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 "lz4defs.h"
 37#include <linux/init.h>
 38#include <linux/module.h>
 39#include <linux/kernel.h>
 40#include <linux/unaligned.h>
 41
 42/*-*****************************
 43 *	Decompression functions
 44 *******************************/
 45
 46#define DEBUGLOG(l, ...) {}	/* disabled */
 47
 48#ifndef assert
 49#define assert(condition) ((void)0)
 50#endif
 51
 52/*
 53 * LZ4_decompress_generic() :
 54 * This generic decompression function covers all use cases.
 55 * It shall be instantiated several times, using different sets of directives.
 56 * Note that it is important for performance that this function really get inlined,
 57 * in order to remove useless branches during compilation optimization.
 58 */
 59static FORCE_INLINE int LZ4_decompress_generic(
 60	 const char * const src,
 61	 char * const dst,
 62	 int srcSize,
 63		/*
 64		 * If endOnInput == endOnInputSize,
 65		 * this value is `dstCapacity`
 66		 */
 67	 int outputSize,
 68	 /* endOnOutputSize, endOnInputSize */
 69	 endCondition_directive endOnInput,
 70	 /* full, partial */
 71	 earlyEnd_directive partialDecoding,
 72	 /* noDict, withPrefix64k, usingExtDict */
 73	 dict_directive dict,
 74	 /* always <= dst, == dst when no prefix */
 75	 const BYTE * const lowPrefix,
 76	 /* only if dict == usingExtDict */
 77	 const BYTE * const dictStart,
 78	 /* note : = 0 if noDict */
 79	 const size_t dictSize
 80	 )
 81{
 82	const BYTE *ip = (const BYTE *) src;
 83	const BYTE * const iend = ip + srcSize;
 84
 85	BYTE *op = (BYTE *) dst;
 86	BYTE * const oend = op + outputSize;
 87	BYTE *cpy;
 88
 89	const BYTE * const dictEnd = (const BYTE *)dictStart + dictSize;
 90	static const unsigned int inc32table[8] = {0, 1, 2, 1, 0, 4, 4, 4};
 91	static const int dec64table[8] = {0, 0, 0, -1, -4, 1, 2, 3};
 92
 93	const int safeDecode = (endOnInput == endOnInputSize);
 94	const int checkOffset = ((safeDecode) && (dictSize < (int)(64 * KB)));
 95
 96	/* Set up the "end" pointers for the shortcut. */
 97	const BYTE *const shortiend = iend -
 98		(endOnInput ? 14 : 8) /*maxLL*/ - 2 /*offset*/;
 99	const BYTE *const shortoend = oend -
100		(endOnInput ? 14 : 8) /*maxLL*/ - 18 /*maxML*/;
101
102	DEBUGLOG(5, "%s (srcSize:%i, dstSize:%i)", __func__,
103		 srcSize, outputSize);
104
105	/* Special cases */
106	assert(lowPrefix <= op);
107	assert(src != NULL);
108
109	/* Empty output buffer */
110	if ((endOnInput) && (unlikely(outputSize == 0)))
111		return ((srcSize == 1) && (*ip == 0)) ? 0 : -1;
112
113	if ((!endOnInput) && (unlikely(outputSize == 0)))
114		return (*ip == 0 ? 1 : -1);
115
116	if ((endOnInput) && unlikely(srcSize == 0))
117		return -1;
118
119	/* Main Loop : decode sequences */
120	while (1) {
121		size_t length;
122		const BYTE *match;
123		size_t offset;
124
125		/* get literal length */
126		unsigned int const token = *ip++;
127		length = token>>ML_BITS;
128
129		/* ip < iend before the increment */
130		assert(!endOnInput || ip <= iend);
131
132		/*
133		 * A two-stage shortcut for the most common case:
134		 * 1) If the literal length is 0..14, and there is enough
135		 * space, enter the shortcut and copy 16 bytes on behalf
136		 * of the literals (in the fast mode, only 8 bytes can be
137		 * safely copied this way).
