1 files changed, 334 insertions, 0 deletions
diff --git a/src/pkg/encoding/base64/base64.go b/src/pkg/encoding/base64/base64.go
new file mode 100644
index 000000000..b4daee3cc
--- /dev/null
+++ b/src/pkg/encoding/base64/base64.go
@@ -0,0 +1,334 @@
+// 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 base64 implements base64 encoding as specified by RFC 4648.
+package base64
+
+import (
+	"bytes";
+	"io";
+	"os";
+	"strconv";
+)
+
+/*
+ * Encodings
+ */
+
+// An Encoding is a radix 64 encoding/decoding scheme, defined by a
+// 64-character alphabet.  The most common encoding is the "base64"
+// encoding defined in RFC 4648 and used in MIME (RFC 2045) and PEM
+// (RFC 1421).  RFC 4648 also defines an alternate encoding, which is
+// the standard encoding with - and _ substituted for + and /.
+type Encoding struct {
+	encode		string;
+	decodeMap	[256]byte;
+}
+
+const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+const encodeURL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
+
+// NewEncoding returns a new Encoding defined by the given alphabet,
+// which must be a 64-byte string.
+func NewEncoding(encoder string) *Encoding {
+	e := new(Encoding);
+	e.encode = encoder;
+	for i := 0; i < len(e.decodeMap); i++ {
+		e.decodeMap[i] = 0xFF;
+	}
+	for i := 0; i < len(encoder); i++ {
+		e.decodeMap[encoder[i]] = byte(i);
+	}
+	return e;
+}
+
+// StdEncoding is the standard base64 encoding, as defined in
+// RFC 4648.
+var StdEncoding = NewEncoding(encodeStd)
+
+// URLEncoding is the alternate base64 encoding defined in RFC 4648.
+// It is typically used in URLs and file names.
+var URLEncoding = NewEncoding(encodeURL)
+
+/*
+ * Encoder
+ */
+
+// Encode encodes src using the encoding enc, writing
+// EncodedLen(len(src)) bytes to dst.
+//
+// The encoding pads the output to a multiple of 4 bytes,
+// so Encode is not appropriate for use on individual blocks
+// of a large data stream.  Use NewEncoder() instead.
+func (enc *Encoding) Encode(src, dst []byte) {
+	if len(src) == 0 {
+		return;
+	}
+
+	for len(src) > 0 {
+		dst[0] = 0;
+		dst[1] = 0;
+		dst[2] = 0;
+		dst[3] = 0;
+
+		// Unpack 4x 6-bit source blocks into a 4 byte
+		// destination quantum
+		switch len(src) {
+		default:
+			dst[3] |= src[2]&0x3F;
+			dst[2] |= src[2]>>6;
+			fallthrough;
+		case 2:
+			dst[2] |= (src[1]<<2)&0x3F;
+			dst[1] |= src[1]>>4;
+			fallthrough;
+		case 1:
+			dst[1] |= (src[0]<<4)&0x3F;
+			dst[0] |= src[0]>>2;
+		}
+
+		// Encode 6-bit blocks using the base64 alphabet
+		for j := 0; j < 4; j++ {
+			dst[j] = enc.encode[dst[j]];
+		}
+
+		// Pad the final quantum
+		if len(src) < 3 {
+			dst[3] = '=';
+			if len(src) < 2 {
+				dst[2] = '=';
+			}
+			break;
+		}
+
+		src = src[3:len(src)];
+		dst = dst[4:len(dst)];
+	}
+}
+
+type encoder struct {
+	err	os.Error;
+	enc	*Encoding;
+	w	io.Writer;
+	buf	[3]byte;	// buffered data waiting to be encoded
+	nbuf	int;		// number of bytes in buf
+	out	[1024]byte;	// output buffer
+}
+
+func (e *encoder) Write(p []byte) (n int, err os.Error) {
+	if e.err != nil {
+		return 0, e.err;
+	}
+
+	// Leading fringe.
+	if e.nbuf > 0 {
+		var i int;
+		for i = 0; i < len(p) && e.nbuf < 3; i++ {
+			e.buf[e.nbuf] = p[i];
+			e.nbuf++;
+		}
+		n += i;
+		p = p[i:len(p)];
+		if e.nbuf < 3 {
+			return;
+		}
+		e.enc.Encode(&e.buf, &e.out);
+		if _, e.err = e.w.Write(e.out[0:4]); e.err != nil {
+			return n, e.err;
+		}
+		e.nbuf = 0;
+	}
+
+	// Large interior chunks.
+	for len(p) >= 3 {
+		nn := len(e.out)/4*3;
+		if nn > len(p) {
+			nn = len(p);
+		}
+		nn -= nn%3;
+		if nn > 0 {
+			e.enc.Encode(p[0:nn], &e.out);
+			if _, e.err = e.w.Write(e.out[0 : nn/3*4]); e.err != nil {
+				return n, e.err;
+			}
+		}
+		n += nn;
+		p = p[nn:len(p)];
+	}
+
+	// Trailing fringe.
+	for i := 0; i < len(p); i++ {
+		e.buf[i] = p[i];
+	}
+	e.nbuf = len(p);
+	n += len(p);
+	return;
+}
+
+// Close flushes any pending output from the encoder.
+// It is an error to call Write after calling Close.
