1 files changed, 326 insertions, 0 deletions
diff --git a/src/encoding/hex/hex.go b/src/encoding/hex/hex.go
new file mode 100644
index 0000000..fbba78f
--- /dev/null
+++ b/src/encoding/hex/hex.go
@@ -0,0 +1,326 @@
+// 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 implements hexadecimal encoding and decoding.
+package hex
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+)
+
+const hextable = "0123456789abcdef"
+
+// EncodedLen returns the length of an encoding of n source bytes.
+// Specifically, it returns n * 2.
+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(dst, src []byte) int {
+	j := 0
+	for _, v := range src {
+		dst[j] = hextable[v>>4]
+		dst[j+1] = hextable[v&0x0f]
+		j += 2
+	}
+	return len(src) * 2
+}
+
+// ErrLength reports an attempt to decode an odd-length input
+// using Decode or DecodeString.
+// The stream-based Decoder returns io.ErrUnexpectedEOF instead of ErrLength.
+var ErrLength = errors.New("encoding/hex: odd length hex string")
+
+// InvalidByteError values describe errors resulting from an invalid byte in a hex string.
+type InvalidByteError byte
+
+func (e InvalidByteError) Error() string {
+	return fmt.Sprintf("encoding/hex: invalid byte: %#U", rune(e))
+}
+
+// DecodedLen returns the length of a decoding of x source bytes.
+// Specifically, it returns x / 2.
+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.
+//
+// Decode expects that src contains only hexadecimal
+// characters and that src has even length.
+// If the input is malformed, Decode returns the number
+// of bytes decoded before the error.
+func Decode(dst, src []byte) (int, error) {
+	i, j := 0, 1
+	for ; j < len(src); j += 2 {
+		a, ok := fromHexChar(src[j-1])
+		if !ok {
+			return i, InvalidByteError(src[j-1])
+		}
+		b, ok := fromHexChar(src[j])
+		if !ok {
+			return i, InvalidByteError(src[j])
+		}
+		dst[i] = (a << 4) | b
+		i++
+	}
+	if len(src)%2 == 1 {
+		// Check for invalid char before reporting bad length,
+		// since the invalid char (if present) is an earlier problem.
+		if _, ok := fromHexChar(src[j-1]); !ok {
+			return i, InvalidByteError(src[j-1])
+		}
+		return i, ErrLength
+	}
+	return i, 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(dst, src)
+	return string(dst)
+}
+
+// DecodeString returns the bytes represented by the hexadecimal string s.
+//
+// DecodeString expects that src contains only hexadecimal
+// characters and that src has even length.
+// If the input is malformed, DecodeString returns
+// the bytes decoded before the error.
+func DecodeString(s string) ([]byte, error) {
+	src := []byte(s)
+	// We can use the source slice itself as the destination
+	// because the decode loop increments by one and then the 'seen' byte is not used anymore.
+	n, err := Decode(src, src)
+	return src[:n], err
+}
+
+// Dump returns a string that contains a hex dump of the given data. The format
+// of the hex dump matches the output of `hexdump -C` on the command line.
+func Dump(data []byte) string {
+	if len(data) == 0 {
+		return ""
+	}
+
+	var buf strings.Builder
+	// Dumper will write 79 bytes per complete 16 byte chunk, and at least
+	// 64 bytes for whatever remains. Round the allocation up, since only a
+	// maximum of 15 bytes will be wasted.
+	buf.Grow((1 + ((len(data) - 1) / 16)) * 79)
+
+	dumper := Dumper(&buf)
+	dumper.Write(data)
+	dumper.Close()
+	return buf.String()
+}
+
+// bufferSize is the number of hexadecimal characters to buffer in encoder and decoder.
+const bufferSize = 1024
+
+type encoder struct {
+	w   io.Writer
+	err error
+	out [bufferSize]byte // output buffer
+}
+
+// NewEncoder returns an io.Writer that writes lowercase hexadecimal characters to w.
+func NewEncoder(w io.Writer) io.Writer {
+	return &encoder{w: w}
+}
+
+func (e *encoder) Write(p []byte) (n int, err error) {
+	for len(p) > 0 && e.err == nil {
+		chunkSize := bufferSize / 2
+		if len(p) < chunkSize {
+			chunkSize = len(p)
+		}
+
+		var written int
+		encoded := Encode(e.out[:], p[:chunkSize])
+		written, e.err = e.w.Write(e.out[:encoded])
+		n += written / 2
+		p = p[chunkSize:]
+	}
+	return n, e.err
+}
+
+type decoder struct {
+	r   io.Reader
+	err error
+	in  []byte           // input buffer (encoded form)
+	arr [bufferSize]byte // backing array for in
+}
+
+// NewDecoder returns an io.Reader that decodes hexadecimal characters from r.
+// NewDecoder expects that r contain only an even number of hexadecimal characters.
