inftrees.c revision 92114
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 <sys/cdefs.h> 7__FBSDID("$FreeBSD: head/lib/libz/inftrees.c 92114 2002-03-11 22:36:26Z green $"); 8 9#include "zutil.h" 10#include "inftrees.h" 11 12#if !defined(BUILDFIXED) && !defined(STDC) 13# define BUILDFIXED /* non ANSI compilers may not accept inffixed.h */ 14#endif 15 16const char inflate_copyright[] = 17 " inflate 1.1.4 Copyright 1995-2002 Mark Adler "; 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 */ 24struct internal_state {int dummy;}; /* for buggy compilers */ 25 26/* simplify the use of the inflate_huft type with some defines */ 27#define exop word.what.Exop 28#define bits word.what.Bits 29 30 31local int huft_build OF(( 32 uIntf *, /* code lengths in bits */ 33 uInt, /* number of codes */ 34 uInt, /* number of "simple" codes */ 35 const uIntf *, /* list of base values for non-simple codes */ 36 const uIntf *, /* list of extra bits for non-simple codes */ 37 inflate_huft * FAR*,/* result: starting table */ 38 uIntf *, /* maximum lookup bits (returns actual) */ 39 inflate_huft *, /* space for trees */ 40 uInt *, /* hufts used in space */ 41 uIntf * )); /* space for values */ 42 43/* Tables for deflate from PKZIP's appnote.txt. */ 44local const uInt cplens[31] = { /* Copy lengths for literal codes 257..285 */ 45 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 46 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; 47 /* see note #13 above about 258 */ 48local const uInt cplext[31] = { /* Extra bits for literal codes 257..285 */ 49 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 50 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 112, 112}; /* 112==invalid */ 51local const uInt cpdist[30] = { /* Copy offsets for distance codes 0..29 */ 52 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, 53 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, 54 8193, 12289, 16385, 24577}; 55local const uInt cpdext[30] = { /* Extra bits for distance codes */ 56 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 57 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 58 12, 12, 13, 13}; 59 60/* 61 Huffman code decoding is performed using a multi-level table lookup. 62 The fastest way to decode is to simply build a lookup table whose 63 size is determined by the longest code. However, the time it takes 64 to build this table can also be a factor if the data being decoded 65 is not very long. The most common codes are necessarily the 66 shortest codes, so those codes dominate the decoding time, and hence 67 the speed. The idea is you can have a shorter table that decodes the 68 shorter, more probable codes, and then point to subsidiary tables for 69 the longer codes. The time it costs to decode the longer codes is 70 then traded against the time it takes to make longer tables. 71 72 This results of this trade are in the variables lbits and dbits 73 below. lbits is the number of bits the first level table for literal/ 74 length codes can decode in one step, and dbits is the same thing for 75 the distance codes. Subsequent tables are also less than or equal to 76 those sizes. These values may be adjusted either when all of the 77 codes are shorter than that, in which case the longest code length in 78 bits is used, or when the shortest code is *longer* than the requested 79 table size, in which case the length of the shortest code in bits is 80 used. 81 82 There are two different values for the two tables, since they code a 83 different number of possibilities each. The literal/length table 84 codes 286 possible values, or in a flat code, a little over eight 85 bits. The distance table codes 30 possible values, or a little less 86 than five bits, flat. The optimum values for speed end up being 87 about one bit more than those, so lbits is 8+1 and dbits is 5+1. 