lib/lz4/lz4_decompress.c

   1 /*
   2  * LZ4 - Fast LZ compression algorithm
   3  * Copyright (C) 2011 - 2016, Yann Collet.
   4  * BSD 2 - Clause License (http://www.opensource.org/licenses/bsd - license.php)
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met:
   8  *      * Redistributions of source code must retain the above copyright
   9  *        notice, this list of conditions and the following disclaimer.
  10  *      * Redistributions in binary form must reproduce the above
  11  * copyright notice, this list of conditions and the following disclaimer
  12  * in the documentation and/or other materials provided with the
  13  * distribution.
  14  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  15  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  16  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  17  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  18  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  19  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  20  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  24  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  * You can contact the author at :
  26  *      - LZ4 homepage : http://www.lz4.org
  27  *      - LZ4 source repository : https://github.com/lz4/lz4
  28  *
  29  *      Changed for kernel usage by:
  30  *      Sven Schmidt <4sschmid@informatik.uni-hamburg.de>
  31  */
  32
  33 /*-************************************
  34  *      Dependencies
  35  **************************************/
  36 #include <linux/lz4.h>
  37 #include "lz4defs.h"
  38 #include <linux/init.h>
  39 #include <linux/module.h>
  40 #include <linux/kernel.h>
  41 #include <asm/unaligned.h>
  42
  43 /*-*****************************
  44  *      Decompression functions
  45  *******************************/
  46
  47 #define DEBUGLOG(l, ...) {}     /* disabled */
  48
  49 #ifndef assert
  50 #define assert(condition) ((void)0)
  51 #endif
  52
  53 /*
  54  * LZ4_decompress_generic() :
  55  * This generic decompression function covers all use cases.
  56  * It shall be instantiated several times, using different sets of directives.
  57  * Note that it is important for performance that this function really get inlined,
  58  * in order to remove useless branches during compilation optimization.
  59  */
  60 static FORCE_INLINE int LZ4_decompress_generic(
  61          const char * const src,
  62          char * const dst,
  63          int srcSize,
  64                 /*
  65                  * If endOnInput == endOnInputSize,
  66                  * this value is `dstCapacity`
  67                  */
  68          int outputSize,
  69          /* endOnOutputSize, endOnInputSize */
  70          endCondition_directive endOnInput,
  71          /* full, partial */
  72          earlyEnd_directive partialDecoding,
  73          /* noDict, withPrefix64k, usingExtDict */
  74          dict_directive dict,
  75          /* always <= dst, == dst when no prefix */
  76          const BYTE * const lowPrefix,
  77          /* only if dict == usingExtDict */
  78          const BYTE * const dictStart,
  79          /* note : = 0 if noDict */
  80          const size_t dictSize
  81          )
  82 {
  83         const BYTE *ip = (const BYTE *) src;
  84         const BYTE * const iend = ip + srcSize;
  85
  86         BYTE *op = (BYTE *) dst;
  87         BYTE * const oend = op + outputSize;
  88         BYTE *cpy;
  89
  90         const BYTE * const dictEnd = (const BYTE *)dictStart + dictSize;
  91         static const unsigned int inc32table[8] = {0, 1, 2, 1, 0, 4, 4, 4};
  92         static const int dec64table[8] = {0, 0, 0, -1, -4, 1, 2, 3};
  93
  94         const int safeDecode = (endOnInput == endOnInputSize);
  95         const int checkOffset = ((safeDecode) && (dictSize < (int)(64 * KB)));
  96
  97         /* Set up the "end" pointers for the shortcut. */
  98         const BYTE *const shortiend = iend -
  99                 (endOnInput ? 14 : 8) /*maxLL*/ - 2 /*offset*/;
