lz4_compress.c

/*
 * LZ4 - Fast LZ compression algorithm
 * Copyright (C) 2011 - 2016, Yann Collet.
 * BSD 2 - Clause License (http://www.opensource.org/licenses/bsd - license.php)
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *	* Redistributions of source code must retain the above copyright
 *	  notice, this list of conditions and the following disclaimer.
 *	* Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * You can contact the author at :
 *	- LZ4 homepage : http://www.lz4.org
 *	- LZ4 source repository : https://github.com/lz4/lz4
 *
 *	Changed for kernel usage by:
 *	Sven Schmidt <4sschmid@informatik.uni-hamburg.de>
 */

/*-************************************
 *	Dependencies
 **************************************/
#include <linux/lz4.h>
#include "lz4defs.h"
#include <linux/module.h>
#include <linux/kernel.h>
#include <asm/unaligned.h>

static const int LZ4_minLength = (MFLIMIT + 1);
static const int LZ4_64Klimit = ((64 * KB) + (MFLIMIT - 1));

/*-******************************
 *	Compression functions
 ********************************/
static FORCE_INLINE U32 LZ4_hash4(
	U32 sequence,
	tableType_t const tableType)
{
	if (tableType == byU16)
		return ((sequence * 2654435761U)
			>> ((MINMATCH * 8) - (LZ4_HASHLOG + 1)));
	else
		return ((sequence * 2654435761U)
			>> ((MINMATCH * 8) - LZ4_HASHLOG));
}

static FORCE_INLINE U32 LZ4_hash5(
	U64 sequence,
	tableType_t const tableType)
{
	const U32 hashLog = (tableType == byU16)
		? LZ4_HASHLOG + 1
		: LZ4_HASHLOG;

#if LZ4_LITTLE_ENDIAN
	static const U64 prime5bytes = 889523592379ULL;

	return (U32)(((sequence << 24) * prime5bytes) >> (64 - hashLog));
#else
	static const U64 prime8bytes = 11400714785074694791ULL;

	return (U32)(((sequence >> 24) * prime8bytes) >> (64 - hashLog));
#endif
}

static FORCE_INLINE U32 LZ4_hashPosition(
	const void *p,
	tableType_t const tableType)
{
#if LZ4_ARCH64
	if (tableType == byU32)
		return LZ4_hash5(LZ4_read_ARCH(p), tableType);
#endif

	return LZ4_hash4(LZ4_read32(p), tableType);
}

static void LZ4_putPositionOnHash(
	const BYTE *p,
	U32 h,
	void *tableBase,
	tableType_t const tableType,
	const BYTE *srcBase)
{
	switch (tableType) {
	case byPtr:
	{
		const BYTE **hashTable = (const BYTE **)tableBase;

		hashTable[h] = p;
		return;
	}
	case byU32:
	{
		U32 *hashTable = (U32 *) tableBase;

		hashTable[h] = (U32)(p - srcBase);
		return;
	}
	case byU16:
	{
		U16 *hashTable = (U16 *) tableBase;

		hashTable[h] = (U16)(p - srcBase);
		return;
	}
	}
}

static FORCE_INLINE void LZ4_putPosition(
	const BYTE *p,
	void *tableBase,
	tableType_t tableType,
	const BYTE *srcBase)
{
	U32 const h = LZ4_hashPosition(p, tableType);

	LZ4_putPositionOnHash(p, h, tableBase, tableType, srcBase);
}

static const BYTE *LZ4_getPositionOnHash(
	U32 h,
	void *tableBase,
	tableType_t tableType,
	const BYTE *srcBase)
{
	if (tableType == byPtr) {
		const BYTE **hashTable = (const BYTE **) tableBase;

		return hashTable[h];
	}

	if (tableType == byU32) {
		const U32 * const hashTable = (U32 *) tableBase;

		return hashTable[h] + srcBase;
	}

	{
		/* default, to ensure a return */
		const U16 * const hashTable = (U16 *) tableBase;

		return hashTable[h] + srcBase;
	}
}

static FORCE_INLINE const BYTE *LZ4_getPosition(
	const BYTE *p,
	void *tableBase,
	tableType_t tableType,
	const BYTE *srcBase)
{
	U32 const h = LZ4_hashPosition(p, tableType);

