1/* 2 * Copyright (c) 2008 Apple Inc. All rights reserved. 3 * 4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. The rights granted to you under the License 10 * may not be used to create, or enable the creation or redistribution of, 11 * unlawful or unlicensed copies of an Apple operating system, or to 12 * circumvent, violate, or enable the circumvention or violation of, any 13 * terms of an Apple operating system software license agreement. 14 * 15 * Please obtain a copy of the License at 16 * http://www.opensource.apple.com/apsl/ and read it before using this file. 17 * 18 * The Original Code and all software distributed under the License are 19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 23 * Please see the License for the specific language governing rights and 24 * limitations under the License. 25 * 26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ 27 */ 28/* inftrees.c -- generate Huffman trees for efficient decoding 29 * Copyright (C) 1995-2005 Mark Adler 30 * For conditions of distribution and use, see copyright notice in zlib.h 31 */ 32 33#include "zutil.h" 34#include "inftrees.h" 35 36#define MAXBITS 15 37 38const char inflate_copyright[] = 39 " inflate 1.2.3 Copyright 1995-2005 Mark Adler "; 40/* 41 If you use the zlib library in a product, an acknowledgment is welcome 42 in the documentation of your product. If for some reason you cannot 43 include such an acknowledgment, I would appreciate that you keep this 44 copyright string in the executable of your product. 45 */ 46 47/* 48 Build a set of tables to decode the provided canonical Huffman code. 49 The code lengths are lens[0..codes-1]. The result starts at *table, 50 whose indices are 0..2^bits-1. work is a writable array of at least 51 lens shorts, which is used as a work area. type is the type of code 52 to be generated, CODES, LENS, or DISTS. On return, zero is success, 53 -1 is an invalid code, and +1 means that ENOUGH isn't enough. table 54 on return points to the next available entry's address. bits is the 55 requested root table index bits, and on return it is the actual root 56 table index bits. It will differ if the request is greater than the 57 longest code or if it is less than the shortest code. 58 */ 59int inflate_table(type, lens, codes, table, bits, work) 60codetype type; 61unsigned short FAR *lens; 62unsigned codes; 63code FAR * FAR *table; 64unsigned FAR *bits; 65unsigned short FAR *work; 66{ 67 unsigned len; /* a code's length in bits */ 68 unsigned sym; /* index of code symbols */ 69 unsigned min, max; /* minimum and maximum code lengths */ 70 unsigned root; /* number of index bits for root table */ 71 unsigned curr; /* number of index bits for current table */ 72 unsigned drop; /* code bits to drop for sub-table */ 73 int left; /* number of prefix codes available */ 74 unsigned used; /* code entries in table used */ 75 unsigned huff; /* Huffman code */ 76 unsigned incr; /* for incrementing code, index */ 77 unsigned fill; /* index for replicating entries */ 78 unsigned low; /* low bits for current root entry */ 79 unsigned mask; /* mask for low root bits */ 80 code this; /* table entry for duplication */ 81 code FAR *next; /* next available space in table */ 82 const unsigned short FAR *base; /* base value table to use */ 83 const unsigned short FAR *extra; /* extra bits table to use */ 84 int end; /* use base and extra for symbol > end */ 85 unsigned short count[MAXBITS+1]; /* number of codes of each length */ 86 unsigned short offs[MAXBITS+1]; /* offsets in table for each length */ 87 static const unsigned short lbase[31] = { /* Length codes 257..285 base */ 88 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 89 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; 90 static const unsigned short lext[31] = { /* Length codes 257..285 extra */ 91 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 92 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 201, 196}; 93 static const unsigned short dbase[32] = { /* Distance codes 0..29 base */ 94 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, 95 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, 96 8193, 12289, 16385, 24577, 0, 0}; 97 static const unsigned short dext[32] = { /* Distance codes 0..29 extra */ 98 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 99 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, 100 28, 28, 29, 29, 64, 64}; 101 102 /* 103 Process a set of code lengths