88 The optimum values may differ though from machine to machine, and 89 possibly even between compilers. Your mileage may vary. 90 */ 91 92 93/* If BMAX needs to be larger than 16, then h and x[] should be uLong. */ 94#define BMAX 15 /* maximum bit length of any code */ 95 96local int huft_build(b, n, s, d, e, t, m, hp, hn, v) 97uIntf *b; /* code lengths in bits (all assumed <= BMAX) */ 98uInt n; /* number of codes (assumed <= 288) */ 99uInt s; /* number of simple-valued codes (0..s-1) */ 100const uIntf *d; /* list of base values for non-simple codes */ 101const uIntf *e; /* list of extra bits for non-simple codes */ 102inflate_huft * FAR *t; /* result: starting table */ 103uIntf *m; /* maximum lookup bits, returns actual */ 104inflate_huft *hp; /* space for trees */ 105uInt *hn; /* hufts used in space */ 106uIntf *v; /* working area: values in order of bit length */ 107/* Given a list of code lengths and a maximum table size, make a set of 108 tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR 109 if the given code set is incomplete (the tables are still built in this 110 case), or Z_DATA_ERROR if the input is invalid. */ 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 register uInt i; /* counter, current code */ 119 register uInt j; /* counter */ 120 register 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 register 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 register 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 /* Generate counts for each bit length */ 135 p = c; 136#define C0 *p++ = 0; 137#define C2 C0 C0 C0 C0 138#define C4 C2 C2 C2 C2 139 C4 /* clear c[]--assume BMAX+1 is 16 */ 140 p = b; i = n; 141 do { 142 c[*p++]++; /* assume all entries <= BMAX */ 143 } while (--i); 144 if (c[0] == n) /* null input--all zero length codes */ 145 { 146 *t = (inflate_huft *)Z_NULL; 147 *m = 0; 148 return Z_OK; 149 } 150 151 152 /* Find minimum and maximum length, bound *m by those */ 153 l = *m; 154 for (j = 1; j <= BMAX; j++) 155 if (c[j]) 156 break; 157 k = j; /* minimum code length */ 158 if ((uInt)l < j) 159 l = j; 160 for (i = BMAX; i; i--) 161 if (c[i]) 162 break; 163 g = i; /* maximum code length */ 164 if ((uInt)l > i) 165 l = i; 166 *m = l; 167 168 169 /* Adjust last length count to fill out codes, if needed */ 170 for (y = 1 << j; j < i; j++, y <<= 1) 171 if ((y -= c[j]) < 0) 172 return Z_DATA_ERROR; 173 if ((y -= c[i]) < 0) 174 return Z_DATA_ERROR; 175 c[i] += y; 176 177 178 /* Generate starting offsets into the value table for each length */ 179 x[1] = j = 0; 180 p = c + 1; xp = x + 2; 181 while (--i) { /* note that i == g from above */ 182 *xp++ = (j += *p++); 183 } 184 185 186 /* Make a table of values in order of bit lengths */ 187 p = b; i = 0; 188 do { 189 if ((j = *p++) != 0) 190 v[x[j]++] = i; 191 } while (++i < n); 192 n = x[g]; /* set n to length of v */ 193 194 195 /* Generate the Huffman codes and for each, make the table entries */ 196 x[0] = i = 0; /* first Huffman code is zero */ 197 p = v; /* grab values in bit order */ 198 h = -1; /* no tables yet--level -1 */ 199 w = -l; /* bits decoded == (l * h) */ 200 u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */ 201 q = (inflate_huft *)Z_NULL; /* ditto */ 202 z = 0; /* ditto */ 203 204 /* go through the bit lengths (k already is bits in shortest code) */ 205 for (; k <= g; k++) 206 { 207 a = c[k]; 208 while (a--) 209 { 210 /* here i is the Huffman code of length k bits for value *p */ 211 /* make tables up to required level */ 212 while (k > w + l) 213 { 214 h++; 215 w += l; /* previous table always l bits */ 216 217 /* compute minimum size table less than or equal to l bits */ 218 z = g - w; 219 z = z > (uInt)l ? l : z; /* table size upper limit */ 220 if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */ 221 { /* too few codes for k-w bit table */ 222 f -= a + 1; /* deduct codes from patterns left */ 223 xp = c + k; 224 if (j < z) 225 while (++j < z) /* try smaller tables up to z bits */ 226 { 227 if ((f <<= 1) <= *++xp) 228 break; /* enough codes to use up j bits */ 229 f -= *xp; /* else deduct codes from patterns */ 230 } 231 } 232 z = 1 << j; /* table entries for j-bit table */ 233 234 /* allocate new table */ 235 if (*hn + z > MANY) /* (note: doesn't matter for fixed) */ 236 return Z_DATA_ERROR; /* overflow of MANY */ 237 u[h] = q = hp + *hn; 238 *hn += z; 239 240 /* connect to last table, if there is one */ 241 if (h) 242 { 243 x[h] = i; /* save pattern for backing up */ 244 r.bits = (Byte)l; /* bits to dump before this table */ 245 r.exop = (Byte)j; /* bits in this table */ 246 j = i >> (w - l); 247 r.base = (uInt)(q - u[h-1] - j); /* offset to this table */ 248 u[h-1][j] = r; /* connect to last table */ 249 } 250 else 251 *t = q; /* first table is returned result */ 252 } 253 254 /* set up table entry in r */ 255 r.bits = (Byte)(k - w); 256 if (p >= v + n) 257 r.exop = 128 + 64; /* out of values--invalid code */ 258 else if (*p < s) 259 { 260 r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */ 261 r.base = *p++; /* simple code is just the value */ 262 } 263 else 264 { 265 r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */ 266 r.base = d[*p++ - s]; 267 } 268 269 /* fill code-like entries with r */ 270 f = 1 << (k - w); 271 for (j = i >> w; j < z; j += f) 272 q[j] = r; 273 274 /* backwards increment the k-bit code i */ 275 for (j = 1 << (k - 1); i & j; j >>= 1) 276 i ^= j; 277 i ^= j; 278 279 /* backup over finished tables */ 280 mask = (1 << w) - 1; /* needed on HP, cc -O bug */ 281 while ((i & mask) != x[h]) 282 { 283 h--; /* don't need to update q */ 284 w -= l; 285 mask = (1 << w) - 1; 286 } 287 } 288 } 289 290 291 /* Return Z_BUF_ERROR if we were given an incomplete table */ 292 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK; 293} 294 295 296int inflate_trees_bits(c, bb, tb, hp, z) 297uIntf *c; /* 19 code lengths */ 298uIntf *bb; /* bits tree desired/actual depth */ 299inflate_huft * FAR *tb; /* bits tree result */ 300inflate_huft *hp; /* space for trees */ 301z_streamp z; /* for messages */ 302{ 303 int r; 304 uInt hn = 0; /* hufts used in space */ 305 uIntf *v; /* work area for huft_build */ 306 307 if ((v = (uIntf*)ZALLOC(z, 19, sizeof(uInt))) == Z_NULL) 308 return Z_MEM_ERROR; 309 r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL, 310 tb, bb, hp, &hn, v); 311 if (r == Z_DATA_ERROR) 312 z->msg = (char*)"oversubscribed dynamic bit lengths tree"; 313 else if (r == Z_BUF_ERROR || *bb == 0) 314 { 315 z->msg = (char*)"incomplete dynamic bit lengths tree"; 316 r = Z_DATA_ERROR; 317 } 318 ZFREE(z, v); 319 return r; 320} 321 322 323int inflate_trees_dynamic(nl, nd, c, bl, bd, tl, td, hp, z) 324uInt nl; /* number of literal/length codes */ 325uInt nd; /* number of distance codes */ 326uIntf *c; /* that many (total) code lengths */ 327uIntf *bl; /* literal desired/actual bit depth */ 328uIntf *bd; /* distance desired/actual bit depth */ 329inflate_huft * FAR *tl; /* literal/length tree result */ 330inflate_huft * FAR *td; /* distance tree result */ 331inflate_huft *hp; /* space for trees */ 332z_streamp z; /* for messages */ 333{ 334 int r; 335 uInt hn = 0; /* hufts used in space */ 336 uIntf *v; /* work area for huft_build */ 337 338 /* allocate work area */ 339 if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) 340 return Z_MEM_ERROR; 341 342 /* build literal/length tree */ 343 r = huft_build(c, nl, 257, cplens, cplext, tl, bl, hp, &hn, v); 344 if (r != Z_OK || *bl == 0) 345 { 346 if (r == Z_DATA_ERROR) 347 z->msg = (char*)"oversubscribed literal/length tree"; 348 else if (r != Z_MEM_ERROR) 349 { 350 z->msg = (char*)"incomplete literal/length tree"; 351 r = Z_DATA_ERROR; 352 } 353 ZFREE(z, v); 354 return r; 355 } 356 357 /* build distance tree */ 358 r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, hp, &hn, v); 359 if (r != Z_OK || (*bd == 0 && nl > 257)) 360 { 361 if (r == Z_DATA_ERROR) 362 z->msg = (char*)"oversubscribed distance tree"; 363 else if (r == Z_BUF_ERROR) { 364#ifdef PKZIP_BUG_WORKAROUND 365 r = Z_OK; 366 } 367#else 368 z->msg = (char*)"incomplete distance tree"; 369 r = Z_DATA_ERROR; 370 } 371 else if (r != Z_MEM_ERROR) 372 { 373 z->msg = (char*)"empty distance tree with lengths"; 374 r = Z_DATA_ERROR; 375 } 376 ZFREE(z, v); 377 return r; 378#endif 379 } 380 381 /* done */ 382 ZFREE(z, v); 383 return Z_OK; 384} 385 386 387/* build fixed tables only once--keep them here */ 388#ifdef BUILDFIXED 389local int fixed_built = 0; 390#define FIXEDH 544 /* number of hufts used by fixed tables */ 391local inflate_huft fixed_mem[FIXEDH]; 392local uInt fixed_bl; 393local uInt fixed_bd; 394local inflate_huft *fixed_tl; 395local inflate_huft *fixed_td; 396#else 397#include "inffixed.h" 398#endif 399 400 401int inflate_trees_fixed(bl, bd, tl, td, z) 402uIntf *bl; /* literal desired/actual bit depth */ 403uIntf *bd; /* distance desired/actual bit depth */ 404inflate_huft * FAR *tl; /* literal/length tree result */ 405inflate_huft * FAR *td; /* distance tree result */ 406z_streamp z; /* for memory allocation */ 407{ 408#ifdef BUILDFIXED 409 /* build fixed tables if not already */ 410 if (!fixed_built) 411 { 412 int k; /* temporary variable */ 413 uInt f = 0; /* number of hufts used in fixed_mem */ 414 uIntf *c; /* length list for huft_build */ 415 uIntf *v; /* work area for huft_build */ 416 417 /* allocate memory */ 418 if ((c = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) 419 return Z_MEM_ERROR; 420 if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL) 421 { 422 ZFREE(z, c); 423 return Z_MEM_ERROR; 424 } 425 426 /* literal table */ 427 for (k = 0; k < 144; k++) 428 c[k] = 8; 429 for (; k < 256; k++) 430 c[k] = 9; 431 for (; k < 280; k++) 432 c[k] = 7; 433 for (; k < 288; k++) 434 c[k] = 8; 435 fixed_bl = 9; 436 huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl, 437 fixed_mem, &f, v); 438 439 /* distance table */ 440 for (k = 0; k < 30; k++) 441 c[k] = 5; 442 fixed_bd = 5; 443 huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd, 444 fixed_mem, &f, v); 445 446 /* done */ 447 ZFREE(z, v); 448 ZFREE(z, c); 449 fixed_built = 1; 450 } 451#endif 452 *bl = fixed_bl; 453 *bd = fixed_bd; 454 *tl = fixed_tl; 455 *td = fixed_td; 456 return Z_OK; 457} 458