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Diffstat (limited to 'src/encoding/base64/base64.go')
| -rw-r--r-- | src/encoding/base64/base64.go | 627 |
1 files changed, 627 insertions, 0 deletions
diff --git a/src/encoding/base64/base64.go b/src/encoding/base64/base64.go new file mode 100644 index 0000000..0e12d90 --- /dev/null +++ b/src/encoding/base64/base64.go @@ -0,0 +1,627 @@ +// 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 ( + "encoding/binary" + "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 + strict bool +} + +const ( + StdPadding rune = '=' // Standard padding character + NoPadding rune = -1 // No padding + decodeMapInitialize = "" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" + + "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +) + +const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" +const encodeURL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_" + +// NewEncoding returns a new padded Encoding defined by the given alphabet, +// which must be a 64-byte string that does not contain the padding character +// or CR / LF ('\r', '\n'). +// 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") + } + for i := 0; i < len(encoder); i++ { + if encoder[i] == '\n' || encoder[i] == '\r' { + panic("encoding alphabet contains newline character") + } + } + + e := new(Encoding) + e.padChar = StdPadding + copy(e.encode[:], encoder) + copy(e.decodeMap[:], decodeMapInitialize) + + 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. +// The padding character must not be '\r' or '\n', must not +// be contained in the encoding's alphabet and must be a rune equal or +// below '\xff'. +func (enc Encoding) WithPadding(padding rune) *Encoding { + if padding == '\r' || padding == '\n' || padding > 0xff { + panic("invalid padding") + } + + for i := 0; i < len(enc.encode); i++ { + if rune(enc.encode[i]) == padding { + panic("padding contained in alphabet") + } + } + + enc.padChar = padding + return &enc +} + +// Strict creates a new encoding identical to enc except with +// strict decoding enabled. In this mode, the decoder requires that +// trailing padding bits are zero, as described in RFC 4648 section 3.5. +// +// Note that the input is still malleable, as new line characters +// (CR and LF) are still ignored. +func (enc Encoding) Strict() *Encoding { + enc.strict = true + 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 + } + // enc is a pointer receiver, so the use of enc.encode within the hot + // loop below means a nil check at every operation. Lift that nil check + // outside of the loop to speed up the encoder. + _ = enc.encode + + 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. + copy(e.buf[:], p) + 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) +} + +// decodeQuantum decodes up to 4 base64 bytes. The received parameters are +// the destination buffer dst, the source buffer src and an index in the +// source buffer si. +// It returns the number of bytes read from src, the number of bytes written +// to dst, and an error, if any. +func (enc *Encoding) decodeQuantum(dst, src []byte, si int) (nsi, n int, err error) { + // Decode quantum using the base64 alphabet + var dbuf [4]byte + dlen := 4 + + // Lift the nil check outside of the loop. + _ = enc.decodeMap + + for j := 0; j < len(dbuf); j++ { + if len(src) == si { + switch { + case j == 0: + return si, 0, nil + case j == 1, enc.padChar != NoPadding: + return si, 0, CorruptInputError(si - j) + } + dlen = j + break + } + in := src[si] + si++ + + out := enc.decodeMap[in] + if out != 0xff { + dbuf[j] = out + continue + } + + if in == '\n' || in == '\r' { + j-- + continue + } + + if rune(in) != enc.padChar { + return si, 0, CorruptInputError(si - 1) + } + + // We've reached the end and there's padding + switch j { + case 0, 1: + // incorrect padding + return si, 0, CorruptInputError(si - 1) + case 2: + // "==" is