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Comparing liblzf/lzf_c.c (file contents):
Revision 1.40 by root, Tue Jun 1 01:50:24 2010 UTC vs.
Revision 1.47 by root, Sun Feb 26 03:17:50 2012 UTC

1/* 1/*
2 * Copyright (c) 2000-2010 Marc Alexander Lehmann <schmorp@schmorp.de> 2 * Copyright (c) 2000-2010,2012 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,
… …
38 38
39#define HSIZE (1 << (HLOG)) 39#define HSIZE (1 << (HLOG))
40 40
41/* 41/*
42 * don't play with this unless you benchmark! 42 * don't play with this unless you benchmark!
43 * decompression is not dependent on the hash function 43 * the data format is not dependent on the hash function.
44 * the hashing function might seem strange, just believe me 44 * the hash function might seem strange, just believe me,
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;
115 114
116 /* off requires a type wide enough to hold a general pointer difference. 115 /* off requires a type wide enough to hold a general pointer difference.
117 * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only 116 * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only
118 * works for differences within a single object). We also assume that no 117 * works for differences within a single object). We also assume that
119 * no bit pattern traps. Since the only platform that is both non-POSIX 118 * no bit pattern traps. Since the only platform that is both non-POSIX
120 * and fails to support both assumptions is windows 64 bit, we make a 119 * and fails to support both assumptions is windows 64 bit, we make a
121 * special workaround for it. 120 * special workaround for it.
122 */ 121 */
123#if defined (WIN32) && defined (_M_X64) 122#if defined (_WIN32) && defined (_M_X64)
124 unsigned _int64 off; /* workaround for missing POSIX compliance */ 123 /* workaround for missing POSIX compliance */
124 #if #if __GNUC__
125 unsigned long long off;
126 #else
127 unsigned __int64 off;
128 #endif
125#else 129#else
126 unsigned long off; 130 unsigned long off;
127#endif 131#endif
128 unsigned int hval; 132 unsigned int hval;
129 int lit; 133 int lit;
… …
131 if (!in_len || !out_len) 135 if (!in_len || !out_len)
132 return 0; 136 return 0;
133 137
134#if INIT_HTAB 138#if INIT_HTAB
135 memset (htab, 0, sizeof (htab)); 139 memset (htab, 0, sizeof (htab));
136# if 0
137 for (hslot = htab; hslot < htab + HSIZE; hslot++)
138 *hslot++ = ip;
139# endif
140#endif 140#endif
141 141
142 lit = 0; op++; /* start run */ 142 lit = 0; op++; /* start run */
143 143
144 hval = FRST (ip); 144 hval = FRST (ip);
145 while (ip < in_end - 2) 145 while (ip < in_end - 2)
146 { 146 {
147 LZF_HSLOT *hslot;
148
147 hval = NEXT (hval, ip); 149 hval = NEXT (hval, ip);
148 hslot = htab + IDX (hval); 150 hslot = htab + IDX (hval);
149 ref = *hslot; *hslot = ip; 151 ref = *hslot + LZF_HSLOT_BIAS; *hslot = ip - LZF_HSLOT_BIAS;
150 152
151 if (1 153 if (1
152#if INIT_HTAB 154#if INIT_HTAB
153 && ref < ip /* the next test will actually take care of this, but this is faster */ 155 && ref < ip /* the next test will actually take care of this, but this is faster */
154#endif 156#endif
155 && (off = ip - ref - 1) < MAX_OFF 157 && (off = ip - ref - 1) < MAX_OFF
156 && ip + 4 < in_end
157 && ref > (u8 *)in_data 158 && ref > (u8 *)in_data
158 && ref[2] == ip[2] 159 && ref[2] == ip[2]
159#if STRICT_ALIGN 160#if STRICT_ALIGN
160 && (ref[1] << 8) | ref[0] == (ip[1] << 8) | ip[0] 161 && ((ref[1] << 8) | ref[0]) == ((ip[1] << 8) | ip[0])
161#else 162#else
162 && *(u16 *)ref == *(u16 *)ip 163 && *(u16 *)ref == *(u16 *)ip
163#endif 164#endif
164 ) 165 )
165 { 166 {
… …
219 *op++ = (off >> 8) + ( 7 << 5); 220 *op++ = (off >> 8) + ( 7 << 5);
220 *op++ = len - 7; 221 *op++ = len - 7;
221 } 222 }
222 223
223 *op++ = off; 224 *op++ = off;
225
224 lit = 0; op++; /* start run */ 226 lit = 0; op++; /* start run */
225 227
226 ip += len + 1; 228 ip += len + 1;
227 229
228 if (expect_false (ip >= in_end - 2)) 230 if (expect_false (ip >= in_end - 2))
… …
234 --ip; 236 --ip;
235# endif 237# endif
236 hval = FRST (ip); 238 hval = FRST (ip);
237 239
238 hval = NEXT (hval, ip); 240 hval = NEXT (hval, ip);
239 htab[IDX (hval)] = ip; 241 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
240 ip++; 242 ip++;
241 243
242# if VERY_FAST && !ULTRA_FAST 244# if VERY_FAST && !ULTRA_FAST
243 hval = NEXT (hval, ip); 245 hval = NEXT (hval, ip);
244 htab[IDX (hval)] = ip; 246 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
245 ip++; 247 ip++;
246# endif 248# endif
247#else 249#else
248 ip -= len + 1; 250 ip -= len + 1;
249 251
250 do 252 do
251 { 253 {
252 hval = NEXT (hval, ip); 254 hval = NEXT (hval, ip);
253 htab[IDX (hval)] = ip; 255 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
254 ip++; 256 ip++;
255 } 257 }
256 while (len--); 258 while (len--);
257#endif 259#endif
258 } 260 }

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