path: root/lz4.c

/*

   LZ4 - Fast LZ compression algorithm

   Copyright (C) 2011, Yann Collet.

   BSD License



   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.

*/

//**************************************

// Includes

//**************************************

#include <stdlib.h>   // for malloc

#include <string.h>   // for memset

#include "lz4.h"



//**************************************

// Performance parameter               

//**************************************

// Increasing this value improves compression ratio

// Lowering this value reduces memory usage

// Lowering may also improve speed, typically on reaching cache size limits (L1 32KB for Intel, 64KB for AMD)

// Memory usage formula for 32 bits systems : N->2^(N+2) Bytes (examples : 17 -> 512KB ; 12 -> 16KB)

#define HASH_LOG 12



//**************************************

// Basic Types

//**************************************

#if defined(_MSC_VER) 

#define BYTE	unsigned __int8

#define U16		unsigned __int16

#define U32		unsigned __int32

#define S32		__int32

#else

#include <stdint.h>

#define BYTE	uint8_t

#define U16		uint16_t

#define U32		uint32_t

#define S32		int32_t

#endif



//**************************************

// Constants

//**************************************

#define MINMATCH 4

#define SKIPSTRENGTH 6

#define STACKLIMIT 13

#define HEAPMODE (HASH_LOG>STACKLIMIT)  // Defines if memory is allocated into the stack (local variable), or into the heap (malloc()).

#define COPYTOKEN 4

#define COPYLENGTH 8

#define LASTLITERALS 5

#define MFLIMIT (COPYLENGTH+MINMATCH)

#define MINLENGTH (MFLIMIT+1)


#define MAXD_LOG 16

#define MAX_DISTANCE ((1 << MAXD_LOG) - 1)


#define HASHTABLESIZE (1 << HASH_LOG)

#define HASH_MASK (HASHTABLESIZE - 1)


#define ML_BITS 4

#define ML_MASK ((1U<<ML_BITS)-1)

#define RUN_BITS (8-ML_BITS)

#define RUN_MASK ((1U<<RUN_BITS)-1)



//**************************************

// Local structures

//**************************************

struct refTables
{
	const BYTE* hashTable[HASHTABLESIZE];
};

#ifdef __GNUC__

#  define _PACKED __attribute__ ((packed))

#else

#  define _PACKED

#endif


typedef struct _U32_S
{
	U32 v;
} _PACKED U32_S;

typedef struct _U16_S
{
	U16 v;
} _PACKED U16_S;

#define A32(x) (((U32_S *)(x))->v)

#define A16(x) (((U16_S *)(x))->v)



//**************************************

// Macros

//**************************************

#define LZ4_HASH_FUNCTION(i)	(((i) * 2654435761U) >> ((MINMATCH*8)-HASH_LOG))

#define LZ4_HASH_VALUE(p)		LZ4_HASH_FUNCTION(A32(p))

#define LZ4_COPYPACKET(s,d)		A32(d) = A32(s); d+=4; s+=4; A32(d) = A32(s); d+=4; s+=4;

#define LZ4_WILDCOPY(s,d,e)		do { LZ4_COPYPACKET(s,d) } while (d<e);

#define LZ4_BLINDCOPY(s,d,l)	{ BYTE* e=d+l; LZ4_WILDCOPY(s,d,e); d=e; }




//****************************

// Compression CODE

//****************************


int LZ4_compressCtx(void** ctx,
				 char* source, 
				 char* dest,
				 int isize)
{	
#if HEAPMODE

	struct refTables *srt = (struct refTables *) (*ctx);
	const BYTE** HashTable;
#else

	const BYTE* HashTable[HASHTABLESIZE] = {0};
#endif


	const BYTE* ip = (BYTE*) source;       
	const BYTE* anchor = ip;
	const BYTE* const iend = ip + isize;
	const BYTE* const mflimit = iend - MFLIMIT;
#define matchlimit (iend - LASTLITERALS)


	BYTE* op = (BYTE*) dest;
	
	int len, length;
	const int skipStrength = SKIPSTRENGTH;
	U32 forwardH;


	// Init 

	if (isize<MINLENGTH) goto _last_literals;
#if HEAPMODE

	if (*ctx == NULL) 
	{
		srt = (struct refTables *) malloc ( sizeof(struct refTables) );
		*ctx = (void*) srt;
	}
	HashTable = srt->hashTable;
	memset((void*)HashTable, 0, sizeof(srt->hashTable));
#else