expected, the first "=" is already consumed. + // skip over newlines + for si < len(src) && (src[si] == '\n' || src[si] == '\r') { + si++ + } + if si == len(src) { + // not enough padding + return si, 0, CorruptInputError(len(src)) + } + if rune(src[si]) != enc.padChar { + // incorrect padding + return si, 0, 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) + } + dlen = j + break + } + + // Convert 4x 6bit source bytes into 3 bytes + val := uint(dbuf[0])<<18 | uint(dbuf[1])<<12 | uint(dbuf[2])<<6 | uint(dbuf[3]) + dbuf[2], dbuf[1], dbuf[0] = byte(val>>0), byte(val>>8), byte(val>>16) + switch dlen { + case 4: + dst[2] = dbuf[2] + dbuf[2] = 0 + fallthrough + case 3: + dst[1] = dbuf[1] + if enc.strict && dbuf[2] != 0 { + return si, 0, CorruptInputError(si - 1) + } + dbuf[1] = 0 + fallthrough + case 2: + dst[0] = dbuf[0] + if enc.strict && (dbuf[1] != 0 || dbuf[2] != 0) { + return si, 0, CorruptInputError(si - 2) + } + } + + return si, dlen - 1, err +} + +// 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 + 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.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.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.err = d.enc.Decode(p, d.buf[:nr]) + } + d.nbuf -= nr + copy(d.buf[:d.nbuf], d.buf[nr:]) + return n, d.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) { + if len(src) == 0 { + return 0, nil + } + + // Lift the nil check outside of the loop. enc.decodeMap is directly + // used later in this function, to let the compiler know that the + // receiver can't be nil. + _ = enc.decodeMap + + si := 0 + for strconv.IntSize >= 64 && len(src)-si >= 8 && len(dst)-n >= 8 { + src2 := src[si : si+8] + if dn, ok := assemble64( + enc.decodeMap[src2[0]], + enc.decodeMap[src2[1]], + enc.decodeMap[src2[2]], + enc.decodeMap[src2[3]], + enc.decodeMap[src2[4]], + enc.decodeMap[src2[5]], + enc.decodeMap[src2[6]], + enc.decodeMap[src2[7]], + ); ok { + binary.BigEndian.PutUint64(dst[n:], dn) + n += 6 + si += 8 + } else { + var ninc int + si, ninc, err = enc.decodeQuantum(dst[n:], src, si) + n += ninc + if err != nil { + return n, err + } + } + } + + for len(src)-si >= 4 && len(dst)-n >= 4 { + src2 := src[si : si+4] + if dn, ok := assemble32( + enc.decodeMap[src2[0]], + enc.decodeMap[src2[1]], + enc.decodeMap[src2[2]], + enc.decodeMap[src2[3]], + ); ok { + binary.BigEndian.PutUint32(dst[n:], dn) + n += 3 + si += 4 + } else { + var ninc int + si, ninc, err = enc.decodeQuantum(dst[n:], src, si) + n += ninc + if err != nil { + return n, err + } + } + } + + for si < len(src) { + var ninc int + si, ninc, err = enc.decodeQuantum(dst[n:], src, si) + n += ninc + if err != nil { + return n, err + } + } + return n, err +} + +// assemble32 assembles 4 base64 digits into 3 bytes. +// Each digit comes from the decode map, and will be 0xff +// if it came from an invalid character. +func assemble32(n1, n2, n3, n4 byte) (dn uint32, ok bool) { + // Check that all the digits are valid. If any of them was 0xff, their + // bitwise OR will be 0xff. + if n1|n2|n3|n4 == 0xff { + return 0, false + } + return uint32(n1)<<26 | + uint32(n2)<<20 | + uint32(n3)<<14 | + uint32(n4)<<8, + true +} + +// assemble64 assembles 8 base64 digits into 6 bytes. +// Each digit comes from the decode map, and will be 0xff +// if it came from an invalid character. +func assemble64(n1, n2, n3, n4, n5, n6, n7, n8 byte) (dn uint64, ok bool) { + // Check that all the digits are valid. If any of them was 0xff, their + // bitwise OR will be 0xff. + if n1|n2|n3|n4|n5|n6|n7|n8 == 0xff { + return 0, false + } + return uint64(n1)<<58 | + uint64(n2)<<52 | + uint64(n3)<<46 | + uint64(n4)<<40 | + uint64(n5)<<34 | + uint64(n6)<<28 | + uint64(n7)<<22 | + uint64(n8)<<16, + true +} + +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 / 8 + } + // Padded base64 should always be a multiple of 4 characters in length. + return n / 4 * 3 +} |