	return LZ4_getPositionOnHash(h, tableBase, tableType, srcBase);
}


/*
 * LZ4_compress_generic() :
 * inlined, to ensure branches are decided at compilation time
 */
static FORCE_INLINE int LZ4_compress_generic(
	LZ4_stream_t_internal * const dictPtr,
	const char * const source,
	char * const dest,
	const int inputSize,
	const int maxOutputSize,
	const limitedOutput_directive outputLimited,
	const tableType_t tableType,
	const dict_directive dict,
	const dictIssue_directive dictIssue,
	const U32 acceleration)
{
	const BYTE *ip = (const BYTE *) source;
	const BYTE *base;
	const BYTE *lowLimit;
	const BYTE * const lowRefLimit = ip - dictPtr->dictSize;
	const BYTE * const dictionary = dictPtr->dictionary;
	const BYTE * const dictEnd = dictionary + dictPtr->dictSize;
	const size_t dictDelta = dictEnd - (const BYTE *)source;
	const BYTE *anchor = (const BYTE *) source;
	const BYTE * const iend = ip + inputSize;
	const BYTE * const mflimit = iend - MFLIMIT;
	const BYTE * const matchlimit = iend - LASTLITERALS;

	BYTE *op = (BYTE *) dest;
	BYTE * const olimit = op + maxOutputSize;

	U32 forwardH;
	size_t refDelta = 0;

	/* Init conditions */
	if ((U32)inputSize > (U32)LZ4_MAX_INPUT_SIZE) {
		/* Unsupported inputSize, too large (or negative) */
		return 0;
	}

	switch (dict) {
	case noDict:
	default:
		base = (const BYTE *)source;
		lowLimit = (const BYTE *)source;
		break;
	case withPrefix64k:
		base = (const BYTE *)source - dictPtr->currentOffset;
		lowLimit = (const BYTE *)source - dictPtr->dictSize;
		break;
	case usingExtDict:
		base = (const BYTE *)source - dictPtr->currentOffset;
		lowLimit = (const BYTE *)source;
		break;
	}

	if ((tableType == byU16)
		&& (inputSize >= LZ4_64Klimit)) {
		/* Size too large (not within 64K limit) */
		return 0;
	}

	if (inputSize < LZ4_minLength) {
		/* Input too small, no compression (all literals) */
		goto _last_literals;
	}

	/* First Byte */
	LZ4_putPosition(ip, dictPtr->hashTable, tableType, base);
	ip++;
	forwardH = LZ4_hashPosition(ip, tableType);

	/* Main Loop */
	for ( ; ; ) {
		const BYTE *match;
		BYTE *token;

		/* Find a match */
		{
			const BYTE *forwardIp = ip;
			unsigned int step = 1;
			unsigned int searchMatchNb = acceleration << LZ4_SKIPTRIGGER;

			do {
				U32 const h = forwardH;

				ip = forwardIp;
				forwardIp += step;
				step = (searchMatchNb++ >> LZ4_SKIPTRIGGER);

				if (unlikely(forwardIp > mflimit))
					goto _last_literals;

				match = LZ4_getPositionOnHash(h,
					dictPtr->hashTable,
					tableType, base);

				if (dict == usingExtDict) {
					if (match < (const BYTE *)source) {
						refDelta = dictDelta;
						lowLimit = dictionary;
					} else {
						refDelta = 0;
						lowLimit = (const BYTE *)source;
				}	 }

				forwardH = LZ4_hashPosition(forwardIp,
					tableType);

				LZ4_putPositionOnHash(ip, h, dictPtr->hashTable,
					tableType, base);
			} while (((dictIssue == dictSmall)
					? (match < lowRefLimit)
					: 0)
				|| ((tableType == byU16)
					? 0
					: (match + MAX_DISTANCE < ip))
				|| (LZ4_read32(match + refDelta)
					!= LZ4_read32(ip)));
		}

		/* Catch up */
		while (((ip > anchor) & (match + refDelta > lowLimit))
				&& (unlikely(ip[-1] == match[refDelta - 1]))) {
			ip--;
			match--;
		}

