src/lzf_c.c

   1 /*
   2  * Copyright (c) 2000-2008 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  * decompression is not dependent on the hash function
  44  * the hashing 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
  93  * LLLooooo oooooooo ; backref L
  94  * 111ooooo LLLLLLLL oooooooo ; backref L+7
  95  *
  96  */
  97
  98 unsigned int
  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 **hslot;
 110   const u8 *ip = (const u8 *)in_data;
 111         u8 *op = (u8 *)out_data;
 112   const u8 *in_end  = ip + in_len;
 113         u8 *out_end = op + out_len;
 114   const u8 *ref;
 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
 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 (htab));
 136 # if 0
 137   for (hslot = htab; hslot < htab + HSIZE; hslot++)
 138     *hslot++ = ip;
 139 # endif
 140 #endif
 141
 142   lit = 0; op++; /* start run */
 143
 144   hval = FRST (ip);
 145   while (ip < in_end - 2)
 146     {
 147       hval = NEXT (hval, ip);
 148       hslot = htab + IDX (hval);
 149       ref = *hslot; *hslot = ip;
 150
 151       if (1
 152 #if INIT_HTAB
 153           && ref < ip /* the next test will actually take care of this, but this is faster */
 154 #endif
 155           && (off = ip - ref - 1) < MAX_OFF
 156           && ip + 4 < in_end
 157           && ref > (u8 *)in_data
 158 #if STRICT_ALIGN
 159           && ref[0] == ip[0]
 160           && ref[1] == ip[1]
 161           && ref[2] == ip[2]
 162 #else
 163           && *(u16 *)ref == *(u16 *)ip
 164           && ref[2] == ip[2]
 165 #endif
 166         )
 167         {
 168           /* match found at *ref++ */
 169           unsigned int len = 2;
 170           unsigned int maxlen = in_end - ip - len;
 171           maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
 172
 173           op [- lit - 1] = lit - 1; /* stop run */
 174           op -= !lit; /* undo run if length is zero */
 175
 176           if (expect_false (op + 3 + 1 >= out_end))
 177             return 0;
 178
 179           for (;;)
 180             {
 181               if (expect_true (maxlen > 16))
 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                   len++; if (ref [len] != ip [len]) break;
 199                   len++; if (ref [len] != ip [len]) break;
 200                   len++; if (ref [len] != ip [len]) break;
 201                   len++; if (ref [len] != ip [len]) break;
 202                 }
 203
 204               do
 205                 len++;
 206               while (len < maxlen && ref[len] == ip[len]);
 207
 208               break;
 209             }
 210
 211           len -= 2; /* len is now #octets - 1 */
 212           ip++;
 213
 214           if (len < 7)
 215             {
 216               *op++ = (off >> 8) + (len << 5);
 217             }
 218           else
 219             {
 220               *op++ = (off >> 8) + (  7 << 5);
 221               *op++ = len - 7;
 222             }
 223
 224           *op++ = off;
 225           lit = 0; op++; /* start run */
 226
 227           ip += len + 1;
 228
 229           if (expect_false (ip >= in_end - 2))
 230             break;
 231
 232 #if ULTRA_FAST || VERY_FAST
 233           --ip;
 234 # if VERY_FAST && !ULTRA_FAST
 235           --ip;
 236 # endif
 237           hval = FRST (ip);
 238
 239           hval = NEXT (hval, ip);
 240           htab[IDX (hval)] = ip;
 241           ip++;
 242
 243 # if VERY_FAST && !ULTRA_FAST
 244           hval = NEXT (hval, ip);
 245           htab[IDX (hval)] = ip;
 246           ip++;
 247 # endif
 248 #else
 249           ip -= len + 1;
 250
 251           do
 252             {
 253               hval = NEXT (hval, ip);
 254               htab[IDX (hval)] = ip;
 255               ip++;
 256             }
 257           while (len--);
 258 #endif
 259         }
 260       else
 261         {
 262           /* one more literal byte we must copy */
 263           if (expect_false (op >= out_end))
 264             return 0;
 265
 266           lit++; *op++ = *ip++;
 267
 268           if (expect_false (lit == MAX_LIT))
 269             {
 270               op [- lit - 1] = lit - 1; /* stop run */
 271               lit = 0; op++; /* start run */
 272             }
 273         }
 274     }
 275
 276   if (op + 3 > out_end) /* at most 3 bytes can be missing here */
 277     return 0;
 278
 279   while (ip < in_end)
 280     {
 281       lit++; *op++ = *ip++;
 282
 283       if (expect_false (lit == MAX_LIT))
 284         {
 285           op [- lit - 1] = lit - 1; /* stop run */
 286           lit = 0; op++; /* start run */
 287         }
 288     }
 289
 290   op [- lit - 1] = lit - 1; /* end run */
 291   op -= !lit; /* undo run if length is zero */
 292
 293   return op - (u8 *)out_data;
 294 }
 295