138		 * 2) Further if the match length is 4..18, copy 18 bytes
139		 * in a similar manner; but we ensure that there's enough
140		 * space in the output for those 18 bytes earlier, upon
141		 * entering the shortcut (in other words, there is a
142		 * combined check for both stages).
143		 *
144		 * The & in the likely() below is intentionally not && so that
145		 * some compilers can produce better parallelized runtime code
146		 */
147		if ((endOnInput ? length != RUN_MASK : length <= 8)
148		   /*
149		    * strictly "less than" on input, to re-enter
150		    * the loop with at least one byte
151		    */
152		   && likely((endOnInput ? ip < shortiend : 1) &
153			     (op <= shortoend))) {
154			/* Copy the literals */
155			LZ4_memcpy(op, ip, endOnInput ? 16 : 8);
156			op += length; ip += length;
157
158			/*
159			 * The second stage:
160			 * prepare for match copying, decode full info.
161			 * If it doesn't work out, the info won't be wasted.
162			 */
163			length = token & ML_MASK; /* match length */
164			offset = LZ4_readLE16(ip);
165			ip += 2;
166			match = op - offset;
167			assert(match <= op); /* check overflow */
168
169			/* Do not deal with overlapping matches. */
170			if ((length != ML_MASK) &&
171			    (offset >= 8) &&
172			    (dict == withPrefix64k || match >= lowPrefix)) {
173				/* Copy the match. */
174				LZ4_memcpy(op + 0, match + 0, 8);
175				LZ4_memcpy(op + 8, match + 8, 8);
176				LZ4_memcpy(op + 16, match + 16, 2);
177				op += length + MINMATCH;
178				/* Both stages worked, load the next token. */
179				continue;
180			}
181
182			/*
183			 * The second stage didn't work out, but the info
184			 * is ready. Propel it right to the point of match
185			 * copying.
186			 */
187			goto _copy_match;
188		}
189
190		/* decode literal length */
191		if (length == RUN_MASK) {
192			unsigned int s;
193
194			if (unlikely(endOnInput ? ip >= iend - RUN_MASK : 0)) {
195				/* overflow detection */
196				goto _output_error;
197			}
198			do {
199				s = *ip++;
200				length += s;
201			} while (likely(endOnInput
202				? ip < iend - RUN_MASK
203				: 1) & (s == 255));
204
205			if ((safeDecode)
206			    && unlikely((uptrval)(op) +
207					length < (uptrval)(op))) {
208				/* overflow detection */
209				goto _output_error;
210			}
211			if ((safeDecode)
212			    && unlikely((uptrval)(ip) +
213					length < (uptrval)(ip))) {
214				/* overflow detection */
215				goto _output_error;
216			}
217		}
218
219		/* copy literals */
220		cpy = op + length;
221		LZ4_STATIC_ASSERT(MFLIMIT >= WILDCOPYLENGTH);
222
223		if (((endOnInput) && ((cpy > oend - MFLIMIT)
224			|| (ip + length > iend - (2 + 1 + LASTLITERALS))))
225			|| ((!endOnInput) && (cpy > oend - WILDCOPYLENGTH))) {
226			if (partialDecoding) {
227				if (cpy > oend) {
228					/*
229					 * Partial decoding :
230					 * stop in the middle of literal segment
231					 */
232					cpy = oend;
233					length = oend - op;
234				}
235				if ((endOnInput)
236					&& (ip + length > iend)) {
237					/*
238					 * Error :
239					 * read attempt beyond
240					 * end of input buffer
241					 */
242					goto _output_error;
243				}
244			} else {
245				if ((!endOnInput)
246					&& (cpy != oend)) {
247					/*
248					 * Error :
249					 * block decoding must
250					 * stop exactly there
251					 */
252					goto _output_error;
253				}
254				if ((endOnInput)
255					&& ((ip + length != iend)
256					|| (cpy > oend))) {
257					/*
258					 * Error :
259					 * input must be consumed
260					 */
261					goto _output_error;
262				}
263			}
264
265			/*
266			 * supports overlapping memory regions; only matters
267			 * for in-place decompression scenarios
268			 */
269			LZ4_memmove(op, ip, length);
270			ip += length;
271			op += length;
272
273			/* Necessarily EOF when !partialDecoding.