 100         const BYTE *const shortoend = oend -
 101                 (endOnInput ? 14 : 8) /*maxLL*/ - 18 /*maxML*/;
 102
 103         DEBUGLOG(5, "%s (srcSize:%i, dstSize:%i)", __func__,
 104                  srcSize, outputSize);
 105
 106         /* Special cases */
 107         assert(lowPrefix <= op);
 108         assert(src != NULL);
 109
 110         /* Empty output buffer */
 111         if ((endOnInput) && (unlikely(outputSize == 0)))
 112                 return ((srcSize == 1) && (*ip == 0)) ? 0 : -1;
 113
 114         if ((!endOnInput) && (unlikely(outputSize == 0)))
 115                 return (*ip == 0 ? 1 : -1);
 116
 117         if ((endOnInput) && unlikely(srcSize == 0))
 118                 return -1;
 119
 120         /* Main Loop : decode sequences */
 121         while (1) {
 122                 size_t length;
 123                 const BYTE *match;
 124                 size_t offset;
 125
 126                 /* get literal length */
 127                 unsigned int const token = *ip++;
 128                 length = token>>ML_BITS;
 129
 130                 /* ip < iend before the increment */
 131                 assert(!endOnInput || ip <= iend);
 132
 133                 /*
 134                  * A two-stage shortcut for the most common case:
 135                  * 1) If the literal length is 0..14, and there is enough
 136                  * space, enter the shortcut and copy 16 bytes on behalf
 137                  * of the literals (in the fast mode, only 8 bytes can be
 138                  * safely copied this way).
 139                  * 2) Further if the match length is 4..18, copy 18 bytes
 140                  * in a similar manner; but we ensure that there's enough
 141                  * space in the output for those 18 bytes earlier, upon
 142                  * entering the shortcut (in other words, there is a
 143                  * combined check for both stages).
 144                  */
 145                 if ((endOnInput ? length != RUN_MASK : length <= 8)
 146                    /*
 147                     * strictly "less than" on input, to re-enter
 148                     * the loop with at least one byte
 149                     */
 150                    && likely((endOnInput ? ip < shortiend : 1) &
 151                              (op <= shortoend))) {
 152                         /* Copy the literals */
 153                         memcpy(op, ip, endOnInput ? 16 : 8);
 154                         op += length; ip += length;
 155
 156                         /*
 157                          * The second stage:
 158                          * prepare for match copying, decode full info.
 159                          * If it doesn't work out, the info won't be wasted.
 160                          */
 161                         length = token & ML_MASK; /* match length */
 162                         offset = LZ4_readLE16(ip);
 163                         ip += 2;
 164                         match = op - offset;
 165                         assert(match <= op); /* check overflow */
 166
 167                         /* Do not deal with overlapping matches. */
 168                         if ((length != ML_MASK) &&
 169                             (offset >= 8) &&
 170                             (dict == withPrefix64k || match >= lowPrefix)) {
 171                                 /* Copy the match. */
 172                                 memcpy(op + 0, match + 0, 8);
 173                                 memcpy(op + 8, match + 8, 8);
 174                                 memcpy(op + 16, match + 16, 2);
 175                                 op += length + MINMATCH;
 176                                 /* Both stages worked, load the next token. */
 177                                 continue;
 178                         }
 179
 180                         /*
 181                          * The second stage didn't work out, but the info
 182                          * is ready. Propel it right to the point of match
 183                          * copying.
