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/cvs/liblzf/lzf_c.c
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Comparing liblzf/lzf_c.c (file contents):
Revision 1.22 by root, Tue Nov 13 10:41:52 2007 UTC vs.
Revision 1.41 by root, Tue Jun 1 02:30:06 2010 UTC

1/* 1/*
2 * Copyright (c) 2000-2007 Marc Alexander Lehmann <schmorp@schmorp.de> 2 * Copyright (c) 2000-2010 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 ULTRA_FAST 50# if ULTRA_FAST
51# define IDX(h) (((h >> (3*8 - HLOG)) - h ) & (HSIZE - 1)) 51# define IDX(h) ((( h >> (3*8 - HLOG)) - h ) & (HSIZE - 1))
52# elif VERY_FAST 52# elif VERY_FAST
53# define IDX(h) (((h >> (3*8 - HLOG)) - h*5) & (HSIZE - 1)) 53# define IDX(h) ((( h >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
54# else 54# else
55# define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1)) 55# define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
56# endif 56# endif
57/*# define IDX(h) ((ip[0] * 121 ^ ip[1] * 33 ^ ip[2] * 1) & (HSIZE-1))*/
58#endif 57#endif
59/* 58/*
60 * IDX works because it is very similar to a multiplicative hash, e.g. 59 * IDX works because it is very similar to a multiplicative hash, e.g.
61 * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1)) 60 * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
62 * the latter is also quite fast on newer CPUs, and compresses similarly. 61 * the latter is also quite fast on newer CPUs, and compresses similarly.
… …
88#define expect_true(expr) expect ((expr) != 0, 1) 87#define expect_true(expr) expect ((expr) != 0, 1)
89 88
90/* 89/*
91 * compressed format 90 * compressed format
92 * 91 *
93 * 000LLLLL <L+1> ; literal 92 * 000LLLLL <L+1> ; literal, L+1=1..33 octets
94 * LLLooooo oooooooo ; backref L 93 * LLLooooo oooooooo ; backref L+1=1..7 octets, o+1=1..4096 offset
95 * 111ooooo LLLLLLLL oooooooo ; backref L+7 94 * 111ooooo LLLLLLLL oooooooo ; backref L+8 octets, o+1=1..4096 offset
96 * 95 *
97 */ 96 */
98 97
99unsigned int 98unsigned int
100lzf_compress (const void *const in_data, unsigned int in_len, 99lzf_compress (const void *const in_data, unsigned int in_len,
… …
112 u8 *op = (u8 *)out_data; 111 u8 *op = (u8 *)out_data;
113 const u8 *in_end = ip + in_len; 112 const u8 *in_end = ip + in_len;
114 u8 *out_end = op + out_len; 113 u8 *out_end = op + out_len;
115 const u8 *ref; 114 const u8 *ref;
116 115
116 /* 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
118 * works for differences within a single object). We also assume that no
119 * 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
121 * special workaround for it.
122 */
123#if defined (WIN32) && defined (_M_X64)
124 unsigned _int64 off; /* workaround for missing POSIX compliance */
125#else
126 unsigned long off;
127#endif
117 unsigned int hval; 128 unsigned int hval;
118 unsigned long off;
119 int lit; 129 int lit;
120 130
121 if (!in_len || !out_len) 131 if (!in_len || !out_len)
122 return 0; 132 return 0;
123 133
… …
137 hval = NEXT (hval, ip); 147 hval = NEXT (hval, ip);
138 hslot = htab + IDX (hval); 148 hslot = htab + IDX (hval);
139 ref = *hslot; *hslot = ip; 149 ref = *hslot; *hslot = ip;
140 150
141 if (1 151 if (1
142#if INIT_HTAB && !USE_MEMCPY 152#if INIT_HTAB
143 && ref < ip /* the next test will actually take care of this, but this is faster */ 153 && ref < ip /* the next test will actually take care of this, but this is faster */
144#endif 154#endif
145 && (off = ip - ref - 1) < MAX_OFF 155 && (off = ip - ref - 1) < MAX_OFF
146 && ip + 4 < in_end 156 && ip + 4 < in_end
147 && ref > (u8 *)in_data 157 && ref > (u8 *)in_data
158 && ref[2] == ip[2]
148#if STRICT_ALIGN 159#if STRICT_ALIGN
149 && ref[0] == ip[0] 160 && (ref[1] << 8) | ref[0] == (ip[1] << 8) | ip[0]
150 && ref[1] == ip[1]
151 && ref[2] == ip[2]