	(void) ctx;
#endif



	// First Byte

	HashTable[LZ4_HASH_VALUE(ip)] = ip;
	ip++; forwardH = LZ4_HASH_VALUE(ip);
	
	// Main Loop

    for ( ; ; ) 
	{
		int findMatchAttempts = (1U << skipStrength) + 3;
		const BYTE* forwardIp = ip;
		const BYTE* ref;
		BYTE* token;

		// Find a match

		do {
			U32 h = forwardH;
			int step = findMatchAttempts++ >> skipStrength;
			ip = forwardIp;
			forwardIp = ip + step;

			if (forwardIp > mflimit) { goto _last_literals; }

			forwardH = LZ4_HASH_VALUE(forwardIp);
			ref = HashTable[h];
			HashTable[h] = ip;

		} while ((ref < ip - MAX_DISTANCE) || (A32(ref) != A32(ip)));

		// Catch up

		while ((ip>anchor) && (ref>(BYTE*)source) && (ip[-1]==ref[-1])) { ip--; ref--; }  

		// Encode Literal length

		length = ip - anchor;
		token = op++;
		if (length>=(int)RUN_MASK) { *token=(RUN_MASK<<ML_BITS); len = length-RUN_MASK; for(; len > 254 ; len-=255) *op++ = 255; *op++ = (BYTE)len; } 
		else *token = (length<<ML_BITS);

		// Copy Literals

		LZ4_BLINDCOPY(anchor, op, length);


_next_match:
		// Encode Offset

		A16(op) = (ip-ref); op+=2;

		// Start Counting

		ip+=MINMATCH; ref+=MINMATCH;   // MinMatch verified

		anchor = ip;
		while (ip<matchlimit-3)
		{
			if (A32(ref) == A32(ip)) { ip+=4; ref+=4; continue; }
			if (A16(ref) == A16(ip)) { ip+=2; ref+=2; }
			if (*ref == *ip) ip++;
			goto _endCount;
		}
		if ((ip<(matchlimit-1)) && (A16(ref) == A16(ip))) { ip+=2; ref+=2; }
		if ((ip<matchlimit) && (*ref == *ip)) ip++;
_endCount:
		len = (ip - anchor);
		
		// Encode MatchLength

		if (len>=(int)ML_MASK) { *token+=ML_MASK; len-=ML_MASK; for(; len > 509 ; len-=510) { *op++ = 255; *op++ = 255; } if (len > 254) { len-=255; *op++ = 255; } *op++ = (BYTE)len; } 
		else *token += len;	

		// Test end of chunk

		if (ip > mflimit) { anchor = ip;  break; }

		// Test next position

		ref = HashTable[LZ4_HASH_VALUE(ip)];
		HashTable[LZ4_HASH_VALUE(ip)] = ip;
		if ((ref > ip - (MAX_DISTANCE + 1)) && (A32(ref) == A32(ip))) { token = op++; *token=0; goto _next_match; }

		// Prepare next loop

		anchor = ip++; 
		forwardH = LZ4_HASH_VALUE(ip);
	}

_last_literals:
	// Encode Last Literals

	{
		int lastRun = iend - anchor;
		if (lastRun>=(int)RUN_MASK) { *op++=(RUN_MASK<<ML_BITS); lastRun-=RUN_MASK; for(; lastRun > 254 ; lastRun-=255) *op++ = 255; *op++ = (BYTE) lastRun; } 
		else *op++ = (lastRun<<ML_BITS);
		memcpy(op, anchor, iend - anchor);
		op += iend-anchor;
	} 

	// End

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



int LZ4_compress(char* source, 
				 char* dest,
				 int isize)
{
#if HEAPMODE

	void* ctx = malloc(sizeof(struct refTables));
	int result = LZ4_compressCtx(&ctx, source, dest, isize);
	free(ctx);
	return result;
#else

	return LZ4_compressCtx(NULL, source, dest, isize);
#endif

}




//****************************

// Decompression CODE

//****************************


// Note : The decoding functions LZ4_uncompress() and LZ4_uncompress_unknownOutputSize() 

//		are safe against "buffer overflow" attack type

//		since they will *never* write outside of the provided output buffer :

//		they both check this condition *before* writing anything.

