1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.util; 18 19 import java.io.UnsupportedEncodingException; 20 21 /** 22 * Utilities for encoding and decoding the Base64 representation of 23 * binary data. See RFCs <a 24 * href="http://www.ietf.org/rfc/rfc2045.txt">2045</a> and <a 25 * href="http://www.ietf.org/rfc/rfc3548.txt">3548</a>. 26 */ 27 public class Base64 { 28 /** 29 * Default values for encoder/decoder flags. 30 */ 31 public static final int DEFAULT = 0; 32 33 /** 34 * Encoder flag bit to omit the padding '=' characters at the end 35 * of the output (if any). 36 */ 37 public static final int NO_PADDING = 1; 38 39 /** 40 * Encoder flag bit to omit all line terminators (i.e., the output 41 * will be on one long line). 42 */ 43 public static final int NO_WRAP = 2; 44 45 /** 46 * Encoder flag bit to indicate lines should be terminated with a 47 * CRLF pair instead of just an LF. Has no effect if {@code 48 * NO_WRAP} is specified as well. 49 */ 50 public static final int CRLF = 4; 51 52 /** 53 * Encoder/decoder flag bit to indicate using the "URL and 54 * filename safe" variant of Base64 (see RFC 3548 section 4) where 55 * {@code -} and {@code _} are used in place of {@code +} and 56 * {@code /}. 57 */ 58 public static final int URL_SAFE = 8; 59 60 /** 61 * Flag to pass to {@link Base64OutputStream} to indicate that it 62 * should not close the output stream it is wrapping when it 63 * itself is closed. 64 */ 65 public static final int NO_CLOSE = 16; 66 67 // -------------------------------------------------------- 68 // shared code 69 // -------------------------------------------------------- 70 71 /* package */ static abstract class Coder { 72 public byte[] output; 73 public int op; 74 75 /** 76 * Encode/decode another block of input data. this.output is 77 * provided by the caller, and must be big enough to hold all 78 * the coded data. On exit, this.opwill be set to the length 79 * of the coded data. 80 * 81 * @param finish true if this is the final call to process for 82 * this object. Will finalize the coder state and 83 * include any final bytes in the output. 84 * 85 * @return true if the input so far is good; false if some 86 * error has been detected in the input stream.. 87 */ 88 public abstract boolean process(byte[] input, int offset, int len, boolean finish); 89 90 /** 91 * @return the maximum number of bytes a call to process() 92 * could produce for the given number of input bytes. This may 93 * be an overestimate. 94 */ 95 public abstract int maxOutputSize(int len); 96 } 97 98 // -------------------------------------------------------- 99 // decoding 100 // -------------------------------------------------------- 101 102 /** 103 * Decode the Base64-encoded data in input and return the data in 104 * a new byte array. 105 * 106 * <p>The padding '=' characters at the end are considered optional, but 107 * if any are present, there must be the correct number of them. 108 * 109 * @param str the input String to decode, which is converted to 110 * bytes using the default charset 111 * @param flags controls certain features of the decoded output. 112 * Pass {@code DEFAULT} to decode standard Base64. 113 * 114 * @throws IllegalArgumentException if the input contains 115 * incorrect padding 116 */ 117 public static byte[] decode(String str, int flags) { 118 return decode(str.getBytes(), flags); 119 } 120 121 /** 122 * Decode the Base64-encoded data in input and return the data in 123 * a new byte array. 124 * 125 * <p>The padding '=' characters at the end are considered optional, but 126 * if any are present, there must be the correct number of them. 127 * 128 * @param input the input array to decode 129 * @param flags controls certain features of the decoded output. 130 * Pass {@code DEFAULT} to decode standard Base64. 131 * 132 * @throws IllegalArgumentException if the input contains 133 * incorrect padding 134 */ 135 public static byte[] decode(byte[] input, int flags) { 136 return decode(input, 0, input.length, flags); 137 } 138 139 /** 140 * Decode the Base64-encoded data in input and return the data in 141 * a new byte array. 142 * 143 * <p>The padding '=' characters at the end are considered optional, but 144 * if any are present, there must be the correct number of them. 145 * 146 * @param input the data to decode 147 * @param offset the position within the input array at which to start 148 * @param len the number of bytes of input to decode 149 * @param flags controls certain features of the decoded output. 