 184                          */
 185                         goto _copy_match;
 186                 }
 187
 188                 /* decode literal length */
 189                 if (length == RUN_MASK) {
 190                         unsigned int s;
 191
 192                         if (unlikely(endOnInput ? ip >= iend - RUN_MASK : 0)) {
 193                                 /* overflow detection */
 194                                 goto _output_error;
 195                         }
 196                         do {
 197                                 s = *ip++;
 198                                 length += s;
 199                         } while (likely(endOnInput
 200                                 ? ip < iend - RUN_MASK
 201                                 : 1) & (s == 255));
 202
 203                         if ((safeDecode)
 204                             && unlikely((uptrval)(op) +
 205                                         length < (uptrval)(op))) {
 206                                 /* overflow detection */
 207                                 goto _output_error;
 208                         }
 209                         if ((safeDecode)
 210                             && unlikely((uptrval)(ip) +
 211                                         length < (uptrval)(ip))) {
 212                                 /* overflow detection */
 213                                 goto _output_error;
 214                         }
 215                 }
 216
 217                 /* copy literals */
 218                 cpy = op + length;
 219                 LZ4_STATIC_ASSERT(MFLIMIT >= WILDCOPYLENGTH);
 220
 221                 if (((endOnInput) && ((cpy > oend - MFLIMIT)
 222                         || (ip + length > iend - (2 + 1 + LASTLITERALS))))
 223                         || ((!endOnInput) && (cpy > oend - WILDCOPYLENGTH))) {
 224                         if (partialDecoding) {
 225                                 if (cpy > oend) {
 226                                         /*
 227                                          * Partial decoding :
 228                                          * stop in the middle of literal segment
 229                                          */
 230                                         cpy = oend;
 231                                         length = oend - op;
 232                                 }
 233                                 if ((endOnInput)
 234                                         && (ip + length > iend)) {
 235                                         /*
 236                                          * Error :
 237                                          * read attempt beyond
 238                                          * end of input buffer
 239                                          */
 240                                         goto _output_error;
 241                                 }
 242                         } else {
 243                                 if ((!endOnInput)
 244                                         && (cpy != oend)) {
 245                                         /*
 246                                          * Error :
 247                                          * block decoding must
 248                                          * stop exactly there
 249                                          */
 250                                         goto _output_error;
 251                                 }
 252                                 if ((endOnInput)
 253                                         && ((ip + length != iend)
 254                                         || (cpy > oend))) {
 255                                         /*
 256                                          * Error :
 257                                          * input must be consumed
 258                                          */
 259                                         goto _output_error;
 260                                 }
 261                         }
 262
 263                         memcpy(op, ip, length);
 264                         ip += length;
 265                         op += length;
 266
 267                         /* Necessarily EOF, due to parsing restrictions */
 268                         if (!partialDecoding || (cpy == oend))
 269                                 break;
 270                 } else {
 271                         /* may overwrite up to WILDCOPYLENGTH beyond cpy */
 272                         LZ4_wildCopy(op, ip, cpy);
 273                         ip += length;
 274                         op = cpy;
 275                 }
 276
 277                 /* get offset */
 278                 offset = LZ4_readLE16(ip);
 279                 ip += 2;
 280                 match = op - offset;
 281
 282                 /* get matchlength */
 283                 length = token & ML_MASK;
 284
 285 _copy_match:
 286                 if ((checkOffset) && (unlikely(match + dictSize < lowPrefix))) {
 287                         /* Error : offset outside buffers */
 288                         goto _output_error;
 289                 }
 290
 291                 /* costs ~1%; silence an msan warning when offset == 0 */
 292                 /*
 293                  * note : when partialDecoding, there is no guarantee that
 294                  * at least 4 bytes remain available in output buffer
 295                  */
 296                 if (!partialDecoding) {
