1 /* inftrees.c -- generate Huffman trees for efficient decoding 2 * Copyright (C) 1995-2002 Mark Adler 3 * For conditions of distribution and use, see copyright notice in zlib.h 4 */ 5 6 #include "zutil.h" 7 #include "inftrees.h" 8 9 #if !defined(BUILDFIXED) && !defined(STDC) 10 # define BUILDFIXED /* non ANSI compilers may not accept inffixed.h */ 11 #endif 12 13 14 #if 0 15 local const char inflate_copyright[] = 16 " inflate 1.1.4 Copyright 1995-2002 Mark Adler "; 17 #endif 18 /* 19 If you use the zlib library in a product, an acknowledgment is welcome 20 in the documentation of your product. If for some reason you cannot 21 include such an acknowledgment, I would appreciate that you keep this 22 copyright string in the executable of your product. 23 */ 24 25 /* simplify the use of the inflate_huft type with some defines */ 26 #define exop word.what.Exop 27 #define bits word.what.Bits 28 29 30 local int huft_build OF(( 31 uIntf *, /* code lengths in bits */ 32 uInt, /* number of codes */ 33 uInt, /* number of "simple" codes */ 34 const uIntf *, /* list of base values for non-simple codes */ 35 const uIntf *, /* list of extra bits for non-simple codes */ 36 inflate_huft * FAR*,/* result: starting table */ 37 uIntf *, /* maximum lookup bits (returns actual) */ 38 inflate_huft *, /* space for trees */ 39 uInt *, /* hufts used in space */ 40 uIntf * )); /* space for values */ 41 42 /* Tables for deflate from PKZIP's appnote.txt. */ 43 local const uInt cplens[31] = { /* Copy lengths for literal codes 257..285 */ 44 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 45 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; 46 /* see note #13 above about 258 */ 47 local const uInt cplext[31] = { /* Extra bits for literal codes 257..285 */ 48 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 49 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 112, 112}; /* 112==invalid */ 50 local const uInt cpdist[30] = { /* Copy offsets for distance codes 0..29 */ 51 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, 52 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, 53 8193, 12289, 16385, 24577}; 54 local const uInt cpdext[30] = { /* Extra bits for distance codes */ 55 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 56 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 57 12, 12, 13, 13}; 58 59 /* 60 Huffman code decoding is performed using a multi-level table lookup. 61 The fastest way to decode is to simply build a lookup table whose 62 size is determined by the longest code. However, the time it takes 63 to build this table can also be a factor if the data being decoded 64 is not very long. The most common codes are necessarily the 65 shortest codes, so those codes dominate the decoding time, and hence 66 the speed. The idea is you can have a shorter table that decodes the 67 shorter, more probable codes, and then point to subsidiary tables for 68 the longer codes. The time it costs to decode the longer codes is 69 then traded against the time it takes to make longer tables. 70 71 This results of this trade are in the variables lbits and dbits 72 below. lbits is the number of bits the first level table for literal/ 73 length codes can decode in one step, and dbits is the same thing for 74 the distance codes. Subsequent tables are also less than or equal to 75 those sizes. These values may be adjusted either when all of the 76 codes are shorter than that, in which case the longest code length in 77 bits is used, or when the shortest code is *longer* than the requested 78 table size, in which case the length of the shortest code in bits is 79 used. 80 81 There are two different values for the two tables, since they code a 82 different number of possibilities each. The literal/length table 83 codes 286 possible values, or in a flat code, a little over eight 84 bits. The distance table codes 30 possible values, or a little less 85 than five bits, flat. The optimum values for speed end up being 86 about one bit more than those, so lbits is 8+1 and dbits is 5+1. 