mirror of
https://github.com/autc04/Retro68.git
synced 2024-09-08 05:54:40 +00:00
467 lines
11 KiB
Go
467 lines
11 KiB
Go
// 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 (
|
|
"io"
|
|
"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 [64]byte
|
|
decodeMap [256]byte
|
|
padChar rune
|
|
}
|
|
|
|
const (
|
|
StdPadding rune = '=' // Standard padding character
|
|
NoPadding rune = -1 // No padding
|
|
)
|
|
|
|
const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
|
|
const encodeURL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
|
|
|
|
// NewEncoding returns a new padded Encoding defined by the given alphabet,
|
|
// which must be a 64-byte string.
|
|
// The resulting Encoding uses the default padding character ('='),
|
|
// which may be changed or disabled via WithPadding.
|
|
func NewEncoding(encoder string) *Encoding {
|
|
if len(encoder) != 64 {
|
|
panic("encoding alphabet is not 64-bytes long")
|
|
}
|
|
|
|
e := new(Encoding)
|
|
e.padChar = StdPadding
|
|
copy(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
|
|
}
|
|
|
|
// WithPadding creates a new encoding identical to enc except
|
|
// with a specified padding character, or NoPadding to disable padding.
|
|
func (enc Encoding) WithPadding(padding rune) *Encoding {
|
|
enc.padChar = padding
|
|
return &enc
|
|
}
|
|
|
|
// 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)
|
|
|
|
// RawStdEncoding is the standard raw, unpadded base64 encoding,
|
|
// as defined in RFC 4648 section 3.2.
|
|
// This is the same as StdEncoding but omits padding characters.
|
|
var RawStdEncoding = StdEncoding.WithPadding(NoPadding)
|
|
|
|
// RawURLEncoding is the unpadded alternate base64 encoding defined in RFC 4648.
|
|
// It is typically used in URLs and file names.
|
|
// This is the same as URLEncoding but omits padding characters.
|
|
var RawURLEncoding = URLEncoding.WithPadding(NoPadding)
|
|
|
|
/*
|
|
* 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
|
|
}
|
|
|
|
di, si := 0, 0
|
|
n := (len(src) / 3) * 3
|
|
for si < n {
|
|
// Convert 3x 8bit source bytes into 4 bytes
|
|
val := uint(src[si+0])<<16 | uint(src[si+1])<<8 | uint(src[si+2])
|
|
|
|
dst[di+0] = enc.encode[val>>18&0x3F]
|
|
dst[di+1] = enc.encode[val>>12&0x3F]
|
|
dst[di+2] = enc.encode[val>>6&0x3F]
|
|
dst[di+3] = enc.encode[val&0x3F]
|
|
|
|
si += 3
|
|
di += 4
|
|
}
|
|
|
|
remain := len(src) - si
|
|
if remain == 0 {
|
|
return
|
|
}
|
|
// Add the remaining small block
|
|
val := uint(src[si+0]) << 16
|
|
if remain == 2 {
|
|
val |= uint(src[si+1]) << 8
|
|
}
|
|
|
|
dst[di+0] = enc.encode[val>>18&0x3F]
|
|
dst[di+1] = enc.encode[val>>12&0x3F]
|
|
|
|
switch remain {
|
|
case 2:
|
|
dst[di+2] = enc.encode[val>>6&0x3F]
|
|
if enc.padChar != NoPadding {
|
|
dst[di+3] = byte(enc.padChar)
|
|
}
|
|
case 1:
|
|
if enc.padChar != NoPadding {
|
|
dst[di+2] = byte(enc.padChar)
|
|
dst[di+3] = byte(enc.padChar)
|
|
}
|
|
}
|
|
}
|
|
|
|
// 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[:], e.buf[:])
|
|
if _, e.err = e.w.Write(e.out[: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[:], p[: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[:], e.buf[:e.nbuf])
|
|
_, e.err = e.w.Write(e.out[:e.enc.EncodedLen(e.nbuf)])
|
|
e.nbuf = 0
|
|
}
|
|
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 {
|
|
if enc.padChar == NoPadding {
|
|
return (n*8 + 5) / 6 // minimum # chars at 6 bits per char
|
|
}
|
|
return (n + 2) / 3 * 4 // minimum # 4-char quanta, 3 bytes each
|
|
}
|
|
|
|
/*
|
|
* 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 or a partial quantum was encountered
|
|
// and thus any additional data is an error.
