lzo1a_cm.ch

lzo-1.08-src.zip 高效的压缩解压代码

/* lzo1a_cm.ch -- implementation of the LZO1A compression 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]>
 */


/* WARNING: this file should *not* be used by applications. It is
   part of the implementation of the library and is subject
   to change.
 */



/***********************************************************************
// code the match in LZO1 compatible format
************************************************************************/

#define THRESHOLD	(M2_MIN_LEN - 1)
#define MSIZE		LZO_SIZE(M2L_BITS)


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

#if (DD_BITS == 0)

		/* we already matched M2_MIN_LEN bytes,
		 * m_pos also already advanced M2_MIN_LEN bytes */
		ip += M2_MIN_LEN;
		assert(m_pos < ip);

		/* try to match another M2_MAX_LEN + 1 - M2_MIN_LEN bytes
		 * to see if we get more than a M2 match */
#define M2_OR_M3	(MATCH_M2)

#else /* (DD_BITS == 0) */

		/* we already matched m_len bytes */
		assert(m_len >= M2_MIN_LEN);
		ip += m_len;
		assert(ip <= in_end);

#define M2_OR_M3	(m_len <= M2_MAX_LEN)

#endif /* (DD_BITS == 0) */


		if (M2_OR_M3)
		{
		/* we've found a short match */
			assert(ip <= in_end);

		/* 2a) compute match parameters */
#if (DD_BITS == 0)
				assert((lzo_moff_t)(ip-m_pos) == m_off);
			--ip;	/* ran one too far, point back to non-match */
			m_len = ip - ii;
#endif
				assert(m_len >= M2_MIN_LEN);
				assert(m_len <= M2_MAX_LEN);

				assert(m_off >= M2_MIN_OFFSET);
				assert(m_off <= M2_MAX_OFFSET);
				assert(ii-m_off == m_pos_sav);
				assert(lzo_memcmp(m_pos_sav,ii,m_len) == 0);

		/* 2b) code the match */
			m_off -= M2_MIN_OFFSET;
			/* code short match len + low offset bits */
			*op++ = LZO_BYTE(((m_len - THRESHOLD) << M2O_BITS) |
			                 (m_off & M2O_MASK));
			/* code high offset bits */
			*op++ = LZO_BYTE(m_off >> M2O_BITS);


			if (ip >= ip_end)
			{
				ii = ip;
				break;
			}


		/* 2c) Insert phrases (beginning with ii+1) into the dictionary. */

#if (CLEVEL == 9) || (CLEVEL >= 7 && M2L_BITS <= 4) || (CLEVEL >= 5 && M2L_BITS <= 3)
		/* Insert the whole match (ii+1)..(ip-1) into dictionary.  */
			++ii;
			do {
				DVAL_NEXT(dv,ii);
#if 0
				UPDATE_D(dict,drun,dv,ii,in);
#else
				dict[ DINDEX(dv,ii) ] = DENTRY(ii,in);
#endif
				MI
			} while (++ii < ip);
			DVAL_NEXT(dv,ii);
			assert(ii == ip);
			DVAL_ASSERT(dv,ip);
#elif (CLEVEL >= 3)
			SI   DI DI   XI
#elif (CLEVEL >= 2)
			SI   DI      XI
#else
			             XI
#endif
		}

		else

		{
		/* we've found a long match - see how far we can still go */
			const lzo_byte *end;

			assert(ip <= in_end);
			assert(ii == ip - (M2_MAX_LEN + 1));
			assert(lzo_memcmp(m_pos_sav,ii,(lzo_uint)(ip-ii)) == 0);

#if (DD_BITS > 0)
			assert(m_len == (lzo_uint)(ip-ii));
			m_pos = ip - m_off;
			assert(m_pos == m_pos_sav + m_len);
#endif

#if defined(__LZO_CHECKER)
			if (in_end - ip <= (lzo_ptrdiff_t) (M3_MAX_LEN - M3_MIN_LEN))
#else
			if (in_end <= ip + (M3_MAX_LEN - M3_MIN_LEN))
#endif
				end = in_end;
			else
			{
				end = ip + (M3_MAX_LEN - M3_MIN_LEN);
				assert(end < in_end);
			}

			while (ip < end  &&  *m_pos == *ip)
				m_pos++, ip++;
			assert(ip <= in_end);

			/* 2a) compute match parameters */
			m_len = (ip - ii);
				assert(m_len >= M3_MIN_LEN);
				assert(m_len <= M3_MAX_LEN);

				assert(m_off >= M3_MIN_OFFSET);
				assert(m_off <= M3_MAX_OFFSET);
				assert(ii-m_off == m_pos_sav);
				assert(lzo_memcmp(m_pos_sav,ii,m_len) == 0);
				assert((lzo_moff_t)(ip-m_pos) == m_off);

		/* 2b) code the match */
			m_off -= M3_MIN_OFFSET - M3_EOF_OFFSET;
			/* code long match flag + low offset bits */
			*op++ = LZO_BYTE(((MSIZE - 1) << M3O_BITS) | (m_off & M3O_MASK));
			/* code high offset bits */
			*op++ = LZO_BYTE(m_off >> M3O_BITS);
			/* code match len */
			*op++ = LZO_BYTE(m_len - M3_MIN_LEN);


			if (ip >= ip_end)
			{
				ii = ip;
				break;
			}


		/* 2c) Insert phrases (beginning with ii+1) into the dictionary. */
#if (CLEVEL == 9)
		/* Insert the whole match (ii+1)..(ip-1) into dictionary.  */
		/* This is not recommended because it can be slow. */
			++ii;
			do {
				DVAL_NEXT(dv,ii);
#if 0
				UPDATE_D(dict,drun,dv,ii,in);
#else
				dict[ DINDEX(dv,ii) ] = DENTRY(ii,in);
#endif
				MI
			} while (++ii < ip);
			DVAL_NEXT(dv,ii);
			assert(ii == ip);
			DVAL_ASSERT(dv,ip);
#elif (CLEVEL >= 8)
			SI   DI DI DI DI DI DI DI DI   XI
#elif (CLEVEL >= 7)
			SI   DI DI DI DI DI DI DI      XI
#elif (CLEVEL >= 6)
			SI   DI DI DI DI DI DI         XI
#elif (CLEVEL >= 5)
			SI   DI DI DI DI               XI
#elif (CLEVEL >= 4)
			SI   DI DI DI                  XI
#elif (CLEVEL >= 3)
			SI   DI DI                     XI
#elif (CLEVEL >= 2)
			SI   DI                        XI
#else
			                               XI
#endif
		}

		/* ii now points to the start of the next literal run */
		assert(ii == ip);


/*
vi:ts=4:et
*/