87 The optimum values may differ though from machine to machine, and 88 possibly even between compilers. Your mileage may vary. 89 */ 90 91 92 /* If BMAX needs to be larger than 16, then h and x[] should be uLong. */ 93 #define BMAX 15 /* maximum bit length of any code */ 94 95 local int huft_build( /* b, n, s, d, e, t, m, hp, hn, v) */ 96 uIntf *b, /* code lengths in bits (all assumed <= BMAX) */ 97 uInt n, /* number of codes (assumed <= 288) */ 98 uInt s, /* number of simple-valued codes (0..s-1) */ 99 const uIntf *d, /* list of base values for non-simple codes */ 100 const uIntf *e, /* list of extra bits for non-simple codes */ 101 inflate_huft * FAR *t, /* result: starting table */ 102 uIntf *m, /* maximum lookup bits, returns actual */ 103 inflate_huft *hp, /* space for trees */ 104 uInt *hn, /* hufts used in space */ 105 uIntf *v /* working area: values in order of bit length */ 106 /* Given a list of code lengths and a maximum table size, make a set of 107 tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR 108 if the given code set is incomplete (the tables are still built in this 109 case), or Z_DATA_ERROR if the input is invalid. */ 110 ) 111 { 112 113 uInt a; /* counter for codes of length k */ 114 uInt c[BMAX+1]; /* bit length count table */ 115 uInt f; /* i repeats in table every f entries */ 116 int g; /* maximum code length */ 117 int h; /* table level */ 118 uInt i; /* counter, current code */ 119 uInt j; /* counter */ 120 int k; /* number of bits in current code */ 121 int l; /* bits per table (returned in m) */ 122 uInt mask; /* (1 << w) - 1, to avoid cc -O bug on HP */ 123 uIntf *p; /* pointer into c[], b[], or v[] */ 124 inflate_huft *q; /* points to current table */ 125 struct inflate_huft_s r; /* table entry for structure assignment */ 126 inflate_huft *u[BMAX]; /* table stack */ 127 int w; /* bits before this table == (l * h) */ 128 uInt x[BMAX+1]; /* bit offsets, then code stack */ 129 uIntf *xp; /* pointer into x */ 130 int y; /* number of dummy codes added */ 131 uInt z; /* number of entries in current table */ 132 133 134 /* Make compiler happy */ 135 r.base = 0; 136 137 /* Generate counts for each bit length */ 138 p = c; 139 #define C0 *p++ = 0; 140 #define C2 C0 C0 C0 C0 141 #define C4 C2 C2 C2 C2 142 C4 /* clear c[]--assume BMAX+1 is 16 */ 143 p = b; i = n; 144 do { 145 c[*p++]++; /* assume all entries <= BMAX */ 146 } while (--i); 147 if (c[0] == n) /* null input--all zero length codes */ 148 { 149 *t = (inflate_huft *)Z_NULL; 150 *m = 0; 151 return Z_OK; 152 } 153 154 155 /* Find minimum and maximum length, bound *m by those */ 156 l = *m; 157 for (j = 1; j <= BMAX; j++) 158 if (c[j]) 159 break; 160 k = j; /* minimum code length */ 161 if ((uInt)l < j) 162 l = j; 163 for (i = BMAX; i; i--) 164 if (c[i]) 165 break; 166 g = i; /* maximum code length */ 167 if ((uInt)l > i) 168 l = i; 169 *m = l; 170 171 172 /* Adjust last length count to fill out codes, if needed */ 173 for (y = 1 << j; j < i; j++, y <<= 1) 174 if ((y -= c[j]) < 0) 175 return Z_DATA_ERROR; 176 if ((y -= c[i]) < 0) 177 return Z_DATA_ERROR; 178 c[i] += y; 179 180 181 /* Generate starting offsets into the value table for each length */ 182 x[1] = j = 0; 183 p = c + 1; xp = x + 2; 184 while (--i) { /* note that i == g from above */ 185 *xp++ = (j += *p++); 186 } 187 188 189 /* Make a table of values in order of bit lengths */ 190 p = b; i = 0; 191 do { 192 if ((j = *p++) != 0) 193 v[x[j]++] = i; 194 } while (++i < n); 195 n = x[g]; /* set n