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1 /*
2  * Copyright (c) 2000-2010 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 ULTRA_FAST
51 #  define IDX(h) ((( h             >> (3*8 - HLOG)) - h  ) & (HSIZE - 1))
52 # elif VERY_FAST
53 #  define IDX(h) ((( h             >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
54 # else
55 #  define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
56 # endif
57 #endif
58 /*
59  * IDX works because it is very similar to a multiplicative hash, e.g.
60  * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
61  * the latter is also quite fast on newer CPUs, and compresses similarly.
62  *
63  * the next one is also quite good, albeit slow ;)
64  * (int)(cos(h & 0xffffff) * 1e6)
65  */
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 #define        MAX_LIT        (1 <<  5)
75 #define        MAX_OFF        (1 << 13)
76 #define        MAX_REF        ((1 << 8) + (1 << 3))
77 
78 #if __GNUC__ >= 3
79 # define expect(expr,value)         __builtin_expect ((expr),(value))
80 # define inline                     inline
81 #else
82 # define expect(expr,value)         (expr)
83 # define inline                     static
84 #endif
85 
86 #define expect_false(expr) expect ((expr) != 0, 0)
87 #define expect_true(expr)  expect ((expr) != 0, 1)
88 
89 /*
90  * compressed format
91  *
92  * 000LLLLL <L+1>    ; literal, L+1=1..33 octets
93  * LLLooooo oooooooo ; backref L+1=1..7 octets, o+1=1..4096 offset
94  * 111ooooo LLLLLLLL oooooooo ; backref L+8 octets, o+1=1..4096 offset
95  *
96  */
97 
98 unsigned int
lzf_compress(const void * const in_data,unsigned int in_len,void * out_data,unsigned int out_len,LZF_STATE htab)99 lzf_compress (const void *const in_data, unsigned int in_len,
100 	      void *out_data, unsigned int out_len
101 #if LZF_STATE_ARG
102               , LZF_STATE htab
103 #endif
104               )
105 {
106 #if !LZF_STATE_ARG
107   LZF_STATE htab;
108 #endif
109   const u8 *ip = (const u8 *)in_data;
110         u8 *op = (u8 *)out_data;
111   const u8 *in_end  = ip + in_len;
112         u8 *out_end = op + out_len;
113   const u8 *ref;
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
127   unsigned int hval;
128   int lit;
129 
130   if (!in_len || !out_len)
131     return 0;
132 
133 #if INIT_HTAB
134   memset (htab, 0, sizeof (htab));
135 #endif
136 
137   lit = 0; op++; /* start run */
138 
139   hval = FRST (ip);
140   while (ip < in_end - 2)
141     {
142       LZF_HSLOT *hslot;
143 
144       hval = NEXT (hval, ip);
145       hslot = htab + IDX (hval);
146       ref = *hslot + LZF_HSLOT_BIAS; *hslot = ip - LZF_HSLOT_BIAS;
147 
148       if (1
149 #if INIT_HTAB
150           && ref < ip /* the next test will actually take care of this, but this is faster */
151 #endif
152           && (off = ip - ref - 1) < MAX_OFF
153           && ref > (u8 *)in_data
154           && ref[2] == ip[2]
155 #if STRICT_ALIGN
156           && ((ref[1] << 8) | ref[0]) == ((ip[1] << 8) | ip[0])
157 #else
158           && *(u16 *)ref == *(u16 *)ip
159 #endif
160         )
161         {
162           /* match found at *ref++ */
163           unsigned int len = 2;
164           unsigned int maxlen = in_end - ip - len;
165           maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
166 
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 */
169               return 0;
170 
171           op [- lit - 1] = lit - 1; /* stop run */
172           op -= !lit; /* undo run if length is zero */
173 
174           for (;;)
175             {
176               if (expect_true (maxlen > 16))
177                 {
178                   len++; if (ref [len] != ip [len]) break;
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 
183                   len++; if (ref [len] != ip [len]) break;
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 
188                   len++; if (ref [len] != ip [len]) break;
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 
193                   len++; if (ref [len] != ip [len]) break;
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                 }
198 
199               do
200                 len++;
201               while (len < maxlen && ref[len] == ip[len]);
202 
203               break;
204             }
205 
206           len -= 2; /* len is now #octets - 1 */
207           ip++;
208 
209           if (len < 7)
210             {
211               *op++ = (off >> 8) + (len << 5);
212             }
213           else
214             {
215               *op++ = (off >> 8) + (  7 << 5);
216               *op++ = len - 7;
217             }
218 
219           *op++ = off;
220 
221           lit = 0; op++; /* start run */
222 
223           ip += len + 1;
224 
225           if (expect_false (ip >= in_end - 2))
226             break;
227 
228 #if ULTRA_FAST || VERY_FAST
229           --ip;
230 # if VERY_FAST && !ULTRA_FAST
231           --ip;
232 # endif
233           hval = FRST (ip);
234 
235           hval = NEXT (hval, ip);
236           htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
237           ip++;
238 
239 # if VERY_FAST && !ULTRA_FAST
240           hval = NEXT (hval, ip);
241           htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
242           ip++;
243 # endif
244 #else
245           ip -= len + 1;
246 
247           do
248             {
249               hval = NEXT (hval, ip);
250               htab[IDX (hval)] = ip - LZF_HSLOT_BIAS;
251               ip++;
252             }
253           while (len--);
254 #endif
255         }
256       else
257         {
258           /* one more literal byte we must copy */
259           if (expect_false (op >= out_end))
260             return 0;
261 
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     {
277       lit++; *op++ = *ip++;
278 
279       if (expect_false (lit == MAX_LIT))
280         {
281           op [- lit - 1] = lit - 1; /* stop run */
282           lit = 0; op++; /* start run */
283         }
284     }
285 
286   op [- lit - 1] = lit - 1; /* end run */
287   op -= !lit; /* undo run if length is zero */
288 
289   return op - (u8 *)out_data;
290 }
291 
292