use copy

R=gri
CC=golang-dev
https://golang.org/cl/2763041

45 files changed, 68 insertions, 199 deletions

diff --git a/src/pkg/archive/tar/writer.go b/src/pkg/archive/tar/writer.go
index 1f2656d324..8673bad316 100644
--- a/src/pkg/archive/tar/writer.go
+++ b/src/pkg/archive/tar/writer.go
@@ -71,9 +71,7 @@ func (tw *Writer) cString(b []byte, s string) {
 		}
 		return
 	}
-	for i, ch := range []byte(s) {
-		b[i] = ch
-	}
+	copy(b, s)
 	if len(s) < len(b) {
 		b[len(s)] = 0
 	}
diff --git a/src/pkg/bufio/bufio.go b/src/pkg/bufio/bufio.go
index 70caf5dae8..b5b8fb3ee6 100644
--- a/src/pkg/bufio/bufio.go
+++ b/src/pkg/bufio/bufio.go
@@ -316,9 +316,7 @@ func (b *Reader) ReadBytes(delim byte) (line []byte, err os.Error) {
 			full = make([][]byte, 16)
 		} else if nfull >= len(full) {
 			newfull := make([][]byte, len(full)*2)
-			for i := 0; i < len(full); i++ {
-				newfull[i] = full[i]
-			}
+			copy(newfull, full)
 			full = newfull
 		}
 
diff --git a/src/pkg/bufio/bufio_test.go b/src/pkg/bufio/bufio_test.go
index 753cf3e77f..ef91d94cae 100644
--- a/src/pkg/bufio/bufio_test.go
+++ b/src/pkg/bufio/bufio_test.go
@@ -179,10 +179,7 @@ type StringReader struct {
 func (r *StringReader) Read(p []byte) (n int, err os.Error) {
 	if r.step < len(r.data) {
 		s := r.data[r.step]
-		for i := 0; i < len(s); i++ {
-			p[i] = s[i]
-		}
-		n = len(s)
+		n = copy(p, s)
 		r.step++
 	} else {
 		err = os.EOF
diff --git a/src/pkg/bytes/buffer.go b/src/pkg/bytes/buffer.go
index 01e6aef674..6f93869584 100644
--- a/src/pkg/bytes/buffer.go
+++ b/src/pkg/bytes/buffer.go
@@ -12,14 +12,6 @@ import (
 	"utf8"
 )
 
-// Copy from string to byte array at offset doff.  Assume there's room.
-func copyString(dst []byte, doff int, str string) {
-	for soff := 0; soff < len(str); soff++ {
-		dst[doff] = str[soff]
-		doff++
-	}
-}
-
 // A Buffer is a variable-sized buffer of bytes with Read and Write methods.
 // The zero value for Buffer is an empty buffer ready to use.
 type Buffer struct {
@@ -99,8 +91,7 @@ func (b *Buffer) Write(p []byte) (n int, err os.Error) {
 // value n is the length of s; err is always nil.
 func (b *Buffer) WriteString(s string) (n int, err os.Error) {
 	m := b.grow(len(s))
-	copyString(b.buf, m, s)
-	return len(s), nil
+	return copy(b.buf[m:], s), nil
 }
 
 // MinRead is the minimum slice size passed to a Read call by
@@ -259,7 +250,5 @@ func NewBuffer(buf []byte) *Buffer { return &Buffer{buf: buf} }
 // initial contents.  It is intended to prepare a buffer to read an existing
 // string.
 func NewBufferString(s string) *Buffer {
-	buf := make([]byte, len(s))
-	copyString(buf, 0, s)
-	return &Buffer{buf: buf}
+	return &Buffer{buf: []byte(s)}
 }
diff --git a/src/pkg/bytes/buffer_test.go b/src/pkg/bytes/buffer_test.go
index 53086a4df7..1ba77493d6 100644
--- a/src/pkg/bytes/buffer_test.go
+++ b/src/pkg/bytes/buffer_test.go
@@ -132,7 +132,7 @@ func TestBasicOperations(t *testing.T) {
 		buf.Truncate(0)
 		check(t, "TestBasicOperations (3)", &buf, "")
 
-		n, err := buf.Write(Bytes(data[0:1]))
+		n, err := buf.Write([]byte(data[0:1]))
 		if n != 1 {
 			t.Errorf("wrote 1 byte, but n == %d", n)
 		}
@@ -144,7 +144,7 @@ func TestBasicOperations(t *testing.T) {
 		buf.WriteByte(data[1])
 		check(t, "TestBasicOperations (5)", &buf, "ab")
 
-		n, err = buf.Write(Bytes(data[2:26]))
+		n, err = buf.Write([]byte(data[2:26]))
 		if n != 24 {
 			t.Errorf("wrote 25 bytes, but n == %d", n)
 		}
diff --git a/src/pkg/bytes/bytes.go b/src/pkg/bytes/bytes.go
index 458f407771..62311d41d6 100644
--- a/src/pkg/bytes/bytes.go
+++ b/src/pkg/bytes/bytes.go
@@ -325,9 +325,7 @@ func Map(mapping func(rune int) int, s []byte) []byte {
 				// Grow the buffer.
 				maxbytes = maxbytes*2 + utf8.UTFMax
 				nb := make([]byte, maxbytes)
-				for i, c := range b[0:nbytes] {
-					nb[i] = c
-				}
+				copy(nb, b[0:nbytes])
 				b = nb
 			}
 			nbytes += utf8.EncodeRune(rune, b[nbytes:maxbytes])
diff --git a/src/pkg/bytes/bytes_test.go b/src/pkg/bytes/bytes_test.go
index a43708e0d8..6f42338eb8 100644
--- a/src/pkg/bytes/bytes_test.go
+++ b/src/pkg/bytes/bytes_test.go
@@ -416,21 +416,11 @@ var trimSpaceTests = []StringTest{
 	{"x ☺ ", "x ☺"},
 }
 
-// Bytes returns a new slice containing the bytes in s.
-// Borrowed from strings to avoid dependency.
-func Bytes(s string) []byte {
-	b := make([]byte, len(s))
-	for i := 0; i < len(s); i++ {
-		b[i] = s[i]
-	}
-	return b
-}
-
 // Execute f on each test case.  funcName should be the name of f; it's used
 // in failure reports.
 func runStringTests(t *testing.T, f func([]byte) []byte, funcName string, testCases []StringTest) {
 	for _, tc := range testCases {
-		actual := string(f(Bytes(tc.in)))
+		actual := string(f([]byte(tc.in)))
 		if actual != tc.out {
 			t.Errorf("%s(%q) = %q; want %q", funcName, tc.in, actual, tc.out)
 		}
@@ -463,7 +453,7 @@ func TestMap(t *testing.T) {
 
 	// 1.  Grow.  This triggers two reallocations in Map.
 	maxRune := func(rune int) int { return unicode.MaxRune }
-	m := Map(maxRune, Bytes(a))
+	m := Map(maxRune, []byte(a))
 	expect := tenRunes(unicode.MaxRune)
 	if string(m) != expect {
 		t.Errorf("growing: expected %q got %q", expect, m)
@@ -471,21 +461,21 @@ func TestMap(t *testing.T) {
 
 	// 2. Shrink
 	minRune := func(rune int) int { return 'a' }
-	m = Map(minRune, Bytes(tenRunes(unicode.MaxRune)))
+	m = Map(minRune, []byte(tenRunes(unicode.MaxRune)))
 	expect = a
 	if string(m) != expect {
 		t.Errorf("shrinking: expected %q got %q", expect, m)
 	}
 
 	// 3. Rot13
-	m = Map(rot13, Bytes("a to zed"))
+	m = Map(rot13, []byte("a to zed"))
 	expect = "n gb mrq"
 	if string(m) != expect {
 		t.Errorf("rot13: expected %q got %q", expect, m)
 	}
 
 	// 4. Rot13^2
-	m = Map(rot13, Map(rot13, Bytes("a to zed")))
+	m = Map(rot13, Map(rot13, []byte("a to zed")))
 	expect = "a to zed"
 	if string(m) != expect {
 		t.Errorf("rot13: expected %q got %q", expect, m)
@@ -498,7 +488,7 @@ func TestMap(t *testing.T) {
 		}
 		return -1
 	}
-	m = Map(dropNotLatin, Bytes("Hello, 세계"))
+	m = Map(dropNotLatin, []byte("Hello, 세계"))
 	expect = "Hello"
 	if string(m) != expect {
 		t.Errorf("drop: expected %q got %q", expect, m)
@@ -526,9 +516,7 @@ var addtests = []AddTest{
 func TestAdd(t *testing.T) {
 	for _, test := range addtests {
 		b := make([]byte, len(test.s), test.cap)
-		for i := 0; i < len(test.s); i++ {
-			b[i] = test.s[i]
-		}
+		copy(b, test.s)
 		b = Add(b, []byte(test.t))
 		if string(b) != test.s+test.t {
 			t.Errorf("Add(%q,%q) = %q", test.s, test.t, string(b))
diff --git a/src/pkg/crypto/block/cbc.go b/src/pkg/crypto/block/cbc.go
index 10235f5411..b0b8bf638e 100644
--- a/src/pkg/crypto/block/cbc.go
+++ b/src/pkg/crypto/block/cbc.go
@@ -27,7 +27,7 @@ func newCBC(c Cipher, iv []byte) *cbcCipher {
 	x := new(cbcCipher)
 	x.c = c
 	x.blockSize = n
-	x.iv = copy(iv)
+	x.iv = dup(iv)
 	x.tmp = make([]byte, n)
 	return x
 }
diff --git a/src/pkg/crypto/block/cfb.go b/src/pkg/crypto/block/cfb.go
index 177ae939d8..2c84b32c5f 100644
--- a/src/pkg/crypto/block/cfb.go
+++ b/src/pkg/crypto/block/cfb.go
@@ -33,7 +33,7 @@ func newCFB(c Cipher, s int, iv []byte) *cfbCipher {
 	x.c = c
 	x.blockSize = s / 8
 	x.cipherSize = b
-	x.iv = copy(iv)
+	x.iv = dup(iv)
 	x.tmp = make([]byte, b)
 	return x
 }
diff --git a/src/pkg/crypto/block/cipher.go b/src/pkg/crypto/block/cipher.go
index 1b786cca49..f95c7a76e3 100644
--- a/src/pkg/crypto/block/cipher.go
+++ b/src/pkg/crypto/block/cipher.go
@@ -49,10 +49,8 @@ func same(p, q []byte) bool {
 	return true
 }
 
-func copy(p []byte) []byte {
+func dup(p []byte) []byte {
 	q := make([]byte, len(p))
-	for i, b := range p {
-		q[i] = b
-	}
+	copy(q, p)
 	return q
 }
diff --git a/src/pkg/crypto/block/ctr.go b/src/pkg/crypto/block/ctr.go
index 085ae05b18..bb9aaaaa0a 100644
--- a/src/pkg/crypto/block/ctr.go
+++ b/src/pkg/crypto/block/ctr.go
@@ -25,7 +25,7 @@ type ctrStream struct {
 func newCTRStream(c Cipher, ctr []byte) *ctrStream {
 	x := new(ctrStream)
 	x.c = c
-	x.ctr = copy(ctr)
+	x.ctr = dup(ctr)
 	x.out = make([]byte, len(ctr))
 	return x
 }
diff --git a/src/pkg/crypto/block/eax.go b/src/pkg/crypto/block/eax.go
index cc3662787c..3f3b96431e 100644
--- a/src/pkg/crypto/block/eax.go
+++ b/src/pkg/crypto/block/eax.go
@@ -45,8 +45,8 @@ func setupEAX(c Cipher, iv, hdr []byte, tagBytes int) (ctrIV, tag []byte, cmac h
 	cmac.Write(buf) // 0
 	cmac.Write(iv)
 	sum := cmac.Sum()
-	ctrIV = copy(sum)
-	tag = copy(sum[0:tagBytes])
+	ctrIV = dup(sum)
+	tag = dup(sum[0:tagBytes])
 
 	cmac.Reset()
 	buf[n-1] = 1
@@ -237,8 +237,8 @@ func (x *eaxDecrypter) checkTag() os.Error {
 	finishEAX(x.tag, x.cr.cmac)
 	if !same(x.tag, x.cr.tag) {
 		e := new(EAXTagError)
-		e.Computed = copy(x.tag)
-		e.Read = copy(x.cr.tag)
+		e.Computed = dup(x.tag)
+		e.Read = dup(x.cr.tag)
 		return e
 	}
 	return nil
diff --git a/src/pkg/crypto/block/ecb.go b/src/pkg/crypto/block/ecb.go
index 73d1d63f71..cf09f7cb3f 100644
--- a/src/pkg/crypto/block/ecb.go
+++ b/src/pkg/crypto/block/ecb.go
@@ -127,9 +127,7 @@ func (x *ecbDecrypter) Read(p []byte) (n int, err os.Error) {
 	// Save it for next time.
 	if i < n {
 		p = p[i:n]
-		for j, v := range p {
-			x.buf[j] = v
-		}
+		copy(x.buf, p)
 		x.crypt = x.buf[0:len(p)]
 		n = i
 	}
@@ -191,11 +189,7 @@ func (x *ecbEncrypter) slidePlain() {
 	if len(x.plain) == 0 {
 		x.plain = x.buf[0:0]
 	} else if cap(x.plain) < cap(x.buf) {
-		// plain and buf share same data,
-		// but buf is before plain, so forward loop is correct
-		for i := 0; i < len(x.plain); i++ {
-			x.buf[i] = x.plain[i]
-		}
+		copy(x.buf, x.plain)
 		x.plain = x.buf[0:len(x.plain)]
 	}
 }
diff --git a/src/pkg/crypto/block/ofb.go b/src/pkg/crypto/block/ofb.go
index 0cd5e73c43..11aaaa4d71 100644
--- a/src/pkg/crypto/block/ofb.go
+++ b/src/pkg/crypto/block/ofb.go
@@ -29,7 +29,7 @@ func newOFBStream(c Cipher, iv []byte) *ofbStream {
 	if n != c.BlockSize() {
 		panic(fmt.Sprintln("crypto/block: newOFBStream: invalid iv size", n, "!=", c.BlockSize()))
 	}
-	x.iv = copy(iv)
+	x.iv = dup(iv)
 	return x
 }
 
diff --git a/src/pkg/crypto/md4/md4.go b/src/pkg/crypto/md4/md4.go
index adbdf29e7c..e13c986e68 100644
--- a/src/pkg/crypto/md4/md4.go
+++ b/src/pkg/crypto/md4/md4.go
@@ -68,10 +68,7 @@ func (d *digest) Write(p []byte) (nn int, err os.Error) {
 	n := _Block(d, p)
 	p = p[n:]
 	if len(p) > 0 {
-		for i, x := range p {
-			d.x[i] = x
-		}
-		d.nx = len(p)
+		d.nx = copy(d.x[:], p)
 	}
 	return
 }
diff --git a/src/pkg/crypto/md5/md5.go b/src/pkg/crypto/md5/md5.go
index a833376512..54fddb63b9 100644
--- a/src/pkg/crypto/md5/md5.go
+++ b/src/pkg/crypto/md5/md5.go
@@ -68,10 +68,7 @@ func (d *digest) Write(p []byte) (nn int, err os.Error) {
 	n := _Block(d, p)
 	p = p[n:]
 	if len(p) > 0 {
-		for i, x := range p {
-			d.x[i] = x
-		}
-		d.nx = len(p)
+		d.nx = copy(d.x[:], p)
 	}
 	return
 }
diff --git a/src/pkg/crypto/ripemd160/ripemd160.go b/src/pkg/crypto/ripemd160/ripemd160.go
index 5d55198424..5614f1360e 100644
--- a/src/pkg/crypto/ripemd160/ripemd160.go
+++ b/src/pkg/crypto/ripemd160/ripemd160.go
@@ -72,10 +72,7 @@ func (d *digest) Write(p []byte) (nn int, err os.Error) {
 	n := _Block(d, p)
 	p = p[n:]
 	if len(p) > 0 {
-		for i, x := range p {
-			d.x[i] = x
-		}
-		d.nx = len(p)
+		d.nx = copy(d.x[:], p)
 	}
 	return
 }
diff --git a/src/pkg/crypto/sha1/sha1.go b/src/pkg/crypto/sha1/sha1.go
index 681870a218..8716c35910 100644
--- a/src/pkg/crypto/sha1/sha1.go
+++ b/src/pkg/crypto/sha1/sha1.go
@@ -70,10 +70,7 @@ func (d *digest) Write(p []byte) (nn int, err os.Error) {
 	n := _Block(d, p)
 	p = p[n:]
 	if len(p) > 0 {
-		for i, x := range p {
-			d.x[i] = x
-		}
-		d.nx = len(p)
+		d.nx = copy(d.x[:], p)
 	}
 	return
 }
diff --git a/src/pkg/crypto/sha256/sha256.go b/src/pkg/crypto/sha256/sha256.go
index df00a72985..57a8ffa0d7 100644
--- a/src/pkg/crypto/sha256/sha256.go
+++ b/src/pkg/crypto/sha256/sha256.go
@@ -112,10 +112,7 @@ func (d *digest) Write(p []byte) (nn int, err os.Error) {
 	n := _Block(d, p)
 	p = p[n:]
 	if len(p) > 0 {
-		for i, x := range p {
-			d.x[i] = x
-		}
-		d.nx = len(p)
+		d.nx = copy(d.x[:], p)
 	}
 	return
 }
diff --git a/src/pkg/crypto/sha512/sha512.go b/src/pkg/crypto/sha512/sha512.go
index 21b030563d..c3cda97d96 100644
--- a/src/pkg/crypto/sha512/sha512.go
+++ b/src/pkg/crypto/sha512/sha512.go
@@ -112,10 +112,7 @@ func (d *digest) Write(p []byte) (nn int, err os.Error) {
 	n := _Block(d, p)
 	p = p[n:]
 	if len(p) > 0 {
-		for i, x := range p {
-			d.x[i] = x
-		}
-		d.nx = len(p)
+		d.nx = copy(d.x[:], p)
 	}
 	return
 }
diff --git a/src/pkg/crypto/x509/x509.go b/src/pkg/crypto/x509/x509.go
index 4005bf0b62..327a5de2ef 100644
