// 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 }