to create a canonical Huffman code. The 104 code lengths are lens[0..codes-1]. Each length corresponds to the 105 symbols 0..codes-1. The Huffman code is generated by first sorting the 106 symbols by length from short to long, and retaining the symbol order 107 for codes with equal lengths. Then the code starts with all zero bits 108 for the first code of the shortest length, and the codes are integer 109 increments for the same length, and zeros are appended as the length 110 increases. For the deflate format, these bits are stored backwards 111 from their more natural integer increment ordering, and so when the 112 decoding tables are built in the large loop below, the integer codes 113 are incremented backwards. 114 115 This routine assumes, but does not check, that all of the entries in 116 lens[] are in the range 0..MAXBITS. The caller must assure this. 117 1..MAXBITS is interpreted as that code length. zero means that that 118 symbol does not occur in this code. 119 120 The codes are sorted by computing a count of codes for each length, 121 creating from that a table of starting indices for each length in the 122 sorted table, and then entering the symbols in order in the sorted 123 table. The sorted table is work[], with that space being provided by 124 the caller. 125 126 The length counts are used for other purposes as well, i.e. finding 127 the minimum and maximum length codes, determining if there are any 128 codes at all, checking for a valid set of lengths, and looking ahead 129 at length counts to determine sub-table sizes when building the 130 decoding tables. 131 */ 132 133 /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */ 134 for (len = 0; len <= MAXBITS; len++) 135 count[len] = 0; 136 for (sym = 0; sym < codes; sym++) 137 count[lens[sym]]++; 138 139 /* bound code lengths, force root to be within code lengths */ 140 root = *bits; 141 for (max = MAXBITS; max >= 1; max--) 142 if (count[max] != 0) break; 143 if (root > max) root = max; 144 if (max == 0) { /* no symbols to code at all */ 145 this.op = (unsigned char)64; /* invalid code marker */ 146 this.bits = (unsigned char)1; 147 this.val = (unsigned short)0; 148 *(*table)++ = this; /* make a table to force an error */ 149 *(*table)++ = this; 150 *bits = 1; 151 return 0; /* no symbols, but wait for decoding to report error */ 152 } 153 for (min = 1; min <= MAXBITS; min++) 154 if (count[min] != 0) break; 155 if (root < min) root = min; 156 157 /* check for an over-subscribed or incomplete set of lengths */ 158 left = 1; 159 for (len = 1; len <= MAXBITS; len++) { 160 left <<= 1; 161 left -= count[len]; 162 if (left < 0) return -1; /* over-subscribed */ 163 } 164 if (left > 0 && (type == CODES || max != 1)) 165 return -1; /* incomplete set */ 166 167 /* generate offsets into symbol table for each length for sorting */ 168 offs[1] = 0; 169 for (len = 1; len < MAXBITS; len++) 170 offs[len + 1] = offs[len] + count[len]; 171 172 /* sort symbols by length, by symbol order within each length */ 173 for (sym = 0; sym < codes; sym++) 174 if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym; 175 176 /* 177 Create and fill in decoding tables. In this loop, the table being 178 filled is at next and has curr index bits. The code being used is huff 179 with length len. That code is converted to an index by dropping drop 180 bits off of the bottom. For codes where len is less than drop + curr, 181 those top drop + curr - len bits are incremented through all values to 182 fill the table with replicated entries. 183 184 root is the number of index bits for the root table. When len exceeds 185 root, sub-tables are created pointed to by the root entry with an index 186 of the low root bits of huff. This is saved in low to check for when a 187 new sub-table should be started. drop is zero when the root table is 188 being filled, and drop is root when sub-tables are being filled. 189 190 When a new sub-table is needed, it is necessary to look ahead in the 191 code lengths to determine what size sub-table is needed. The length 192 counts are used for this, and so count[] is decremented as codes are 193 entered in the tables. 194 195 used keeps track of how many table entries have been allocated from the 196 provided *table space. It is checked when a LENS table is being made 197 against the space in *table, ENOUGH, minus the maximum space needed by 198 the worst case distance code, MAXD. This should never happen, but the 199 sufficiency of ENOUGH has not been proven exhaustively, hence the check. 