150 * Pass {@code DEFAULT} to decode standard Base64. 151 * 152 * @throws IllegalArgumentException if the input contains 153 * incorrect padding 154 */ 155 public static byte[] decode(byte[] input, int offset, int len, int flags) { 156 // Allocate space for the most data the input could represent. 157 // (It could contain less if it contains whitespace, etc.) 158 Decoder decoder = new Decoder(flags, new byte[len*3/4]); 159 160 if (!decoder.process(input, offset, len, true)) { 161 throw new IllegalArgumentException("bad base-64"); 162 } 163 164 // Maybe we got lucky and allocated exactly enough output space. 165 if (decoder.op == decoder.output.length) { 166 return decoder.output; 167 } 168 169 // Need to shorten the array, so allocate a new one of the 170 // right size and copy. 171 byte[] temp = new byte[decoder.op]; 172 System.arraycopy(decoder.output, 0, temp, 0, decoder.op); 173 return temp; 174 } 175 176 /* package */ static class Decoder extends Coder { 177 /** 178 * Lookup table for turning bytes into their position in the 179 * Base64 alphabet. 180 */ 181 private static final int DECODE[] = { 182 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 183 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 184 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 185 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, 186 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 187 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, 188 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 189 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, 190 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 191 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 192 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 193 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 194 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 195 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 196 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 197 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 198 }; 199 200 /** 201 * Decode lookup table for the "web safe" variant (RFC 3548 202 * sec. 4) where - and _ replace + and /. 203 */ 204 private static final int DECODE_WEBSAFE[] = { 205 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 206 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 207 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, 208 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, 209 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 210 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63, 211 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 212 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, 213 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 214 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 215 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 216 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 217 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 218 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 219 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 220 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 221 }; 222 223 /** Non-data values in the DECODE arrays. */ 224 private static final int SKIP = -1; 225 private static final int EQUALS = -2; 226 227 /** 228 * States 0-3 are reading through the next input tuple. 229 * State 4 is having read one '=' and expecting exactly 230 * one more. 231 * State 5 is expecting no more data or padding characters 232 * in the input. 233 * State 6 is the error state; an error has been detected 234 * in the input and no future input can "fix" it. 235 */ 236 private int state; // state number (0 to 6) 237 private int value; 238 239 final private int[] alphabet; 240 241 public Decoder(int flags, byte[] output) { 242 this.output = output; 243 244 alphabet = ((flags & URL_SAFE) == 0) ? DECODE : DECODE_WEBSAFE; 245 state = 0; 246 value = 0; 247 } 248 249 /** 250 * @return an overestimate for the number of bytes {@code 251 * len} bytes could decode to. 252 */ 253 public int maxOutputSize(int len) { 254 return len * 3/4 + 10; 255 } 256 257 /** 258 * Decode another block of input data. 259 * 260 * @return true if the state machine is still healthy. false if 261 * bad base-64 data has been detected in the input stream. 