1 files changed, 108 insertions, 0 deletions
diff --git a/src/pkg/encoding/hex/hex.go b/src/pkg/encoding/hex/hex.go
new file mode 100644
index 0000000000..32ec42e245
--- /dev/null
+++ b/src/pkg/encoding/hex/hex.go
@@ -0,0 +1,108 @@
+// 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;
+}