200 This assumes that when type == LENS, bits == 9. 201 202 sym increments through all symbols, and the loop terminates when 203 all codes of length max, i.e. all codes, have been processed. This 204 routine permits incomplete codes, so another loop after this one fills 205 in the rest of the decoding tables with invalid code markers. 206 */ 207 208 /* set up for code type */ 209 switch (type) { 210 case CODES: 211 base = extra = work; /* dummy value--not used */ 212 end = 19; 213 break; 214 case LENS: 215 base = lbase; 216 base -= 257; 217 extra = lext; 218 extra -= 257; 219 end = 256; 220 break; 221 default: /* DISTS */ 222 base = dbase; 223 extra = dext; 224 end = -1; 225 } 226 227 /* initialize state for loop */ 228 huff = 0; /* starting code */ 229 sym = 0; /* starting code symbol */ 230 len = min; /* starting code length */ 231 next = *table; /* current table to fill in */ 232 curr = root; /* current table index bits */ 233 drop = 0; /* current bits to drop from code for index */ 234 low = (unsigned)(-1); /* trigger new sub-table when len > root */ 235 used = 1U << root; /* use root table entries */ 236 mask = used - 1; /* mask for comparing low */ 237 238 /* check available table space */ 239 if (type == LENS && used >= ENOUGH - MAXD) 240 return 1; 241 242 /* process all codes and make table entries */ 243 for (;;) { 244 /* create table entry */ 245 this.bits = (unsigned char)(len - drop); 246 if ((int)(work[sym]) < end) { 247 this.op = (unsigned char)0; 248 this.val = work[sym]; 249 } 250 else if ((int)(work[sym]) > end) { 251 this.op = (unsigned char)(extra[work[sym]]); 252 this.val = base[work[sym]]; 253 } 254 else { 255 this.op = (unsigned char)(32 + 64); /* end of block */ 256 this.val = 0; 257 } 258 259 /* replicate for those indices with low len bits equal to huff */ 260 incr = 1U << (len - drop); 261 fill = 1U << curr; 262 min = fill; /* save offset to next table */ 263 do { 264 fill -= incr; 265 next[(huff >> drop) + fill] = this; 266 } while (fill != 0); 267 268 /* backwards increment the len-bit code huff */ 269 incr = 1U << (len - 1); 270 while (huff & incr) 271 incr >>= 1; 272 if (incr != 0) { 273 huff &= incr - 1; 274 huff += incr; 275 } 276 else 277 huff = 0; 278 279 /* go to next symbol, update count, len */ 280 sym++; 281 if (--(count[len]) == 0) { 282 if (len == max) break; 283 len = lens[work[sym]]; 284 } 285 286 /* create new sub-table if needed */ 287 if (len > root && (huff & mask) != low) { 288 /* if first time, transition to sub-tables */ 289 if (drop == 0) 290 drop = root; 291 292 /* increment past last table */ 293 next += min; /* here min is 1 << curr */ 294 295 /* determine length of next table */ 296 curr = len - drop; 297 left = (int)(1 << curr); 298 while (curr + drop < max) { 299 left -= count[curr + drop]; 300 if (left <= 0) break; 301 curr++; 302 left <<= 1; 303 } 304 305 /* check for enough space */ 306 used += 1U << curr; 307 if (type == LENS && used >= ENOUGH - MAXD) 308 return 1; 309 310 /* point entry in root table to sub-table */ 311 low = huff & mask; 312 (*table)[low].op = (unsigned char)curr; 313 (*table)[low].bits = (unsigned char)root; 314 (*table)[low].val = (unsigned short)(next - *table); 315 } 316 } 317 318 /* 319 Fill in rest of table for incomplete codes. This loop is similar to the 320 loop above in incrementing huff for table indices. It is assumed that 321 len is equal to curr + drop, so there is no loop needed to increment 322 through high index bits. When the current sub-table is filled, the loop 323 drops back to the root table to fill in any remaining entries there. 324 */ 325 this.op = (unsigned char)64; /* invalid code marker */ 326 this.bits = (unsigned char)(len - drop); 327 this.val = (unsigned short)0; 328 while (huff != 0) { 329 /* when done with sub-table, drop back to root table */ 330 if (drop != 0 && (huff & mask) != low) { 331 drop = 0; 332 len = root; 333 next = *table; 334 this.bits = (unsigned char)len; 335 } 336 337 /* put invalid code marker in table */ 338 next[huff >> drop] = this; 339 340 /* backwards increment the len-bit code huff */ 341 incr = 1U << (len - 1); 342 while (huff & incr) 343 incr >>= 1; 344 if (incr != 0) { 345 huff &= incr - 1; 346 huff += incr; 347 } 348 else 349 huff = 0; 350 } 351 352 /* set return parameters */ 353 *table += used; 354 *bits = root; 355 return 0; 356} 357