github.com/guyezi/gofrontend@v0.0.0-20200228202240-7a62a49e62c0/libgo/go/encoding/base32/base32.go (about) 1 // Copyright 2011 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Package base32 implements base32 encoding as specified by RFC 4648. 6 package base32 7 8 import ( 9 "io" 10 "strconv" 11 ) 12 13 /* 14 * Encodings 15 */ 16 17 // An Encoding is a radix 32 encoding/decoding scheme, defined by a 18 // 32-character alphabet. The most common is the "base32" encoding 19 // introduced for SASL GSSAPI and standardized in RFC 4648. 20 // The alternate "base32hex" encoding is used in DNSSEC. 21 type Encoding struct { 22 encode [32]byte 23 decodeMap [256]byte 24 padChar rune 25 } 26 27 const ( 28 StdPadding rune = '=' // Standard padding character 29 NoPadding rune = -1 // No padding 30 ) 31 32 const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567" 33 const encodeHex = "0123456789ABCDEFGHIJKLMNOPQRSTUV" 34 35 // NewEncoding returns a new Encoding defined by the given alphabet, 36 // which must be a 32-byte string. 37 func NewEncoding(encoder string) *Encoding { 38 if len(encoder) != 32 { 39 panic("encoding alphabet is not 32-bytes long") 40 } 41 42 e := new(Encoding) 43 copy(e.encode[:], encoder) 44 e.padChar = StdPadding 45 46 for i := 0; i < len(e.decodeMap); i++ { 47 e.decodeMap[i] = 0xFF 48 } 49 for i := 0; i < len(encoder); i++ { 50 e.decodeMap[encoder[i]] = byte(i) 51 } 52 return e 53 } 54 55 // StdEncoding is the standard base32 encoding, as defined in 56 // RFC 4648. 57 var StdEncoding = NewEncoding(encodeStd) 58 59 // HexEncoding is the ``Extended Hex Alphabet'' defined in RFC 4648. 60 // It is typically used in DNS. 61 var HexEncoding = NewEncoding(encodeHex) 62 63 // WithPadding creates a new encoding identical to enc except 64 // with a specified padding character, or NoPadding to disable padding. 65 // The padding character must not be '\r' or '\n', must not 66 // be contained in the encoding's alphabet and must be a rune equal or 67 // below '\xff'. 68 func (enc Encoding) WithPadding(padding rune) *Encoding { 69 if padding == '\r' || padding == '\n' || padding > 0xff { 70 panic("invalid padding") 71 } 72 73 for i := 0; i < len(enc.encode); i++ { 74 if rune(enc.encode[i]) == padding { 75 panic("padding contained in alphabet") 76 } 77 } 78 79 enc.padChar = padding 80 return &enc 81 } 82 83 /* 84 * Encoder 85 */ 86 87 // Encode encodes src using the encoding enc, writing 88 // EncodedLen(len(src)) bytes to dst. 89 // 90 // The encoding pads the output to a multiple of 8 bytes, 91 // so Encode is not appropriate for use on individual blocks 92 // of a large data stream. Use NewEncoder() instead. 93 func (enc *Encoding) Encode(dst, src []byte) { 94 for len(src) > 0 { 95 var b [8]byte 96 97 // Unpack 8x 5-bit source blocks into a 5 byte 98 // destination quantum 99 switch len(src) { 100 default: 101 b[7] = src[4] & 0x1F 102 b[6] = src[4] >> 5 103 fallthrough 104 case 4: 105 b[6] |= (src[3] << 3) & 0x1F 106 b[5] = (src[3] >> 2) & 0x1F 107 b[4] = src[3] >> 7 108 fallthrough 109 case 3: 110 b[4] |= (src[2] << 1) & 0x1F 111 b[3] = (src[2] >> 4) & 0x1F 112 fallthrough 113 case 2: 114 b[3] |= (src[1] << 4) & 0x1F 115 b[2] = (src[1] >> 1) & 0x1F 116 b[1] = (src[1] >> 6) & 0x1F 117 fallthrough 118 case 1: 119 b[1] |= (src[0] << 2) & 0x1F 120 b[0] = src[0] >> 3 121 } 122 123 // Encode 5-bit blocks using the base32 alphabet 124 size := len(dst) 125 if size >= 8 { 126 // Common case, unrolled for extra performance 127 dst[0] = enc.encode[b[0]&31] 128 dst[1] = enc.encode[b[1]&31] 