 297                         assert(oend > op);
 298                         assert(oend - op >= 4);
 299
 300                         LZ4_write32(op, (U32)offset);
 301                 }
 302
 303                 if (length == ML_MASK) {
 304                         unsigned int s;
 305
 306                         do {
 307                                 s = *ip++;
 308
 309                                 if ((endOnInput) && (ip > iend - LASTLITERALS))
 310                                         goto _output_error;
 311
 312                                 length += s;
 313                         } while (s == 255);
 314
 315                         if ((safeDecode)
 316                                 && unlikely(
 317                                         (uptrval)(op) + length < (uptrval)op)) {
 318                                 /* overflow detection */
 319                                 goto _output_error;
 320                         }
 321                 }
 322
 323                 length += MINMATCH;
 324
 325                 /* match starting within external dictionary */
 326                 if ((dict == usingExtDict) && (match < lowPrefix)) {
 327                         if (unlikely(op + length > oend - LASTLITERALS)) {
 328                                 /* doesn't respect parsing restriction */
 329                                 if (!partialDecoding)
 330                                         goto _output_error;
 331                                 length = min(length, (size_t)(oend - op));
 332                         }
 333
 334                         if (length <= (size_t)(lowPrefix - match)) {
 335                                 /*
 336                                  * match fits entirely within external
 337                                  * dictionary : just copy
 338                                  */
 339                                 memmove(op, dictEnd - (lowPrefix - match),
 340                                         length);
 341                                 op += length;
 342                         } else {
 343                                 /*
 344                                  * match stretches into both external
 345                                  * dictionary and current block
 346                                  */
 347                                 size_t const copySize = (size_t)(lowPrefix - match);
 348                                 size_t const restSize = length - copySize;
 349
 350                                 memcpy(op, dictEnd - copySize, copySize);
 351                                 op += copySize;
 352                                 if (restSize > (size_t)(op - lowPrefix)) {
 353                                         /* overlap copy */
 354                                         BYTE * const endOfMatch = op + restSize;
 355                                         const BYTE *copyFrom = lowPrefix;
 356
 357                                         while (op < endOfMatch)
 358                                                 *op++ = *copyFrom++;
 359                                 } else {
 360                                         memcpy(op, lowPrefix, restSize);
 361                                         op += restSize;
 362                                 }
 363                         }
 364                         continue;
 365                 }
 366
 367                 /* copy match within block */
 368                 cpy = op + length;
 369
 370                 /*
 371                  * partialDecoding :
 372                  * may not respect endBlock parsing restrictions
 373                  */
 374                 assert(op <= oend);
 375                 if (partialDecoding &&
 376                     (cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
 377                         size_t const mlen = min(length, (size_t)(oend - op));
 378                         const BYTE * const matchEnd = match + mlen;
 379                         BYTE * const copyEnd = op + mlen;
 380
 381                         if (matchEnd > op) {
 382                                 /* overlap copy */
 383                                 while (op < copyEnd)
 384                                         *op++ = *match++;
 385                         } else {
 386                                 memcpy(op, match, mlen);
 387                         }
 388                         op = copyEnd;
 389                         if (op == oend)
 390                                 break;
 391                         continue;
 392                 }
 393
 394                 if (unlikely(offset < 8)) {
 395                         op[0] = match[0];
 396                         op[1] = match[1];
 397                         op[2] = match[2];
 398                         op[3] = match[3];
 399                         match += inc32table[offset];
 400                         memcpy(op + 4, match, 4);
 401                         match -= dec64table[offset];
 402                 } else {
 403                         LZ4_copy8(op, match);
 404                         match += 8;
 405                 }
 406
 407                 op += 8;
 408
 409                 if (unlikely(cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
 410                         BYTE * const oCopyLimit = oend - (WILDCOPYLENGTH - 1);
 411
 412                         if (cpy > oend - LASTLITERALS) {
