ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/liblzf/lzf_c.c
(Generate patch)

Comparing liblzf/lzf_c.c (file contents):
Revision 1.29 by root, Fri Nov 30 10:35:02 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])
… …
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
… …
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
158 && ref[2] == ip[2]
147#if STRICT_ALIGN 159#if STRICT_ALIGN
148 && ref[0] == ip[0] 160 && (ref[1] << 8) | ref[0] == (ip[1] << 8) | ip[0]
149 && ref[1] == ip[1]
150 && ref[2] == ip[2]
151#else 161#else
152 && *(u16 *)ref == *(u16 *)ip 162 && *(u16 *)ref == *(u16 *)ip
153 && ref[2] == ip[2]
154#endif 163#endif
155 ) 164 )
156 { 165 {
157 /* match found at *ref++ */ 166 /* match found at *ref++ */
158 unsigned int len = 2; 167 unsigned int len = 2;
159 unsigned int maxlen = in_end - ip - len; 168 unsigned int maxlen = in_end - ip - len;
160 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen; 169 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
161 170
162 if (maxlen > 8) maxlen = 8;//D 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 */
173 return 0;
163 174
164 op [- lit - 1] = lit - 1; /* stop run */ 175 op [- lit - 1] = lit - 1; /* stop run */
165 op -= !lit; /* undo run if length is zero */ 176 op -= !lit; /* undo run if length is zero */
166
167 if (expect_false (op + 3 + 1 >= out_end))
168 return 0;
169 177
170 for (;;) 178 for (;;)
171 { 179 {
172 if (expect_true (maxlen > 16)) 180 if (expect_true (maxlen > 16))
173 { 181 {
… …
197 while (len < maxlen && ref[len] == ip[len]); 205 while (len < maxlen && ref[len] == ip[len]);
198 206
199 break; 207 break;
200 } 208 }
201 209
202 len -= 2; 210 len -= 2; /* len is now #octets - 1 */
203 ip++; 211 ip++;
204 212
205 if (len < 7) 213 if (len < 7)
206 { 214 {
207 *op++ = (off >> 8) + (len << 5); 215 *op++ = (off >> 8) + (len << 5);
… …
211 *op++ = (off >> 8) + ( 7 << 5); 219 *op++ = (off >> 8) + ( 7 << 5);
212 *op++ = len - 7; 220 *op++ = len - 7;
213 } 221 }
214 222
215 *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;
216 230
217#if ULTRA_FAST || VERY_FAST 231#if ULTRA_FAST || VERY_FAST
218 ip += len;
219#if VERY_FAST && !ULTRA_FAST
220 --ip; 232 --ip;
233# if VERY_FAST && !ULTRA_FAST
234 --ip;
221#endif 235# endif
222 hval = FRST (ip); 236 hval = FRST (ip);
223 237
224 hval = NEXT (hval, ip); 238 hval = NEXT (hval, ip);
225 htab[IDX (hval)] = ip; 239 htab[IDX (hval)] = ip;
226 ip++; 240 ip++;
227 241
228#if VERY_FAST && !ULTRA_FAST 242# if VERY_FAST && !ULTRA_FAST
229 hval = NEXT (hval, ip); 243 hval = NEXT (hval, ip);
230 htab[IDX (hval)] = ip; 244 htab[IDX (hval)] = ip;
231 ip++; 245 ip++;
232#endif 246# endif
233#else 247#else
248 ip -= len + 1;
249
234 do 250 do
235 { 251 {
236 hval = NEXT (hval, ip); 252 hval = NEXT (hval, ip);
237 htab[IDX (hval)] = ip; 253 htab[IDX (hval)] = ip;
238 ip++; 254 ip++;
239 } 255 }
240 while (len--); 256 while (len--);
241#endif 257#endif
242
243 lit = 0; op++; /* start run */
244 } 258 }
245 else 259 else
246 { 260 {
247 /* one more literal byte we must copy */ 261 /* one more literal byte we must copy */
248 if (expect_false (op >= out_end)) 262 if (expect_false (op >= out_end))

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines