Add encoding/hex

R=rsc
http://go/go-review/1015012

src/pkg/Make.deps

@@ -5,8 +5,8 @@ bignum.install: fmt.install
 bufio.install: io.install os.install strconv.install utf8.install
 bytes.install: os.install unicode.install utf8.install
 compress/flate.install: bufio.install bytes.install io.install math.install os.install sort.install strconv.install
-compress/gzip.install: bufio.install compress/flate.install hash.install hash/crc32.install io.install os.install
-compress/zlib.install: bufio.install compress/flate.install hash.install hash/adler32.install io.install os.install
+compress/gzip.install: bufio.install compress/flate.install hash/crc32.install hash.install io.install os.install
+compress/zlib.install: bufio.install compress/flate.install hash/adler32.install hash.install io.install os.install
 container/heap.install: sort.install
 container/list.install:
 container/ring.install:
@@ -26,16 +26,17 @@ ebnf.install: container/vector.install go/scanner.install go/token.install os.in
 encoding/ascii85.install: bytes.install io.install os.install strconv.install
 encoding/base64.install: bytes.install io.install os.install strconv.install
 encoding/binary.install: io.install math.install os.install reflect.install
+encoding/hex.install: os.install strconv.install strings.install
 encoding/git85.install: bytes.install io.install os.install strconv.install
 encoding/pem.install: bytes.install encoding/base64.install strings.install
 exec.install: os.install strings.install
 exp/datafmt.install: bytes.install container/vector.install fmt.install go/scanner.install go/token.install io.install os.install reflect.install runtime.install strconv.install strings.install
-exp/eval.install: bignum.install fmt.install go/ast.install go/parser.install go/scanner.install go/token.install log.install os.install reflect.install runtime.install strconv.install strings.install
+exp/eval.install: bignum.install fmt.install go/ast.install go/parser.install go/scanner.install go/token.install log.install os.install reflect.install runtime.install sort.install strconv.install strings.install
 exp/iterable.install: container/vector.install
 expvar.install: bytes.install fmt.install http.install log.install strconv.install sync.install
 flag.install: fmt.install os.install strconv.install
 fmt.install: io.install os.install reflect.install strconv.install utf8.install
-go/ast.install: go/token.install unicode.install utf8.install
+go/ast.install: fmt.install go/token.install unicode.install utf8.install
 go/doc.install: container/vector.install go/ast.install go/token.install io.install regexp.install sort.install strings.install template.install
 go/parser.install: bytes.install container/vector.install fmt.install go/ast.install go/scanner.install go/token.install io.install os.install path.install strings.install
 go/printer.install: bytes.install container/vector.install fmt.install go/ast.install go/token.install io.install os.install reflect.install runtime.install strings.install tabwriter.install
@@ -47,7 +48,7 @@ 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: bufio.install compress/zlib.install hash.install hash/crc32.install image.install io.install os.install strconv.install
+image/png.install: bufio.install compress/zlib.install hash/crc32.install hash.install image.install io.install os.install strconv.install
 io.install: bytes.install os.install sort.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

src/pkg/Makefile

@@ -41,6 +41,7 @@ DIRS=\
 	encoding/base64\
 	encoding/binary\
 	encoding/git85\
+	encoding/hex\
 	encoding/pem\
 	exec\
 	exp/datafmt\

src/pkg/encoding/hex/Makefile

+# 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.
+
+include $(GOROOT)/src/Make.$(GOARCH)
+
+TARG=encoding/hex
+GOFILES=\
+	hex.go\
+
+include $(GOROOT)/src/Make.pkg