--- a/src/pkg/crypto/x509/x509.go
+++ b/src/pkg/crypto/x509/x509.go
@@ -504,9 +504,7 @@ func parsePublicKey(algo PublicKeyAlgorithm, asn1Data []byte) (interface{}, os.E
 func appendString(in []string, v string) (out []string) {
 	if cap(in)-len(in) < 1 {
 		out = make([]string, len(in)+1, len(in)*2+1)
-		for i, v := range in {
-			out[i] = v
-		}
+		copy(out, in)
 	} else {
 		out = in[0 : len(in)+1]
 	}
diff --git a/src/pkg/debug/dwarf/type.go b/src/pkg/debug/dwarf/type.go
index 5d4a516539..dc2e8b116d 100644
--- a/src/pkg/debug/dwarf/type.go
+++ b/src/pkg/debug/dwarf/type.go
@@ -454,9 +454,7 @@ func (d *Data) Type(off Offset) (Type, os.Error) {
 				n := len(t.Field)
 				if n >= cap(t.Field) {
 					fld := make([]*StructField, n, n*2)
-					for i, f := range t.Field {
-						fld[i] = f
-					}
+					copy(fld, t.Field)
 					t.Field = fld
 				}
 				t.Field = t.Field[0 : n+1]
@@ -505,9 +503,7 @@ func (d *Data) Type(off Offset) (Type, os.Error) {
 				n := len(t.Val)
 				if n >= cap(t.Val) {
 					val := make([]*EnumValue, n, n*2)
-					for i, f := range t.Val {
-						val[i] = f
-					}
+					copy(val, t.Val)
 					t.Val = val
 				}
 				t.Val = t.Val[0 : n+1]
@@ -561,9 +557,7 @@ func (d *Data) Type(off Offset) (Type, os.Error) {
 			n := len(t.ParamType)
 			if n >= cap(t.ParamType) {
 				param := make([]Type, n, n*2)
-				for i, t := range t.ParamType {
-					param[i] = t
-				}
+				copy(param, t.ParamType)
 				t.ParamType = param
 			}
 			t.ParamType = t.ParamType[0 : n+1]
diff --git a/src/pkg/debug/macho/file.go b/src/pkg/debug/macho/file.go
index 246dad8e78..4664f0190d 100644
--- a/src/pkg/debug/macho/file.go
+++ b/src/pkg/debug/macho/file.go
@@ -306,9 +306,7 @@ func (f *File) pushSection(sh *Section, r io.ReaderAt) {
 	if n >= cap(f.Sections) {
 		m := (n + 1) * 2
 		new := make([]*Section, n, m)
-		for i, sh := range f.Sections {
-			new[i] = sh
-		}
+		copy(new, f.Sections)
 		f.Sections = new
 	}
 	f.Sections = f.Sections[0 : n+1]
diff --git a/src/pkg/exp/4s/4s.go b/src/pkg/exp/4s/4s.go
index 271af78e27..ccc0d0051f 100644
--- a/src/pkg/exp/4s/4s.go
+++ b/src/pkg/exp/4s/4s.go
@@ -65,9 +65,7 @@ func audioServer() {
 			println(n, len(b)*2)
 		}
 		a := make([]uint16, n/2)
-		for i := range b {
-			a[i] = b[i]
-		}
+		copy(a, b)
 		n, err = av.AudioStream(a)
 	}
 }
diff --git a/src/pkg/exp/eval/expr.go b/src/pkg/exp/eval/expr.go
index 2cde189692..823f240188 100644
--- a/src/pkg/exp/eval/expr.go
+++ b/src/pkg/exp/eval/expr.go
@@ -1174,12 +1174,8 @@ func (a *exprInfo) compileCallExpr(b *block, l *expr, as []*expr) *expr {
 