 413                                 /*
 414                                  * Error : last LASTLITERALS bytes
 415                                  * must be literals (uncompressed)
 416                                  */
 417                                 goto _output_error;
 418                         }
 419
 420                         if (op < oCopyLimit) {
 421                                 LZ4_wildCopy(op, match, oCopyLimit);
 422                                 match += oCopyLimit - op;
 423                                 op = oCopyLimit;
 424                         }
 425                         while (op < cpy)
 426                                 *op++ = *match++;
 427                 } else {
 428                         LZ4_copy8(op, match);
 429                         if (length > 16)
 430                                 LZ4_wildCopy(op + 8, match + 8, cpy);
 431                 }
 432                 op = cpy; /* wildcopy correction */
 433         }
 434
 435         /* end of decoding */
 436         if (endOnInput) {
 437                 /* Nb of output bytes decoded */
 438                 return (int) (((char *)op) - dst);
 439         } else {
 440                 /* Nb of input bytes read */
 441                 return (int) (((const char *)ip) - src);
 442         }
 443
 444         /* Overflow error detected */
 445 _output_error:
 446         return (int) (-(((const char *)ip) - src)) - 1;
 447 }
 448
 449 int LZ4_decompress_safe(const char *source, char *dest,
 450         int compressedSize, int maxDecompressedSize)
 451 {
 452         return LZ4_decompress_generic(source, dest,
 453                                       compressedSize, maxDecompressedSize,
 454                                       endOnInputSize, decode_full_block,
 455                                       noDict, (BYTE *)dest, NULL, 0);
 456 }
 457
 458 int LZ4_decompress_safe_partial(const char *src, char *dst,
 459         int compressedSize, int targetOutputSize, int dstCapacity)
 460 {
 461         dstCapacity = min(targetOutputSize, dstCapacity);
 462         return LZ4_decompress_generic(src, dst, compressedSize, dstCapacity,
 463                                       endOnInputSize, partial_decode,
 464                                       noDict, (BYTE *)dst, NULL, 0);
 465 }
 466
 467 int LZ4_decompress_fast(const char *source, char *dest, int originalSize)
 468 {
 469         return LZ4_decompress_generic(source, dest, 0, originalSize,
 470                                       endOnOutputSize, decode_full_block,
 471                                       withPrefix64k,
 472                                       (BYTE *)dest - 64 * KB, NULL, 0);
 473 }
 474
 475 /* ===== Instantiate a few more decoding cases, used more than once. ===== */
 476
 477 int LZ4_decompress_safe_withPrefix64k(const char *source, char *dest,
 478                                       int compressedSize, int maxOutputSize)
 479 {
 480         return LZ4_decompress_generic(source, dest,
 481                                       compressedSize, maxOutputSize,
 482                                       endOnInputSize, decode_full_block,
 483                                       withPrefix64k,
 484                                       (BYTE *)dest - 64 * KB, NULL, 0);
 485 }
 486
 487 static int LZ4_decompress_safe_withSmallPrefix(const char *source, char *dest,
 488                                                int compressedSize,
 489                                                int maxOutputSize,
 490                                                size_t prefixSize)
 491 {
 492         return LZ4_decompress_generic(source, dest,
 493                                       compressedSize, maxOutputSize,
 494                                       endOnInputSize, decode_full_block,
 495                                       noDict,
 496                                       (BYTE *)dest - prefixSize, NULL, 0);
 497 }
 498
 499 int LZ4_decompress_safe_forceExtDict(const char *source, char *dest,
 500                                      int compressedSize, int maxOutputSize,
 501                                      const void *dictStart, size_t dictSize)
 502 {
 503         return LZ4_decompress_generic(source, dest,
 504                                       compressedSize, maxOutputSize,
 505                                       endOnInputSize, decode_full_block,
 506                                       usingExtDict, (BYTE *)dest,
 507                                       (const BYTE *)dictStart, dictSize);
 508 }
 509
 510 static int LZ4_decompress_fast_extDict(const char *source, char *dest,
 511                                        int originalSize,
 512                                        const void *dictStart, size_t dictSize)
 513 {
 514         return LZ4_decompress_generic(source, dest,
 515                                       0, originalSize,
 516                                       endOnOutputSize, decode_full_block,
 517                                       usingExtDict, (BYTE *)dest,
 518                                       (const BYTE *)dictStart, dictSize);
 519 }
 520
 521 /*
 522  * The "double dictionary" mode, for use with e.g. ring buffers: the first part
 523  * of the dictionary is passed as prefix, and the second via dictStart + dictSize.
 524  * These routines are used only once, in LZ4_decompress_*_continue().
