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"


//**************************************
// Basic Types
//**************************************
#define BYTE	unsigned char
#define U16		unsigned short
#define U32		unsigned long
#define S32		signed long
#define U64		unsigned long long


//**************************************
// Constants
//**************************************
#define MINMATCH 4
#define INCOMPRESSIBLE 128

#define MAXD_LOG 16
#define MAX_DISTANCE ((1 << MAXD_LOG) - 1)

#define HASH_LOG 17                        // <--- Lower this value to lower memory usage. N->2^(N+2) Bytes (ex : 17 -> 512KB)
#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
{
	BYTE* hashTable[HASHTABLESIZE];
};


//**************************************
// Macros
//**************************************
#define HASH_FUNCTION(i)	((i * 2654435761) >> ((MINMATCH*8)-HASH_LOG))
#define HASH_VALUE(p)		HASH_FUNCTION(*(U32*)p)
#define HASH_POINTER(p)		HashTable[HASH_VALUE(p)]



//****************************
// Compression CODE
//****************************

int LZ4_compress(char* source, 
				 char* dest,
				 int isize)
{
	void* ctx = malloc(sizeof(struct refTables));
	int result = LZ4_compressCtx(&ctx, source, dest, isize);
	free(ctx);

	return result;
}



int LZ4_compressCtx(void** ctx,
				 char* source, 
				 char* dest,
				 int isize)
{	
	struct refTables *srt = (struct refTables *) (*ctx);
	BYTE**  HashTable;

	BYTE	*ip = (BYTE*) source,      /* input pointer */ 
			*anchor = (BYTE*) source,
			*iend = (BYTE*) source + isize,
			*ilimit = iend - MINMATCH - 1;

	BYTE	*op = (BYTE*) dest,  /* output pointer */
			*ref,
			*orun, *l_end;
	
	int		len, length, sequence, h;
	U32		step=1;
	S32		limit=INCOMPRESSIBLE;


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

	// Main Loop
	while (ip < ilimit)
	{
		sequence = *(U32*)ip;
		h = HASH_FUNCTION(sequence);
		ref = HashTable[h];
		HashTable[h] = ip;

		// Min Match
		if (( ((ip-ref) >> MAXD_LOG) != 0) || (*(U32*)ref != sequence))
		{ 
			if (ip-anchor>limit) { limit<<=1; step += 1 + (step>>2); }
			ip+=step; 
			continue; 
		}	

		// catch up
		if (step>1) 
		{ 
			HashTable[h] = ref;
			ip -= (step-1);
			step=1; 
			continue;
		}
		limit=INCOMPRESSIBLE; 

		// Encode Literal length
		len = length = ip - anchor;
		orun=op++;
		if (len>(RUN_MASK-1)) { *orun=(RUN_MASK<<ML_BITS); len-=RUN_MASK; for(; len > 254 ; len-=255) *op++ = 255; *op++ = (BYTE)len; } 
		else *orun = (len<<ML_BITS);

		// Copy Literals
		l_end = op + length;
		while (op<l_end)  { *(U32*)op = *(U32*)anchor; op+=4; anchor+=4; }
		op = l_end;

		// Encode Offset
		*(U16*)op = (ip-ref); op+=2;

		// Start Counting
		ip+=MINMATCH;  ref+=MINMATCH;   // MinMatch verified
		anchor = ip;
		while ((ip<iend) && (*ref == *ip)) { ip++; ref++; }   // Ends at *ip!=*ref
		len = (ip - anchor);
		
		// Encode MatchLength
		if (len>(ML_MASK-1)) { *orun+=ML_MASK; len-=ML_MASK; for(; len > 254 ; len-=255) *op++ = 255; *op++ = (BYTE)len; } 
		else *orun += len;			

		// Prepare next loop
		anchor = ip; 
	}


	// Encode Last Literals
	len = length = iend - anchor;
    orun=op++;
    if (len>(RUN_MASK-1)) { *orun=(RUN_MASK<<ML_BITS); len-=RUN_MASK; for(; len > 254 ; len-=255) *op++ = 255; *op++ = (BYTE) len; } 
	else *orun = (len<<ML_BITS);
	for(;length>0;length-=4) { *(U32*)op = *(U32*)anchor; op+=4; anchor+=4; }
	op += length;    // correction

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



//****************************
// Decompression CODE
//****************************
int LZ4_decode ( char* source, 
				 char* dest,
				 int isize)
{	
	// Local Variables
	BYTE	*ip = (BYTE*) source,      
			*iend = (BYTE*) source + isize;

	BYTE	*op = (BYTE*) dest, 
			*ref, *cpy,
			runcode;
	
	U32		dec[4]={0, 3, 2, 3};
	int		len, length;


	// Main Loop
	while (ip < iend)
	{
		// get runlength
		runcode = *ip++;
		if ((length=(runcode>>ML_BITS)) == RUN_MASK)  { for (;(len=*ip++)==255;length+=255){} length += len; } 

		// copy literals
		ref = op+length;
#ifdef SAFEWRITEBUFFER
		if (ref>iend-4) { while(op<iend-3) { *(U32*)op=*(U32*)ip; op+=4; ip+=4; } while(op<ref) *op++=*ip++; } 
		else
#endif
		while (op<ref) { *(U32*)op = *(U32*)ip; op+=4; ip+=4; }
		ip-=(op-ref); op=ref;	// correction
		if (ip>=iend) break;    // Check EOF

		// get offset
		ref -= *(U16*)ip; ip+=2;

		// get matchlength
		if ((length=(runcode&ML_MASK)) == ML_MASK) { for (;(len=*ip++)==255;length+=255){} length += len; } 
		length += MINMATCH;

		// copy repeated sequence
		cpy = op + length;
		if (op-ref<4)
		{
			*op++ = *ref++;
			*op++ = *ref++;
			*op++ = *ref++;
			*op++ = *ref++;
			ref -= dec[op-ref];
		}
#ifdef SAFEWRITEBUFFER
		if (cpy>iend-4) { while(op<iend-3) { *(U32*)op=*(U32*)ref; op+=4; ref+=4; } while(op<cpy) *op++=*ref++; } 
		else
#endif
		while(op<cpy) { *(U32*)op=*(U32*)ref; op+=4; ref+=4; }
		op=cpy;		// correction
	}

	// end of decoding
	return (int) (((char*)op)-dest);
}