129 dst[2] = enc.encode[b[2]&31] 130 dst[3] = enc.encode[b[3]&31] 131 dst[4] = enc.encode[b[4]&31] 132 dst[5] = enc.encode[b[5]&31] 133 dst[6] = enc.encode[b[6]&31] 134 dst[7] = enc.encode[b[7]&31] 135 } else { 136 for i := 0; i < size; i++ { 137 dst[i] = enc.encode[b[i]&31] 138 } 139 } 140 141 // Pad the final quantum 142 if len(src) < 5 { 143 if enc.padChar == NoPadding { 144 break 145 } 146 147 dst[7] = byte(enc.padChar) 148 if len(src) < 4 { 149 dst[6] = byte(enc.padChar) 150 dst[5] = byte(enc.padChar) 151 if len(src) < 3 { 152 dst[4] = byte(enc.padChar) 153 if len(src) < 2 { 154 dst[3] = byte(enc.padChar) 155 dst[2] = byte(enc.padChar) 156 } 157 } 158 } 159 160 break 161 } 162 163 src = src[5:] 164 dst = dst[8:] 165 } 166 } 167 168 // EncodeToString returns the base32 encoding of src. 169 func (enc *Encoding) EncodeToString(src []byte) string { 170 buf := make([]byte, enc.EncodedLen(len(src))) 171 enc.Encode(buf, src) 172 return string(buf) 173 } 174 175 type encoder struct { 176 err error 177 enc *Encoding 178 w io.Writer 179 buf [5]byte // buffered data waiting to be encoded 180 nbuf int // number of bytes in buf 181 out [1024]byte // output buffer 182 } 183 184 func (e *encoder) Write(p []byte) (n int, err error) { 185 if e.err != nil { 186 return 0, e.err 187 } 188 189 // Leading fringe. 190 if e.nbuf > 0 { 191 var i int 192 for i = 0; i < len(p) && e.nbuf < 5; i++ { 193 e.buf[e.nbuf] = p[i] 194 e.nbuf++ 195 } 196 n += i 197 p = p[i:] 198 if e.nbuf < 5 { 199 return 200 } 201 e.enc.Encode(e.out[0:], e.buf[0:]) 202 if _, e.err = e.w.Write(e.out[0:8]); e.err != nil { 203 return n, e.err 204 } 205 e.nbuf = 0 206 } 207 208 // Large interior chunks. 209 for len(p) >= 5 { 210 nn := len(e.out) / 8 * 5 211 if nn > len(p) { 212 nn = len(p) 213 nn -= nn % 5 214 } 215 e.enc.Encode(e.out[0:], p[0:nn]) 216 if _, e.err = e.w.Write(e.out[0 : nn/5*8]); e.err != nil { 217 return n, e.err 218 } 219 n += nn 220 p = p[nn:] 221 } 222 223 // Trailing fringe. 224 for i := 0; i < len(p); i++ { 225 e.buf[i] = p[i] 226 } 227 e.nbuf = len(p) 228 n += len(p) 229 return 230 } 231 232 // Close flushes any pending output from the encoder. 233 // It is an error to call Write after calling Close. 234 func (e *encoder) Close() error { 235 // If there's anything left in the buffer, flush it out 236 if e.err == nil && e.nbuf > 0 { 237 e.enc.Encode(e.out[0:], e.buf[0:e.nbuf]) 238 encodedLen := e.enc.EncodedLen(e.nbuf) 239 e.nbuf = 0 240 _, e.err = e.w.Write(e.out[0:encodedLen]) 241 } 242 return e.err 243 } 244 245 // NewEncoder returns a new base32 stream encoder. Data written to 246 // the returned writer will be encoded using enc and then written to w. 247 // Base32 encodings operate in 5-byte blocks; when finished 248 // writing, the caller must Close the returned encoder to flush any 249 // partially written blocks. 250 func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser { 251 return &encoder{enc: enc, w: w} 252 } 253 254 // EncodedLen returns the length in bytes of the base32 encoding 255 // of an input buffer of length n. 256 func (enc *Encoding) EncodedLen(n int) int { 257 if enc.padChar == NoPadding { 258 return (n*8 + 4) / 5 259 } 260 return (n + 4) / 5 * 8 261 } 262 263 /* 264 * Decoder 265 */ 266 267 type CorruptInputError int64 268 269 func (e CorruptInputError) Error() string { 270 return "illegal base32 data at input byte " + strconv.FormatInt(int64(e), 10) 271 } 272 273 // decode is like Decode but returns an additional 'end' value, which 274 // indicates if end-of-message padding was encountered and thus any 275 // additional data is an error. This method assumes that src has been 276 // stripped of all supported whitespace ('\r' and '\n'). 