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 "lzf.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_r (const void *const in_data, unsigned int in_len, 100 void *out_data, unsigned int out_len, LZF_STATE htab) 101 { 102 const u8 **hslot; 103 const u8 *ip = (const u8 *)in_data; 104 u8 *op = (u8 *)out_data; 105 const u8 *in_end = ip + in_len; 106 u8 *out_end = op + out_len; 107 const u8 *ref; 108 109 /* off requires a type wide enough to hold a general pointer difference. 110 * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only 111 * works for differences within a single object). We also assume that no 112 * no bit pattern traps. Since the only platform that is both non-POSIX 113 * and fails to support both assumptions is windows 64 bit, we make a 114 * special workaround for it. 115 */ 116 #if defined (WIN32) && defined (_M_X64) 117 unsigned _int64 off; /* workaround for missing POSIX compliance */ 118 #else 119 unsigned long off; 120 #endif 121 unsigned int hval; 122 int lit; 123 124 if (!in_len || !out_len) 125 return 0; 126 127 #if INIT_HTAB 128 memset (htab, 0, sizeof (htab)); 129 # if 0 130 for (hslot = htab; hslot < htab + HSIZE; hslot++) 131 *hslot++ = ip; 132 # endif 133 #endif 134 135 lit = 0; op++; /* start run */ 136 137 hval = FRST (ip); 138 while (ip < in_end - 2) 139 { 140 hval = NEXT (hval, ip); 141 hslot = htab + IDX (hval); 142 ref = *hslot; *hslot = ip; 143 144 if (/*CONSTCOND*/1 145 #if INIT_HTAB 146 && ref < ip /* the next test will actually take care of this, but this is faster */ 147 #endif 148 && (off = ip - ref - 1) < MAX_OFF 149 && ip + 4 < in_end 150 && ref > (u8 *)in_data 151 #if STRICT_ALIGN 152 && ref[0] == ip[0] 153 && ref[1] == ip[1] 154 && ref[2] == ip[2] 155 #else 156 && *(const u16 *)(const void *)ref == *(const u16 *)(const void *)ip 157 && ref[2] == ip[2] 158 #endif 159 ) 160 { 161 /* match found at *ref++ */ 162 unsigned int len = 2; 163 unsigned int maxlen = (unsigned)(in_end - ip) - len; 164 maxlen = maxlen > MAX_REF ? MAX_REF : maxlen; 165 166 if (expect_false (op + 3 + 1 >= out_end)) /* first a faster conservative test */ 167 if (op - !lit + 3 + 1 >= out_end) /* second the exact but rare test */ 168 return 0; 169 170 op [- lit - 1] = lit - 1; /* stop run */ 171 op -= !lit; /* undo run if length is zero */ 172 173 for (;;) 174 { 175 if (expect_true (maxlen > 16)) 176 { 177 len++; if (ref [len] != ip [len]) break; 178 len++; if (ref [len] != ip [len]) break; 179 len++; if (ref [len] != ip [len]) break; 180 len++; if (ref [len] != ip [len]) break; 181 182 len++; if (ref [len] != ip [len]) break; 183 len++; if (ref [len] != ip [len]) break; 184 len++; if (ref [len] != ip [len]) break; 185 len++; if (ref [len] != ip [len]) break; 186 187 len++; if (ref [len] != ip [len]) break; 188 len++; if (ref [len] != ip [len]) break; 189 len++; if (ref [len] != ip [len]) break; 190 len++; if (ref [len] != ip [len]) break; 191 192 len++; if (ref [len] != ip [len]) break; 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 } 197 198 do 199 len++; 200 while (len < maxlen && ref[len] == ip[len]); 201 202 break; 203 } 204 205 len -= 2; /* len is now #octets - 1 */ 206 ip++; 207 208 if (len < 7) 209 { 210 *op++ = (unsigned char)((off >> 8) + (len << 5)); 211 } 212 else 213 { 214 *op++ = (unsigned char)((off >> 8) + ( 7 << 5)); 215 *op++ = len - 7; 216 } 217 218 *op++ = (unsigned char)off; 219 lit = 0; op++; /* start run */ 220 221 ip += len + 1; 222 223 if (expect_false (ip >= in_end - 2)) 224 break; 225 226 #if ULTRA_FAST || VERY_FAST 227 --ip; 228 # if VERY_FAST && !ULTRA_FAST 229 --ip; 230 # endif 231 hval = FRST (ip); 232 233 hval = NEXT (hval, ip); 234 htab[IDX (hval)] = ip; 235 ip++; 236 237 # if VERY_FAST && !ULTRA_FAST 238 hval = NEXT (hval, ip); 239 htab[IDX (hval)] = ip; 240 ip++; 241 # endif 242 #else 243 ip -= len + 1; 244 245 do 246 { 247 hval = NEXT (hval, ip); 248 htab[IDX (hval)] = ip; 249 ip++; 250 } 251 while (len--); 252 #endif 253 } 254 else 255 { 256 /* one more literal byte we must copy */ 257 if (expect_false (op >= out_end)) 258 return 0; 259 260 lit++; *op++ = *ip++; 261 262 /*LINTED*/ 263 if (expect_false (lit == MAX_LIT)) 264 { 265 op [- lit - 1] = lit - 1; /* stop run */ 266 lit = 0; op++; /* start run */ 267 } 268 } 269 } 270 271 if (op + 3 > out_end) /* at most 3 bytes can be missing here */ 272 return 0; 273 274 while (ip < in_end) 275 { 276 lit++; *op++ = *ip++; 277 278 /*LINTED*/ 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 (unsigned)(op - (u8 *)out_data); 290 } 291