1 /* 2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. Oracle designates this 7 * particular file as subject to the "Classpath" exception as provided 8 * by Oracle in the LICENSE file that accompanied this code. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 */ 24 25 /* inftrees.c -- generate Huffman trees for efficient decoding 26 * Copyright (C) 1995-2010 Mark Adler 27 * For conditions of distribution and use, see copyright notice in zlib.h 28 */ 29 30 #include "zutil.h" 31 #include "inftrees.h" 32 33 #define MAXBITS 15 34 35 const char inflate_copyright[] = 36 " inflate 1.2.5 Copyright 1995-2010 Mark Adler "; 37 /* 38 If you use the zlib library in a product, an acknowledgment is welcome 39 in the documentation of your product. If for some reason you cannot 40 include such an acknowledgment, I would appreciate that you keep this 41 copyright string in the executable of your product. 42 */ 43 44 /* 45 Build a set of tables to decode the provided canonical Huffman code. 46 The code lengths are lens[0..codes-1]. The result starts at *table, 47 whose indices are 0..2^bits-1. work is a writable array of at least 48 lens shorts, which is used as a work area. type is the type of code 49 to be generated, CODES, LENS, or DISTS. On return, zero is success, 50 -1 is an invalid code, and +1 means that ENOUGH isn't enough. table 51 on return points to the next available entry's address. bits is the 52 requested root table index bits, and on return it is the actual root 53 table index bits. It will differ if the request is greater than the 54 longest code or if it is less than the shortest code. 55 */ 56 int ZLIB_INTERNAL inflate_table(type, lens, codes, table, bits, work) 57 codetype type; 58 unsigned short FAR *lens; 59 unsigned codes; 60 code FAR * FAR *table; 61 unsigned FAR *bits; 62 unsigned short FAR *work; 63 { 64 unsigned len; /* a code's length in bits */ 65 unsigned sym; /* index of code symbols */ 66 unsigned min, max; /* minimum and maximum code lengths */ 67 unsigned root; /* number of index bits for root table */ 68 unsigned curr; /* number of index bits for current table */ 69 unsigned drop; /* code bits to drop for sub-table */ 70 int left; /* number of prefix codes available */ 71 unsigned used; /* code entries in table used */ 72 unsigned huff; /* Huffman code */ 73 unsigned incr; /* for incrementing code, index */ 74 unsigned fill; /* index for replicating entries */ 75 unsigned low; /* low bits for current root entry */ 76 unsigned mask; /* mask for low root bits */ 77 code here; /* table entry for duplication */ 78 code FAR *next; /* next available space in table */ 79 const unsigned short FAR *base; /* base value table to use */ 80 const unsigned short FAR *extra; /* extra bits table to use */ 81 int end; /* use base and extra for symbol > end */ 82 unsigned short count[MAXBITS+1]; /* number of codes of each length */ 83 unsigned short offs[MAXBITS+1]; /* offsets in table for each length */ 84 static const unsigned short lbase[31] = { /* Length codes 257..285 base */ 85 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 86 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; 87 static const unsigned short lext[31] = { /* Length codes 257..285 extra */ 88 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 89 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 73, 195}; 90 static const unsigned short dbase[32] = { /* Distance codes 0..29 base */ 91 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, 92 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, 93 8193, 12289, 16385, 24577, 0, 0}; 94 static const unsigned short dext[32] = { /* Distance codes 0..29 extra */ 95 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 96 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, 97 28, 28, 29, 29, 64, 64}; 98 99 /* 100 Process a set of code lengths to create a canonical Huffman code. The 101 code lengths are lens[0..codes-1]. Each length corresponds to the 102 symbols 0..codes-1. The Huffman code is generated by first sorting the 103 symbols by length from short to long, and retaining the symbol order 104 for codes with equal lengths. Then the code starts with all zero bits 105 for the first code of the shortest length, and the codes are integer 106 increments for the same length, and zeros are appended as the length 107 increases. For the deflate format, these bits are stored backwards 108 from their more natural integer increment ordering, and so when the 109 decoding tables are built in the large loop below, the integer codes 110 are incremented backwards. 