| 1 | /* blast.c |
| 2 | * Copyright (C) 2003, 2012, 2013 Mark Adler |
| 3 | * For conditions of distribution and use, see copyright notice in blast.h |
| 4 | * version 1.3, 24 Aug 2013 |
| 5 | * |
| 6 | * blast.c decompresses data compressed by the PKWare Compression Library. |
| 7 | * This function provides functionality similar to the explode() function of |
| 8 | * the PKWare library, hence the name "blast". |
| 9 | * |
| 10 | * This decompressor is based on the excellent format description provided by |
| 11 | * Ben Rudiak-Gould in comp.compression on August 13, 2001. Interestingly, the |
| 12 | * example Ben provided in the post is incorrect. The distance 110001 should |
| 13 | * instead be 111000. When corrected, the example byte stream becomes: |
| 14 | * |
| 15 | * 00 04 82 24 25 8f 80 7f |
| 16 | * |
| 17 | * which decompresses to "AIAIAIAIAIAIA" (without the quotes). |
| 18 | */ |
| 19 | |
| 20 | /* |
| 21 | * Change history: |
| 22 | * |
| 23 | * 1.0 12 Feb 2003 - First version |
| 24 | * 1.1 16 Feb 2003 - Fixed distance check for > 4 GB uncompressed data |
| 25 | * 1.2 24 Oct 2012 - Add note about using binary mode in stdio |
| 26 | * - Fix comparisons of differently signed integers |
| 27 | * 1.3 24 Aug 2013 - Return unused input from blast() |
| 28 | * - Fix test code to correctly report unused input |
| 29 | * - Enable the provision of initial input to blast() |
| 30 | */ |
| 31 | |
| 32 | #include <stddef.h> /* for NULL */ |
| 33 | #include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ |
| 34 | #include "blast.h" /* prototype for blast() */ |
| 35 | |
| 36 | #define local static /* for local function definitions */ |
| 37 | #define MAXBITS 13 /* maximum code length */ |
| 38 | #define MAXWIN 4096 /* maximum window size */ |
| 39 | |
| 40 | /* input and output state */ |
| 41 | struct state { |
| 42 | /* input state */ |
| 43 | blast_in infun; /* input function provided by user */ |
| 44 | void *inhow; /* opaque information passed to infun() */ |
| 45 | unsigned char *in; /* next input location */ |
| 46 | unsigned left; /* available input at in */ |
| 47 | int bitbuf; /* bit buffer */ |
| 48 | int bitcnt; /* number of bits in bit buffer */ |
| 49 | |
| 50 | /* input limit error return state for bits() and decode() */ |
| 51 | jmp_buf env; |
| 52 | |
| 53 | /* output state */ |
| 54 | blast_out outfun; /* output function provided by user */ |
| 55 | void *outhow; /* opaque information passed to outfun() */ |
| 56 | unsigned next; /* index of next write location in out[] */ |
| 57 | int first; /* true to check distances (for first 4K) */ |
| 58 | unsigned char out[MAXWIN]; /* output buffer and sliding window */ |
| 59 | }; |
| 60 | |
| 61 | /* |
| 62 | * Return need bits from the input stream. This always leaves less than |
| 63 | * eight bits in the buffer. bits() works properly for need == 0. |
| 64 | * |
| 65 | * Format notes: |
| 66 | * |
| 67 | * - Bits are stored in bytes from the least significant bit to the most |
| 68 | * significant bit. Therefore bits are dropped from the bottom of the bit |
| 69 | * buffer, using shift right, and new bytes are appended to the top of the |
| 70 | * bit buffer, using shift left. |
| 71 | */ |
| 72 | local int bits(struct state *s, int need) |
| 73 | { |
| 74 | int val; /* bit accumulator */ |
| 75 | |
| 76 | /* load at least need bits into val */ |
| 77 | val = s->bitbuf; |
| 78 | while (s->bitcnt < need) { |
| 79 | if (s->left == 0) { |
| 80 | s->left = s->infun(s->inhow, &(s->in)); |
| 81 | if (s->left == 0) longjmp(s->env, 1); /* out of input */ |
| 82 | } |
| 83 | val |= (int)(*(s->in)++) << s->bitcnt; /* load eight bits */ |
| 84 | s->left--; |
| 85 | s->bitcnt += 8; |
| 86 | } |
| 87 | |
| 88 | /* drop need bits and update buffer, always zero to seven bits left */ |
| 89 | s->bitbuf = val >> need; |
| 90 | s->bitcnt -= need; |
| 91 | |
| 92 | /* return need bits, zeroing the bits above that */ |
| 93 | return val & ((1 << need) - 1); |
| 94 | } |
| 95 | |
| 96 | /* |
| 97 | * Huffman code decoding tables. count[1..MAXBITS] is the number of symbols of |
| 98 | * each length, which for a canonical code are stepped through in order. |
| 99 | * symbol[] are the symbol values in canonical order, where the number of |