 	// Gather argument and out types to initialize frame variables
 	vts := make([]Type, nin+nout)
-	for i, t := range lt.In {
-		vts[i] = t
-	}
-	for i, t := range lt.Out {
-		vts[i+nin] = t
-	}
+	copy(vts, lt.In)
+	copy(vts[nin:], lt.Out)
 
 	// Compile
 	lf := l.asFunc()
diff --git a/src/pkg/exp/eval/func.go b/src/pkg/exp/eval/func.go
index e672d0783e..777f7e5f64 100644
--- a/src/pkg/exp/eval/func.go
+++ b/src/pkg/exp/eval/func.go
@@ -46,9 +46,7 @@ func (b *codeBuf) push(instr func(*Thread)) {
 	n := len(b.instrs)
 	if n >= cap(b.instrs) {
 		a := make(code, n, n*2)
-		for i := range b.instrs {
-			a[i] = b.instrs[i]
-		}
+		copy(a, b.instrs)
 		b.instrs = a
 	}
 	b.instrs = b.instrs[0 : n+1]
@@ -60,9 +58,7 @@ func (b *codeBuf) nextPC() uint { return uint(len(b.instrs)) }
 func (b *codeBuf) get() code {
 	// Freeze this buffer into an array of exactly the right size
 	a := make(code, len(b.instrs))
-	for i := range b.instrs {
-		a[i] = b.instrs[i]
-	}
+	copy(a, b.instrs)
 	return code(a)
 }
 
diff --git a/src/pkg/exp/eval/type.go b/src/pkg/exp/eval/type.go
index 534bc3587c..6c465dd727 100644
--- a/src/pkg/exp/eval/type.go
+++ b/src/pkg/exp/eval/type.go
@@ -870,9 +870,7 @@ func NewInterfaceType(methods []IMethod, embeds []*InterfaceType) *InterfaceType
 
 	// Combine methods
 	allMethods := make([]IMethod, nMethods)
-	for i, m := range methods {
-		allMethods[i] = m
-	}
+	copy(allMethods, methods)
 	n := len(methods)
 	for _, e := range embeds {
 		for _, m := range e.methods {
diff --git a/src/pkg/exp/nacl/srpc/msg.go b/src/pkg/exp/nacl/srpc/msg.go
index fe36dbdeb5..92601ed373 100644
--- a/src/pkg/exp/nacl/srpc/msg.go
+++ b/src/pkg/exp/nacl/srpc/msg.go
@@ -126,9 +126,7 @@ func (r *msgReceiver) recv() (*msg, os.Error) {
 	// The system call *did* update r.hdr.ndesc.
 	if r.hdr.ndesc > 0 {
 		m.rdesc = make([]int32, r.hdr.ndesc)
-		for i := range m.rdesc {
-			m.rdesc[i] = r.desc[i]
-		}
+		copy(m.rdesc, r.desc)
 	}
 
 	return m, nil
@@ -253,9 +251,7 @@ func (m *msg) wbytes(p []byte) { copy(m.grow(len(p)), p) }
 
 func (m *msg) wstring(s string) {
 	b := m.grow(len(s))
-	for i := range b {
-		b[i] = s[i]
-	}
+	copy(b, s)
 }
 
 // Parsing of RPC header and arguments.
diff --git a/src/pkg/exp/nacl/srpc/server.go b/src/pkg/exp/nacl/srpc/server.go
index 433484b4ea..0abc6df418 100644
--- a/src/pkg/exp/nacl/srpc/server.go
+++ b/src/pkg/exp/nacl/srpc/server.go
@@ -56,9 +56,7 @@ func Add(name, fmt string, handler Handler) {
 	n := len(rpcMethod)
 	if n >= cap(rpcMethod) {
 		a := make([]method, n, (n+4)*2)
-		for i := range a {
-			a[i] = rpcMethod[i]
-		}
+		copy(a, rpcMethod)
 		rpcMethod = a
 	}
 	rpcMethod = rpcMethod[0 : n+1]
diff --git a/src/pkg/exp/ogle/process.go b/src/pkg/exp/ogle/process.go
index a3aa22f9f4..2c59c79fc9 100644
--- a/src/pkg/exp/ogle/process.go
+++ b/src/pkg/exp/ogle/process.go
@@ -396,9 +396,7 @@ func (p *Process) postEvent(ev Event) {
 		m = 4
 	}
 	posted := make([]Event, n+1, m)
-	for i, p := range p.posted {
-		posted[i] = p
-	}
+	copy(posted, p.posted)
 	posted[n] = ev
 	p.posted = posted
 }
diff --git a/src/pkg/go/doc/doc.go b/src/pkg/go/doc/doc.go
index 6f044ee689..39950525ad 100644
--- a/src/pkg/go/doc/doc.go
+++ b/src/pkg/go/doc/doc.go
@@ -277,11 +277,9 @@ func (doc *docReader) addDecl(decl ast.Decl) {
 
 
 func copyCommentList(list []*ast.Comment) []*ast.Comment {
-	copy := make([]*ast.Comment, len(list))
-	for i, c := range list {
-		copy[i] = c
-	}
-	return copy
+	nlist := make([]*ast.Comment, len(list))
+	copy(nlist, list)
+	return nlist
 }
 