|
|
func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) {
|
|
si := 0
|
|
|
|
// skip over newlines
|
|
for si < len(src) && (src[si] == '\n' || src[si] == '\r') {
|
|
si++
|
|
}
|
|
|
|
for si < len(src) && !end {
|
|
// Decode quantum using the base64 alphabet
|
|
var dbuf [4]byte
|
|
dinc, dlen := 3, 4
|
|
|
|
for j := range dbuf {
|
|
if len(src) == si {
|
|
if enc.padChar != NoPadding || j < 2 {
|
|
return n, false, CorruptInputError(si - j)
|
|
}
|
|
dinc, dlen, end = j-1, j, true
|
|
break
|
|
}
|
|
in := src[si]
|
|
|
|
si++
|
|
// skip over newlines
|
|
for si < len(src) && (src[si] == '\n' || src[si] == '\r') {
|
|
si++
|
|
}
|
|
|
|
if rune(in) == enc.padChar {
|
|
// We've reached the end and there's padding
|
|
switch j {
|
|
case 0, 1:
|
|
// incorrect padding
|
|
return n, false, CorruptInputError(si - 1)
|
|
case 2:
|
|
// "==" is expected, the first "=" is already consumed.
|
|
if si == len(src) {
|
|
// not enough padding
|
|
return n, false, CorruptInputError(len(src))
|
|
}
|
|
if rune(src[si]) != enc.padChar {
|
|
// incorrect padding
|
|
return n, false, CorruptInputError(si - 1)
|
|
}
|
|
|
|
si++
|
|
// skip over newlines
|
|
for si < len(src) && (src[si] == '\n' || src[si] == '\r') {
|
|
si++
|
|
}
|
|
}
|
|
if si < len(src) {
|
|
// trailing garbage
|
|
err = CorruptInputError(si)
|
|
}
|
|
dinc, dlen, end = 3, j, true
|
|
break
|
|
}
|
|
dbuf[j] = enc.decodeMap[in]
|
|
if dbuf[j] == 0xFF {
|
|
return n, false, CorruptInputError(si - 1)
|
|
}
|
|
}
|
|
|
|
// Convert 4x 6bit source bytes into 3 bytes
|
|
val := uint(dbuf[0])<<18 | uint(dbuf[1])<<12 | uint(dbuf[2])<<6 | uint(dbuf[3])
|
|
switch dlen {
|
|
case 4:
|
|
dst[2] = byte(val >> 0)
|
|
fallthrough
|
|
case 3:
|
|
dst[1] = byte(val >> 8)
|
|
fallthrough
|
|
case 2:
|
|
dst[0] = byte(val >> 16)
|
|
}
|
|
dst = dst[dinc:]
|
|
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) {
|
|
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) {
|
|
dbuf := make([]byte, enc.DecodedLen(len(s)))
|
|
n, _, err := enc.decode(dbuf, []byte(s))
|
|
return dbuf[:n], err
|
|
}
|
|
|
|
type decoder struct {
|
|
err error
|
|
readErr error // error from r.Read
|
|
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) {
|
|
// 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
|
|
}
|
|
|
|
if d.err != nil {
|
|
return 0, d.err
|
|
}
|
|
|
|
// This code assumes that d.r strips supported whitespace ('\r' and '\n').
|
|
|
|
// Refill buffer.
|
|
for d.nbuf < 4 && d.readErr == nil {
|
|
nn := len(p) / 3 * 4
|
|
if nn < 4 {
|
|
nn = 4
|
|
}
|
|
if nn > len(d.buf) {
|
|
nn = len(d.buf)
|
|
}
|
|
nn, d.readErr = d.r.Read(d.buf[d.nbuf:nn])
|
|
d.nbuf += nn
|
|
}
|
|
|
|
if d.nbuf < 4 {
|
|
if d.enc.padChar == NoPadding && d.nbuf > 0 {
|
|
// Decode final fragment, without padding.
|
|
var nw int
|
|
nw, _, d.err = d.enc.decode(d.outbuf[:], d.buf[:d.nbuf])
|
|
d.nbuf = 0
|
|
d.end = true
|
|
d.out = d.outbuf[:nw]
|
|
n = copy(p, d.out)
|
|
d.out = d.out[n:]
|
|
if n > 0 || len(p) == 0 && len(d.out) > 0 {
|
|
return n, nil
|
|
}
|
|
if d.err != nil {
|
|
return 0, d.err
|
|
}
|
|
}
|
|
d.err = d.readErr
|
|
if d.err == io.EOF && d.nbuf > 0 {
|
|
d.err = io.ErrUnexpectedEOF
|
|
}
|
|
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[:], d.buf[:nr])
|
|
d.out = d.outbuf[:nw]
|
|
n = copy(p, d.out)
|
|
d.out = d.out[n:]
|
|
} else {
|
|
n, d.end, d.err = d.enc.decode(p, d.buf[:nr])
|
|
}
|
|
d.nbuf -= nr
|
|
copy(d.buf[:d.nbuf], d.buf[nr:])
|
|
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[: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 {
|
|
if enc.padChar == NoPadding {
|
|
// Unpadded data may end with partial block of 2-3 characters.
|
|
return (n*6 + 7) / 8
|
|
}
|
|
// Padded base64 should always be a multiple of 4 characters in length.
|
|
return n / 4 * 3
|
|
}
|