111 112 This routine assumes, but does not check, that all of the entries in 113 lens[] are in the range 0..MAXBITS. The caller must assure this. 114 1..MAXBITS is interpreted as that code length. zero means that that 115 symbol does not occur in this code. 116 117 The codes are sorted by computing a count of codes for each length, 118 creating from that a table of starting indices for each length in the 119 sorted table, and then entering the symbols in order in the sorted 120 table. The sorted table is work[], with that space being provided by 121 the caller. 122 123 The length counts are used for other purposes as well, i.e. finding 124 the minimum and maximum length codes, determining if there are any 125 codes at all, checking for a valid set of lengths, and looking ahead 126 at length counts to determine sub-table sizes when building the 127 decoding tables. 128 */ 129 130 /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */ 131 for (len = 0; len <= MAXBITS; len++) 132 count[len] = 0; 133 for (sym = 0; sym < codes; sym++) 134 count[lens[sym]]++; 135 136 /* bound code lengths, force root to be within code lengths */ 137 root = *bits; 138 for (max = MAXBITS; max >= 1; max--) 139 if (count[max] != 0) break; 140 if (root > max) root = max; 141 if (max == 0) { /* no symbols to code at all */ 142 here.op = (unsigned char)64; /* invalid code marker */ 143 here.bits = (unsigned char)1; 144 here.val = (unsigned short)0; 145 *(*table)++ = here; /* make a table to force an error */ 146 *(*table)++ = here; 147 *bits = 1; 148 return 0; /* no symbols, but wait for decoding to report error */ 149 } 150 for (min = 1; min < max; min++) 151 if (count[min] != 0) break; 152 if (root < min) root = min; 153 154 /* check for an over-subscribed or incomplete set of lengths */ 155 left = 1; 156 for (len = 1; len <= MAXBITS; len++) { 157 left <<= 1; 158 left -= count[len]; 159 if (left < 0) return -1; /* over-subscribed */ 160 } 161 if (left > 0 && (type == CODES || max != 1)) 162 return -1; /* incomplete set */ 163 164 /* generate offsets into symbol table for each length for sorting */ 165 offs[1] = 0; 166 for (len = 1; len < MAXBITS; len++) 167 offs[len + 1] = offs[len] + count[len]; 168 169 /* sort symbols by length, by symbol order within each length */ 170 for (sym = 0; sym < codes; sym++) 171 if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym; 172 173 /* 174 Create and fill in decoding tables. In this loop, the table being 175 filled is at next and has curr index bits. The code being used is huff 176 with length len. That code is converted to an index by dropping drop 177 bits off of the bottom. For codes where len is less than drop + curr, 178 those top drop + curr - len bits are incremented through all values to 179 fill the table with replicated entries. 180 181 root is the number of index bits for the root table. When len exceeds 182 root, sub-tables are created pointed to by the root entry with an index 183 of the low root bits of huff. This is saved in low to check for when a 184 new sub-table should be started. drop is zero when the root table is 185 being filled, and drop is root when sub-tables are being filled. 186 187 When a new sub-table is needed, it is necessary to look ahead in the 188 code lengths to determine what size sub-table is needed. The length 189 counts are used for this, and so count[] is decremented as codes are 190 entered in the tables. 191 192 used keeps track of how many table entries have been allocated from the 193 provided *table space. It is checked for LENS and DIST tables against 194 the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in 195 the initial root table size constants. See the comments in inftrees.h 196 for more information. 197 198 sym increments through all symbols, and the loop terminates when 199 all codes of length max, i.e. all codes, have been processed. This 200 routine permits incomplete codes, so another loop after this one fills 201 in the rest of the decoding tables with invalid code markers. 