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path: root/src/encoding/base32/base32.go
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-rw-r--r--src/encoding/base32/base32.go426
1 files changed, 426 insertions, 0 deletions
diff --git a/src/encoding/base32/base32.go b/src/encoding/base32/base32.go
new file mode 100644
index 000000000..5a9e86919
--- /dev/null
+++ b/src/encoding/base32/base32.go
@@ -0,0 +1,426 @@
+// Copyright 2011 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 base32 implements base32 encoding as specified by RFC 4648.
+package base32
+
+import (
+ "bytes"
+ "io"
+ "strconv"
+ "strings"
+)
+
+/*
+ * Encodings
+ */
+
+// An Encoding is a radix 32 encoding/decoding scheme, defined by a
+// 32-character alphabet. The most common is the "base32" encoding
+// introduced for SASL GSSAPI and standardized in RFC 4648.
+// The alternate "base32hex" encoding is used in DNSSEC.
+type Encoding struct {
+ encode string
+ decodeMap [256]byte
+}
+
+const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
+const encodeHex = "0123456789ABCDEFGHIJKLMNOPQRSTUV"
+
+// NewEncoding returns a new Encoding defined by the given alphabet,
+// which must be a 32-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 base32 encoding, as defined in
+// RFC 4648.
+var StdEncoding = NewEncoding(encodeStd)
+
+// HexEncoding is the ``Extended Hex Alphabet'' defined in RFC 4648.
+// It is typically used in DNS.
+var HexEncoding = NewEncoding(encodeHex)
+
+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 8 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, b4, b5, b6, b7 byte
+
+ // Unpack 8x 5-bit source blocks into a 5 byte
+ // destination quantum
+ switch len(src) {
+ default:
+ b7 = src[4] & 0x1F
+ b6 = src[4] >> 5
+ fallthrough
+ case 4:
+ b6 |= (src[3] << 3) & 0x1F
+ b5 = (src[3] >> 2) & 0x1F
+ b4 = src[3] >> 7
+ fallthrough
+ case 3:
+ b4 |= (src[2] << 1) & 0x1F
+ b3 = (src[2] >> 4) & 0x1F
+ fallthrough
+ case 2:
+ b3 |= (src[1] << 4) & 0x1F
+ b2 = (src[1] >> 1) & 0x1F
+ b1 = (src[1] >> 6) & 0x1F
+ fallthrough
+ case 1:
+ b1 |= (src[0] << 2) & 0x1F
+ b0 = src[0] >> 3
+ }
+
+ // Encode 5-bit blocks using the base32 alphabet
+ dst[0] = enc.encode[b0]
+ dst[1] = enc.encode[b1]
+ dst[2] = enc.encode[b2]
+ dst[3] = enc.encode[b3]
+ dst[4] = enc.encode[b4]
+ dst[5] = enc.encode[b5]
+ dst[6] = enc.encode[b6]
+ dst[7] = enc.encode[b7]
+
+ // Pad the final quantum
+ if len(src) < 5 {
+ dst[7] = '='
+ if len(src) < 4 {
+ dst[6] = '='
+ dst[5] = '='
+ if len(src) < 3 {
+ dst[4] = '='
+ if len(src) < 2 {
+ dst[3] = '='
+ dst[2] = '='
+ }
+ }
+ }
+ break
+ }
+ src = src[5:]
+ dst = dst[8:]
+ }
+}
+
+// EncodeToString returns the base32 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 [5]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 < 5; i++ {
+ e.buf[e.nbuf] = p[i]
+ e.nbuf++
+ }
+ n += i
+ p = p[i:]
+ if e.nbuf < 5 {
+ return
+ }
+ e.enc.Encode(e.out[0:], e.buf[0:])
+ if _, e.err = e.w.Write(e.out[0:8]); e.err != nil {
+ return n, e.err
+ }
+ e.nbuf = 0
+ }
+
+ // Large interior chunks.