 
diff --git a/src/pkg/net/dnsmsg.go b/src/pkg/net/dnsmsg.go
index 1d1b62eebb..dc195caf80 100644
--- a/src/pkg/net/dnsmsg.go
+++ b/src/pkg/net/dnsmsg.go
@@ -430,10 +430,7 @@ func packStructValue(val *reflect.StructValue, msg []byte, off int) (off1 int, o
 				}
 				msg[off] = byte(len(s))
 				off++
-				for i := 0; i < len(s); i++ {
-					msg[off+i] = s[i]
-				}
-				off += len(s)
+				off += copy(msg[off:], s)
 			}
 		}
 	}
diff --git a/src/pkg/os/dir_darwin.go b/src/pkg/os/dir_darwin.go
index f9f51221da..a512190bb5 100644
--- a/src/pkg/os/dir_darwin.go
+++ b/src/pkg/os/dir_darwin.go
@@ -66,9 +66,7 @@ func (file *File) Readdirnames(count int) (names []string, err Error) {
 			count--
 			if len(names) == cap(names) {
 				nnames := make([]string, len(names), 2*len(names))
-				for i := 0; i < len(names); i++ {
-					nnames[i] = names[i]
-				}
+				copy(nnames, names)
 				names = nnames
 			}
 			names = names[0 : len(names)+1]
diff --git a/src/pkg/os/dir_freebsd.go b/src/pkg/os/dir_freebsd.go
index b32c474e69..9c4b446994 100644
--- a/src/pkg/os/dir_freebsd.go
+++ b/src/pkg/os/dir_freebsd.go
@@ -61,9 +61,7 @@ func (file *File) Readdirnames(count int) (names []string, err Error) {
 			count--
 			if len(names) == cap(names) {
 				nnames := make([]string, len(names), 2*len(names))
-				for i := 0; i < len(names); i++ {
-					nnames[i] = names[i]
-				}
+				copy(nnames, names)
 				names = nnames
 			}
 			names = names[0 : len(names)+1]
diff --git a/src/pkg/os/dir_linux.go b/src/pkg/os/dir_linux.go
index 42cc88a8a7..2177625e2d 100644
--- a/src/pkg/os/dir_linux.go
+++ b/src/pkg/os/dir_linux.go
@@ -64,9 +64,7 @@ func (file *File) Readdirnames(count int) (names []string, err Error) {
 			count--
 			if len(names) == cap(names) {
 				nnames := make([]string, len(names), 2*len(names))
-				for i := 0; i < len(names); i++ {
-					nnames[i] = names[i]
-				}
+				copy(nnames, names)
 				names = nnames
 			}
 			names = names[0 : len(names)+1]
diff --git a/src/pkg/os/dir_nacl.go b/src/pkg/os/dir_nacl.go
index 42cc88a8a7..2177625e2d 100644
--- a/src/pkg/os/dir_nacl.go
+++ b/src/pkg/os/dir_nacl.go
@@ -64,9 +64,7 @@ func (file *File) Readdirnames(count int) (names []string, err Error) {
 			count--
 			if len(names) == cap(names) {
 				nnames := make([]string, len(names), 2*len(names))
-				for i := 0; i < len(names); i++ {
-					nnames[i] = names[i]
-				}
+				copy(nnames, names)
 				names = nnames
 			}
 			names = names[0 : len(names)+1]
diff --git a/src/pkg/os/env_windows.go b/src/pkg/os/env_windows.go
index 557f5c03b8..ed34481555 100644
--- a/src/pkg/os/env_windows.go
+++ b/src/pkg/os/env_windows.go
@@ -89,9 +89,7 @@ func Environ() []string {
 			}
 			if len(r) == cap(r) {
 				nr := make([]string, len(r), 2*len(r))
-				for k := 0; k < len(r); k++ {
-					nr[k] = r[k]
-				}
+				copy(nr, r)
 				r = nr
 			}
 			r = r[0 : len(r)+1]
diff --git a/src/pkg/os/file_windows.go b/src/pkg/os/file_windows.go
index d5978a83c3..f13911ad82 100644
--- a/src/pkg/os/file_windows.go
+++ b/src/pkg/os/file_windows.go
@@ -159,9 +159,7 @@ func (file *File) Readdir(count int) (fi []FileInfo, err Error) {
 		count--
 		if len(fi) == cap(fi) {
 			nfi := make([]FileInfo, len(fi), 2*len(fi))
-			for i := 0; i < len(fi); i++ {
-				nfi[i] = fi[i]
-			}
+			copy(nfi, fi)
 			fi = nfi
 		}
 		fi = fi[0 : len(fi)+1]
diff --git a/src/pkg/scanner/scanner_test.go b/src/pkg/scanner/scanner_test.go
index a9d46dd1bc..506f434fe7 100644
--- a/src/pkg/scanner/scanner_test.go
+++ b/src/pkg/scanner/scanner_test.go
@@ -23,10 +23,7 @@ type StringReader struct {
 func (r *StringReader) Read(p []byte) (n int, err os.Error) {
 	if r.step < len(r.data) {
 		s := r.data[r.step]
-		for i := 0; i < len(s); i++ {
-			p[i] = s[i]
-		}
-		n = len(s)
+		n = copy(p, s)
 		r.step++
 	} else {
 		err = os.EOF
diff --git a/src/pkg/strings/strings.go b/src/pkg/strings/strings.go
index 6fbf67b3e6..431e3f82ea 100644
--- a/src/pkg/strings/strings.go
+++ b/src/pkg/strings/strings.go
@@ -527,21 +527,10 @@ func Replace(s, old, new string, n int) string {
 		} else {
 			j += Index(s[start:], old)
 		}
-		w += copyString(t[w:], s[start:j])
-		w += copyString(t[w:], new)
+		w += copy(t[w:], s[start:j])
+		w += copy(t[w:], new)
 		start = j + len(old)
 	}
-	w += copyString(t[w:], s[start:])
+	w += copy(t[w:], s[start:])
 	return string(t[0:w])
 }
-
-func copyString(dst []byte, src string) int {
-	n := len(dst)
-	if n > len(src) {
-		n = len(src)
-	}
-	for i := 0; i < n; i++ {
-		dst[i] = src[i]
-	}
-	return n
-}
diff --git a/src/pkg/syscall/syscall.go b/src/pkg/syscall/syscall.go
index 46f5c98764..b7761a699e 100644
--- a/src/pkg/syscall/syscall.go
+++ b/src/pkg/syscall/syscall.go
@@ -21,9 +21,7 @@ func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2, err uintptr)
 // containing the text of s.
 func StringByteSlice(s string) []byte {
 	a := make([]byte, len(s)+1)
-	for i := 0; i < len(s); i++ {
-		a[i] = s[i]
-	}
+	copy(a, s)
 	return a
 }
 
