1 files changed, 391 insertions, 0 deletions
diff --git a/src/encoding/base64/base64.go b/src/encoding/base64/base64.go
new file mode 100644
index 000000000..ad3abe662
--- /dev/null
+++ b/src/encoding/base64/base64.go
@@ -0,0 +1,391 @@
+// 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"
+	"strconv"
+	"strings"
+)
+
+/*
+ * 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)
+
+var removeNewlinesMapper = func(r rune) rune {
+	if r == '\r' || r == '\n' {
+		return -1
+	}
+	return r
+}
+
+/*
+ * 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(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
+
+	for len(src) > 0 {
+		var b0, b1, b2, b3 byte
+
+		// Unpack 4x 6-bit source blocks into a 4 byte
+		// destination quantum
+		switch len(src) {
+		default:
+			b3 = src[2] & 0x3F
+			b2 = src[2] >> 6
+			fallthrough
+		case 2:
+			b2 |= (src[1] << 2) & 0x3F
+			b1 = src[1] >> 4
+			fallthrough
+		case 1:
+			b1 |= (src[0] << 4) & 0x3F
+			b0 = src[0] >> 2
+		}
+
+		// Encode 6-bit blocks using the base64 alphabet
+		dst[0] = enc.encode[b0]
+		dst[1] = enc.encode[b1]
+		dst[2] = enc.encode[b2]
+		dst[3] = enc.encode[b3]
+
+		// Pad the final quantum
+		if len(src) < 3 {
+			dst[3] = '='
+			if len(src) < 2 {
+				dst[2] = '='
+			}
+			break
+		}
+
+		src = src[3:]
+		dst = dst[4:]
+	}
+}
+
+// EncodeToString returns the base64 encoding of src.
+func (enc *Encoding) EncodeToString(src []byte) string {
+	buf := make([]byte, enc.EncodedLen(len(src)))
+	enc.Encode(buf, src)
+	return string(buf)
+}
+
+type encoder struct {
+	err  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 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:]
+		if e.nbuf < 3 {
+			return
+		}
+		e.enc.Encode(e.out[0:], e.buf[0:])
+		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
+		}
+		e.enc.Encode(e.out[0:], p[0:nn])
+		if _, e.err = e.w.Write(e.out[0 : nn/3*4]); e.err != nil {
+			return n, e.err
+		}
+		n += nn
+		p = p[nn:]
+	}
+
+	// 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() error {
+	// If there's anything left in the buffer, flush it out
+	if e.err == nil && e.nbuf > 0 {
+		e.enc.Encode(e.out[0:], e.buf[0:e.nbuf])
+		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) Error() string {
+	return "illegal base64 data at input byte " + strconv.FormatInt(int64(e), 10)
+}
+
+// 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. This method assumes that src has been
+// stripped of all supported whitespace ('\r' and '\n').
+func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
+	olen := len(src)
+	for len(src) > 0 && !end {
+		// Decode quantum using the base64 alphabet
+		var dbuf [4]byte
+		dlen := 4
+
+		for j := range dbuf {
+			if len(src) == 0 {
+				return n, false, CorruptInputError(olen - len(src) - j)
+			}
+			in := src[0]
+			src = src[1:]
+			if in == '=' {
+				// We've reached the end and there's padding
+				switch j {
+				case 0, 1:
+					// incorrect padding
+					return n, false, CorruptInputError(olen - len(src) - 1)
+				case 2:
+					// "==" is expected, the first "=" is already consumed.
+					if len(src) == 0 {
+						// not enough padding
+						return n, false, CorruptInputError(olen)
+					}
+					if src[0] != '=' {
+						// incorrect padding
+						return n, false, CorruptInputError(olen - len(src) - 1)
+					}
+					src = src[1:]
+				}
+				if len(src) > 0 {
+					// trailing garbage
+					err = CorruptInputError(olen - len(src))
+				}
+				dlen, end = j, true
+				break
+			}
+			dbuf[j] = enc.decodeMap[in]
+			if dbuf[j] == 0xFF {
+				return n, false, CorruptInputError(olen - len(src) - 1)
+			}
+		}
+
+		// Pack 4x 6-bit source blocks into 3 byte destination
+		// quantum
+		switch dlen {
+		case 4:
+			dst[2] = dbuf[2]<<6 | dbuf[3]
+			fallthrough
+		case 3:
+			dst[1] = dbuf[1]<<4 | dbuf[2]>>2
+			fallthrough
+		case 2:
+			dst[0] = dbuf[0]<<2 | dbuf[1]>>4
+		}
+		dst = dst[3:]
+		n += dlen - 1
+	}
+
+	return n, end, err
+}
+
+// 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.
+// New line characters (\r and \n) are ignored.
+func (enc *Encoding) Decode(dst, src []byte) (n int, err error) {
+	src = bytes.Map(removeNewlinesMapper, src)
+	n, _, err = enc.decode(dst, src)
+	return
+}
+
+// DecodeString returns the bytes represented by the base64 string s.
+func (enc *Encoding) DecodeString(s string) ([]byte, error) {
+	s = strings.Map(removeNewlinesMapper, s)
+	dbuf := make([]byte, enc.DecodedLen(len(s)))
+	n, _, err := enc.decode(dbuf, []byte(s))
+	return dbuf[:n], err
+}
+
+type decoder struct {
+	err    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 error) {
+	if d.err != nil {
+		return 0, d.err
+	}
+
+	// Use leftover decoded output from last read.
+	if len(d.out) > 0 {
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+		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.err != nil || 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.outbuf[0:], d.buf[0:nr])
+		d.out = d.outbuf[0:nw]
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+	} else {
+		n, d.end, d.err = d.enc.decode(p, d.buf[0:nr])
+	}
+	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
+}
+
+type newlineFilteringReader struct {
+	wrapped io.Reader
+}
+
+func (r *newlineFilteringReader) Read(p []byte) (int, error) {
+	n, err := r.wrapped.Read(p)
+	for n > 0 {
+		offset := 0
+		for i, b := range p[0:n] {
+			if b != '\r' && b != '\n' {
+				if i != offset {
+					p[offset] = b
+				}
+				offset++
+			}
+		}
+		if offset > 0 {
+			return offset, err
+		}
+		// Previous buffer entirely whitespace, read again
+		n, err = r.wrapped.Read(p)
+	}
+	return n, err
+}
+
+// NewDecoder constructs a new base64 stream decoder.
+func NewDecoder(enc *Encoding, r io.Reader) io.Reader {
+	return &decoder{enc: enc, r: &newlineFilteringReader{r}}
+}
+
+// DecodedLen 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 }