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/cvs/liblzf/lzf_c.c
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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 1.9 by root, Tue Mar 8 19:59:52 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#define FRST(p) (((p[0]) << 8) + p[1]) 49#define FRST(p) (((p[0]) << 8) | p[1])
50#define NEXT(v,p) (((v) << 8) + p[2]) 50#define NEXT(v,p) (((v) << 8) | p[2])
51#define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) + h*3) & (HSIZE - 1)) 51#define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
52/* 52/*
53 * IDX works because it is very similar to a multiplicative hash, e.g. 53 * IDX works because it is very similar to a multiplicative hash, e.g.
54 * (h * 57321 >> (3*8 - HLOG)) 54 * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
55 * the latter is also quite fast on newer CPUs, and sligthly better
56 *
55 * the next one is also quite good, albeit slow ;) 57 * the next one is also quite good, albeit slow ;)
56 * (int)(cos(h & 0xffffff) * 1e6) 58 * (int)(cos(h & 0xffffff) * 1e6)
57 */ 59 */
58 60
59#if 0 61#if 0
60/* original lzv-like hash function */ 62/* original lzv-like hash function, much worse and thus slower */
61# define FRST(p) (p[0] << 5) ^ p[1] 63# define FRST(p) (p[0] << 5) ^ p[1]
62# define NEXT(v,p) ((v) << 5) ^ p[2] 64# define NEXT(v,p) ((v) << 5) ^ p[2]
63# define IDX(h) ((h) & (HSIZE - 1)) 65# define IDX(h) ((h) & (HSIZE - 1))
64#endif 66#endif
65 67
… …
135 /* match found at *ref++ */ 137 /* match found at *ref++ */
136 unsigned int len = 2; 138 unsigned int len = 2;
137 unsigned int maxlen = in_end - ip - len; 139 unsigned int maxlen = in_end - ip - len;
138 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen; 140 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
139 141
142 if (op + lit + 1 + 3 >= out_end)
143 return 0;
144
140 do 145 do
141 len++; 146 len++;
142 while (len < maxlen && ref[len] == ip[len]); 147 while (len < maxlen && ref[len] == ip[len]);
143
144 if (op + lit + 1 + 3 >= out_end)
145 return 0;
146 148
147 if (lit) 149 if (lit)
148 { 150 {
149 *op++ = lit - 1; 151 *op++ = lit - 1;
150 lit = -lit; 152 lit = -lit;
… …
166 *op++ = len - 7; 168 *op++ = len - 7;
167 } 169 }
168 170
169 *op++ = off; 171 *op++ = off;
170 172
171#if ULTRA_FAST 173#if ULTRA_FAST || VERY_FAST
172 ip += len; 174 ip += len;
175#if VERY_FAST && !ULTRA_FAST
176 --ip;
177#endif
173 hval = FRST (ip); 178 hval = FRST (ip);
179
174 hval = NEXT (hval, ip); 180 hval = NEXT (hval, ip);
175 htab[IDX (hval)] = ip; 181 htab[IDX (hval)] = ip;
176 ip++; 182 ip++;
183
184#if VERY_FAST && !ULTRA_FAST
185 hval = NEXT (hval, ip);
186 htab[IDX (hval)] = ip;
187 ip++;
188#endif
177#else 189#else
178 do 190 do
179 { 191 {
180 hval = NEXT (hval, ip); 192 hval = NEXT (hval, ip);
181 htab[IDX (hval)] = ip; 193 htab[IDX (hval)] = ip;

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