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/cvs/liblzf/lzf_c.c
Revision: 1.51
Committed: Wed May 24 18:37:18 2017 UTC (7 years, 1 month ago) by root
Content type: text/plain
Branch: MAIN
CVS Tags: HEAD
Changes since 1.50: +1 -1 lines
Log Message:
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File Contents

# Content
1 /*
2 * Copyright (c) 2000-2010,2012 Marc Alexander Lehmann <schmorp@schmorp.de>
3 *
4 * Redistribution and use in source and binary forms, with or without modifica-
5 * tion, are permitted provided that the following conditions are met:
6 *
7 * 1. Redistributions of source code must retain the above copyright notice,
8 * this list of conditions and the following disclaimer.
9 *
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
15 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
16 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
17 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
18 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
20 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
21 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
22 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
23 * OF THE POSSIBILITY OF SUCH DAMAGE.
24 *
25 * Alternatively, the contents of this file may be used under the terms of
26 * the GNU General Public License ("GPL") version 2 or any later version,
27 * in which case the provisions of the GPL are applicable instead of
28 * the above. If you wish to allow the use of your version of this file
29 * only under the terms of the GPL and not to allow others to use your
30 * version of this file under the BSD license, indicate your decision
31 * by deleting the provisions above and replace them with the notice
32 * and other provisions required by the GPL. If you do not delete the
33 * provisions above, a recipient may use your version of this file under
34 * either the BSD or the GPL.
35 */
36
37 #include "lzfP.h"
38
39 #define HSIZE (1 << (HLOG))
40
41 /*
42 * don't play with this unless you benchmark!
43 * the data format is not dependent on the hash function.
44 * the hash function might seem strange, just believe me,
45 * it works ;)
46 */
47 #ifndef FRST
48 # define FRST(p) (((p[0]) << 8) | p[1])
49 # define NEXT(v,p) (((v) << 8) | p[2])
50 # if MULTIPLICATION_IS_SLOW
51 # if ULTRA_FAST
52 # define IDX(h) ((( h >> (3*8 - HLOG)) - h ) & (HSIZE - 1))
53 # elif VERY_FAST
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
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 */
63 # define IDX(h) (((h * 0x1e35a7bdU) >> (32 - HLOG - 8)) & (HSIZE - 1))
64 # endif
65 #endif
66
67 #if 0
68 /* original lzv-like hash function, much worse and thus slower */
69 # define FRST(p) (p[0] << 5) ^ p[1]
70 # define NEXT(v,p) ((v) << 5) ^ p[2]
71 # define IDX(h) ((h) & (HSIZE - 1))
72 #endif
73
74 #if __GNUC__ >= 3
75 # define expect(expr,value) __builtin_expect ((expr),(value))
76 # define inline inline
77 #else
78 # define expect(expr,value) (expr)
79 # define inline static
80 #endif
81
82 #define expect_false(expr) expect ((expr) != 0, 0)
83 #define expect_true(expr) expect ((expr) != 0, 1)
84
85 /*
86 * compressed format
87 *
88 * 000LLLLL <L+1> ; literal, L+1=1..33 octets
89 * LLLooooo oooooooo ; backref L+1=1..7 octets, o+1=1..4096 offset
90 * 111ooooo LLLLLLLL oooooooo ; backref L+8 octets, o+1=1..4096 offset
91 *
92 */
93
94 unsigned int
95 lzf_compress (const void *const in_data, unsigned int in_len,
96 void *out_data, unsigned int out_len
97 #if LZF_STATE_ARG
98 , LZF_STATE htab
99 #endif
100 )
101 {
102 #if !LZF_STATE_ARG
103 LZF_STATE htab;
104 #endif
105 const u8 *ip = (const u8 *)in_data;
106 u8 *op = (u8 *)out_data;
107 const u8 *in_end = ip + in_len;
108 u8 *out_end = op + out_len;
109 const u8 *ref;
110
111 /* off requires a type wide enough to hold a general pointer difference.
112 * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only
113 * works for differences within a single object). We also assume that
114 * no bit pattern traps. Since the only platform that is both non-POSIX
115 * and fails to support both assumptions is windows 64 bit, we make a
116 * special workaround for it.