262 */ 263 public boolean process(byte[] input, int offset, int len, boolean finish) { 264 if (this.state == 6) return false; 265 266 int p = offset; 267 len += offset; 268 269 // Using local variables makes the decoder about 12% 270 // faster than if we manipulate the member variables in 271 // the loop. (Even alphabet makes a measurable 272 // difference, which is somewhat surprising to me since 273 // the member variable is final.) 274 int state = this.state; 275 int value = this.value; 276 int op = 0; 277 final byte[] output = this.output; 278 final int[] alphabet = this.alphabet; 279 280 while (p < len) { 281 // Try the fast path: we're starting a new tuple and the 282 // next four bytes of the input stream are all data 283 // bytes. This corresponds to going through states 284 // 0-1-2-3-0. We expect to use this method for most of 285 // the data. 286 // 287 // If any of the next four bytes of input are non-data 288 // (whitespace, etc.), value will end up negative. (All 289 // the non-data values in decode are small negative 290 // numbers, so shifting any of them up and or'ing them 291 // together will result in a value with its top bit set.) 292 // 293 // You can remove this whole block and the output should 294 // be the same, just slower. 295 if (state == 0) { 296 while (p+4 <= len && 297 (value = ((alphabet[input[p] & 0xff] << 18) | 298 (alphabet[input[p+1] & 0xff] << 12) | 299 (alphabet[input[p+2] & 0xff] << 6) | 300 (alphabet[input[p+3] & 0xff]))) >= 0) { 301 output[op+2] = (byte) value; 302 output[op+1] = (byte) (value >> 8); 303 output[op] = (byte) (value >> 16); 304 op += 3; 305 p += 4; 306 } 307 if (p >= len) break; 308 } 309 310 // The fast path isn't available -- either we've read a 311 // partial tuple, or the next four input bytes aren't all 312 // data, or whatever. Fall back to the slower state 313 // machine implementation. 314 315 int d = alphabet[input[p++] & 0xff]; 316 317 switch (state) { 318 case 0: 319 if (d >= 0) { 320 value = d; 321 ++state; 322 } else if (d != SKIP) { 323 this.state = 6; 324 return false; 325 } 326 break; 327 328 case 1: 329 if (d >= 0) { 330 value = (value << 6) | d; 331 ++state; 332 } else if (d != SKIP) { 333 this.state = 6; 334 return false; 335 } 336 break; 337 338 case 2: 339 if (d >= 0) { 340 value = (value << 6) | d; 341 ++state; 342 } else if (d == EQUALS) { 343 // Emit the last (partial) output tuple; 344 // expect exactly one more padding character. 345 output[op++] = (byte) (value >> 4); 346 state = 4; 347 } else if (d != SKIP) { 348 this.state = 6; 349 return false; 350 } 351 break; 352 353 case 3: 354 if (d >= 0) { 355 // Emit the output triple and return to state 0. 356 value = (value << 6) | d; 357 output[op+2] = (byte) value; 358 output[op+1] = (byte) (value >> 8); 359 output[op] = (byte) (value >> 16); 360 op += 3; 361 state = 0; 362 } else if (d == EQUALS) { 363 // Emit the last (partial) output tuple; 364 // expect no further data or padding characters. 365 output[op+1] = (byte) (value >> 2); 366 output[op] = (byte) (value >> 10); 367 op += 2; 368 state = 5; 369 } else if (d != SKIP) { 370 this.state = 6; 371 return false; 372 } 373 break; 374 375 case 4: 376 if (d == EQUALS) { 377 ++state; 378 } else if (d != SKIP) { 379 this.state = 6; 380 return false; 381 } 382 break; 383 384 case 5: 385 if (d != SKIP) { 386 this.state = 6; 387 return false; 388 } 389 break; 390 } 391 } 392 393 if (!finish) { 394 // We're out of input, but a future call could provide 395 // more. 396 this.state = state; 397 this.value = value; 398 this.op = op; 399 return true; 400 } 401 402 // Done reading input. Now figure out where we are left in 403 // the state machine and finish up. 404 405 switch (state) { 406 case 0: 407 // Output length is a multiple of three. Fine. 408 break; 409 case 1: 410 // Read one extra input byte, which isn't enough to 411 // make another output byte. Illegal. 412 this.state = 6; 413 return false; 414 case 2: 415 // Read two extra input bytes, enough to emit 1 more 416 // output byte. Fine. 417 output[op++] = (byte) (value >> 4); 418 break; 419 case 3: 420 // Read three extra input bytes, enough to emit 2 more 421 // output bytes. Fine. 422 output[op++] = (byte) (value >> 10); 423 output[op++] = (byte) (value >> 2); 424 break; 425 case 4: 426 // Read one padding '=' when we expected 2. Illegal. 