+func NewDecoder(r io.Reader) io.Reader {
+	return &decoder{r: r}
+}
+
+func (d *decoder) Read(p []byte) (n int, err error) {
+	// Fill internal buffer with sufficient bytes to decode
+	if len(d.in) < 2 && d.err == nil {
+		var numCopy, numRead int
+		numCopy = copy(d.arr[:], d.in) // Copies either 0 or 1 bytes
+		numRead, d.err = d.r.Read(d.arr[numCopy:])
+		d.in = d.arr[:numCopy+numRead]
+		if d.err == io.EOF && len(d.in)%2 != 0 {
+			if _, ok := fromHexChar(d.in[len(d.in)-1]); !ok {
+				d.err = InvalidByteError(d.in[len(d.in)-1])
+			} else {
+				d.err = io.ErrUnexpectedEOF
+			}
+		}
+	}
+
+	// Decode internal buffer into output buffer
+	if numAvail := len(d.in) / 2; len(p) > numAvail {
+		p = p[:numAvail]
+	}
+	numDec, err := Decode(p, d.in[:len(p)*2])
+	d.in = d.in[2*numDec:]
+	if err != nil {
+		d.in, d.err = nil, err // Decode error; discard input remainder
+	}
+
+	if len(d.in) < 2 {
+		return numDec, d.err // Only expose errors when buffer fully consumed
+	}
+	return numDec, nil
+}
+
+// Dumper returns a WriteCloser that writes a hex dump of all written data to
+// w. The format of the dump matches the output of `hexdump -C` on the command
+// line.
+func Dumper(w io.Writer) io.WriteCloser {
+	return &dumper{w: w}
+}
+
+type dumper struct {
+	w          io.Writer
+	rightChars [18]byte
+	buf        [14]byte
+	used       int  // number of bytes in the current line
+	n          uint // number of bytes, total
+	closed     bool
+}
+
+func toChar(b byte) byte {
+	if b < 32 || b > 126 {
+		return '.'
+	}
+	return b
+}
+
+func (h *dumper) Write(data []byte) (n int, err error) {
+	if h.closed {
+		return 0, errors.New("encoding/hex: dumper closed")
+	}
+
+	// Output lines look like:
+	// 00000010  2e 2f 30 31 32 33 34 35  36 37 38 39 3a 3b 3c 3d  |./0123456789:;<=|
+	// ^ offset                          ^ extra space              ^ ASCII of line.
+	for i := range data {
+		if h.used == 0 {
+			// At the beginning of a line we print the current
+			// offset in hex.
+			h.buf[0] = byte(h.n >> 24)
+			h.buf[1] = byte(h.n >> 16)
+			h.buf[2] = byte(h.n >> 8)
+			h.buf[3] = byte(h.n)
+			Encode(h.buf[4:], h.buf[:4])
+			h.buf[12] = ' '
+			h.buf[13] = ' '
+			_, err = h.w.Write(h.buf[4:])
+			if err != nil {
+				return
+			}
+		}
+		Encode(h.buf[:], data[i:i+1])
+		h.buf[2] = ' '
+		l := 3
+		if h.used == 7 {
+			// There's an additional space after the 8th byte.
+			h.buf[3] = ' '
+			l = 4
+		} else if h.used == 15 {
+			// At the end of the line there's an extra space and
+			// the bar for the right column.
+			h.buf[3] = ' '
+			h.buf[4] = '|'
+			l = 5
+		}
+		_, err = h.w.Write(h.buf[:l])
+		if err != nil {
+			return
+		}
+		n++
+		h.rightChars[h.used] = toChar(data[i])
+		h.used++
+		h.n++
+		if h.used == 16 {
+			h.rightChars[16] = '|'
+			h.rightChars[17] = '\n'
+			_, err = h.w.Write(h.rightChars[:])
+			if err != nil {
+				return
+			}
+			h.used = 0
+		}
+	}
+	return
+}
+
+func (h *dumper) Close() (err error) {
+	// See the comments in Write() for the details of this format.
+	if h.closed {
+		return
+	}
+	h.closed = true
+	if h.used == 0 {
+		return
+	}
+	h.buf[0] = ' '
+	h.buf[1] = ' '
+	h.buf[2] = ' '
+	h.buf[3] = ' '
+	h.buf[4] = '|'
+	nBytes := h.used
+	for h.used < 16 {
+		l := 3
+		if h.used == 7 {
+			l = 4
+		} else if h.used == 15 {
+			l = 5
+		}
+		_, err = h.w.Write(h.buf[:l])
+		if err != nil {
+			return
+		}
+		h.used++
+	}
+	h.rightChars[nBytes] = '|'
+	h.rightChars[nBytes+1] = '\n'
+	_, err = h.w.Write(h.rightChars[:nBytes+2])
+	return
+}