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 << 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;
}
Revision:	1.2
Committed:	Thu Sep 5 03:31:00 2002 UTC (21 years, 8 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.1:	+3 -3 lines
Log Message:	* empty log message *
#	Content
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 << 5)) >> (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	}