152#else 161#else
153 && *(u16 *)ref == *(u16 *)ip 162 && *(u16 *)ref == *(u16 *)ip
154 && ref[2] == ip[2]
155#endif 163#endif
156 ) 164 )
157 { 165 {
158 /* match found at *ref++ */ 166 /* match found at *ref++ */
159 unsigned int len = 2; 167 unsigned int len = 2;
160 unsigned int maxlen = in_end - ip - len; 168 unsigned int maxlen = in_end - ip - len;
161 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen; 169 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
162 170
163 if (expect_false (op + 1 + 3 >= out_end)) 171 if (expect_false (op + 3 + 1 >= out_end)) /* first a faster conservative test */
172 if (op - !lit + 3 + 1 >= out_end) /* second the exact but rare test */
164 return 0; 173 return 0;
165 174
166 op [- lit - 1] = lit - 1; /* stop run */ 175 op [- lit - 1] = lit - 1; /* stop run */
167 op -= !lit; /* undo run if length is zero */ 176 op -= !lit; /* undo run if length is zero */
168 177
169 for (;;) 178 for (;;)
… …
196 while (len < maxlen && ref[len] == ip[len]); 205 while (len < maxlen && ref[len] == ip[len]);
197 206
198 break; 207 break;
199 } 208 }
200 209
201 len -= 2; 210 len -= 2; /* len is now #octets - 1 */
202 ip++; 211 ip++;
203 212
204 if (len < 7) 213 if (len < 7)
205 { 214 {
206 *op++ = (off >> 8) + (len << 5); 215 *op++ = (off >> 8) + (len << 5);
… …
210 *op++ = (off >> 8) + ( 7 << 5); 219 *op++ = (off >> 8) + ( 7 << 5);
211 *op++ = len - 7; 220 *op++ = len - 7;
212 } 221 }
213 222
214 *op++ = off; 223 *op++ = off;
224 lit = 0; op++; /* start run */
225
226 ip += len + 1;
227
228 if (expect_false (ip >= in_end - 2))
229 break;
215 230
216#if ULTRA_FAST || VERY_FAST 231#if ULTRA_FAST || VERY_FAST
217 ip += len;
218#if VERY_FAST && !ULTRA_FAST
219 --ip; 232 --ip;
233# if VERY_FAST && !ULTRA_FAST
234 --ip;
220#endif 235# endif
221 hval = FRST (ip); 236 hval = FRST (ip);
222 237
223 hval = NEXT (hval, ip); 238 hval = NEXT (hval, ip);
224 htab[IDX (hval)] = ip; 239 htab[IDX (hval)] = ip;
225 ip++; 240 ip++;
226 241
227#if VERY_FAST && !ULTRA_FAST 242# if VERY_FAST && !ULTRA_FAST
228 hval = NEXT (hval, ip); 243 hval = NEXT (hval, ip);
229 htab[IDX (hval)] = ip; 244 htab[IDX (hval)] = ip;
230 ip++; 245 ip++;
231#endif 246# endif
232#else 247#else
248 ip -= len + 1;
249
233 do 250 do
234 { 251 {
235 hval = NEXT (hval, ip); 252 hval = NEXT (hval, ip);
236 htab[IDX (hval)] = ip; 253 htab[IDX (hval)] = ip;
237 ip++; 254 ip++;
238 } 255 }
239 while (len--); 256 while (len--);
240#endif 257#endif
241 lit = 0; op++; /* start run */
242 continue;
243 } 258 }
244 259 else
260 {
245 /* one more literal byte we must copy */ 261 /* one more literal byte we must copy */
246
247 if (expect_false (op >= out_end)) 262 if (expect_false (op >= out_end))
248 return 0; 263 return 0;
249 264
250 lit++; 265 lit++; *op++ = *ip++;
266
267 if (expect_false (lit == MAX_LIT))
268 {
269 op [- lit - 1] = lit - 1; /* stop run */
270 lit = 0; op++; /* start run */
271 }
272 }
273 }
274
275 if (op + 3 > out_end) /* at most 3 bytes can be missing here */
276 return 0;
277
278 while (ip < in_end)
279 {
251 *op++ = *ip++; 280 lit++; *op++ = *ip++;
252 281
253 if (expect_false (lit == MAX_LIT)) 282 if (expect_false (lit == MAX_LIT))
254 { 283 {
255 op [- lit - 1] = lit - 1; /* stop run */ 284 op [- lit - 1] = lit - 1; /* stop run */
256 lit = 0; op++; /* start run */ 285 lit = 0; op++; /* start run */
257 } 286 }
258 } 287 }
259 288
260 if (op + lit + 2 >= out_end)
261 return 0;
262
263 while (ip < in_end)
264 {
265 lit++;
266 *op++ = *ip++;
267 }
268
269 op [- lit - 1] = lit - 1; 289 op [- lit - 1] = lit - 1; /* end run */
290 op -= !lit; /* undo run if length is zero */
270 291
271 return op - (u8 *)out_data; 292 return op - (u8 *)out_data;
272} 293}
273 294

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