 525  */
 526 static FORCE_INLINE
 527 int LZ4_decompress_safe_doubleDict(const char *source, char *dest,
 528                                    int compressedSize, int maxOutputSize,
 529                                    size_t prefixSize,
 530                                    const void *dictStart, size_t dictSize)
 531 {
 532         return LZ4_decompress_generic(source, dest,
 533                                       compressedSize, maxOutputSize,
 534                                       endOnInputSize, decode_full_block,
 535                                       usingExtDict, (BYTE *)dest - prefixSize,
 536                                       (const BYTE *)dictStart, dictSize);
 537 }
 538
 539 static FORCE_INLINE
 540 int LZ4_decompress_fast_doubleDict(const char *source, char *dest,
 541                                    int originalSize, size_t prefixSize,
 542                                    const void *dictStart, size_t dictSize)
 543 {
 544         return LZ4_decompress_generic(source, dest,
 545                                       0, originalSize,
 546                                       endOnOutputSize, decode_full_block,
 547                                       usingExtDict, (BYTE *)dest - prefixSize,
 548                                       (const BYTE *)dictStart, dictSize);
 549 }
 550
 551 /* ===== streaming decompression functions ===== */
 552
 553 int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
 554         const char *dictionary, int dictSize)
 555 {
 556         LZ4_streamDecode_t_internal *lz4sd =
 557                 &LZ4_streamDecode->internal_donotuse;
 558
 559         lz4sd->prefixSize = (size_t) dictSize;
 560         lz4sd->prefixEnd = (const BYTE *) dictionary + dictSize;
 561         lz4sd->externalDict = NULL;
 562         lz4sd->extDictSize      = 0;
 563         return 1;
 564 }
 565
 566 /*
 567  * *_continue() :
 568  * These decoding functions allow decompression of multiple blocks
 569  * in "streaming" mode.
 570  * Previously decoded blocks must still be available at the memory
 571  * position where they were decoded.
 572  * If it's not possible, save the relevant part of
 573  * decoded data into a safe buffer,
 574  * and indicate where it stands using LZ4_setStreamDecode()
 575  */
 576 int LZ4_decompress_safe_continue(LZ4_streamDecode_t *LZ4_streamDecode,
 577         const char *source, char *dest, int compressedSize, int maxOutputSize)
 578 {
 579         LZ4_streamDecode_t_internal *lz4sd =
 580                 &LZ4_streamDecode->internal_donotuse;
 581         int result;
 582
 583         if (lz4sd->prefixSize == 0) {
 584                 /* The first call, no dictionary yet. */
 585                 assert(lz4sd->extDictSize == 0);
 586                 result = LZ4_decompress_safe(source, dest,
 587                         compressedSize, maxOutputSize);
 588                 if (result <= 0)
 589                         return result;
 590                 lz4sd->prefixSize = result;
 591                 lz4sd->prefixEnd = (BYTE *)dest + result;
 592         } else if (lz4sd->prefixEnd == (BYTE *)dest) {
 593                 /* They're rolling the current segment. */
 594                 if (lz4sd->prefixSize >= 64 * KB - 1)
 595                         result = LZ4_decompress_safe_withPrefix64k(source, dest,
 596                                 compressedSize, maxOutputSize);
 597                 else if (lz4sd->extDictSize == 0)
 598                         result = LZ4_decompress_safe_withSmallPrefix(source,
 599                                 dest, compressedSize, maxOutputSize,
 600                                 lz4sd->prefixSize);
 601                 else
 602                         result = LZ4_decompress_safe_doubleDict(source, dest,
 603                                 compressedSize, maxOutputSize,
 604                                 lz4sd->prefixSize,
 605                                 lz4sd->externalDict, lz4sd->extDictSize);
 606                 if (result <= 0)
 607                         return result;
 608                 lz4sd->prefixSize += result;
 609                 lz4sd->prefixEnd  += result;
 610         } else {
 611                 /*
 612                  * The buffer wraps around, or they're
 613                  * switching to another buffer.
