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Diffstat (limited to 'src/encoding/base64/base64.go')
-rw-r--r--src/encoding/base64/base64.go614
1 files changed, 614 insertions, 0 deletions
diff --git a/src/encoding/base64/base64.go b/src/encoding/base64/base64.go
new file mode 100644
index 0000000..0c33f8e
--- /dev/null
+++ b/src/encoding/base64/base64.go
@@ -0,0 +1,614 @@
+// 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
+)
+
+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)
+
+ 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.
+// 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.
+ 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)
+}
+
+// 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
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-01 07:08:14 +0000