+ for len(p) >= 5 {
+ nn := len(e.out) / 8 * 5
+ if nn > len(p) {
+ nn = len(p)
+ nn -= nn % 5
+ }
+ e.enc.Encode(e.out[0:], p[0:nn])
+ if _, e.err = e.w.Write(e.out[0 : nn/5*8]); 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[0:8])
+ }
+ return e.err
+}
+
+// NewEncoder returns a new base32 stream encoder. Data written to
+// the returned writer will be encoded using enc and then written to w.
+// Base32 encodings operate in 5-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 base32 encoding
+// of an input buffer of length n.
+func (enc *Encoding) EncodedLen(n int) int { return (n + 4) / 5 * 8 }
+
+/*
+ * Decoder
+ */
+
+type CorruptInputError int64
+
+func (e CorruptInputError) Error() string {
+ return "illegal base32 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 base32 alphabet
+ var dbuf [8]byte
+ dlen := 8
+
+ for j := 0; j < 8; {
+ if len(src) == 0 {
+ return n, false, CorruptInputError(olen - len(src) - j)
+ }
+ in := src[0]
+ src = src[1:]
+ if in == '=' && j >= 2 && len(src) < 8 {
+ // We've reached the end and there's padding
+ if len(src)+j < 8-1 {
+ // not enough padding
+ return n, false, CorruptInputError(olen)
+ }
+ for k := 0; k < 8-1-j; k++ {
+ if len(src) > k && src[k] != '=' {
+ // incorrect padding
+ return n, false, CorruptInputError(olen - len(src) + k - 1)
+ }
+ }
+ dlen, end = j, true
+ // 7, 5 and 2 are not valid padding lengths, and so 1, 3 and 6 are not
+ // valid dlen values. See RFC 4648 Section 6 "Base 32 Encoding" listing
+ // the five valid padding lengths, and Section 9 "Illustrations and
+ // Examples" for an illustration for how the 1st, 3rd and 6th base32
+ // src bytes do not yield enough information to decode a dst byte.
+ if dlen == 1 || dlen == 3 || dlen == 6 {
+ return n, false, CorruptInputError(olen - len(src) - 1)
+ }
+ break
+ }
+ dbuf[j] = enc.decodeMap[in]
+ if dbuf[j] == 0xFF {
+ return n, false, CorruptInputError(olen - len(src) - 1)
+ }
+ j++
+ }
+
+ // Pack 8x 5-bit source blocks into 5 byte destination
+ // quantum
+ switch dlen {
+ case 8:
+ dst[4] = dbuf[6]<<5 | dbuf[7]
+ fallthrough
+ case 7:
+ dst[3] = dbuf[4]<<7 | dbuf[5]<<2 | dbuf[6]>>3
+ fallthrough
+ case 5:
+ dst[2] = dbuf[3]<<4 | dbuf[4]>>1
+ fallthrough
+ case 4:
+ dst[1] = dbuf[1]<<6 | dbuf[2]<<1 | dbuf[3]>>4
+ fallthrough
+ case 2:
+ dst[0] = dbuf[0]<<3 | dbuf[1]>>2
+ }
+ dst = dst[5:]
+ switch dlen {
+ case 2:
+ n += 1
+ case 4:
+ n += 2
+ case 5:
+ n += 3
+ case 7:
+ n += 4
+ case 8:
+ n += 5
+ }
+ }
+ 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 base32 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 base32 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 / 8 * 5]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) / 5 * 8
+ if nn < 8 {
+ nn = 8
+ }
+ if nn > len(d.buf) {
+ nn = len(d.buf)
+ }
+ nn, d.err = io.ReadAtLeast(d.r, d.buf[d.nbuf:nn], 8-d.nbuf)
+ d.nbuf += nn
+ if d.nbuf < 8 {
+ return 0, d.err
+ }
+
+ // Decode chunk into p, or d.out and then p if p is too small.
+ nr := d.nbuf / 8 * 8
+ nw := d.nbuf / 8 * 5
+ 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 base32 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 base32-encoded data.
+func (enc *Encoding) DecodedLen(n int) int { return n / 8 * 5 }
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