| 100 | * entries is the sum of the counts in count[]. The decoding process can be |
| 101 | * seen in the function decode() below. |
| 102 | */ |
| 103 | struct huffman { |
| 104 | short *count; /* number of symbols of each length */ |
| 105 | short *symbol; /* canonically ordered symbols */ |
| 106 | }; |
| 107 | |
| 108 | /* |
| 109 | * Decode a code from the stream s using huffman table h. Return the symbol or |
| 110 | * a negative value if there is an error. If all of the lengths are zero, i.e. |
| 111 | * an empty code, or if the code is incomplete and an invalid code is received, |
| 112 | * then -9 is returned after reading MAXBITS bits. |
| 113 | * |
| 114 | * Format notes: |
| 115 | * |
| 116 | * - The codes as stored in the compressed data are bit-reversed relative to |
| 117 | * a simple integer ordering of codes of the same lengths. Hence below the |
| 118 | * bits are pulled from the compressed data one at a time and used to |
| 119 | * build the code value reversed from what is in the stream in order to |
| 120 | * permit simple integer comparisons for decoding. |
| 121 | * |
| 122 | * - The first code for the shortest length is all ones. Subsequent codes of |
| 123 | * the same length are simply integer decrements of the previous code. When |
| 124 | * moving up a length, a one bit is appended to the code. For a complete |
| 125 | * code, the last code of the longest length will be all zeros. To support |
| 126 | * this ordering, the bits pulled during decoding are inverted to apply the |
| 127 | * more "natural" ordering starting with all zeros and incrementing. |
| 128 | */ |
| 129 | local int decode(struct state *s, struct huffman *h) |
| 130 | { |
| 131 | int len; /* current number of bits in code */ |
| 132 | int code; /* len bits being decoded */ |
| 133 | int first; /* first code of length len */ |
| 134 | int count; /* number of codes of length len */ |
| 135 | int index; /* index of first code of length len in symbol table */ |
| 136 | int bitbuf; /* bits from stream */ |
| 137 | int left; /* bits left in next or left to process */ |
| 138 | short *next; /* next number of codes */ |
| 139 | |
| 140 | bitbuf = s->bitbuf; |
| 141 | left = s->bitcnt; |
| 142 | code = first = index = 0; |
| 143 | len = 1; |
| 144 | next = h->count + 1; |
| 145 | while (1) { |
| 146 | while (left--) { |
| 147 | code |= (bitbuf & 1) ^ 1; /* invert code */ |
| 148 | bitbuf >>= 1; |
| 149 | count = *next++; |
| 150 | if (code < first + count) { /* if length len, return symbol */ |
| 151 | s->bitbuf = bitbuf; |
| 152 | s->bitcnt = (s->bitcnt - len) & 7; |
| 153 | return h->symbol[index + (code - first)]; |
| 154 | } |
| 155 | index += count; /* else update for next length */ |
| 156 | first += count; |
| 157 | first <<= 1; |
| 158 | code <<= 1; |
| 159 | len++; |
| 160 | } |
| 161 | left = (MAXBITS+1) - len; |
| 162 | if (left == 0) break; |
| 163 | if (s->left == 0) { |
| 164 | s->left = s->infun(s->inhow, &(s->in)); |
| 165 | if (s->left == 0) longjmp(s->env, 1); /* out of input */ |
| 166 | } |
| 167 | bitbuf = *(s->in)++; |
| 168 | s->left--; |
| 169 | if (left > 8) left = 8; |
| 170 | } |
| 171 | return -9; /* ran out of codes */ |
| 172 | } |
| 173 | |
| 174 | /* |
| 175 | * Given a list of repeated code lengths rep[0..n-1], where each byte is a |
| 176 | * count (high four bits + 1) and a code length (low four bits), generate the |
| 177 | * list of code lengths. This compaction reduces the size of the object code. |
| 178 | * Then given the list of code lengths length[0..n-1] representing a canonical |
| 179 | * Huffman code for n symbols, construct the tables required to decode those |
| 180 | * codes. Those tables are the number of codes of each length, and the symbols |
| 181 | * sorted by length, retaining their original order within each length. The |
| 182 | * return value is zero for a complete code set, negative for an over- |
| 183 | * subscribed code set, and positive for an incomplete code set. The tables |
| 184 | * can be used if the return value is zero or positive, but they cannot be used |
| 185 | * if the return value is negative. If the return value is zero, it is not |
| 186 | * possible for decode() using that table to return an error--any stream of |