274			 * When partialDecoding, it is EOF if we've either
275			 * filled the output buffer or
276			 * can't proceed with reading an offset for following match.
277			 */
278			if (!partialDecoding || (cpy == oend) || (ip >= (iend - 2)))
279				break;
280		} else {
281			/* may overwrite up to WILDCOPYLENGTH beyond cpy */
282			LZ4_wildCopy(op, ip, cpy);
283			ip += length;
284			op = cpy;
285		}
286
287		/* get offset */
288		offset = LZ4_readLE16(ip);
289		ip += 2;
290		match = op - offset;
291
292		/* get matchlength */
293		length = token & ML_MASK;
294
295_copy_match:
296		if ((checkOffset) && (unlikely(match + dictSize < lowPrefix))) {
297			/* Error : offset outside buffers */
298			goto _output_error;
299		}
300
301		/* costs ~1%; silence an msan warning when offset == 0 */
302		/*
303		 * note : when partialDecoding, there is no guarantee that
304		 * at least 4 bytes remain available in output buffer
305		 */
306		if (!partialDecoding) {
307			assert(oend > op);
308			assert(oend - op >= 4);
309
310			LZ4_write32(op, (U32)offset);
311		}
312
313		if (length == ML_MASK) {
314			unsigned int s;
315
316			do {
317				s = *ip++;
318
319				if ((endOnInput) && (ip > iend - LASTLITERALS))
320					goto _output_error;
321
322				length += s;
323			} while (s == 255);
324
325			if ((safeDecode)
326				&& unlikely(
327					(uptrval)(op) + length < (uptrval)op)) {
328				/* overflow detection */
329				goto _output_error;
330			}
331		}
332
333		length += MINMATCH;
334
335		/* match starting within external dictionary */
336		if ((dict == usingExtDict) && (match < lowPrefix)) {
337			if (unlikely(op + length > oend - LASTLITERALS)) {
338				/* doesn't respect parsing restriction */
339				if (!partialDecoding)
340					goto _output_error;
341				length = min(length, (size_t)(oend - op));
342			}
343
344			if (length <= (size_t)(lowPrefix - match)) {
345				/*
346				 * match fits entirely within external
347				 * dictionary : just copy
348				 */
349				memmove(op, dictEnd - (lowPrefix - match),
350					length);
351				op += length;
352			} else {
353				/*
354				 * match stretches into both external
355				 * dictionary and current block
356				 */
357				size_t const copySize = (size_t)(lowPrefix - match);
358				size_t const restSize = length - copySize;
359
360				LZ4_memcpy(op, dictEnd - copySize, copySize);
361				op += copySize;
362				if (restSize > (size_t)(op - lowPrefix)) {
363					/* overlap copy */
364					BYTE * const endOfMatch = op + restSize;
365					const BYTE *copyFrom = lowPrefix;
366
367					while (op < endOfMatch)
368						*op++ = *copyFrom++;
369				} else {
370					LZ4_memcpy(op, lowPrefix, restSize);
371					op += restSize;
372				}
373			}
374			continue;
375		}
376
377		/* copy match within block */
378		cpy = op + length;
379
380		/*
381		 * partialDecoding :
382		 * may not respect endBlock parsing restrictions
383		 */
384		assert(op <= oend);
385		if (partialDecoding &&
386		    (cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
387			size_t const mlen = min(length, (size_t)(oend - op));
388			const BYTE * const matchEnd = match + mlen;
389			BYTE * const copyEnd = op + mlen;
390
391			if (matchEnd > op) {
392				/* overlap copy */
393				while (op < copyEnd)
394					*op++ = *match++;
395			} else {
396				LZ4_memcpy(op, match, mlen);
397			}
398			op = copyEnd;
399			if (op == oend)
400				break;
401			continue;
402		}
403
404		if (unlikely(offset < 8)) {
405			op[0] = match[0];
406			op[1] = match[1];
407			op[2] = match[2];
408			op[3] = match[3];
409			match += inc32table[offset];
410			LZ4_memcpy(op + 4, match, 4);
411			match -= dec64table[offset];
412		} else {
413			LZ4_copy8(op, match);
414			match += 8;
415		}
416
417		op += 8;
418
419		if (unlikely(cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
420			BYTE * const oCopyLimit = oend - (WILDCOPYLENGTH - 1);
421
422			if (cpy > oend - LASTLITERALS) {
423				/*
424				 * Error : last LASTLITERALS bytes
425				 * must be literals (uncompressed)
426				 */
427				goto _output_error;
428			}
429
430			if (op < oCopyLimit) {
431				LZ4_wildCopy(op, match, oCopyLimit);
432				match += oCopyLimit - op;
433				op = oCopyLimit;
434			}
435			while (op < cpy)
436				*op++ = *match++;
437		} else {
438			LZ4_copy8(op, match);
439			if (length > 16)
440				LZ4_wildCopy(op + 8, match + 8, cpy);
441		}
442		op = cpy; /* wildcopy correction */
443	}
444
445	/* end of decoding */
446	if (endOnInput) {
447		/* Nb of output bytes decoded */
448		return (int) (((char *)op) - dst);
449	} else {
450		/* Nb of input bytes read */
451		return (int) (((const char *)ip) - src);
452	}
453
454	/* Overflow error detected */
455_output_error:
456	return (int) (-(((const char *)ip) - src)) - 1;
457}
458
459int LZ4_decompress_safe(const char *source, char *dest,
460	int compressedSize, int maxDecompressedSize)
461{
462	return LZ4_decompress_generic(source, dest,
463				      compressedSize, maxDecompressedSize,
464				      endOnInputSize, decode_full_block,
465				      noDict, (BYTE *)dest, NULL, 0);
466}
467
468int LZ4_decompress_safe_partial(const char *src, char *dst,
469	int compressedSize, int targetOutputSize, int dstCapacity)
470{
471	dstCapacity = min(targetOutputSize, dstCapacity);
472	return LZ4_decompress_generic(src, dst, compressedSize, dstCapacity,
473				      endOnInputSize, partial_decode,
474				      noDict, (BYTE *)dst, NULL, 0);
475}
476
477int LZ4_decompress_fast(const char *source, char *dest, int originalSize)
478{
479	return LZ4_decompress_generic(source, dest, 0, originalSize,
480				      endOnOutputSize, decode_full_block,
481				      withPrefix64k,
482				      (BYTE *)dest - 64 * KB, NULL, 0);
483}
484
485/* ===== Instantiate a few more decoding cases, used more than once. ===== */
486
487static int LZ4_decompress_safe_withPrefix64k(const char *source, char *dest,
488				      int compressedSize, int maxOutputSize)
489{
490	return LZ4_decompress_generic(source, dest,
491				      compressedSize, maxOutputSize,
492				      endOnInputSize, decode_full_block,
493				      withPrefix64k,
494				      (BYTE *)dest - 64 * KB, NULL, 0);
495}
496
497static int LZ4_decompress_safe_withSmallPrefix(const char *source, char *dest,
498					       int compressedSize,
499					       int maxOutputSize,
500					       size_t prefixSize)
501{
502	return LZ4_decompress_generic(source, dest,
503				      compressedSize, maxOutputSize,
504				      endOnInputSize, decode_full_block,
505				      noDict,
506				      (BYTE *)dest - prefixSize, NULL, 0);
507}
508
509static int LZ4_decompress_safe_forceExtDict(const char *source, char *dest,
510					    int compressedSize, int maxOutputSize,
511					    const void *dictStart, size_t dictSize)
512{
513	return LZ4_decompress_generic(source, dest,
514				      compressedSize, maxOutputSize,
515				      endOnInputSize, decode_full_block,
516				      usingExtDict, (BYTE *)dest,
517				      (const BYTE *)dictStart, dictSize);
518}
519
520static int LZ4_decompress_fast_extDict(const char *source, char *dest,
521				       int originalSize,
522				       const void *dictStart, size_t dictSize)
523{
524	return LZ4_decompress_generic(source, dest,
525				      0, originalSize,
526				      endOnOutputSize, decode_full_block,
527				      usingExtDict, (BYTE *)dest,
528				      (const BYTE *)dictStart, dictSize);
529}
530
531/*
532 * The "double dictionary" mode, for use with e.g. ring buffers: the first part
533 * of the dictionary is passed as prefix, and the second via dictStart + dictSize.