src/pkg/encoding/hex/hex.go

+// 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.
+
+// This package implements hexadecimal encoding and decoding.
+package hex
+
+import (
+	"os";
+	"strconv";
+	"strings";
+)
+
+const hextable = "0123456789abcdef"
+
+// EncodedLen returns the length of an encoding of n source bytes.
+func EncodedLen(n int) int {
+	return n*2;
+}
+
+// Encode encodes src into EncodedLen(len(src))
+// bytes of dst.  As a convenience, it returns the number
+// of bytes written to dst, but this value is always EncodedLen(len(src)).
+// Encode implements hexadecimal encoding.
+func Encode(src, dst []byte) int {
+	for i, v := range src {
+		dst[i*2] = hextable[v>>4];
+		dst[i*2 + 1] = hextable[v&0x0f];
+	}
+
+	return len(src)*2;
+}
+
+// OddLengthInputError results from decoding an odd length slice.
+type OddLengthInputError struct{}
+
+func (OddLengthInputError) String() string {
+	return "odd length hex string";
+}
+
+// InvalidHexCharError results from finding an invalid character in a hex string.
+type InvalidHexCharError byte
+
+func (e InvalidHexCharError) String() string {
+	return "invalid hex char: " + strconv.Itoa(int(e));
+}
+
+
+func DecodedLen(x int) int {
+	return x/2;
+}
+
+// Decode decodes src into DecodedLen(len(src)) bytes, returning the actual
+// number of bytes written to dst.
+//
+// If Decode encounters invalid input, it returns an OddLengthInputError or an
+// InvalidHexCharError.
+func Decode(src, dst []byte) (int, os.Error) {
+	if len(src)%2 == 1 {
+		return 0, OddLengthInputError{};
+	}
+
+	for i := 0; i < len(src)/2; i++ {
+		a, ok := fromHexChar(src[i*2]);
+		if !ok {
+			return 0, InvalidHexCharError(src[i*2]);
+		}
+		b, ok := fromHexChar(src[i*2 + 1]);
+		if !ok {
+			return 0, InvalidHexCharError(src[i*2 + 1]);
+		}
+		dst[i] = (a<<4)|b;
+	}
+
+	return len(src)/2, nil;
+}
+
+// fromHexChar converts a hex character into its value and a success flag.
+func fromHexChar(c byte) (byte, bool) {
+	switch {
+	case 0 <= c && c <= '9':
+		return c-'0', true;
+	case 'a' <= c && c <= 'f':
+		return c-'a'+10, true;
+	case 'A' <= c && c <= 'F':
+		return c-'A'+10, true;
+	}
+
+	return 0, false;
+}
+
+// EncodeToString returns the hexadecimal encoding of src.
+func EncodeToString(src []byte) string {
+	dst := make([]byte, EncodedLen(len(src)));
+	Encode(src, dst);
+	return string(dst);
+}
+
+// DecodeString returns the bytes represented by the hexadecimal string s.
+func DecodeString(s string) ([]byte, os.Error) {
+	src := strings.Bytes(s);
+	dst := make([]byte, DecodedLen(len(src)));
+	_, err := Decode(src, dst);
+	if err != nil {
+		return nil, err;
+	}
+	return dst, nil;
+}

