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Comparing liblzf/lzf_c.c (file contents):
Revision 1.6 by pcg, Tue Apr 20 18:11:58 2004 UTC vs.
Revision 1.10 by root, Thu Apr 14 20:38:50 2005 UTC

1/* 1/*
2 * Copyright (c) 2000-2003 Marc Alexander Lehmann <pcg@goof.com> 2 * Copyright (c) 2000-2005 Marc Alexander Lehmann <schmorp@schmorp.de>
3 * 3 *
4 * Redistribution and use in source and binary forms, with or without modifica- 4 * Redistribution and use in source and binary forms, with or without modifica-
5 * tion, are permitted provided that the following conditions are met: 5 * tion, are permitted provided that the following conditions are met:
6 * 6 *
7 * 1. Redistributions of source code must retain the above copyright notice, 7 * 1. Redistributions of source code must retain the above copyright notice,
… …
44 * don't play with this unless you benchmark! 44 * don't play with this unless you benchmark!
45 * decompression is not dependent on the hash function 45 * decompression is not dependent on the hash function
46 * the hashing function might seem strange, just believe me 46 * the hashing function might seem strange, just believe me
47 * it works ;) 47 * it works ;)
48 */ 48 */
49#ifndef FRST
49#define FRST(p) (((p[0]) << 8) + p[1]) 50# define FRST(p) (((p[0]) << 8) | p[1])
50#define NEXT(v,p) (((v) << 8) + p[2]) 51# define NEXT(v,p) (((v) << 8) | p[2])
51#define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) + h*3) & (HSIZE - 1)) 52# define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
53#endif
52/* 54/*
53 * IDX works because it is very similar to a multiplicative hash, e.g. 55 * IDX works because it is very similar to a multiplicative hash, e.g.
54 * (h * 57321 >> (3*8 - HLOG)) 56 * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
57 * the latter is also quite fast on newer CPUs, and sligthly better
58 *
55 * the next one is also quite good, albeit slow ;) 59 * the next one is also quite good, albeit slow ;)
56 * (int)(cos(h & 0xffffff) * 1e6) 60 * (int)(cos(h & 0xffffff) * 1e6)
57 */ 61 */
58 62
59#if 0 63#if 0
60/* original lzv-like hash function */ 64/* original lzv-like hash function, much worse and thus slower */
61# define FRST(p) (p[0] << 5) ^ p[1] 65# define FRST(p) (p[0] << 5) ^ p[1]
62# define NEXT(v,p) ((v) << 5) ^ p[2] 66# define NEXT(v,p) ((v) << 5) ^ p[2]
63# define IDX(h) ((h) & (HSIZE - 1)) 67# define IDX(h) ((h) & (HSIZE - 1))
64#endif 68#endif
65 69
… …
69 73
70/* 74/*
71 * compressed format 75 * compressed format
72 * 76 *
73 * 000LLLLL <L+1> ; literal 77 * 000LLLLL <L+1> ; literal
74 * LLLOOOOO oooooooo ; backref L 78 * LLLooooo oooooooo ; backref L
75 * 111OOOOO LLLLLLLL oooooooo ; backref L+7 79 * 111ooooo LLLLLLLL oooooooo ; backref L+7
76 * 80 *
77 */ 81 */
78 82
79unsigned int 83unsigned int
80lzf_compress (const void *const in_data, unsigned int in_len, 84lzf_compress (const void *const in_data, unsigned int in_len,
… …
135 /* match found at *ref++ */ 139 /* match found at *ref++ */
136 unsigned int len = 2; 140 unsigned int len = 2;
137 unsigned int maxlen = in_end - ip - len; 141 unsigned int maxlen = in_end - ip - len;
138 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen; 142 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
139 143
144 if (op + lit + 1 + 3 >= out_end)
145 return 0;
146
140 do 147 do
141 len++; 148 len++;
142 while (len < maxlen && ref[len] == ip[len]); 149 while (len < maxlen && ref[len] == ip[len]);
143
144 if (op + lit + 1 + 3 >= out_end)
145 return 0;
146 150
147 if (lit) 151 if (lit)
148 { 152 {
149 *op++ = lit - 1; 153 *op++ = lit - 1;
150 lit = -lit; 154 lit = -lit;
… …
166 *op++ = len - 7; 170 *op++ = len - 7;
167 } 171 }
168 172
169 *op++ = off; 173 *op++ = off;
170 174
171#if ULTRA_FAST 175#if ULTRA_FAST || VERY_FAST
172 ip += len; 176 ip += len;
177#if VERY_FAST && !ULTRA_FAST
178 --ip;
179#endif
173 hval = FRST (ip); 180 hval = FRST (ip);
181
174 hval = NEXT (hval, ip); 182 hval = NEXT (hval, ip);
175 htab[IDX (hval)] = ip; 183 htab[IDX (hval)] = ip;
176 ip++; 184 ip++;
185
186#if VERY_FAST && !ULTRA_FAST
187 hval = NEXT (hval, ip);
188 htab[IDX (hval)] = ip;
189 ip++;
190#endif
177#else 191#else
178 do 192 do
179 { 193 {
180 hval = NEXT (hval, ip); 194 hval = NEXT (hval, ip);
181 htab[IDX (hval)] = ip; 195 htab[IDX (hval)] = ip;

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