277 func (enc *Encoding) decode(dst, src []byte) (n int, end bool, err error) { 278 // Lift the nil check outside of the loop. 279 _ = enc.decodeMap 280 281 dsti := 0 282 olen := len(src) 283 284 for len(src) > 0 && !end { 285 // Decode quantum using the base32 alphabet 286 var dbuf [8]byte 287 dlen := 8 288 289 for j := 0; j < 8; { 290 291 if len(src) == 0 { 292 if enc.padChar != NoPadding { 293 // We have reached the end and are missing padding 294 return n, false, CorruptInputError(olen - len(src) - j) 295 } 296 // We have reached the end and are not expecting any padding 297 dlen, end = j, true 298 break 299 } 300 in := src[0] 301 src = src[1:] 302 if in == byte(enc.padChar) && j >= 2 && len(src) < 8 { 303 // We've reached the end and there's padding 304 if len(src)+j < 8-1 { 305 // not enough padding 306 return n, false, CorruptInputError(olen) 307 } 308 for k := 0; k < 8-1-j; k++ { 309 if len(src) > k && src[k] != byte(enc.padChar) { 310 // incorrect padding 311 return n, false, CorruptInputError(olen - len(src) + k - 1) 312 } 313 } 314 dlen, end = j, true 315 // 7, 5 and 2 are not valid padding lengths, and so 1, 3 and 6 are not 316 // valid dlen values. See RFC 4648 Section 6 "Base 32 Encoding" listing 317 // the five valid padding lengths, and Section 9 "Illustrations and 318 // Examples" for an illustration for how the 1st, 3rd and 6th base32 319 // src bytes do not yield enough information to decode a dst byte. 320 if dlen == 1 || dlen == 3 || dlen == 6 { 321 return n, false, CorruptInputError(olen - len(src) - 1) 322 } 323 break 324 } 325 dbuf[j] = enc.decodeMap[in] 326 if dbuf[j] == 0xFF { 327 return n, false, CorruptInputError(olen - len(src) - 1) 328 } 329 j++ 330 } 331 332 // Pack 8x 5-bit source blocks into 5 byte destination 333 // quantum 334 switch dlen { 335 case 8: 336 dst[dsti+4] = dbuf[6]<<5 | dbuf[7] 337 n++ 338 fallthrough 339 case 7: 340 dst[dsti+3] = dbuf[4]<<7 | dbuf[5]<<2 | dbuf[6]>>3 341 n++ 342 fallthrough 343 case 5: 344 dst[dsti+2] = dbuf[3]<<4 | dbuf[4]>>1 345 n++ 346 fallthrough 347 case 4: 348 dst[dsti+1] = dbuf[1]<<6 | dbuf[2]<<1 | dbuf[3]>>4 349 n++ 350 fallthrough 351 case 2: 352 dst[dsti+0] = dbuf[0]<<3 | dbuf[1]>>2 353 n++ 354 } 355 dsti += 5 356 } 357 return n, end, nil 358 } 359 360 // Decode decodes src using the encoding enc. It writes at most 361 // DecodedLen(len(src)) bytes to dst and returns the number of bytes 362 // written. If src contains invalid base32 data, it will return the 363 // number of bytes successfully written and CorruptInputError. 364 // New line characters (\r and \n) are ignored. 365 func (enc *Encoding) Decode(dst, src []byte) (n int, err error) { 366 buf := make([]byte, len(src)) 367 l := stripNewlines(buf, src) 368 n, _, err = enc.decode(dst, buf[:l]) 369 return 370 } 371 372 // DecodeString returns the bytes represented by the base32 string s. 373 func (enc *Encoding) DecodeString(s string) ([]byte, error) { 374 buf := []byte(s) 375 l := stripNewlines(buf, buf) 376 n, _, err := enc.decode(buf, buf[:l]) 377 return buf[:n], err 378 } 379 380 type decoder struct { 381 err error 382 enc *Encoding 383 r io.Reader 384 end bool // saw end of message 385 buf [1024]byte // leftover input 386 nbuf int 387 out []byte // leftover decoded output 388 outbuf [1024 / 8 * 5]byte 389 } 390 391 func readEncodedData(r io.Reader, buf []byte, min int, expectsPadding