liblzf/lzf_c.c

/*
 * 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 << 4)) >> (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;
}
Revision:	1.1
Committed:	Sun Jun 9 22:41:34 2002 UTC (21 years, 11 months ago) by root
Content type:	text/plain
Branch:	MAIN
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	/*
2			* Copyright (c) 2000 Marc Alexander Lehmann <pcg@goof.com>
3			*
4			* Redistribution and use in source and binary forms, with or without modifica-
5			* tion, are permitted provided that the following conditions are met:
6			*
7			* 1. Redistributions of source code must retain the above copyright notice,
8			* this list of conditions and the following disclaimer.
9			*
10			* 2. Redistributions in binary form must reproduce the above copyright
11			* notice, this list of conditions and the following disclaimer in the
12			* documentation and/or other materials provided with the distribution.
13			*
14			* 3. The name of the author may not be used to endorse or promote products
15			* derived from this software without specific prior written permission.
16			*
17			* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18			* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19			* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20			* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21			* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22			* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23			* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24			* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25			* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26			* OF THE POSSIBILITY OF SUCH DAMAGE.
27			*/
28
29			#include "lzfP.h"
30
31			#define HSIZE (1 << (HLOG))
32
33			/*
34			* don't play with this unless you benchmark!
35			* decompression is not dependent on the hash function
36			* the hashing function might seem strange, just believe me
37			* it works ;)
38			*/
39			#define FRST(p) (((p[0]) << 8) + p[1])
40			#define NEXT(v,p) (((v) << 8) + p[2])
41			#define IDX(h) ((((h ^ (h << 4)) >> (38 - HLOG)) + h3) & (HSIZE - 1))
42			/*
43			* IDX works because it is very similar to a multiplicative hash, e.g.
44			* (h * 57321 >> (3*8 - HLOG))
45			* the next one is also quite good, albeit slow ;)
46			* (int)(cos(h & 0xffffff) * 1e6)
47			*/
48
49			#if 0
50			/* original lzv-like hash function */
51			# define FRST(p) (p[0] << 5) ^ p[1]
52			# define NEXT(v,p) (v << 5) ^ p[2]
53			# define IDX(h) (h) & (HSIZE - 1)
54			#endif
55
56			#define MAX_LIT (1 << 5)
57			#define MAX_OFF (1 << 13)
58			#define MAX_REF ((1 << 8) + (1 << 3))
59
60			/*
61			* compressed format
62			*
63			* 000LLLLL <L+1> ; literal
64			* LLLOOOOO oooooooo ; backref L
65			* 111OOOOO LLLLLLLL oooooooo ; backref L+7
66			*
67			*/
68
69			unsigned int
70			lzf_compress (const void *const in_data, unsigned int in_len,
71			void *out_data, unsigned int out_len)
72			{
73			const u8 *htab[HSIZE];
74			const u8 **hslot;
75			const u8 *ip = in_data;
76			u8 *op = out_data;
77			const u8 *in_end = ip + in_len;
78			u8 *out_end = op + out_len;
79			const u8 *ref;
80
81			unsigned int hval = FRST (ip);
82			unsigned long off;
83			int lit = 0;
84
85			#if INIT_HTAB
86			# if USE_MEMCPY
87			memset (htab, 0, sizeof (htab));
88			# else
89			for (hslot = htab; hslot < htab + HSIZE; hslot++)
90			*hslot++ = ip;
91			# endif
92			#endif
93
94			do
95			{
96			hval = NEXT (hval, ip);
97			hslot = htab + IDX (hval);
98			ref = hslot; hslot = ip;
99
100			if (1
101			#if INIT_HTAB && !USE_MEMCPY
102			&& ref < ip /* the next test will actually take care of this, but it is faster */
103			#endif
104			&& (off = ip - ref - 1) < MAX_OFF
105			&& ip + 4 < in_end
106			&& ref > (u8 *)in_data
107			#if STRICT_ALIGN
108			&& ref[0] == ip[0]
109			&& ref[1] == ip[1]
110			&& ref[2] == ip[2]
111			#else
112			&& (u16 )ref == (u16 )ip
113			&& ref[2] == ip[2]
114			#endif
115			)
116			{
117			/* match found at ref++ /
118			unsigned int len = 2;
119			unsigned int maxlen = in_end - ip - len;
120			maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
121
122			do
123			len++;
124			while (len < maxlen && ref[len] == ip[len]);
125
126			if (op + lit + 1 + 3 >= out_end)
127			return 0;
128
129			if (lit)
130			{
131			*op++ = lit - 1;
132			lit = -lit;
133			do
134			*op++ = ip[lit];
135			while (++lit);
136			}
137
138			len -= 2;
139			ip++;
140
141			if (len < 7)
142			{
143			*op++ = (off >> 8) + (len << 5);
144			}
145			else
146			{
147			*op++ = (off >> 8) + ( 7 << 5);
148			*op++ = len - 7;
149			}
150
151			*op++ = off;
152
153			#if ULTRA_FAST
154			ip += len;
155			hval = FRST (ip);
156			hval = NEXT (hval, ip);
157			htab[IDX (hval)] = ip;
158			ip++;
159			#else
160			do
161			{
162			hval = NEXT (hval, ip);
163			htab[IDX (hval)] = ip;
164			ip++;
165			}
166			while (len--);
167			#endif
168			}
169			else
170			{
171			/* one more literal byte we must copy */
172			lit++;
173			ip++;
174
175			if (lit == MAX_LIT)
176			{
177			if (op + 1 + MAX_LIT >= out_end)
178			return 0;
179
180			*op++ = MAX_LIT - 1;
181			#if USE_MEMCPY
182			memcpy (op, ip - MAX_LIT, MAX_LIT);
183			op += MAX_LIT;
184			lit = 0;
185			#else
186			lit = -lit;
187			do
188			*op++ = ip[lit];
189			while (++lit);
190			#endif
191			}
192			}
193			}
194			while (ip < in_end);
195
196			if (lit)
197			{
198			if (op + lit + 1 >= out_end)
199			return 0;
200
201			*op++ = lit - 1;
202			lit = -lit;
203			do
204			*op++ = ip[lit];
205			while (++lit);
206			}
207
208			return op - (u8 *) out_data;
209			}