		/* Encode Literals */
		{
			unsigned const int litLength = (unsigned int)(ip - anchor);

			token = op++;

			if ((outputLimited) &&
				/* Check output buffer overflow */
				(unlikely(op + litLength +
					(2 + 1 + LASTLITERALS) +
					(litLength / 255) > olimit)))
				return 0;

			if (litLength >= RUN_MASK) {
				int len = (int)litLength - RUN_MASK;

				*token = (RUN_MASK << ML_BITS);

				for (; len >= 255; len -= 255)
					*op++ = 255;
				*op++ = (BYTE)len;
			} else
				*token = (BYTE)(litLength << ML_BITS);

			/* Copy Literals */
			LZ4_wildCopy(op, anchor, op + litLength);
			op += litLength;
		}

_next_match:
		/* Encode Offset */
		LZ4_writeLE16(op, (U16)(ip - match));
		op += 2;

		/* Encode MatchLength */
		{
			unsigned int matchCode;

			if ((dict == usingExtDict)
				&& (lowLimit == dictionary)) {
				const BYTE *limit;

				match += refDelta;
				limit = ip + (dictEnd - match);

				if (limit > matchlimit)
					limit = matchlimit;

				matchCode = LZ4_count(ip + MINMATCH,
					match + MINMATCH, limit);

				ip += MINMATCH + matchCode;

				if (ip == limit) {
					unsigned const int more = LZ4_count(ip,
						(const BYTE *)source,
						matchlimit);

					matchCode += more;
					ip += more;
				}
			} else {
				matchCode = LZ4_count(ip + MINMATCH,
					match + MINMATCH, matchlimit);
				ip += MINMATCH + matchCode;
			}

			if (outputLimited &&
				/* Check output buffer overflow */
				(unlikely(op +
					(1 + LASTLITERALS) +
					(matchCode >> 8) > olimit)))
				return 0;

			if (matchCode >= ML_MASK) {
				*token += ML_MASK;
				matchCode -= ML_MASK;
				LZ4_write32(op, 0xFFFFFFFF);

				while (matchCode >= 4 * 255) {
					op += 4;
					LZ4_write32(op, 0xFFFFFFFF);
					matchCode -= 4 * 255;
				}

				op += matchCode / 255;
				*op++ = (BYTE)(matchCode % 255);
			} else
				*token += (BYTE)(matchCode);
		}

		anchor = ip;

		/* Test end of chunk */
		if (ip > mflimit)
			break;

		/* Fill table */
		LZ4_putPosition(ip - 2, dictPtr->hashTable, tableType, base);

		/* Test next position */
		match = LZ4_getPosition(ip, dictPtr->hashTable,
			tableType, base);

		if (dict == usingExtDict) {
			if (match < (const BYTE *)source) {
				refDelta = dictDelta;
				lowLimit = dictionary;
			} else {
				refDelta = 0;
				lowLimit = (const BYTE *)source;
			}
		}

		LZ4_putPosition(ip, dictPtr->hashTable, tableType, base);

		if (((dictIssue == dictSmall) ? (match >= lowRefLimit) : 1)
			&& (match + MAX_DISTANCE >= ip)
			&& (LZ4_read32(match + refDelta) == LZ4_read32(ip))) {
			token = op++;
			*token = 0;
			goto _next_match;
		}

		/* Prepare next loop */
		forwardH = LZ4_hashPosition(++ip, tableType);
	}

_last_literals:
	/* Encode Last Literals */
	{
		size_t const lastRun = (size_t)(iend - anchor);

		if ((outputLimited) &&
			/* Check output buffer overflow */
			((op - (BYTE *)dest) + lastRun + 1 +
			((lastRun + 255 - RUN_MASK) / 255) > (U32)maxOutputSize))
			return 0;

		if (lastRun >= RUN_MASK) {
			size_t accumulator = lastRun - RUN_MASK;
			*op++ = RUN_MASK << ML_BITS;
			for (; accumulator >= 255; accumulator -= 255)
				*op++ = 255;
			*op++ = (BYTE) accumulator;
		} else {
			*op++ = (BYTE)(lastRun << ML_BITS);
		}

