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/cvs/liblzf/lzf_c.c
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Comparing liblzf/lzf_c.c (file contents):
Revision 1.41 by root, Tue Jun 1 02:30:06 2010 UTC vs.
Revision 1.45 by root, Sun Mar 27 23:53:23 2011 UTC

… …
45 * it works ;) 45 * it works ;)
46 */ 46 */
47#ifndef FRST 47#ifndef FRST
48# define FRST(p) (((p[0]) << 8) | p[1]) 48# define FRST(p) (((p[0]) << 8) | p[1])
49# define NEXT(v,p) (((v) << 8) | p[2]) 49# define NEXT(v,p) (((v) << 8) | p[2])
50# if MULTIPLICATION_IS_SLOW
50# if ULTRA_FAST 51# if ULTRA_FAST
51# define IDX(h) ((( h >> (3*8 - HLOG)) - h ) & (HSIZE - 1)) 52# define IDX(h) ((( h >> (3*8 - HLOG)) - h ) & (HSIZE - 1))
52# elif VERY_FAST 53# elif VERY_FAST
53# define IDX(h) ((( h >> (3*8 - HLOG)) - h*5) & (HSIZE - 1)) 54# define IDX(h) ((( h >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
55# else
56# define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
57# endif
54# else 58# else
59/* this one was developed with sesse,
60 * and is very similar to the one in snappy.
61 * it does need a modern enough cpu with a fast multiplication.
62 */
55# define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1)) 63# define IDX(h) (((h * 0x1e35a7bdU) >> (32 - HLOG - 8)) & (HSIZE - 1))
56# endif 64# endif
57#endif 65#endif
58/*
59 * IDX works because it is very similar to a multiplicative hash, e.g.
60 * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
61 * the latter is also quite fast on newer CPUs, and compresses similarly.
62 *
63 * the next one is also quite good, albeit slow ;)
64 * (int)(cos(h & 0xffffff) * 1e6)
65 */
66 66
67#if 0 67#if 0
68/* original lzv-like hash function, much worse and thus slower */ 68/* original lzv-like hash function, much worse and thus slower */
69# define FRST(p) (p[0] << 5) ^ p[1] 69# define FRST(p) (p[0] << 5) ^ p[1]
70# define NEXT(v,p) ((v) << 5) ^ p[2] 70# define NEXT(v,p) ((v) << 5) ^ p[2]
… …
104 ) 104 )
105{ 105{
106#if !LZF_STATE_ARG 106#if !LZF_STATE_ARG
107 LZF_STATE htab; 107 LZF_STATE htab;
108#endif 108#endif
109 const u8 **hslot;
110 const u8 *ip = (const u8 *)in_data; 109 const u8 *ip = (const u8 *)in_data;
111 u8 *op = (u8 *)out_data; 110 u8 *op = (u8 *)out_data;
112 const u8 *in_end = ip + in_len; 111 const u8 *in_end = ip + in_len;
113 u8 *out_end = op + out_len; 112 u8 *out_end = op + out_len;
114 const u8 *ref; 113 const u8 *ref;
… …
131 if (!in_len || !out_len) 130 if (!in_len || !out_len)
132 return 0; 131 return 0;
133 132
134#if INIT_HTAB 133#if INIT_HTAB
135 memset (htab, 0, sizeof (htab)); 134 memset (htab, 0, sizeof (htab));
136# if 0
137 for (hslot = htab; hslot < htab + HSIZE; hslot++)
138 *hslot++ = ip;
139# endif
140#endif 135#endif
141 136
142 lit = 0; op++; /* start run */ 137 lit = 0; op++; /* start run */
143 138
144 hval = FRST (ip); 139 hval = FRST (ip);
145 while (ip < in_end - 2) 140 while (ip < in_end - 2)
146 { 141 {
142 LZF_HSLOT *hslot;
143
147 hval = NEXT (hval, ip); 144 hval = NEXT (hval, ip);
148 hslot = htab + IDX (hval); 145 hslot = htab + IDX (hval);
149 ref = *hslot; *hslot = ip; 146 ref = *hslot + LZF_HSLOT_BIAS; *hslot = ip - LZF_HSLOT_BIAS;
150 147
151 if (1 148 if (1
152#if INIT_HTAB 149#if INIT_HTAB
153 && ref < ip /* the next test will actually take care of this, but this is faster */ 150 && ref < ip /* the next test will actually take care of this, but this is faster */
154#endif 151#endif
155 && (off = ip - ref - 1) < MAX_OFF 152 && (off = ip - ref - 1) < MAX_OFF
156 && ip + 4 < in_end
157 && ref > (u8 *)in_data 153 && ref > (u8 *)in_data
158 && ref[2] == ip[2] 154 && ref[2] == ip[2]
159#if STRICT_ALIGN 155#if STRICT_ALIGN
160 && (ref[1] << 8) | ref[0] == (ip[1] << 8) | ip[0] 156 && ((ref[1] << 8) | ref[0]) == ((ip[1] << 8) | ip[0])
161#else 157#else
162 && *(u16 *)ref == *(u16 *)ip 158 && *(u16 *)ref == *(u16 *)ip
163#endif 159#endif
164 ) 160 )
165 { 161 {
… …
219 *op++ = (off >> 8) + ( 7 << 5); 215 *op++ = (off >> 8) + ( 7 << 5);
220 *op++ = len - 7; 216 *op++ = len - 7;
221 } 217 }
222 218
223 *op++ = off; 219 *op++ = off;
220
224 lit = 0; op++; /* start run */ 221 lit = 0; op++; /* start run */
225 222
226 ip += len + 1; 223 ip += len + 1;
227 224
228 if (expect_false (ip >= in_end - 2)) 225 if (expect_false (ip >= in_end - 2))
… …
234 --ip; 231 --ip;
235# endif 232# endif
236 hval = FRST (ip); 233 hval = FRST (ip);
237 234
238 hval = NEXT (hval, ip); 235 hval = NEXT (hval, ip);
239 htab[IDX (hval)] = ip; 236 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
240 ip++; 237 ip++;
241 238
242# if VERY_FAST && !ULTRA_FAST 239# if VERY_FAST && !ULTRA_FAST
243 hval = NEXT (hval, ip); 240 hval = NEXT (hval, ip);
244 htab[IDX (hval)] = ip; 241 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
245 ip++; 242 ip++;
246# endif 243# endif
247#else 244#else
248 ip -= len + 1; 245 ip -= len + 1;
249 246
250 do 247 do
251 { 248 {
252 hval = NEXT (hval, ip); 249 hval = NEXT (hval, ip);
253 htab[IDX (hval)] = ip; 250 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
254 ip++; 251 ip++;
255 } 252 }
256 while (len--); 253 while (len--);
257#endif 254#endif
258 } 255 }

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