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/cvs/liblzf/lzf_c.c
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Comparing liblzf/lzf_c.c (file contents):
Revision 1.24 by root, Tue Nov 13 10:56:57 2007 UTC vs.
Revision 1.44 by root, Tue Jun 1 09:11:33 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,
… …
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
115 /* off requires a type wide enough to hold a general pointer difference.
116 * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only
117 * works for differences within a single object). We also assume that no
118 * no bit pattern traps. Since the only platform that is both non-POSIX
119 * and fails to support both assumptions is windows 64 bit, we make a
120 * special workaround for it.
121 */
122#if defined (WIN32) && defined (_M_X64)
123 unsigned _int64 off; /* workaround for missing POSIX compliance */
124#else
125 unsigned long off;
126#endif
116 unsigned int hval; 127 unsigned int hval;
117 unsigned long off;
118 int lit; 128 int lit;
119 129
120 if (!in_len || !out_len) 130 if (!in_len || !out_len)
121 return 0; 131 return 0;
122 132
123#if INIT_HTAB 133#if INIT_HTAB
124 memset (htab, 0, sizeof (htab)); 134 memset (htab, 0, sizeof (htab));
125# if 0
126 for (hslot = htab; hslot < htab + HSIZE; hslot++)
127 *hslot++ = ip;
128# endif
129#endif 135#endif
130 136
131 lit = 0; op++; /* start run */ 137 lit = 0; op++; /* start run */
132 138
133 hval = FRST (ip); 139 hval = FRST (ip);
134 while (ip < in_end - 2) 140 while (ip < in_end - 2)
135 { 141 {
142 LZF_HSLOT *hslot;
143
136 hval = NEXT (hval, ip); 144 hval = NEXT (hval, ip);
137 hslot = htab + IDX (hval); 145 hslot = htab + IDX (hval);
138 ref = *hslot; *hslot = ip; 146 ref = *hslot + LZF_HSLOT_BIAS; *hslot = ip - LZF_HSLOT_BIAS;
139 147
140 if (1 148 if (1
141#if INIT_HTAB && !USE_MEMCPY 149#if INIT_HTAB
142 && 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 */
143#endif 151#endif
144 && (off = ip - ref - 1) < MAX_OFF 152 && (off = ip - ref - 1) < MAX_OFF
145 && ip + 4 < in_end
146 && ref > (u8 *)in_data 153 && ref > (u8 *)in_data
154 && ref[2] == ip[2]
147#if STRICT_ALIGN 155#if STRICT_ALIGN
148 && ref[0] == ip[0] 156 && ((ref[1] << 8) | ref[0]) == ((ip[1] << 8) | ip[0])
149 && ref[1] == ip[1]
150 && ref[2] == ip[2]
151#else 157#else
152 && *(u16 *)ref == *(u16 *)ip 158 && *(u16 *)ref == *(u16 *)ip
153 && ref[2] == ip[2]
154#endif 159#endif
155 ) 160 )
156 { 161 {
157 /* match found at *ref++ */ 162 /* match found at *ref++ */
158 unsigned int len = 2; 163 unsigned int len = 2;
159 unsigned int maxlen = in_end - ip - len; 164 unsigned int maxlen = in_end - ip - len;
160 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen; 165 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
161 166
162 if (expect_false (op + 1 + 3 >= out_end)) 167 if (expect_false (op + 3 + 1 >= out_end)) /* first a faster conservative test */
168 if (op - !lit + 3 + 1 >= out_end) /* second the exact but rare test */
163 return 0; 169 return 0;
164 170
165 op [- lit - 1] = lit - 1; /* stop run */ 171 op [- lit - 1] = lit - 1; /* stop run */
166 op -= !lit; /* undo run if length is zero */ 172 op -= !lit; /* undo run if length is zero */
167 173
168 for (;;) 174 for (;;)
… …
195 while (len < maxlen && ref[len] == ip[len]); 201 while (len < maxlen && ref[len] == ip[len]);
196 202
197 break; 203 break;
198 } 204 }
199 205
200 len -= 2; 206 len -= 2; /* len is now #octets - 1 */
201 ip++; 207 ip++;
202 208
203 if (len < 7) 209 if (len < 7)
204 { 210 {
205 *op++ = (off >> 8) + (len << 5); 211 *op++ = (off >> 8) + (len << 5);
… …
210 *op++ = len - 7; 216 *op++ = len - 7;
211 } 217 }
212 218
213 *op++ = off; 219 *op++ = off;
214 220
221 lit = 0; op++; /* start run */
222
223 ip += len + 1;
224
225 if (expect_false (ip >= in_end - 2))
226 break;
227
215#if ULTRA_FAST || VERY_FAST 228#if ULTRA_FAST || VERY_FAST
216 ip += len;
217#if VERY_FAST && !ULTRA_FAST
218 --ip; 229 --ip;
230# if VERY_FAST && !ULTRA_FAST
231 --ip;
219#endif 232# endif
220 hval = FRST (ip); 233 hval = FRST (ip);
221 234
222 hval = NEXT (hval, ip); 235 hval = NEXT (hval, ip);
223 htab[IDX (hval)] = ip; 236 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
224 ip++; 237 ip++;
225 238
226#if VERY_FAST && !ULTRA_FAST 239# if VERY_FAST && !ULTRA_FAST
227 hval = NEXT (hval, ip); 240 hval = NEXT (hval, ip);
228 htab[IDX (hval)] = ip; 241 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
229 ip++; 242 ip++;
230#endif 243# endif
231#else 244#else
245 ip -= len + 1;
246
232 do 247 do
233 { 248 {
234 hval = NEXT (hval, ip); 249 hval = NEXT (hval, ip);
235 htab[IDX (hval)] = ip; 250 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
236 ip++; 251 ip++;
237 } 252 }
238 while (len--); 253 while (len--);
239#endif 254#endif
240 lit = 0; op++; /* start run */
241 continue;
242 } 255 }
243 256 else
257 {
244 /* one more literal byte we must copy */ 258 /* one more literal byte we must copy */
245
246 if (expect_false (op >= out_end)) 259 if (expect_false (op >= out_end))
247 return 0; 260 return 0;
248 261
249 lit++; 262 lit++; *op++ = *ip++;
263
264 if (expect_false (lit == MAX_LIT))
265 {
266 op [- lit - 1] = lit - 1; /* stop run */
267 lit = 0; op++; /* start run */
268 }
269 }
270 }
271
272 if (op + 3 > out_end) /* at most 3 bytes can be missing here */
273 return 0;
274
275 while (ip < in_end)
276 {
250 *op++ = *ip++; 277 lit++; *op++ = *ip++;
251 278
252 if (expect_false (lit == MAX_LIT)) 279 if (expect_false (lit == MAX_LIT))
253 { 280 {
254 op [- lit - 1] = lit - 1; /* stop run */ 281 op [- lit - 1] = lit - 1; /* stop run */
255 lit = 0; op++; /* start run */ 282 lit = 0; op++; /* start run */
256 } 283 }
257 } 284 }
258 285
259 if (op + 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; /* end run */ 286 op [- lit - 1] = lit - 1; /* end run */
269 op -= !lit; /* undo run if length is zero */ 287 op -= !lit; /* undo run if length is zero */
270 288
271 return op - (u8 *)out_data; 289 return op - (u8 *)out_data;
272} 290}

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