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/cvs/liblzf/lzf_c.c
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Comparing liblzf/lzf_c.c (file contents):
Revision 1.23 by root, Tue Nov 13 10:48:02 2007 UTC vs.
Revision 1.39 by root, Sun May 30 05:52:57 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,
… …
87#define expect_true(expr) expect ((expr) != 0, 1) 87#define expect_true(expr) expect ((expr) != 0, 1)
88 88
89/* 89/*
90 * compressed format 90 * compressed format
91 * 91 *
92 * 000LLLLL <L+1> ; literal 92 * 000LLLLL <L+1> ; literal, L+1=1..33 octets
93 * LLLooooo oooooooo ; backref L 93 * LLLooooo oooooooo ; backref L+1=1..7 octets, o+1=1..4096 offset
94 * 111ooooo LLLLLLLL oooooooo ; backref L+7 94 * 111ooooo LLLLLLLL oooooooo ; backref L+8 octets, o+1=1..4096 offset
95 * 95 *
96 */ 96 */
97 97
98unsigned int 98unsigned int
99lzf_compress (const void *const in_data, unsigned int in_len, 99lzf_compress (const void *const in_data, unsigned int in_len,
… …
111 u8 *op = (u8 *)out_data; 111 u8 *op = (u8 *)out_data;
112 const u8 *in_end = ip + in_len; 112 const u8 *in_end = ip + in_len;
113 u8 *out_end = op + out_len; 113 u8 *out_end = op + out_len;
114 const u8 *ref; 114 const u8 *ref;
115 115
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
116 unsigned int hval; 128 unsigned int hval;
117 unsigned long off;
118 int lit; 129 int lit;
119 130
120 if (!in_len || !out_len) 131 if (!in_len || !out_len)
121 return 0; 132 return 0;
122 133
… …
136 hval = NEXT (hval, ip); 147 hval = NEXT (hval, ip);
137 hslot = htab + IDX (hval); 148 hslot = htab + IDX (hval);
138 ref = *hslot; *hslot = ip; 149 ref = *hslot; *hslot = ip;
139 150
140 if (1 151 if (1
141#if INIT_HTAB && !USE_MEMCPY 152#if INIT_HTAB
142 && 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 */
143#endif 154#endif
144 && (off = ip - ref - 1) < MAX_OFF 155 && (off = ip - ref - 1) < MAX_OFF
145 && ip + 4 < in_end 156 && ip + 4 < in_end
146 && ref > (u8 *)in_data 157 && ref > (u8 *)in_data
… …
157 /* match found at *ref++ */ 168 /* match found at *ref++ */
158 unsigned int len = 2; 169 unsigned int len = 2;
159 unsigned int maxlen = in_end - ip - len; 170 unsigned int maxlen = in_end - ip - len;
160 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen; 171 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
161 172
162 if (expect_false (op + 1 + 3 >= out_end)) 173 if (expect_false (op + 3 + 1 >= out_end)) /* first a faster conservative test */
174 if (op - !lit + 3 + 1 >= out_end) /* second the exact but rare test */
163 return 0; 175 return 0;
164 176
165 op [- lit - 1] = lit - 1; /* stop run */ 177 op [- lit - 1] = lit - 1; /* stop run */
166 op -= !lit; /* undo run if length is zero */ 178 op -= !lit; /* undo run if length is zero */
167 179
168 for (;;) 180 for (;;)
… …
195 while (len < maxlen && ref[len] == ip[len]); 207 while (len < maxlen && ref[len] == ip[len]);
196 208
197 break; 209 break;
198 } 210 }
199 211
200 len -= 2; 212 len -= 2; /* len is now #octets - 1 */
201 ip++; 213 ip++;
202 214
203 if (len < 7) 215 if (len < 7)
204 { 216 {
205 *op++ = (off >> 8) + (len << 5); 217 *op++ = (off >> 8) + (len << 5);
… …
209 *op++ = (off >> 8) + ( 7 << 5); 221 *op++ = (off >> 8) + ( 7 << 5);
210 *op++ = len - 7; 222 *op++ = len - 7;
211 } 223 }
212 224
213 *op++ = off; 225 *op++ = off;
226 lit = 0; op++; /* start run */
227
228 ip += len + 1;
229
230 if (expect_false (ip >= in_end - 2))
231 break;
214 232
215#if ULTRA_FAST || VERY_FAST 233#if ULTRA_FAST || VERY_FAST
216 ip += len;
217#if VERY_FAST && !ULTRA_FAST
218 --ip; 234 --ip;
235# if VERY_FAST && !ULTRA_FAST
236 --ip;
219#endif 237# endif
220 hval = FRST (ip); 238 hval = FRST (ip);
221 239
222 hval = NEXT (hval, ip); 240 hval = NEXT (hval, ip);
223 htab[IDX (hval)] = ip; 241 htab[IDX (hval)] = ip;
224 ip++; 242 ip++;
225 243
226#if VERY_FAST && !ULTRA_FAST 244# if VERY_FAST && !ULTRA_FAST
227 hval = NEXT (hval, ip); 245 hval = NEXT (hval, ip);
228 htab[IDX (hval)] = ip; 246 htab[IDX (hval)] = ip;
229 ip++; 247 ip++;
230#endif 248# endif
231#else 249#else
250 ip -= len + 1;
251
232 do 252 do
233 { 253 {
234 hval = NEXT (hval, ip); 254 hval = NEXT (hval, ip);
235 htab[IDX (hval)] = ip; 255 htab[IDX (hval)] = ip;
236 ip++; 256 ip++;
237 } 257 }
238 while (len--); 258 while (len--);
239#endif 259#endif
240 lit = 0; op++; /* start run */
241 continue;
242 } 260 }
243 261 else
262 {
244 /* one more literal byte we must copy */ 263 /* one more literal byte we must copy */
245
246 if (expect_false (op >= out_end)) 264 if (expect_false (op >= out_end))
247 return 0; 265 return 0;
248 266
249 lit++; 267 lit++; *op++ = *ip++;
268
269 if (expect_false (lit == MAX_LIT))
270 {
271 op [- lit - 1] = lit - 1; /* stop run */
272 lit = 0; op++; /* start run */
273 }
274 }
275 }
276
277 if (op + 3 > out_end) /* at most 3 bytes can be missing here */
278 return 0;
279
280 while (ip < in_end)
281 {
250 *op++ = *ip++; 282 lit++; *op++ = *ip++;
251 283
252 if (expect_false (lit == MAX_LIT)) 284 if (expect_false (lit == MAX_LIT))
253 { 285 {
254 op [- lit - 1] = lit - 1; /* stop run */ 286 op [- lit - 1] = lit - 1; /* stop run */
255 lit = 0; op++; /* start run */ 287 lit = 0; op++; /* start run */
256 } 288 }
257 } 289 }
258 290
259 if (op + lit + 2 >= out_end)
260 return 0;
261
262 while (ip < in_end)
263 {
264 lit++;
265 *op++ = *ip++;
266 }
267
268 op [- lit - 1] = lit - 1; 291 op [- lit - 1] = lit - 1; /* end run */
292 op -= !lit; /* undo run if length is zero */
269 293
270 return op - (u8 *)out_data; 294 return op - (u8 *)out_data;
271} 295}
272 296

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