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/*
* Copyright (c) 2000 Marc Alexander Lehmann <pcg@goof.com>
*
* Redistribution and use in source and binary forms, with or without modifica-
* tion, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. 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.
*
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
* CIAL, 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 OTH-
* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "lzfP.h"
#define HSIZE (1 << (HLOG))
/*
* don't play with this unless you benchmark!
* decompression is not dependent on the hash function
* the hashing function might seem strange, just believe me
* it works ;)
*/
#define FRST(p) (((p[0]) << 8) + p[1])
#define NEXT(v,p) (((v) << 8) + p[2])
#define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) + h*3) & (HSIZE - 1))
/*
* IDX works because it is very similar to a multiplicative hash, e.g.
* (h * 57321 >> (3*8 - HLOG))
* the next one is also quite good, albeit slow ;)
* (int)(cos(h & 0xffffff) * 1e6)
*/
#if 0
/* original lzv-like hash function */
# define FRST(p) (p[0] << 5) ^ p[1]
# define NEXT(v,p) ((v) << 5) ^ p[2]
# define IDX(h) ((h) & (HSIZE - 1))
#endif
#define MAX_LIT (1 << 5)
#define MAX_OFF (1 << 13)
#define MAX_REF ((1 << 8) + (1 << 3))
/*
* compressed format
*
* 000LLLLL <L+1> ; literal
* LLLOOOOO oooooooo ; backref L
* 111OOOOO LLLLLLLL oooooooo ; backref L+7
*
*/
unsigned int
lzf_compress (const void *const in_data, unsigned int in_len,
void *out_data, unsigned int out_len)
{
const u8 *htab[HSIZE];
const u8 **hslot;
const u8 *ip = in_data;
u8 *op = out_data;
const u8 *in_end = ip + in_len;
u8 *out_end = op + out_len;
const u8 *ref;
unsigned int hval = FRST (ip);
unsigned long off;
int lit = 0;
#if INIT_HTAB
# if USE_MEMCPY
memset (htab, 0, sizeof (htab));
# else
for (hslot = htab; hslot < htab + HSIZE; hslot++)
*hslot++ = ip;
# endif
#endif
do
{
hval = NEXT (hval, ip);
hslot = htab + IDX (hval);
ref = *hslot; *hslot = ip;
if (1
#if INIT_HTAB && !USE_MEMCPY
&& ref < ip /* the next test will actually take care of this, but it is faster */
#endif
&& (off = ip - ref - 1) < MAX_OFF
&& ip + 4 < in_end
&& ref > (u8 *)in_data
#if STRICT_ALIGN
&& ref[0] == ip[0]
&& ref[1] == ip[1]
&& ref[2] == ip[2]
#else
&& *(u16 *)ref == *(u16 *)ip
&& ref[2] == ip[2]
#endif
)
{
/* match found at *ref++ */
unsigned int len = 2;
unsigned int maxlen = in_end - ip - len;
maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
do
len++;
while (len < maxlen && ref[len] == ip[len]);
if (op + lit + 1 + 3 >= out_end)
return 0;
if (lit)
{
*op++ = lit - 1;
lit = -lit;
do
*op++ = ip[lit];
while (++lit);
}
len -= 2;
ip++;
if (len < 7)
{
*op++ = (off >> 8) + (len << 5);
}
else
{
*op++ = (off >> 8) + ( 7 << 5);
*op++ = len - 7;
}
*op++ = off;
#if ULTRA_FAST
ip += len;
hval = FRST (ip);
hval = NEXT (hval, ip);
htab[IDX (hval)] = ip;
ip++;
#else
do
{
hval = NEXT (hval, ip);
htab[IDX (hval)] = ip;
ip++;
}
while (len--);
#endif
}
else
{
/* one more literal byte we must copy */
lit++;
ip++;
if (lit == MAX_LIT)
{
if (op + 1 + MAX_LIT >= out_end)
return 0;
*op++ = MAX_LIT - 1;
#if USE_MEMCPY
memcpy (op, ip - MAX_LIT, MAX_LIT);
op += MAX_LIT;
lit = 0;
#else
lit = -lit;
do
*op++ = ip[lit];
while (++lit);
#endif
}
}
}
while (ip < in_end);
if (lit)
{
if (op + lit + 1 >= out_end)
return 0;
*op++ = lit - 1;
lit = -lit;
do
*op++ = ip[lit];
while (++lit);
}
return op - (u8 *) out_data;
}
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