to length of v */ 196 197 198 /* Generate the Huffman codes and for each, make the table entries */ 199 x[0] = i = 0; /* first Huffman code is zero */ 200 p = v; /* grab values in bit order */ 201 h = -1; /* no tables yet--level -1 */ 202 w = -l; /* bits decoded == (l * h) */ 203 u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */ 204 q = (inflate_huft *)Z_NULL; /* ditto */ 205 z = 0; /* ditto */ 206 207 /* go through the bit lengths (k already is bits in shortest code) */ 208 for (; k <= g; k++) 209 { 210 a = c[k]; 211 while (a--) 212 { 213 /* here i is the Huffman code of length k bits for value *p */ 214 /* make tables up to required level */ 215 while (k > w + l) 216 { 217 h++; 218 w += l; /* previous table always l bits */ 219 220 /* compute minimum size table less than or equal to l bits */ 221 z = g - w; 222 z = z > (uInt)l ? (uInt)l : z; /* table size upper limit */ 223 if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */ 224 { /* too few codes for k-w bit table */ 225 f -= a + 1; /* deduct codes from patterns left */ 226 xp = c + k; 227 if (j < z) 228 while (++j < z) /* try smaller tables up to z bits */ 229 { 230 if ((f <<= 1) <= *++xp) 231 break; /* enough codes to use up j bits */ 232 f -= *xp; /* else deduct codes from patterns */ 233 } 234 } 235 z = 1 << j; /* table entries for j-bit table */ 236 237 /* allocate new table */ 238 if (*hn + z > MANY) /* (note: doesn't matter for fixed) */ 239 return Z_DATA_ERROR; /* overflow of MANY */ 240 u[h] = q = hp + *hn; 241 *hn += z; 242 243 /* connect to last table, if there is one */ 244 if (h) 245 { 246 x[h] = i; /* save pattern for backing up */ 247 r.bits = (Byte)l; /* bits to dump before this table */ 248 r.exop = (Byte)j; /* bits in this table */ 249 j = i >> (w - l); 250 r.base = (uInt)(q - u[h-1] - j); /* offset to this table */ 251 u[h-1][j] = r; /* connect to last table */ 252 } 253 else 254 *t = q; /* first table is returned result */ 255 } 256 257 /* set up table entry in r */ 258 r.bits = (Byte)(k - w); 259 if (p >= v + n) 260 r.exop = 128 + 64; /* out of values--invalid code */ 261 else if (*p < s) 262 { 263 r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */ 264 r.base = *p++; /* simple code is just the value */ 265 } 266 else 267 { 268 r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */ 269 r.base = d[*p++ - s]; 270 } 271 272 /* fill code-like entries with r */ 273 f = 1 << (k - w); 274 for (j = i >> w; j < z; j += f) 275 q[j] = r; 276 277 /* backwards increment the k-bit code i */ 278 for (j = 1 << (k - 1); i & j; j >>= 1) 279 i ^= j; 280 i ^= j; 281 282 /* backup over finished tables */ 283 mask = (1 << w) - 1; /* needed on HP, cc -O bug */ 284 while ((i & mask) != x[h]) 285 { 286 h--; /* don't need to update q */ 287 w -= l; 288 mask = (1 << w) - 1; 289 } 290 } 291 } 292 293 294 /* Return Z_BUF_ERROR if we were given an incomplete table */ 295 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK; 296 } 297 298 299 local int inflate_trees_bits( /* c, bb, tb, hp, z) */ 300 uIntf *c, /* 19 code lengths */ 301 uIntf *bb, /* bits tree desired/actual depth */ 302 inflate_huft * FAR *tb, /* bits tree result */ 303 inflate_huft *hp, /* space for trees */ 304 z_streamp z /* for messages */ 305 ) 306 { 307 int r; 308 uInt hn = 0; /* hufts used in space */ 309 uIntf *v; /* work area for huft_build */ 310 311 if ((v = (uIntf*)ZALLOC(z, 19, sizeof(uInt))) == Z_NULL) 312 return Z_MEM_ERROR; 313 r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL, 314 tb, bb, hp, &hn, v); 315 if (r == Z_DATA_ERROR) 316 z->msg = (char*)"oversubscribed dynamic bit lengths tree"; 317 else if (r == Z_BUF_ERROR || *bb == 0) 318 { 319 z->msg = (char*)"incomplete dynamic bit lengths tree"; 320 r = Z_DATA_ERROR; 321 } 322 ZFREE(z, v); 323 return r; 