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
98unsigned int
99lzf_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