lzo-2.03/src/lzo1a_cm.ch

/* lzo1a_cm.ch -- implementation of the LZO1A compression algorithm

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

   Copyright (C) 2008 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2007 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2006 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2005 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2004 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2003 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2002 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2001 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2000 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1999 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1998 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1997 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996 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.,
   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

   Markus F.X.J. Oberhumer
   <markus@oberhumer.com>
   http://www.oberhumer.com/opensource/lzo/
 */


/* 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(pd(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_bytep 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 (pd(in_end,ip) <= (M3_MAX_LEN - M3_MIN_LEN))
                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 = pd(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(pd(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
*/