diff --git a/src/pkg/template/template.go b/src/pkg/template/template.go
index 455b6ccb91..a575ce1af0 100644
--- a/src/pkg/template/template.go
+++ b/src/pkg/template/template.go
@@ -320,9 +320,7 @@ func words(buf []byte) []string {
 		}
 		if i == cap(s) {
 			ns := make([]string, 2*cap(s))
-			for j := range s {
-				ns[j] = s[j]
-			}
+			copy(ns, s)
 			s = ns
 		}
 		s = s[0 : i+1]
diff --git a/src/pkg/testing/regexp.go b/src/pkg/testing/regexp.go
index 76baf1ec06..8f15b27625 100644
--- a/src/pkg/testing/regexp.go
+++ b/src/pkg/testing/regexp.go
@@ -170,9 +170,7 @@ func (cclass *_CharClass) addRange(a, b int) {
 	n := len(cclass.ranges)
 	if n >= cap(cclass.ranges) {
 		nr := make([]int, n, 2*n)
-		for i, j := range nr {
-			nr[i] = j
-		}
+		copy(nr, cclass.ranges)
 		cclass.ranges = nr
 	}
 	cclass.ranges = cclass.ranges[0 : n+2]
@@ -255,9 +253,7 @@ func (re *Regexp) add(i instr) instr {
 	i.setIndex(len(re.inst))
 	if n >= cap(re.inst) {
 		ni := make([]instr, n, 2*n)
-		for i, j := range re.inst {
-			ni[i] = j
-		}
+		copy(ni, re.inst)
 		re.inst = ni
 	}
 	re.inst = re.inst[0 : n+1]
diff --git a/src/pkg/unicode/maketables.go b/src/pkg/unicode/maketables.go
index 4fc41cdea0..102b034a54 100644
--- a/src/pkg/unicode/maketables.go
+++ b/src/pkg/unicode/maketables.go
@@ -496,9 +496,7 @@ func parseScript(line string, scripts map[string][]Script) {
 	s, ok := scripts[name]
 	if !ok || len(s) == cap(s) {
 		ns := make([]Script, len(s), len(s)+100)
-		for i, sc := range s {
-			ns[i] = sc
-		}
+		copy(ns, s)
 		s = ns
 	}
 	s = s[0 : len(s)+1]
diff --git a/src/pkg/xml/xml.go b/src/pkg/xml/xml.go
index 0a43393ecc..eed9355547 100644
--- a/src/pkg/xml/xml.go
+++ b/src/pkg/xml/xml.go
@@ -595,9 +595,7 @@ func (p *Parser) RawToken() (Token, os.Error) {
 		n := len(attr)
 		if n >= cap(attr) {
 			nattr := make([]Attr, n, 2*cap(attr))
-			for i, a := range attr {
-				nattr[i] = a
-			}
+			copy(nattr, attr)
 			attr = nattr
 		}
 		attr = attr[0 : n+1]