+func (e *encoder) Close() os.Error {
+	// If there's anything left in the buffer, flush it out
+	if e.err == nil && e.nbuf > 0 {
+		e.enc.Encode(e.buf[0 : e.nbuf], &e.out);
+		e.nbuf = 0;
+		_, e.err = e.w.Write(e.out[0:4]);
+	}
+	return e.err;
+}
+
+// NewEncoder returns a new base64 stream encoder.  Data written to
+// the returned writer will be encoded using enc and then written to w.
+// Base64 encodings operate in 4-byte blocks; when finished
+// writing, the caller must Close the returned encoder to flush any
+// partially written blocks.
+func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser {
+	return &encoder{enc: enc, w: w};
+}
+
+// EncodedLen returns the length in bytes of the base64 encoding
+// of an input buffer of length n.
+func (enc *Encoding) EncodedLen(n int) int {
+	return (n+2)/3*4;
+}
+
+/*
+ * Decoder
+ */
+
+type CorruptInputError int64
+
+func (e CorruptInputError) String() string {
+	return "illegal base64 data at input byte" + strconv.Itoa64(int64(e));
+}
+
+// decode is like Decode but returns an additional 'end' value, which
+// indicates if end-of-message padding was encountered and thus any
+// additional data is an error.  decode also assumes len(src)%4==0,
+// since it is meant for internal use.
+func (enc *Encoding) decode(src, dst []byte) (n int, end bool, err os.Error) {
+	for i := 0; i < len(src)/4 && !end; i++ {
+		// Decode quantum using the base64 alphabet
+		var dbuf [4]byte;
+		dlen := 4;
+
+	dbufloop:
+		for j := 0; j < 4; j++ {
+			in := src[i*4 + j];
+			if in == '=' && j >= 2 && i == len(src)/4 - 1 {
+				// We've reached the end and there's
+				// padding
+				if src[i*4 + 3] != '=' {
+					return n, false, CorruptInputError(i*4 + 2);
+				}
+				dlen = j;
+				end = true;
+				break dbufloop;
+			}
+			dbuf[j] = enc.decodeMap[in];
+			if dbuf[j] == 0xFF {
+				return n, false, CorruptInputError(i*4 + j);
+			}
+		}
+
+		// Pack 4x 6-bit source blocks into 3 byte destination
+		// quantum
+		switch dlen {
+		case 4:
+			dst[i*3 + 2] = dbuf[2]<<6 | dbuf[3];
+			fallthrough;
+		case 3:
+			dst[i*3 + 1] = dbuf[1]<<4 | dbuf[2]>>2;
+			fallthrough;
+		case 2:
+			dst[i*3 + 0] = dbuf[0]<<2 | dbuf[1]>>4;
+		}
+		n += dlen-1;
+	}
+
+	return n, end, nil;
+}
+
+// Decode decodes src using the encoding enc.  It writes at most
+// DecodedLen(len(src)) bytes to dst and returns the number of bytes
+// written.  If src contains invalid base64 data, it will return the
+// number of bytes successfully written and CorruptInputError.
+func (enc *Encoding) Decode(src, dst []byte) (n int, err os.Error) {
+	if len(src)%4 != 0 {
+		return 0, CorruptInputError(len(src)/4*4);
+	}
+
+	n, _, err = enc.decode(src, dst);
+	return;
+}
+
+type decoder struct {
+	err	os.Error;
+	enc	*Encoding;
+	r	io.Reader;
+	end	bool;		// saw end of message
+	buf	[1024]byte;	// leftover input
+	nbuf	int;
+	out	[]byte;	// leftover decoded output
+	outbuf	[1024/4*3]byte;
+}
+
+func (d *decoder) Read(p []byte) (n int, err os.Error) {
+	if d.err != nil {
+		return 0, d.err;
+	}
+
+	// Use leftover decoded output from last read.
+	if len(d.out) > 0 {
+		n = bytes.Copy(p, d.out);
+		d.out = d.out[n:len(d.out)];
+		return n, nil;
+	}
+
+	// Read a chunk.
+	nn := len(p)/3*4;
+	if nn < 4 {
+		nn = 4;
+	}
+	if nn > len(d.buf) {
+		nn = len(d.buf);
+	}
+	nn, d.err = io.ReadAtLeast(d.r, d.buf[d.nbuf : nn], 4 - d.nbuf);
+	d.nbuf += nn;
+	if d.nbuf < 4 {
+		return 0, d.err;
+	}
+
+	// Decode chunk into p, or d.out and then p if p is too small.
+	nr := d.nbuf / 4 * 4;
+	nw := d.nbuf / 4 * 3;
+	if nw > len(p) {
+		nw, d.end, d.err = d.enc.decode(d.buf[0:nr], &d.outbuf);
+		d.out = d.outbuf[0:nw];
+		n = bytes.Copy(p, d.out);
+		d.out = d.out[n:len(d.out)];
+	} else {
+		n, d.end, d.err = d.enc.decode(d.buf[0:nr], p);
+	}
+	d.nbuf -= nr;
+	for i := 0; i < d.nbuf; i++ {
+		d.buf[i] = d.buf[i+nr];
+	}
+
+	if d.err == nil {
+		d.err = err;
+	}
+	return n, d.err;
+}
+
+// NewDecoder constructs a new base64 stream decoder.
+func NewDecoder(enc *Encoding, r io.Reader) io.Reader {
+	return &decoder{enc: enc, r: r};
+}
+
+// DecodeLen returns the maximum length in bytes of the decoded data
+// corresponding to n bytes of base64-encoded data.
+func (enc *Encoding) DecodedLen(n int) int {
+	return n/4*3;
+}