427 this.state = 6; 428 return false; 429 case 5: 430 // Read all the padding '='s we expected and no more. 431 // Fine. 432 break; 433 } 434 435 this.state = state; 436 this.op = op; 437 return true; 438 } 439 } 440 441 // -------------------------------------------------------- 442 // encoding 443 // -------------------------------------------------------- 444 445 /** 446 * Base64-encode the given data and return a newly allocated 447 * String with the result. 448 * 449 * @param input the data to encode 450 * @param flags controls certain features of the encoded output. 451 * Passing {@code DEFAULT} results in output that 452 * adheres to RFC 2045. 453 */ 454 public static String encodeToString(byte[] input, int flags) { 455 try { 456 return new String(encode(input, flags), "US-ASCII"); 457 } catch (UnsupportedEncodingException e) { 458 // US-ASCII is guaranteed to be available. 459 throw new AssertionError(e); 460 } 461 } 462 463 /** 464 * Base64-encode the given data and return a newly allocated 465 * String with the result. 466 * 467 * @param input the data to encode 468 * @param offset the position within the input array at which to 469 * start 470 * @param len the number of bytes of input to encode 471 * @param flags controls certain features of the encoded output. 472 * Passing {@code DEFAULT} results in output that 473 * adheres to RFC 2045. 474 */ 475 public static String encodeToString(byte[] input, int offset, int len, int flags) { 476 try { 477 return new String(encode(input, offset, len, flags), "US-ASCII"); 478 } catch (UnsupportedEncodingException e) { 479 // US-ASCII is guaranteed to be available. 480 throw new AssertionError(e); 481 } 482 } 483 484 /** 485 * Base64-encode the given data and return a newly allocated 486 * byte[] with the result. 487 * 488 * @param input the data to encode 489 * @param flags controls certain features of the encoded output. 490 * Passing {@code DEFAULT} results in output that 491 * adheres to RFC 2045. 492 */ 493 public static byte[] encode(byte[] input, int flags) { 494 return encode(input, 0, input.length, flags); 495 } 496 497 /** 498 * Base64-encode the given data and return a newly allocated 499 * byte[] with the result. 500 * 501 * @param input the data to encode 502 * @param offset the position within the input array at which to 503 * start 504 * @param len the number of bytes of input to encode 505 * @param flags controls certain features of the encoded output. 506 * Passing {@code DEFAULT} results in output that 507 * adheres to RFC 2045. 508 */ 509 public static byte[] encode(byte[] input, int offset, int len, int flags) { 510 Encoder encoder = new Encoder(flags, null); 511 512 // Compute the exact length of the array we will produce. 513 int output_len = len / 3 * 4; 514 515 // Account for the tail of the data and the padding bytes, if any. 516 if (encoder.do_padding) { 517 if (len % 3 > 0) { 518 output_len += 4; 519 } 520 } else { 521 switch (len % 3) { 522 case 0: break; 523 case 1: output_len += 2; break; 524 case 2: output_len += 3; break; 525 } 526 } 527 528 // Account for the newlines, if any. 529 if (encoder.do_newline && len > 0) { 530 output_len += (((len-1) / (3 * Encoder.LINE_GROUPS)) + 1) * 531 (encoder.do_cr ? 2 : 1); 532 } 533 534 encoder.output = new byte[output_len]; 535 encoder.process(input, offset, len, true); 536 537 assert encoder.op == output_len; 538 539 return encoder.output; 540 } 541 542 /* package */ static class Encoder extends Coder { 543 /** 544 * Emit a new line every this many output tuples. Corresponds to 545 * a 76-character line length (the maximum allowable according to 546 * <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>). 547 */ 548 public static final int LINE_GROUPS = 19; 549 550 /** 551 * Lookup table for turning Base64 alphabet positions (6 bits) 552 * into output bytes. 553 */ 554 private static final byte ENCODE[] = { 555 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 556 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 557 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 558 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/', 559 }; 560 561 /** 562 * Lookup table for turning Base64 alphabet positions (6 bits) 563 * into output bytes. 