bool) (n int, err error) { 392 for n < min && err == nil { 393 var nn int 394 nn, err = r.Read(buf[n:]) 395 n += nn 396 } 397 // data was read, less than min bytes could be read 398 if n < min && n > 0 && err == io.EOF { 399 err = io.ErrUnexpectedEOF 400 } 401 // no data was read, the buffer already contains some data 402 // when padding is disabled this is not an error, as the message can be of 403 // any length 404 if expectsPadding && min < 8 && n == 0 && err == io.EOF { 405 err = io.ErrUnexpectedEOF 406 } 407 return 408 } 409 410 func (d *decoder) Read(p []byte) (n int, err error) { 411 // Use leftover decoded output from last read. 412 if len(d.out) > 0 { 413 n = copy(p, d.out) 414 d.out = d.out[n:] 415 if len(d.out) == 0 { 416 return n, d.err 417 } 418 return n, nil 419 } 420 421 if d.err != nil { 422 return 0, d.err 423 } 424 425 // Read a chunk. 426 nn := len(p) / 5 * 8 427 if nn < 8 { 428 nn = 8 429 } 430 if nn > len(d.buf) { 431 nn = len(d.buf) 432 } 433 434 // Minimum amount of bytes that needs to be read each cycle 435 var min int 436 var expectsPadding bool 437 if d.enc.padChar == NoPadding { 438 min = 1 439 expectsPadding = false 440 } else { 441 min = 8 - d.nbuf 442 expectsPadding = true 443 } 444 445 nn, d.err = readEncodedData(d.r, d.buf[d.nbuf:nn], min, expectsPadding) 446 d.nbuf += nn 447 if d.nbuf < min { 448 return 0, d.err 449 } 450 451 // Decode chunk into p, or d.out and then p if p is too small. 452 var nr int 453 if d.enc.padChar == NoPadding { 454 nr = d.nbuf 455 } else { 456 nr = d.nbuf / 8 * 8 457 } 458 nw := d.enc.DecodedLen(d.nbuf) 459 460 if nw > len(p) { 461 nw, d.end, err = d.enc.decode(d.outbuf[0:], d.buf[0:nr]) 462 d.out = d.outbuf[0:nw] 463 n = copy(p, d.out) 464 d.out = d.out[n:] 465 } else { 466 n, d.end, err = d.enc.decode(p, d.buf[0:nr]) 467 } 468 d.nbuf -= nr 469 for i := 0; i < d.nbuf; i++ { 470 d.buf[i] = d.buf[i+nr] 471 } 472 473 if err != nil && (d.err == nil || d.err == io.EOF) { 474 d.err = err 475 } 476 477 if len(d.out) > 0 { 478 // We cannot return all the decoded bytes to the caller in this 479 // invocation of Read, so we return a nil error to ensure that Read 480 // will be called again. The error stored in d.err, if any, will be 481 // returned with the last set of decoded bytes. 482 return n, nil 483 } 484 485 return n, d.err 486 } 487 488 type newlineFilteringReader struct { 489 wrapped io.Reader 490 } 491 492 // stripNewlines removes newline characters and returns the number 493 // of non-newline characters copied to dst. 494 func stripNewlines(dst, src []byte) int { 495 offset := 0 496 for _, b := range src { 497 if b == '\r' || b == '\n' { 498 continue 499 } 500 dst[offset] = b 501 offset++ 502 } 503 return offset 504 } 505 506 func (r *newlineFilteringReader) Read(p []byte) (int, error) { 507 n, err := r.wrapped.Read(p) 508 for n > 0 { 509 s := p[0:n] 510 offset := stripNewlines(s, s) 511 if err != nil || offset > 0 { 512 return offset, err 513 } 514 // Previous buffer entirely whitespace, read again 515 n, err = r.wrapped.Read(p) 516 } 517 return n, err 518 } 519 520 // NewDecoder constructs a new base32 stream decoder. 521 func NewDecoder(enc *Encoding, r io.Reader) io.Reader { 522 return &decoder{enc: enc, r: &newlineFilteringReader{r}} 523 } 524 525 // DecodedLen returns the maximum length in bytes of the decoded data 526 // corresponding to n bytes of base32-encoded data. 527 func (enc *Encoding) DecodedLen(n int) int { 528 if enc.padChar == NoPadding { 529 return n * 5 / 8 530 } 531 532 return n / 8 * 5 533 }