		LZ4_memcpy(op, anchor, lastRun);

		op += lastRun;
	}

	/* End */
	return (int) (((char *)op) - dest);
}

static int LZ4_compress_fast_extState(
	void *state,
	const char *source,
	char *dest,
	int inputSize,
	int maxOutputSize,
	int acceleration)
{
	LZ4_stream_t_internal *ctx = &((LZ4_stream_t *)state)->internal_donotuse;
#if LZ4_ARCH64
	const tableType_t tableType = byU32;
#else
	const tableType_t tableType = byPtr;
#endif

	LZ4_resetStream((LZ4_stream_t *)state);

	if (acceleration < 1)
		acceleration = LZ4_ACCELERATION_DEFAULT;

	if (maxOutputSize >= LZ4_COMPRESSBOUND(inputSize)) {
		if (inputSize < LZ4_64Klimit)
			return LZ4_compress_generic(ctx, source,
				dest, inputSize, 0,
				noLimit, byU16, noDict,
				noDictIssue, acceleration);
		else
			return LZ4_compress_generic(ctx, source,
				dest, inputSize, 0,
				noLimit, tableType, noDict,
				noDictIssue, acceleration);
	} else {
		if (inputSize < LZ4_64Klimit)
			return LZ4_compress_generic(ctx, source,
				dest, inputSize,
				maxOutputSize, limitedOutput, byU16, noDict,
				noDictIssue, acceleration);
		else
			return LZ4_compress_generic(ctx, source,
				dest, inputSize,
				maxOutputSize, limitedOutput, tableType, noDict,
				noDictIssue, acceleration);
	}
}

int LZ4_compress_fast(const char *source, char *dest, int inputSize,
	int maxOutputSize, int acceleration, void *wrkmem)
{
	return LZ4_compress_fast_extState(wrkmem, source, dest, inputSize,
		maxOutputSize, acceleration);
}
EXPORT_SYMBOL(LZ4_compress_fast);

int LZ4_compress_default(const char *source, char *dest, int inputSize,
	int maxOutputSize, void *wrkmem)
{
	return LZ4_compress_fast(source, dest, inputSize,
		maxOutputSize, LZ4_ACCELERATION_DEFAULT, wrkmem);
}
EXPORT_SYMBOL(LZ4_compress_default);

/*-******************************
 *	*_destSize() variant
 ********************************/
static int LZ4_compress_destSize_generic(
	LZ4_stream_t_internal * const ctx,
	const char * const src,
	char * const dst,
	int * const srcSizePtr,
	const int targetDstSize,
	const tableType_t tableType)
{
	const BYTE *ip = (const BYTE *) src;
	const BYTE *base = (const BYTE *) src;
	const BYTE *lowLimit = (const BYTE *) src;
	const BYTE *anchor = ip;
	const BYTE * const iend = ip + *srcSizePtr;
	const BYTE * const mflimit = iend - MFLIMIT;
	const BYTE * const matchlimit = iend - LASTLITERALS;

	BYTE *op = (BYTE *) dst;
	BYTE * const oend = op + targetDstSize;
	BYTE * const oMaxLit = op + targetDstSize - 2 /* offset */
		- 8 /* because 8 + MINMATCH == MFLIMIT */ - 1 /* token */;
	BYTE * const oMaxMatch = op + targetDstSize
		- (LASTLITERALS + 1 /* token */);
	BYTE * const oMaxSeq = oMaxLit - 1 /* token */;

	U32 forwardH;

	/* Init conditions */
	/* Impossible to store anything */
	if (targetDstSize < 1)
		return 0;
	/* Unsupported input size, too large (or negative) */
	if ((U32)*srcSizePtr > (U32)LZ4_MAX_INPUT_SIZE)
		return 0;
	/* Size too large (not within 64K limit) */
	if ((tableType == byU16) && (*srcSizePtr >= LZ4_64Klimit))
		return 0;
	/* Input too small, no compression (all literals) */
	if (*srcSizePtr < LZ4_minLength)
		goto _last_literals;