564 */ 565 private static final byte ENCODE_WEBSAFE[] = { 566 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 567 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 568 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 569 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_', 570 }; 571 572 final private byte[] tail; 573 /* package */ int tailLen; 574 private int count; 575 576 final public boolean do_padding; 577 final public boolean do_newline; 578 final public boolean do_cr; 579 final private byte[] alphabet; 580 581 public Encoder(int flags, byte[] output) { 582 this.output = output; 583 584 do_padding = (flags & NO_PADDING) == 0; 585 do_newline = (flags & NO_WRAP) == 0; 586 do_cr = (flags & CRLF) != 0; 587 alphabet = ((flags & URL_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE; 588 589 tail = new byte[2]; 590 tailLen = 0; 591 592 count = do_newline ? LINE_GROUPS : -1; 593 } 594 595 /** 596 * @return an overestimate for the number of bytes {@code 597 * len} bytes could encode to. 598 */ 599 public int maxOutputSize(int len) { 600 return len * 8/5 + 10; 601 } 602 603 public boolean process(byte[] input, int offset, int len, boolean finish) { 604 // Using local variables makes the encoder about 9% faster. 605 final byte[] alphabet = this.alphabet; 606 final byte[] output = this.output; 607 int op = 0; 608 int count = this.count; 609 610 int p = offset; 611 len += offset; 612 int v = -1; 613 614 // First we need to concatenate the tail of the previous call 615 // with any input bytes available now and see if we can empty 616 // the tail. 617 618 switch (tailLen) { 619 case 0: 620 // There was no tail. 621 break; 622 623 case 1: 624 if (p+2 <= len) { 625 // A 1-byte tail with at least 2 bytes of 626 // input available now. 627 v = ((tail[0] & 0xff) << 16) | 628 ((input[p++] & 0xff) << 8) | 629 (input[p++] & 0xff); 630 tailLen = 0; 631 }; 632 break; 633 634 case 2: 635 if (p+1 <= len) { 636 // A 2-byte tail with at least 1 byte of input. 637 v = ((tail[0] & 0xff) << 16) | 638 ((tail[1] & 0xff) << 8) | 639 (input[p++] & 0xff); 640 tailLen = 0; 641 } 642 break; 643 } 644 645 if (v != -1) { 646 output[op++] = alphabet[(v >> 18) & 0x3f]; 647 output[op++] = alphabet[(v >> 12) & 0x3f]; 648 output[op++] = alphabet[(v >> 6) & 0x3f]; 649 output[op++] = alphabet[v & 0x3f]; 650 if (--count == 0) { 651 if (do_cr) output[op++] = '\r'; 652 output[op++] = '\n'; 653 count = LINE_GROUPS; 654 } 655 } 656 657 // At this point either there is no tail, or there are fewer 658 // than 3 bytes of input available. 659 660 // The main loop, turning 3 input bytes into 4 output bytes on 661 // each iteration. 662 while (p+3 <= len) { 663 v = ((input[p] & 0xff) << 16) | 664 ((input[p+1] & 0xff) << 8) | 665 (input[p+2] & 0xff); 666 output[op] = alphabet[(v >> 18) & 0x3f]; 667 output[op+1] = alphabet[(v >> 12) & 0x3f]; 668 output[op+2] = alphabet[(v >> 6) & 0x3f]; 669 output[op+3] = alphabet[v & 0x3f]; 670 p += 3; 671 op += 4; 672 if (--count == 0) { 673 if (do_cr) output[op++] = '\r'; 674 output[op++] = '\n'; 675 count = LINE_GROUPS; 676 } 677 } 678 679 if (finish) { 680 // Finish up the tail of the input. Note that we need to 681 // consume any bytes in tail before any bytes 682 // remaining in input; there should be at most two bytes 683 // total. 684 685 if (p-tailLen == len-1) { 686 int t = 0; 687 v = ((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 4; 688 tailLen -= t; 689 output[op++] = alphabet[(v >> 6) & 0x3f]; 690 output[op++] = alphabet[v & 0x3f]; 691 if (do_padding) { 692 output[op++] = '='; 693 output[op++] = '='; 694 } 695 if (do_newline) { 696 if (do_cr) output[op++] = '\r'; 697 output[op++] = '\n'; 698 } 699 } else if (p-tailLen == len-2) { 700 int t = 0; 701 v = (((tailLen > 1 ? tail[t++] : input[p++]) & 0xff) << 10) | 702 (((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 2); 703 tailLen -= t; 704 output[op++] = alphabet[(v >> 12) & 0x3f]; 705 output[op++] = alphabet[(v >> 6) & 0x3f]; 706 output[op++] = alphabet[v & 0x3f]; 707 if (do_padding) { 708 output[op++] = '='; 709 } 710 if (do_newline) { 711 if (do_cr) output[op++] = '\r'; 712 output[op++] = '\n'; 713 } 714 } else if (do_newline && op > 0 && count != LINE_GROUPS) { 715 if (do_cr) output[op++] = '\r'; 716 output[op++] = '\n'; 717 } 718 719 assert tailLen == 0; 720 assert p == len; 721 } else { 722 // Save the leftovers in tail to be consumed on the next 723 // call to encodeInternal. 724 725 if (p == len-1) { 726 tail[tailLen++] = input[p]; 727 } else if (p == len-2) { 728 tail[tailLen++] = input[p]; 729 tail[tailLen++] = input[p+1]; 730 } 731 } 732 733 this.op = op; 734 this.count = count; 735 736 return true; 737 } 738 } 739 740 private Base64() { } // don't instantiate 741 } 742
