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/* lzo1a_cm.ch -- implementation of the LZO1A compression algorithm
This file is part of the LZO real-time data compression library.
Copyright (C) 1996-2017 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);
/* vim:set ts=4 sw=4 et: */
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