	/* First Byte */
	*srcSizePtr = 0;
	LZ4_putPosition(ip, ctx->hashTable, tableType, base);
	ip++; forwardH = LZ4_hashPosition(ip, tableType);

	/* Main Loop */
	for ( ; ; ) {
		const BYTE *match;
		BYTE *token;

		/* Find a match */
		{
			const BYTE *forwardIp = ip;
			unsigned int step = 1;
			unsigned int searchMatchNb = 1 << LZ4_SKIPTRIGGER;

			do {
				U32 h = forwardH;

				ip = forwardIp;
				forwardIp += step;
				step = (searchMatchNb++ >> LZ4_SKIPTRIGGER);

				if (unlikely(forwardIp > mflimit))
					goto _last_literals;

				match = LZ4_getPositionOnHash(h, ctx->hashTable,
					tableType, base);
				forwardH = LZ4_hashPosition(forwardIp,
					tableType);
				LZ4_putPositionOnHash(ip, h,
					ctx->hashTable, tableType,
					base);

			} while (((tableType == byU16)
				? 0
				: (match + MAX_DISTANCE < ip))
				|| (LZ4_read32(match) != LZ4_read32(ip)));
		}

		/* Catch up */
		while ((ip > anchor)
			&& (match > lowLimit)
			&& (unlikely(ip[-1] == match[-1]))) {
			ip--;
			match--;
		}

		/* Encode Literal length */
		{
			unsigned int litLength = (unsigned int)(ip - anchor);

			token = op++;
			if (op + ((litLength + 240) / 255)
				+ litLength > oMaxLit) {
				/* Not enough space for a last match */
				op--;
				goto _last_literals;
			}
			if (litLength >= RUN_MASK) {
				unsigned int len = litLength - RUN_MASK;
				*token = (RUN_MASK<<ML_BITS);
				for (; len >= 255; len -= 255)
					*op++ = 255;
				*op++ = (BYTE)len;
			} else
				*token = (BYTE)(litLength << ML_BITS);

			/* Copy Literals */
			LZ4_wildCopy(op, anchor, op + litLength);
			op += litLength;
		}

_next_match:
		/* Encode Offset */
		LZ4_writeLE16(op, (U16)(ip - match)); op += 2;

		/* Encode MatchLength */
		{
			size_t matchLength = LZ4_count(ip + MINMATCH,
			match + MINMATCH, matchlimit);

			if (op + ((matchLength + 240)/255) > oMaxMatch) {
				/* Match description too long : reduce it */
				matchLength = (15 - 1) + (oMaxMatch - op) * 255;
			}
			ip += MINMATCH + matchLength;

			if (matchLength >= ML_MASK) {
				*token += ML_MASK;
				matchLength -= ML_MASK;
				while (matchLength >= 255) {
					matchLength -= 255;
					*op++ = 255;
				}
				*op++ = (BYTE)matchLength;
			} else
				*token += (BYTE)(matchLength);
		}

		anchor = ip;

		/* Test end of block */
		if (ip > mflimit)
			break;
		if (op > oMaxSeq)
			break;

		/* Fill table */
		LZ4_putPosition(ip - 2, ctx->hashTable, tableType, base);

		/* Test next position */
		match = LZ4_getPosition(ip, ctx->hashTable, tableType, base);
		LZ4_putPosition(ip, ctx->hashTable, tableType, base);

		if ((match + MAX_DISTANCE >= ip)
			&& (LZ4_read32(match) == LZ4_read32(ip))) {
			token = op++; *token = 0;
			goto _next_match;
		}

		/* Prepare next loop */
		forwardH = LZ4_hashPosition(++ip, tableType);
	}

_last_literals:
	/* Encode Last Literals */
	{
		size_t lastRunSize = (size_t)(iend - anchor);

		if (op + 1 /* token */
			+ ((lastRunSize + 240) / 255) /* litLength */
			+ lastRunSize /* literals */ > oend) {
			/* adapt lastRunSize to fill 'dst' */
			lastRunSize	= (oend - op) - 1;
			lastRunSize -= (lastRunSize + 240) / 255;
		}
		ip = anchor + lastRunSize;

		if (lastRunSize >= RUN_MASK) {
			size_t accumulator = lastRunSize - RUN_MASK;