534 * These routines are used only once, in LZ4_decompress_*_continue().
535 */
536static FORCE_INLINE
537int LZ4_decompress_safe_doubleDict(const char *source, char *dest,
538				   int compressedSize, int maxOutputSize,
539				   size_t prefixSize,
540				   const void *dictStart, size_t dictSize)
541{
542	return LZ4_decompress_generic(source, dest,
543				      compressedSize, maxOutputSize,
544				      endOnInputSize, decode_full_block,
545				      usingExtDict, (BYTE *)dest - prefixSize,
546				      (const BYTE *)dictStart, dictSize);
547}
548
549static FORCE_INLINE
550int LZ4_decompress_fast_doubleDict(const char *source, char *dest,
551				   int originalSize, size_t prefixSize,
552				   const void *dictStart, size_t dictSize)
553{
554	return LZ4_decompress_generic(source, dest,
555				      0, originalSize,
556				      endOnOutputSize, decode_full_block,
557				      usingExtDict, (BYTE *)dest - prefixSize,
558				      (const BYTE *)dictStart, dictSize);
559}
560
561/* ===== streaming decompression functions ===== */
562
563int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
564	const char *dictionary, int dictSize)
565{
566	LZ4_streamDecode_t_internal *lz4sd =
567		&LZ4_streamDecode->internal_donotuse;
568
569	lz4sd->prefixSize = (size_t) dictSize;
570	lz4sd->prefixEnd = (const BYTE *) dictionary + dictSize;
571	lz4sd->externalDict = NULL;
572	lz4sd->extDictSize	= 0;
573	return 1;
574}
575
576/*
577 * *_continue() :
578 * These decoding functions allow decompression of multiple blocks
579 * in "streaming" mode.
580 * Previously decoded blocks must still be available at the memory
581 * position where they were decoded.
582 * If it's not possible, save the relevant part of
583 * decoded data into a safe buffer,
584 * and indicate where it stands using LZ4_setStreamDecode()
585 */
586int LZ4_decompress_safe_continue(LZ4_streamDecode_t *LZ4_streamDecode,
587	const char *source, char *dest, int compressedSize, int maxOutputSize)
588{
589	LZ4_streamDecode_t_internal *lz4sd =
590		&LZ4_streamDecode->internal_donotuse;
591	int result;
592
593	if (lz4sd->prefixSize == 0) {
594		/* The first call, no dictionary yet. */
595		assert(lz4sd->extDictSize == 0);
596		result = LZ4_decompress_safe(source, dest,
597			compressedSize, maxOutputSize);
598		if (result <= 0)
599			return result;
600		lz4sd->prefixSize = result;
601		lz4sd->prefixEnd = (BYTE *)dest + result;
602	} else if (lz4sd->prefixEnd == (BYTE *)dest) {
603		/* They're rolling the current segment. */
604		if (lz4sd->prefixSize >= 64 * KB - 1)
605			result = LZ4_decompress_safe_withPrefix64k(source, dest,
606				compressedSize, maxOutputSize);
607		else if (lz4sd->extDictSize == 0)
608			result = LZ4_decompress_safe_withSmallPrefix(source,
609				dest, compressedSize, maxOutputSize,
610				lz4sd->prefixSize);
611		else
612			result = LZ4_decompress_safe_doubleDict(source, dest,
613				compressedSize, maxOutputSize,
614				lz4sd->prefixSize,
615				lz4sd->externalDict, lz4sd->extDictSize);
616		if (result <= 0)
617			return result;
618		lz4sd->prefixSize += result;
619		lz4sd->prefixEnd  += result;
620	} else {
621		/*
622		 * The buffer wraps around, or they're
623		 * switching to another buffer.
