := w.Write(b)
+	if m > len(b) {
+		panic("bytes.Reader.WriteTo: invalid Write count")
+	}
+	r.i += m
+	n = int64(m)
+	if m != len(b) && err == nil {
+		err = io.ErrShortWrite
+	}
+	return
+}
+
 // NewReader returns a new Reader reading from b.
 func NewReader(b []byte) *Reader { return &Reader{b, 0, -1} }
diff --git a/src/pkg/bytes/reader_test.go b/src/pkg/bytes/reader_test.go
index 2e4b1f26e..f0a3e26c4 100644
--- a/src/pkg/bytes/reader_test.go
+++ b/src/pkg/bytes/reader_test.go
@@ -8,6 +8,7 @@ import (
 	. "bytes"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"testing"
 )
@@ -86,3 +87,51 @@ func TestReaderAt(t *testing.T) {
 		}
 	}
 }
+
+func TestReaderWriteTo(t *testing.T) {
+	for i := 0; i < 30; i += 3 {
+		var l int
+		if i > 0 {
+			l = len(data) / i
+		}
+		s := data[:l]
+		r := NewReader(testBytes[:l])
+		var b Buffer
+		n, err := r.WriteTo(&b)
+		if expect := int64(len(s)); n != expect {
+			t.Errorf("got %v; want %v", n, expect)
+		}
+		if err != nil {
+			t.Errorf("for length %d: got error = %v; want nil", l, err)
+		}
+		if b.String() != s {
+			t.Errorf("got string %q; want %q", b.String(), s)
+		}
+		if r.Len() != 0 {
+			t.Errorf("reader contains %v bytes; want 0", r.Len())
+		}
+	}
+}
+
+// verify that copying from an empty reader always has the same results,
+// regardless of the presence of a WriteTo method.
+func TestReaderCopyNothing(t *testing.T) {
+	type nErr struct {
+		n   int64
+		err error
+	}
+	type justReader struct {
+		io.Reader
+	}
+	type justWriter struct {
+		io.Writer
+	}
+	discard := justWriter{ioutil.Discard} // hide ReadFrom
+
+	var with, withOut nErr
+	with.n, with.err = io.Copy(discard, NewReader(nil))
+	withOut.n, withOut.err = io.Copy(discard, justReader{NewReader(nil)})
+	if with != withOut {
+		t.Errorf("behavior differs: with = %#v; without: %#v", with, withOut)
+	}
+}