117 */
118 #if defined (_WIN32) && defined (_M_X64)
119 /* workaround for missing POSIX compliance */
120 #if __GNUC__
121 unsigned long long off;
122 #else
123 unsigned __int64 off;
124 #endif
125 #else
126 unsigned long off;
127 #endif
128 unsigned int hval;
129 int lit;
130
131 if (!in_len || !out_len)
132 return 0;
133
134 #if INIT_HTAB
135 memset (htab, 0, sizeof (LZF_STATE));
136 #endif
137
138 lit = 0; op++; /* start run */
139
140 hval = FRST (ip);
141 while (ip < in_end - 2)
142 {
143 LZF_HSLOT *hslot;
144
145 hval = NEXT (hval, ip);
146 hslot = htab + IDX (hval);
147 ref = *hslot + LZF_HSLOT_BIAS; *hslot = ip - LZF_HSLOT_BIAS;
148
149 if (1
150 #if INIT_HTAB
151 && ref < ip /* the next test will actually take care of this, but this is faster */
152 #endif
153 && (off = ip - ref - 1) < LZF_MAX_OFF
154 && ref > (u8 *)in_data
155 && ref[2] == ip[2]
156 #if STRICT_ALIGN
157 && ((ref[1] << 8) | ref[0]) == ((ip[1] << 8) | ip[0])
158 #else
159 && *(u16 *)ref == *(u16 *)ip
160 #endif
161 )
162 {
163 /* match found at *ref++ */
164 unsigned int len = 2;
165 unsigned int maxlen = in_end - ip - len;
166 maxlen = maxlen > LZF_MAX_REF ? LZF_MAX_REF : maxlen;
167
168 if (expect_false (op + 3 + 1 >= out_end)) /* first a faster conservative test */
169 if (op - !lit + 3 + 1 >= out_end) /* second the exact but rare test */
170 return 0;
171
172 op [- lit - 1] = lit - 1; /* stop run */
173 op -= !lit; /* undo run if length is zero */
174
175 for (;;)
176 {
177 if (expect_true (maxlen > 16))
178 {
179 len++; if (ref [len] != ip [len]) break;
180 len++; if (ref [len] != ip [len]) break;
181 len++; if (ref [len] != ip [len]) break;
182 len++; if (ref [len] != ip [len]) break;
183
184 len++; if (ref [len] != ip [len]) break;
185 len++; if (ref [len] != ip [len]) break;
186 len++; if (ref [len] != ip [len]) break;
187 len++; if (ref [len] != ip [len]) break;
188
189 len++; if (ref [len] != ip [len]) break;
190 len++; if (ref [len] != ip [len]) break;
191 len++; if (ref [len] != ip [len]) break;
192 len++; if (ref [len] != ip [len]) break;
193
194 len++; if (ref [len] != ip [len]) break;
195 len++; if (ref [len] != ip [len]) break;
196 len++; if (ref [len] != ip [len]) break;
197 len++; if (ref [len] != ip [len]) break;
198 }
199
200 do
201 len++;
202 while (len < maxlen && ref[len] == ip[len]);
203
204 break;
205 }
206
207 len -= 2; /* len is now #octets - 1 */
208 ip++;
209
210 if (len < 7)
211 {
212 *op++ = (off >> 8) + (len << 5);
213 }
214 else
215 {
216 *op++ = (off >> 8) + ( 7 << 5);
217 *op++ = len - 7;
218 }
219
220 *op++ = off;
221
222 lit = 0; op++; /* start run */
223
224 ip += len + 1;
225
226 if (expect_false (ip >= in_end - 2))
227 break;
228
229 #if ULTRA_FAST || VERY_FAST
230 --ip;
231 # if VERY_FAST && !ULTRA_FAST
232 --ip;
233 # endif
234 hval = FRST (ip);
235
236 hval = NEXT (hval, ip);
237 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
238 ip++;
239
240 # if VERY_FAST && !ULTRA_FAST
241 hval = NEXT (hval, ip);
242 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
243 ip++;
244 # endif
245 #else
246 ip -= len + 1;
247
248 do
249 {
250 hval = NEXT (hval, ip);
251 htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
252 ip++;
253 }
254 while (len--);
255 #endif
256 }
257 else
258 {
259 /* one more literal byte we must copy */
260 if (expect_false (op >= out_end))
261 return 0;
262
263 lit++; *op++ = *ip++;
264
265 if (expect_false (lit == LZF_MAX_LIT))
266 {
267 op [- lit - 1] = lit - 1; /* stop run */
268 lit = 0; op++; /* start run */
269 }
270 }
271 }
272
273 if (op + 3 > out_end) /* at most 3 bytes can be missing here */
274 return 0;
275
276 while (ip < in_end)
277 {
278 lit++; *op++ = *ip++;
279
280 if (expect_false (lit == LZF_MAX_LIT))
281 {
282 op [- lit - 1] = lit - 1; /* stop run */
283 lit = 0; op++; /* start run */
284 }
285 }
286
287 op [- lit - 1] = lit - 1; /* end run */
288 op -= !lit; /* undo run if length is zero */
289
290 return op - (u8 *)out_data;
291 }
292