624		 */
625		lz4sd->extDictSize = lz4sd->prefixSize;
626		lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
627		result = LZ4_decompress_safe_forceExtDict(source, dest,
628			compressedSize, maxOutputSize,
629			lz4sd->externalDict, lz4sd->extDictSize);
630		if (result <= 0)
631			return result;
632		lz4sd->prefixSize = result;
633		lz4sd->prefixEnd  = (BYTE *)dest + result;
634	}
635
636	return result;
637}
638
639int LZ4_decompress_fast_continue(LZ4_streamDecode_t *LZ4_streamDecode,
640	const char *source, char *dest, int originalSize)
641{
642	LZ4_streamDecode_t_internal *lz4sd = &LZ4_streamDecode->internal_donotuse;
643	int result;
644
645	if (lz4sd->prefixSize == 0) {
646		assert(lz4sd->extDictSize == 0);
647		result = LZ4_decompress_fast(source, dest, originalSize);
648		if (result <= 0)
649			return result;
650		lz4sd->prefixSize = originalSize;
651		lz4sd->prefixEnd = (BYTE *)dest + originalSize;
652	} else if (lz4sd->prefixEnd == (BYTE *)dest) {
653		if (lz4sd->prefixSize >= 64 * KB - 1 ||
654		    lz4sd->extDictSize == 0)
655			result = LZ4_decompress_fast(source, dest,
656						     originalSize);
657		else
658			result = LZ4_decompress_fast_doubleDict(source, dest,
659				originalSize, lz4sd->prefixSize,
660				lz4sd->externalDict, lz4sd->extDictSize);
661		if (result <= 0)
662			return result;
663		lz4sd->prefixSize += originalSize;
664		lz4sd->prefixEnd  += originalSize;
665	} else {
666		lz4sd->extDictSize = lz4sd->prefixSize;
667		lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
668		result = LZ4_decompress_fast_extDict(source, dest,
669			originalSize, lz4sd->externalDict, lz4sd->extDictSize);
670		if (result <= 0)
671			return result;
672		lz4sd->prefixSize = originalSize;
673		lz4sd->prefixEnd = (BYTE *)dest + originalSize;
674	}
675	return result;
676}
677
678int LZ4_decompress_safe_usingDict(const char *source, char *dest,
679				  int compressedSize, int maxOutputSize,
680				  const char *dictStart, int dictSize)
681{
682	if (dictSize == 0)
683		return LZ4_decompress_safe(source, dest,
684					   compressedSize, maxOutputSize);
685	if (dictStart+dictSize == dest) {
686		if (dictSize >= 64 * KB - 1)
687			return LZ4_decompress_safe_withPrefix64k(source, dest,
688				compressedSize, maxOutputSize);
689		return LZ4_decompress_safe_withSmallPrefix(source, dest,
690			compressedSize, maxOutputSize, dictSize);
691	}
692	return LZ4_decompress_safe_forceExtDict(source, dest,
693		compressedSize, maxOutputSize, dictStart, dictSize);
694}
695
696int LZ4_decompress_fast_usingDict(const char *source, char *dest,
697				  int originalSize,
698				  const char *dictStart, int dictSize)
699{
700	if (dictSize == 0 || dictStart + dictSize == dest)
701		return LZ4_decompress_fast(source, dest, originalSize);
702
703	return LZ4_decompress_fast_extDict(source, dest, originalSize,
704		dictStart, dictSize);
705}
706
707#ifndef STATIC
708EXPORT_SYMBOL(LZ4_decompress_safe);
709EXPORT_SYMBOL(LZ4_decompress_safe_partial);
710EXPORT_SYMBOL(LZ4_decompress_fast);
711EXPORT_SYMBOL(LZ4_setStreamDecode);
712EXPORT_SYMBOL(LZ4_decompress_safe_continue);
713EXPORT_SYMBOL(LZ4_decompress_fast_continue);
714EXPORT_SYMBOL(LZ4_decompress_safe_usingDict);
715EXPORT_SYMBOL(LZ4_decompress_fast_usingDict);
716
717MODULE_LICENSE("Dual BSD/GPL");
718MODULE_DESCRIPTION("LZ4 decompressor");
719#endif