//		A corrupted packet however can make them *read* within the first 64K before the output buffer.


int LZ4_uncompress(char* source, 
				 char* dest,
				 int osize)
{	
	// Local Variables

	const BYTE* ip = (const BYTE*) source;
	BYTE* ref;

	BYTE* op = (BYTE*) dest;
	BYTE* const oend = op + osize;
	BYTE* cpy;

	BYTE token;
	
	U32	dec[4]={0, 3, 2, 3};
	int	len, length;


	// Main Loop

	while (1)
	{
		// get runlength

		token = *ip++;
		if ((length=(token>>ML_BITS)) == RUN_MASK)  { for (;(len=*ip++)==255;length+=255){} length += len; } 

		// copy literals

		ref = op+length;
		if (ref>oend-COPYLENGTH) 
		{ 
			if (ref > oend) goto _output_error;
			memcpy(op, ip, length);
			ip += length;
			break;    // Necessarily EOF

		}
		LZ4_WILDCOPY(ip, op, ref); ip -= (op-ref); op = ref;


		// get offset

		ref -= A16(ip); ip+=2;

		// get matchlength

		if ((length=(token&ML_MASK)) == ML_MASK) { for (;*ip==255;length+=255) {ip++;} length += *ip++; } 

		// copy repeated sequence

		if (op-ref<COPYTOKEN)
		{
			*op++ = *ref++;
			*op++ = *ref++;
			*op++ = *ref++;
			*op++ = *ref++;
			ref -= dec[op-ref];
			A32(op)=A32(ref); 
		} else { A32(op)=A32(ref); op+=4; ref+=4; }
		cpy = op + length;
		if (cpy > oend-COPYLENGTH)
		{
			if (cpy > oend) goto _output_error;	
			LZ4_WILDCOPY(ref, op, (oend-COPYLENGTH));
			while(op<cpy) *op++=*ref++;
			op=cpy;
			if (op == oend) break;    // Check EOF (should never happen, since last 5 bytes are supposed to be literals)

			continue;
		}
		LZ4_WILDCOPY(ref, op, cpy);
		op=cpy;		// correction

	}

	// end of decoding

	return (int) (((char*)ip)-source);

	// write overflow error detected

_output_error:
	return (int) (-(((char*)ip)-source));
}


int LZ4_uncompress_unknownOutputSize(
				char* source, 
				char* dest,
				int isize,
				int maxOutputSize)
{	
	// Local Variables

	const BYTE* ip = (const BYTE*) source;
	const BYTE* const iend = ip + isize;
	BYTE* ref;

	BYTE* op = (BYTE*) dest;
	BYTE* const oend = op + maxOutputSize;
	BYTE* cpy;

	BYTE token;
	
	U32	dec[4]={0, 3, 2, 3};
	int	len, length;


	// Main Loop

	while (ip<iend)
	{
		// get runlength

		token = *ip++;
		if ((length=(token>>ML_BITS)) == RUN_MASK)  { for (;(len=*ip++)==255;length+=255){} length += len; } 

		// copy literals

		ref = op+length;
		if (ref>oend-COPYLENGTH) 
		{ 
			if (ref > oend) goto _output_error;
			memcpy(op, ip, length);
			ip += length;
			break;    // Necessarily EOF

		}
		LZ4_WILDCOPY(ip, op, ref); ip -= (op-ref); op = ref;
		if (ip>=iend) break;    // check EOF



		// get offset

		ref -= A16(ip); ip+=2;

		// get matchlength

		if ((length=(token&ML_MASK)) == ML_MASK) { for (;(len=*ip++)==255;length+=255){} length += len; }

		// copy repeated sequence

		if (op-ref<COPYTOKEN)
		{
			*op++ = *ref++;
			*op++ = *ref++;
			*op++ = *ref++;
			*op++ = *ref++;
			ref -= dec[op-ref];
			A32(op)=A32(ref); 
		} else { A32(op)=A32(ref); op+=4; ref+=4; }
		cpy = op + length;
		if (cpy>oend-COPYLENGTH)
		{
			if (cpy > oend) goto _output_error;	
			LZ4_WILDCOPY(ref, op, (oend-COPYLENGTH));
			while(op<cpy) *op++=*ref++;
			op=cpy;
			if (op == oend) break;    // Check EOF (should never happen, since last 5 bytes are supposed to be literals)

			continue;
		}
		LZ4_WILDCOPY(ref, op, cpy);
		op=cpy;		// correction

	}

	// end of decoding

	return (int) (((char*)op)-dest);

	// write overflow error detected

_output_error:
	return (int) (-(((char*)ip)-source));
}