202 */ 203 204 /* set up for code type */ 205 switch (type) { 206 case CODES: 207 base = extra = work; /* dummy value--not used */ 208 end = 19; 209 break; 210 case LENS: 211 base = lbase; 212 base -= 257; 213 extra = lext; 214 extra -= 257; 215 end = 256; 216 break; 217 default: /* DISTS */ 218 base = dbase; 219 extra = dext; 220 end = -1; 221 } 222 223 /* initialize state for loop */ 224 huff = 0; /* starting code */ 225 sym = 0; /* starting code symbol */ 226 len = min; /* starting code length */ 227 next = *table; /* current table to fill in */ 228 curr = root; /* current table index bits */ 229 drop = 0; /* current bits to drop from code for index */ 230 low = (unsigned)(-1); /* trigger new sub-table when len > root */ 231 used = 1U << root; /* use root table entries */ 232 mask = used - 1; /* mask for comparing low */ 233 234 /* check available table space */ 235 if ((type == LENS && used >= ENOUGH_LENS) || 236 (type == DISTS && used >= ENOUGH_DISTS)) 237 return 1; 238 239 /* process all codes and make table entries */ 240 for (;;) { 241 /* create table entry */ 242 here.bits = (unsigned char)(len - drop); 243 if ((int)(work[sym]) < end) { 244 here.op = (unsigned char)0; 245 here.val = work[sym]; 246 } 247 else if ((int)(work[sym]) > end) { 248 here.op = (unsigned char)(extra[work[sym]]); 249 here.val = base[work[sym]]; 250 } 251 else { 252 here.op = (unsigned char)(32 + 64); /* end of block */ 253 here.val = 0; 254 } 255 256 /* replicate for those indices with low len bits equal to huff */ 257 incr = 1U << (len - drop); 258 fill = 1U << curr; 259 min = fill; /* save offset to next table */ 260 do { 261 fill -= incr; 262 next[(huff >> drop) + fill] = here; 263 } while (fill != 0); 264 265 /* backwards increment the len-bit code huff */ 266 incr = 1U << (len - 1); 267 while (huff & incr) 268 incr >>= 1; 269 if (incr != 0) { 270 huff &= incr - 1; 271 huff += incr; 272 } 273 else 274 huff = 0; 275 276 /* go to next symbol, update count, len */ 277 sym++; 278 if (--(count[len]) == 0) { 279 if (len == max) break; 280 len = lens[work[sym]]; 281 } 282 283 /* create new sub-table if needed */ 284 if (len > root && (huff & mask) != low) { 285 /* if first time, transition to sub-tables */ 286 if (drop == 0) 287 drop = root; 288 289 /* increment past last table */ 290 next += min; /* here min is 1 << curr */ 291 292 /* determine length of next table */ 293 curr = len - drop; 294 left = (int)(1 << curr); 295 while (curr + drop < max) { 296 left -= count[curr + drop]; 297 if (left <= 0) break; 298 curr++; 299 left <<= 1; 300 } 301 302 /* check for enough space */ 303 used += 1U << curr; 304 if ((type == LENS && used >= ENOUGH_LENS) || 305 (type == DISTS && used >= ENOUGH_DISTS)) 306 return 1; 307 308 /* point entry in root table to sub-table */ 309 low = huff & mask; 310 (*table)[low].op = (unsigned char)curr; 311 (*table)[low].bits = (unsigned char)root; 312 (*table)[low].val = (unsigned short)(next - *table); 313 } 314 } 315 316 /* 317 Fill in rest of table for incomplete codes. This loop is similar to the 318 loop above in incrementing huff for table indices. It is assumed that 319 len is equal to curr + drop, so there is no loop needed to increment 320 through high index bits. When the current sub-table is filled, the loop 321 drops back to the root table to fill in any remaining entries there. 322 */ 323 here.op = (unsigned char)64; /* invalid code marker */ 324 here.bits = (unsigned char)(len - drop); 325 here.val = (unsigned short)0; 326 while (huff != 0) { 327 /* when done with sub-table, drop back to root table */ 328 if (drop != 0 && (huff & mask) != low) { 329 drop = 0; 330 len = root; 331 next = *table; 332 here.bits = (unsigned char)len; 333 } 334 335 /* put invalid code marker in table */ 336 next[huff >> drop] = here; 337 338 /* backwards increment the len-bit code huff */ 339 incr = 1U << (len - 1); 340 while (huff & incr) 341 incr >>= 1; 342 if (incr != 0) { 343 huff &= incr - 1; 344 huff += incr; 345 } 346 else 347 huff = 0; 348 } 349 350 /* set return parameters */ 351 *table += used; 352 *bits = root; 353 return 0; 354 }