			*op++ = RUN_MASK << ML_BITS;
			for (; accumulator >= 255; accumulator -= 255)
				*op++ = 255;
			*op++ = (BYTE) accumulator;
		} else {
			*op++ = (BYTE)(lastRunSize<<ML_BITS);
		}
		LZ4_memcpy(op, anchor, lastRunSize);
		op += lastRunSize;
	}

	/* End */
	*srcSizePtr = (int) (((const char *)ip) - src);
	return (int) (((char *)op) - dst);
}

static int LZ4_compress_destSize_extState(
	LZ4_stream_t *state,
	const char *src,
	char *dst,
	int *srcSizePtr,
	int targetDstSize)
{
#if LZ4_ARCH64
	const tableType_t tableType = byU32;
#else
	const tableType_t tableType = byPtr;
#endif

	LZ4_resetStream(state);

	if (targetDstSize >= LZ4_COMPRESSBOUND(*srcSizePtr)) {
		/* compression success is guaranteed */
		return LZ4_compress_fast_extState(
			state, src, dst, *srcSizePtr,
			targetDstSize, 1);
	} else {
		if (*srcSizePtr < LZ4_64Klimit)
			return LZ4_compress_destSize_generic(
				&state->internal_donotuse,
				src, dst, srcSizePtr,
				targetDstSize, byU16);
		else
			return LZ4_compress_destSize_generic(
				&state->internal_donotuse,
				src, dst, srcSizePtr,
				targetDstSize, tableType);
	}
}


int LZ4_compress_destSize(
	const char *src,
	char *dst,
	int *srcSizePtr,
	int targetDstSize,
	void *wrkmem)
{
	return LZ4_compress_destSize_extState(wrkmem, src, dst, srcSizePtr,
		targetDstSize);
}
EXPORT_SYMBOL(LZ4_compress_destSize);

/*-******************************
 *	Streaming functions
 ********************************/
void LZ4_resetStream(LZ4_stream_t *LZ4_stream)
{
	memset(LZ4_stream, 0, sizeof(LZ4_stream_t));
}

int LZ4_loadDict(LZ4_stream_t *LZ4_dict,
	const char *dictionary, int dictSize)
{
	LZ4_stream_t_internal *dict = &LZ4_dict->internal_donotuse;
	const BYTE *p = (const BYTE *)dictionary;
	const BYTE * const dictEnd = p + dictSize;
	const BYTE *base;

	if ((dict->initCheck)
		|| (dict->currentOffset > 1 * GB)) {
		/* Uninitialized structure, or reuse overflow */
		LZ4_resetStream(LZ4_dict);
	}

	if (dictSize < (int)HASH_UNIT) {
		dict->dictionary = NULL;
		dict->dictSize = 0;
		return 0;
	}

	if ((dictEnd - p) > 64 * KB)
		p = dictEnd - 64 * KB;
	dict->currentOffset += 64 * KB;
	base = p - dict->currentOffset;
	dict->dictionary = p;
	dict->dictSize = (U32)(dictEnd - p);
	dict->currentOffset += dict->dictSize;

	while (p <= dictEnd - HASH_UNIT) {
		LZ4_putPosition(p, dict->hashTable, byU32, base);
		p += 3;
	}

	return dict->dictSize;
}
EXPORT_SYMBOL(LZ4_loadDict);

static void LZ4_renormDictT(LZ4_stream_t_internal *LZ4_dict,
	const BYTE *src)
{
	if ((LZ4_dict->currentOffset > 0x80000000) ||
		((uptrval)LZ4_dict->currentOffset > (uptrval)src)) {
		/* address space overflow */
		/* rescale hash table */
		U32 const delta = LZ4_dict->currentOffset - 64 * KB;
		const BYTE *dictEnd = LZ4_dict->dictionary + LZ4_dict->dictSize;
		int i;