src/pkg/encoding/hex/hex_test.go

+// 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 hex
+
+import (
+	"bytes";
+	"testing";
+)
+
+type encodeTest struct {
+	in, out []byte;
+}
+
+var encodeTests = []encodeTest{
+	encodeTest{[]byte{}, []byte{}},
+	encodeTest{[]byte{0x01}, []byte{'0', '1'}},
+	encodeTest{[]byte{0xff}, []byte{'f', 'f'}},
+	encodeTest{[]byte{0xff, 00}, []byte{'f', 'f', '0', '0'}},
+	encodeTest{[]byte{0}, []byte{'0', '0'}},
+	encodeTest{[]byte{1}, []byte{'0', '1'}},
+	encodeTest{[]byte{2}, []byte{'0', '2'}},
+	encodeTest{[]byte{3}, []byte{'0', '3'}},
+	encodeTest{[]byte{4}, []byte{'0', '4'}},
+	encodeTest{[]byte{5}, []byte{'0', '5'}},
+	encodeTest{[]byte{6}, []byte{'0', '6'}},
+	encodeTest{[]byte{7}, []byte{'0', '7'}},
+	encodeTest{[]byte{8}, []byte{'0', '8'}},
+	encodeTest{[]byte{9}, []byte{'0', '9'}},
+	encodeTest{[]byte{10}, []byte{'0', 'a'}},
+	encodeTest{[]byte{11}, []byte{'0', 'b'}},
+	encodeTest{[]byte{12}, []byte{'0', 'c'}},
+	encodeTest{[]byte{13}, []byte{'0', 'd'}},
+	encodeTest{[]byte{14}, []byte{'0', 'e'}},
+	encodeTest{[]byte{15}, []byte{'0', 'f'}},
+}
+
+func TestEncode(t *testing.T) {
+	for i, test := range encodeTests {
+		dst := make([]byte, EncodedLen(len(test.in)));
+		n := Encode(test.in, dst);
+		if n != len(dst) {
+			t.Errorf("#%d: bad return value: got: %d want: %d", i, n, len(dst));
+		}
+		if bytes.Compare(dst, test.out) != 0 {
+			t.Errorf("#%d: got: %#v want: %#v", i, dst, test.out);
+		}
+	}
+}
+
+type decodeTest struct {
+	in, out		[]byte;
+	ok	bool;
+}
+
+var decodeTests = []decodeTest{
+	decodeTest{[]byte{}, []byte{}, true},
+	decodeTest{[]byte{'0'}, []byte{}, false},
+	decodeTest{[]byte{'0', 'g'}, []byte{}, false},
+	decodeTest{[]byte{'0', '0'}, []byte{0}, true},
+	decodeTest{[]byte{'0', '1'}, []byte{1}, true},
+	decodeTest{[]byte{'0', '2'}, []byte{2}, true},
+	decodeTest{[]byte{'0', '3'}, []byte{3}, true},
+	decodeTest{[]byte{'0', '4'}, []byte{4}, true},
+	decodeTest{[]byte{'0', '5'}, []byte{5}, true},
+	decodeTest{[]byte{'0', '6'}, []byte{6}, true},
+	decodeTest{[]byte{'0', '7'}, []byte{7}, true},
+	decodeTest{[]byte{'0', '8'}, []byte{8}, true},
+	decodeTest{[]byte{'0', '9'}, []byte{9}, true},
+	decodeTest{[]byte{'0', 'a'}, []byte{10}, true},
+	decodeTest{[]byte{'0', 'b'}, []byte{11}, true},
+	decodeTest{[]byte{'0', 'c'}, []byte{12}, true},
+	decodeTest{[]byte{'0', 'd'}, []byte{13}, true},
+	decodeTest{[]byte{'0', 'e'}, []byte{14}, true},
+	decodeTest{[]byte{'0', 'f'}, []byte{15}, true},
+	decodeTest{[]byte{'0', 'A'}, []byte{10}, true},
+	decodeTest{[]byte{'0', 'B'}, []byte{11}, true},
+	decodeTest{[]byte{'0', 'C'}, []byte{12}, true},
+	decodeTest{[]byte{'0', 'D'}, []byte{13}, true},
+	decodeTest{[]byte{'0', 'E'}, []byte{14}, true},
+	decodeTest{[]byte{'0', 'F'}, []byte{15}, true},
+}
+
+func TestDecode(t *testing.T) {
+	for i, test := range decodeTests {
+		dst := make([]byte, DecodedLen(len(test.in)));
+		n, err := Decode(test.in, dst);
+		if err == nil && n != len(dst) {
+			t.Errorf("#%d: bad return value: got:%d want:%d", i, n, len(dst));
+		}
+		if test.ok != (err == nil) {
+			t.Errorf("#%d: unexpected err value: %s", i, err);
+		}
+		if err == nil && bytes.Compare(dst, test.out) != 0 {
+			t.Errorf("#%d: got: %#v want: %#v", i, dst, test.out);
+		}
+	}
+}
+
+type encodeStringTest struct {
+	in	[]byte;
+	out	string;
+}
+
+var encodeStringTests = []encodeStringTest{
+	encodeStringTest{[]byte{}, ""},
+	encodeStringTest{[]byte{0}, "00"},
+	encodeStringTest{[]byte{0, 1}, "0001"},
+	encodeStringTest{[]byte{0, 1, 255}, "0001ff"},
+}
+
+func TestEncodeToString(t *testing.T) {
+	for i, test := range encodeStringTests {
+		s := EncodeToString(test.in);
+		if s != test.out {
+			t.Errorf("#%d got:%s want:%s", i, s, test.out);
+		}
+	}
+}
+
+type decodeStringTest struct {
+	in		string;
+	out		[]byte;
+	ok	bool;
+}
+
+var decodeStringTests = []decodeStringTest{
+	decodeStringTest{"", []byte{}, true},
+	decodeStringTest{"0", []byte{}, false},
+	decodeStringTest{"00", []byte{0}, true},
+	decodeStringTest{"0g", []byte{}, false},
+	decodeStringTest{"00ff00", []byte{0, 255, 0}, true},
+	decodeStringTest{"0000ff", []byte{0, 0, 255}, true},
+}
+
+func TestDecodeString(t *testing.T) {
+	for i, test := range decodeStringTests {
+		dst, err := DecodeString(test.in);
+		if test.ok != (err == nil) {
+			t.Errorf("#%d: unexpected err value: %s", i, err);
+		}
+		if err == nil && bytes.Compare(dst, test.out) != 0 {
+			t.Errorf("#%d: got: %#v want: #%v", i, dst, test.out);
+		}
+	}
+}