 614                  */
 615                 lz4sd->extDictSize = lz4sd->prefixSize;
 616                 lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
 617                 result = LZ4_decompress_safe_forceExtDict(source, dest,
 618                         compressedSize, maxOutputSize,
 619                         lz4sd->externalDict, lz4sd->extDictSize);
 620                 if (result <= 0)
 621                         return result;
 622                 lz4sd->prefixSize = result;
 623                 lz4sd->prefixEnd  = (BYTE *)dest + result;
 624         }
 625
 626         return result;
 627 }
 628
 629 int LZ4_decompress_fast_continue(LZ4_streamDecode_t *LZ4_streamDecode,
 630         const char *source, char *dest, int originalSize)
 631 {
 632         LZ4_streamDecode_t_internal *lz4sd = &LZ4_streamDecode->internal_donotuse;
 633         int result;
 634
 635         if (lz4sd->prefixSize == 0) {
 636                 assert(lz4sd->extDictSize == 0);
 637                 result = LZ4_decompress_fast(source, dest, originalSize);
 638                 if (result <= 0)
 639                         return result;
 640                 lz4sd->prefixSize = originalSize;
 641                 lz4sd->prefixEnd = (BYTE *)dest + originalSize;
 642         } else if (lz4sd->prefixEnd == (BYTE *)dest) {
 643                 if (lz4sd->prefixSize >= 64 * KB - 1 ||
 644                     lz4sd->extDictSize == 0)
 645                         result = LZ4_decompress_fast(source, dest,
 646                                                      originalSize);
 647                 else
 648                         result = LZ4_decompress_fast_doubleDict(source, dest,
 649                                 originalSize, lz4sd->prefixSize,
 650                                 lz4sd->externalDict, lz4sd->extDictSize);
 651                 if (result <= 0)
 652                         return result;
 653                 lz4sd->prefixSize += originalSize;
 654                 lz4sd->prefixEnd  += originalSize;
 655         } else {
 656                 lz4sd->extDictSize = lz4sd->prefixSize;
 657                 lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
 658                 result = LZ4_decompress_fast_extDict(source, dest,
 659                         originalSize, lz4sd->externalDict, lz4sd->extDictSize);
 660                 if (result <= 0)
 661                         return result;
 662                 lz4sd->prefixSize = originalSize;
 663                 lz4sd->prefixEnd = (BYTE *)dest + originalSize;
 664         }
 665         return result;
 666 }
 667
 668 int LZ4_decompress_safe_usingDict(const char *source, char *dest,
 669                                   int compressedSize, int maxOutputSize,
 670                                   const char *dictStart, int dictSize)
 671 {
 672         if (dictSize == 0)
 673                 return LZ4_decompress_safe(source, dest,
 674                                            compressedSize, maxOutputSize);
 675         if (dictStart+dictSize == dest) {
 676                 if (dictSize >= 64 * KB - 1)
 677                         return LZ4_decompress_safe_withPrefix64k(source, dest,
 678                                 compressedSize, maxOutputSize);
 679                 return LZ4_decompress_safe_withSmallPrefix(source, dest,
 680                         compressedSize, maxOutputSize, dictSize);
 681         }
 682         return LZ4_decompress_safe_forceExtDict(source, dest,
 683                 compressedSize, maxOutputSize, dictStart, dictSize);
 684 }
 685
 686 int LZ4_decompress_fast_usingDict(const char *source, char *dest,
 687                                   int originalSize,
 688                                   const char *dictStart, int dictSize)
 689 {
 690         if (dictSize == 0 || dictStart + dictSize == dest)
 691                 return LZ4_decompress_fast(source, dest, originalSize);
 692
 693         return LZ4_decompress_fast_extDict(source, dest, originalSize,
 694                 dictStart, dictSize);
 695 }
 696
 697 #ifndef STATIC
 698 EXPORT_SYMBOL(LZ4_decompress_safe);
 699 EXPORT_SYMBOL(LZ4_decompress_safe_partial);
 700 EXPORT_SYMBOL(LZ4_decompress_fast);
 701 EXPORT_SYMBOL(LZ4_setStreamDecode);
 702 EXPORT_SYMBOL(LZ4_decompress_safe_continue);
 703 EXPORT_SYMBOL(LZ4_decompress_fast_continue);
 704 EXPORT_SYMBOL(LZ4_decompress_safe_usingDict);
 705 EXPORT_SYMBOL(LZ4_decompress_fast_usingDict);
 706
 707 MODULE_LICENSE("Dual BSD/GPL");
 708 MODULE_DESCRIPTION("LZ4 decompressor");
 709 #endif