		for (i = 0; i < LZ4_HASH_SIZE_U32; i++) {
			if (LZ4_dict->hashTable[i] < delta)
				LZ4_dict->hashTable[i] = 0;
			else
				LZ4_dict->hashTable[i] -= delta;
		}
		LZ4_dict->currentOffset = 64 * KB;
		if (LZ4_dict->dictSize > 64 * KB)
			LZ4_dict->dictSize = 64 * KB;
		LZ4_dict->dictionary = dictEnd - LZ4_dict->dictSize;
	}
}

int LZ4_saveDict(LZ4_stream_t *LZ4_dict, char *safeBuffer, int dictSize)
{
	LZ4_stream_t_internal * const dict = &LZ4_dict->internal_donotuse;
	const BYTE * const previousDictEnd = dict->dictionary + dict->dictSize;

	if ((U32)dictSize > 64 * KB) {
		/* useless to define a dictionary > 64 * KB */
		dictSize = 64 * KB;
	}
	if ((U32)dictSize > dict->dictSize)
		dictSize = dict->dictSize;

	memmove(safeBuffer, previousDictEnd - dictSize, dictSize);

	dict->dictionary = (const BYTE *)safeBuffer;
	dict->dictSize = (U32)dictSize;

	return dictSize;
}
EXPORT_SYMBOL(LZ4_saveDict);

int LZ4_compress_fast_continue(LZ4_stream_t *LZ4_stream, const char *source,
	char *dest, int inputSize, int maxOutputSize, int acceleration)
{
	LZ4_stream_t_internal *streamPtr = &LZ4_stream->internal_donotuse;
	const BYTE * const dictEnd = streamPtr->dictionary
		+ streamPtr->dictSize;

	const BYTE *smallest = (const BYTE *) source;

	if (streamPtr->initCheck) {
		/* Uninitialized structure detected */
		return 0;
	}

	if ((streamPtr->dictSize > 0) && (smallest > dictEnd))
		smallest = dictEnd;

	LZ4_renormDictT(streamPtr, smallest);

	if (acceleration < 1)
		acceleration = LZ4_ACCELERATION_DEFAULT;

	/* Check overlapping input/dictionary space */
	{
		const BYTE *sourceEnd = (const BYTE *) source + inputSize;

		if ((sourceEnd > streamPtr->dictionary)
			&& (sourceEnd < dictEnd)) {
			streamPtr->dictSize = (U32)(dictEnd - sourceEnd);
			if (streamPtr->dictSize > 64 * KB)
				streamPtr->dictSize = 64 * KB;
			if (streamPtr->dictSize < 4)
				streamPtr->dictSize = 0;
			streamPtr->dictionary = dictEnd - streamPtr->dictSize;
		}
	}

	/* prefix mode : source data follows dictionary */
	if (dictEnd == (const BYTE *)source) {
		int result;

		if ((streamPtr->dictSize < 64 * KB) &&
			(streamPtr->dictSize < streamPtr->currentOffset)) {
			result = LZ4_compress_generic(
				streamPtr, source, dest, inputSize,
				maxOutputSize, limitedOutput, byU32,
				withPrefix64k, dictSmall, acceleration);
		} else {
			result = LZ4_compress_generic(
				streamPtr, source, dest, inputSize,
				maxOutputSize, limitedOutput, byU32,
				withPrefix64k, noDictIssue, acceleration);
		}
		streamPtr->dictSize += (U32)inputSize;
		streamPtr->currentOffset += (U32)inputSize;
		return result;
	}

	/* external dictionary mode */
	{
		int result;

		if ((streamPtr->dictSize < 64 * KB) &&
			(streamPtr->dictSize < streamPtr->currentOffset)) {
			result = LZ4_compress_generic(
				streamPtr, source, dest, inputSize,
				maxOutputSize, limitedOutput, byU32,
				usingExtDict, dictSmall, acceleration);
		} else {
			result = LZ4_compress_generic(
				streamPtr, source, dest, inputSize,
				maxOutputSize, limitedOutput, byU32,
				usingExtDict, noDictIssue, acceleration);
		}
		streamPtr->dictionary = (const BYTE *)source;
		streamPtr->dictSize = (U32)inputSize;
		streamPtr->currentOffset += (U32)inputSize;
		return result;
	}
}
EXPORT_SYMBOL(LZ4_compress_fast_continue);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("LZ4 compressor");