324 } 325 326 327 local int inflate_trees_dynamic( /* nl, nd, c, bl, bd, tl, td, hp, z) */ 328 uInt nl, /* number of literal/length codes */ 329 uInt nd, /* number of distance codes */ 330 uIntf *c, /* that many (total) code lengths */ 331 uIntf *bl, /* literal desired/actual bit depth */ 332 uIntf *bd, /* distance desired/actual bit depth */ 333 inflate_huft * FAR *tl, /* literal/length tree result */ 334 inflate_huft * FAR *td, /* distance tree result */ 335 inflate_huft *hp, /* space for trees */ 336 z_streamp z /* for messages */ 337 ) 338 { 339 int r; 340 uInt hn = 0; /* hufts used in space */ 341 uIntf *v; /* work area for huft_build */ 342 343 /* allocate work area */ 344 if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) 345 return Z_MEM_ERROR; 346 347 /* build literal/length tree */ 348 r = huft_build(c, nl, 257, cplens, cplext, tl, bl, hp, &hn, v); 349 if (r != Z_OK || *bl == 0) 350 { 351 if (r == Z_DATA_ERROR) 352 z->msg = (char*)"oversubscribed literal/length tree"; 353 else if (r != Z_MEM_ERROR) 354 { 355 z->msg = (char*)"incomplete literal/length tree"; 356 r = Z_DATA_ERROR; 357 } 358 ZFREE(z, v); 359 return r; 360 } 361 362 /* build distance tree */ 363 r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, hp, &hn, v); 364 if (r != Z_OK || (*bd == 0 && nl > 257)) 365 { 366 if (r == Z_DATA_ERROR) 367 z->msg = (char*)"oversubscribed distance tree"; 368 else if (r == Z_BUF_ERROR) { 369 #if 0 370 { 371 #endif 372 #ifdef PKZIP_BUG_WORKAROUND 373 r = Z_OK; 374 } 375 #else 376 z->msg = (char*)"incomplete distance tree"; 377 r = Z_DATA_ERROR; 378 } 379 else if (r != Z_MEM_ERROR) 380 { 381 z->msg = (char*)"empty distance tree with lengths"; 382 r = Z_DATA_ERROR; 383 } 384 ZFREE(z, v); 385 return r; 386 #endif 387 } 388 389 /* done */ 390 ZFREE(z, v); 391 return Z_OK; 392 } 393 394 395 /* build fixed tables only once--keep them here */ 396 #ifdef BUILDFIXED 397 local int fixed_built = 0; 398 #define FIXEDH 544 /* number of hufts used by fixed tables */ 399 local inflate_huft fixed_mem[FIXEDH]; 400 local uInt fixed_bl; 401 local uInt fixed_bd; 402 local inflate_huft *fixed_tl; 403 local inflate_huft *fixed_td; 404 #else 405 #include "inffixed.h" 406 #endif 407 408 409 local int inflate_trees_fixed( /* bl, bd, tl, td, z) */ 410 uIntf *bl, /* literal desired/actual bit depth */ 411 uIntf *bd, /* distance desired/actual bit depth */ 412 const inflate_huft * FAR *tl, /* literal/length tree result */ 413 const inflate_huft * FAR *td, /* distance tree result */ 414 z_streamp z /* for memory allocation */ 415 ) 416 { 417 #ifdef BUILDFIXED 418 /* build fixed tables if not already */ 419 if (!fixed_built) 420 { 421 int k; /* temporary variable */ 422 uInt f = 0; /* number of hufts used in fixed_mem */ 423 uIntf *c; /* length list for huft_build */ 424 uIntf *v; /* work area for huft_build */ 425 426 /* allocate memory */ 427 if ((c = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) 428 return Z_MEM_ERROR; 429 if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) 430 { 431 ZFREE(z, c); 432 return Z_MEM_ERROR; 433 } 434 435 /* literal table */ 436 for (k = 0; k < 144; k++) 437 c[k] = 8; 438 for (; k < 256; k++) 439 c[k] = 9; 440 for (; k < 280; k++) 441 c[k] = 7; 442 for (; k < 288; k++) 443 c[k] = 8; 444 fixed_bl = 9; 445 huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl, 446 fixed_mem, &f, v); 447 448 /* distance table */ 449 for (k = 0; k < 30; k++) 450 c[k] = 5; 451 fixed_bd = 5; 452 huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd, 453 fixed_mem, &f, v); 454 455 /* done */ 456 ZFREE(z, v); 457 ZFREE(z, c); 458 fixed_built = 1; 459 } 460 #else 461 FT_UNUSED(z); 462 #endif 463 *bl = fixed_bl; 464 *bd = fixed_bd; 465 *tl = fixed_tl; 466 *td = fixed_td; 467 return Z_OK; 468 } 469
