lzo1.c

lzo-1.08-src.zip 高效的压缩解压代码

/* lzo1.c -- implementation of the LZO1 algorithm

   This file is part of the LZO real-time data compression library.

   Copyright (C) 1996-2002 Markus Franz Xaver Johannes Oberhumer
   All Rights Reserved.

   The LZO library is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of
   the License, or (at your option) any later version.

   The LZO library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with the LZO library; see the file COPYING.
   If not, write to the Free Software Foundation, Inc.,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer
   <[e-mail]>
 */


#include <lzo1.h>
#include "lzo_conf.h"


/***********************************************************************
// The next two defines can be changed to customize LZO1.
// The default version is LZO1-5/1.
************************************************************************/

/* run bits (3 - 5) - the compressor and the decompressor
 * must use the same value. */
#if !defined(RBITS)
#  define RBITS		5
#endif

/* compression level (1 - 9) - this only affects the compressor.
 * 1 is fastest, 9 is best compression ratio */
#if !defined(CLEVEL)
#  define CLEVEL	1			/* fastest by default */
#endif


/* check configuration */
#if (RBITS < 3 || RBITS > 5)
#  error "invalid RBITS"
#endif
#if (CLEVEL < 1 || CLEVEL > 9)
#  error "invalid CLEVEL"
#endif


/***********************************************************************
// You should not have to change anything below this line.
************************************************************************/

#include "lzo_util.h"


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

/*
     Format of the marker byte


	 76543210
	 --------
	 00000000	a long run (a 'R0' run) - there are short and long R0 runs
	 000rrrrr	a short run with len r
	 mmmooooo	a short match (len = 2+m, o = offset low bits)
	 111ooooo	a long match (o = offset low bits)
*/


#define RSIZE	(1 << RBITS)
#define RMASK	(RSIZE - 1)

#define OBITS	RBITS				/* offset and run-length use same bits */
#define OSIZE	(1 << OBITS)
#define OMASK	(OSIZE - 1)

#define MBITS	(8 - OBITS)
#define MSIZE	(1 << MBITS)
#define MMASK	(MSIZE - 1)


/* sanity checks */
#if (OBITS < 3 || OBITS > 5)
#  error "invalid OBITS"
#endif
#if (MBITS < 3 || MBITS > 5)
#  error "invalid MBITS"
#endif


/***********************************************************************
// some macros to improve readability
************************************************************************/

/* Minimum len of a match */
#define	MIN_MATCH			3
#define	THRESHOLD			(MIN_MATCH - 1)

/* Minimum len of match coded in 2 bytes */
#define	MIN_MATCH_SHORT		MIN_MATCH

/* Maximum len of match coded in 2 bytes */
#define	MAX_MATCH_SHORT		(THRESHOLD + (MSIZE - 2))
/* MSIZE - 2: 0 is used to indicate runs,
 *            MSIZE-1 is used to indicate a long match */

/* Minimum len of match coded in 3 bytes */
#define	MIN_MATCH_LONG		(MAX_MATCH_SHORT + 1)

/* Maximum len of match coded in 3 bytes */
#define	MAX_MATCH_LONG		(MIN_MATCH_LONG + 255)

/* Maximum offset of a match */
#define	MAX_OFFSET			(1 << (8 + OBITS))


/*

RBITS | MBITS  MIN  THR.  MSIZE  MAXS  MINL  MAXL   MAXO  R0MAX R0FAST
======+===============================================================
  3   |   5      3    2     32    32    33    288   2048    263   256
  4   |   4      3    2     16    16    17    272   4096    271   264
  5   |   3      3    2      8     8     9    264   8192    287   280

 */


/***********************************************************************
// internal configuration
// all of these affect compression only
************************************************************************/

/* return -1 instead of copying if the data cannot be compressed */
#undef LZO_RETURN_IF_NOT_COMPRESSIBLE


/* choose the hashing strategy */
#ifndef LZO_HASH
#define LZO_HASH	LZO_HASH_LZO_INCREMENTAL_A
#endif
#define D_INDEX1(d,p)		d = DM((0x21*DX2(p,5,5)) >> 5)
#define D_INDEX2(d,p)		d = d ^ D_MASK

#define DBITS		(8 + RBITS)
#include "lzo_dict.h"
#define DVAL_LEN	DVAL_LOOKAHEAD


/***********************************************************************
// get algorithm info, return memory required for compression
************************************************************************/

LZO_EXTERN(lzo_uint) lzo1_info ( int *rbits, int *clevel );

LZO_PUBLIC(lzo_uint)
lzo1_info ( int *rbits, int *clevel )
{
	if (rbits)
		*rbits = RBITS;
	if (clevel)
		*clevel = CLEVEL;
	return D_SIZE * lzo_sizeof(lzo_byte *);
}


/***********************************************************************
// decode a R0 literal run (a long run)
************************************************************************/

#define	R0MIN	(RSIZE)				/* Minimum len of R0 run of literals */
#define	R0MAX	(R0MIN + 255)		/* Maximum len of R0 run of literals */
#define	R0FAST	(R0MAX & ~7u)		/* R0MAX aligned to 8 byte boundary */

#if (R0MAX - R0FAST != 7) || ((R0FAST & 7) != 0)
#  error "something went wrong"
#endif

/* 7 special codes from R0FAST+1 .. R0MAX
 * these codes mean long R0 runs with lengths
 * 512, 1024, 2048, 4096, 8192, 16384, 32768 */


/***********************************************************************
// LZO1 decompress a block of data.
//
// Could be easily translated into assembly code.
************************************************************************/

LZO_PUBLIC(int)
lzo1_decompress  ( const lzo_byte *in , lzo_uint  in_len,
                         lzo_byte *out, lzo_uintp out_len,
                         lzo_voidp wrkmem )
{
	lzo_byte *op;
	const lzo_byte *ip;
	const lzo_byte * const ip_end = in + in_len;
	lzo_uint t;

	LZO_UNUSED(wrkmem);

#if defined(__LZO_QUERY_DECOMPRESS)
	if (__LZO_IS_DECOMPRESS_QUERY(in,in_len,out,out_len,wrkmem))
		return __LZO_QUERY_DECOMPRESS(in,in_len,out,out_len,wrkmem,0,0);
#endif

	op = out;
	ip = in;
	while (ip < ip_end)
	{
		t = *ip++;	/* get marker */

		if (t < R0MIN)			/* a literal run */
		{
			if (t == 0)				/* a R0 literal run */
			{
				t = *ip++;
				if (t >= R0FAST - R0MIN)			/* a long R0 run */
				{
					t -= R0FAST - R0MIN;
					if (t == 0)
						t = R0FAST;
					else
					{
#if 0
						t = 256u << ((unsigned) t);
#else
						/* help the optimizer */
						lzo_uint tt = 256;
						do tt <<= 1; while (--t > 0);
						t = tt;
#endif
					}
					MEMCPY8_DS(op,ip,t);
					continue;
				}
				t += R0MIN;
			}
			MEMCPY_DS(op,ip,t);
		}
		else					/* a match */
		{
			lzo_uint tt;
			/* get match offset */
			const lzo_byte *m_pos = op - 1;
			m_pos -= (lzo_uint)(t & OMASK) | (((lzo_uint) *ip++) << OBITS);

			/* get match len */
			if (t >= ((MSIZE - 1) << OBITS))				/* all m-bits set */
				tt = (MIN_MATCH_LONG - THRESHOLD) + *ip++;	/* a long match */
			else
				tt = t >> OBITS;							/* a short match */

			assert(m_pos >= out);
			assert(m_pos <  op);
			/* a half unrolled loop */
			*op++ = *m_pos++;
			*op++ = *m_pos++;
			MEMMOVE_DS(op,m_pos,tt);
		}
	}

	*out_len = op - out;

	/* the next line is the only check in the decompressor ! */
	return (ip == ip_end ? LZO_E_OK :
	       (ip < ip_end  ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN));
}


/***********************************************************************
// code a literal run
************************************************************************/

static lzo_byte *
store_run(lzo_byte *op, const lzo_byte *ii, lzo_uint r_len)
{
	assert(r_len > 0);

	/* code a long R0 run */
	if (r_len >= 512)
	{
		unsigned r_bits = 7;		/* 256 << 7 == 32768 */
		do {
			while (r_len >= (256u << r_bits))
			{
				r_len -= (256u << r_bits);
				*op++ = 0; *op++ = LZO_BYTE((R0FAST - R0MIN) + r_bits);
				MEMCPY8_DS(op, ii, (256u << r_bits));
			}
		} while (--r_bits > 0);
	}
	while (r_len >= R0FAST)
	{
		r_len -= R0FAST;
		*op++ = 0; *op++ = R0FAST - R0MIN;
		MEMCPY8_DS(op, ii, R0FAST);
	}

	if (r_len >= R0MIN)
	{
		/* code a short R0 run */
		*op++ = 0; *op++ = LZO_BYTE(r_len - R0MIN);
		MEMCPY_DS(op, ii, r_len);
	}
	else if (r_len > 0)
	{
		/* code a 'normal' run */
		*op++ = LZO_BYTE(r_len);
		MEMCPY_DS(op, ii, r_len);