| 187 | * enough bits will resolve to a symbol. If the return value is positive, then |
| 188 | * it is possible for decode() using that table to return an error for received |
| 189 | * codes past the end of the incomplete lengths. |
| 190 | */ |
| 191 | local int construct(struct huffman *h, const unsigned char *rep, int n) |
| 192 | { |
| 193 | int symbol; /* current symbol when stepping through length[] */ |
| 194 | int len; /* current length when stepping through h->count[] */ |
| 195 | int left; /* number of possible codes left of current length */ |
| 196 | short offs[MAXBITS+1]; /* offsets in symbol table for each length */ |
| 197 | short length[256]; /* code lengths */ |
| 198 | |
| 199 | /* convert compact repeat counts into symbol bit length list */ |
| 200 | symbol = 0; |
| 201 | do { |
| 202 | len = *rep++; |
| 203 | left = (len >> 4) + 1; |
| 204 | len &= 15; |
| 205 | do { |
| 206 | length[symbol++] = len; |
| 207 | } while (--left); |
| 208 | } while (--n); |
| 209 | n = symbol; |
| 210 | |
| 211 | /* count number of codes of each length */ |
| 212 | for (len = 0; len <= MAXBITS; len++) |
| 213 | h->count[len] = 0; |
| 214 | for (symbol = 0; symbol < n; symbol++) |
| 215 | (h->count[length[symbol]])++; /* assumes lengths are within bounds */ |
| 216 | if (h->count[0] == n) /* no codes! */ |
| 217 | return 0; /* complete, but decode() will fail */ |
| 218 | |
| 219 | /* check for an over-subscribed or incomplete set of lengths */ |
| 220 | left = 1; /* one possible code of zero length */ |
| 221 | for (len = 1; len <= MAXBITS; len++) { |
| 222 | left <<= 1; /* one more bit, double codes left */ |
| 223 | left -= h->count[len]; /* deduct count from possible codes */ |
| 224 | if (left < 0) return left; /* over-subscribed--return negative */ |
| 225 | } /* left > 0 means incomplete */ |
| 226 | |
| 227 | /* generate offsets into symbol table for each length for sorting */ |
| 228 | offs[1] = 0; |
| 229 | for (len = 1; len < MAXBITS; len++) |
| 230 | offs[len + 1] = offs[len] + h->count[len]; |
| 231 | |
| 232 | /* |
| 233 | * put symbols in table sorted by length, by symbol order within each |
| 234 | * length |
| 235 | */ |
| 236 | for (symbol = 0; symbol < n; symbol++) |
| 237 | if (length[symbol] != 0) |
| 238 | h->symbol[offs[length[symbol]]++] = symbol; |
| 239 | |
| 240 | /* return zero for complete set, positive for incomplete set */ |
| 241 | return left; |
| 242 | } |
| 243 | |
| 244 | /* |
| 245 | * Decode PKWare Compression Library stream. |
| 246 | * |
| 247 | * Format notes: |
| 248 | * |
| 249 | * - First byte is 0 if literals are uncoded or 1 if they are coded. Second |
| 250 | * byte is 4, 5, or 6 for the number of extra bits in the distance code. |
| 251 | * This is the base-2 logarithm of the dictionary size minus six. |
| 252 | * |
| 253 | * - Compressed data is a combination of literals and length/distance pairs |
| 254 | * terminated by an end code. Literals are either Huffman coded or |
| 255 | * uncoded bytes. A length/distance pair is a coded length followed by a |
| 256 | * coded distance to represent a string that occurs earlier in the |
| 257 | * uncompressed data that occurs again at the current location. |
| 258 | * |
| 259 | * - A bit preceding a literal or length/distance pair indicates which comes |
| 260 | * next, 0 for literals, 1 for length/distance. |
| 261 | * |
| 262 | * - If literals are uncoded, then the next eight bits are the literal, in the |
| 263 | * normal bit order in the stream, i.e. no bit-reversal is needed. Similarly, |
| 264 | * no bit reversal is needed for either the length extra bits or the distance |
| 265 | * extra bits. |
| 266 | * |
| 267 | * - Literal bytes are simply written to the output. A length/distance pair is |
| 268 | * an instruction to copy previously uncompressed bytes to the output. The |
| 269 | * copy is from distance bytes back in the output stream, copying for length |
| 270 | * bytes. |
| 271 | * |
| 272 | * - Distances pointing before the beginning of the output data are not |
| 273 | * permitted. |
| 274 | * |
| 275 | * - Overlapped copies, where the length is greater than the distance, are |
| 276 | * allowed and common. For example, a distance of one and a length of 518 |
| 277 | * simply copies the last byte 518 times. A distance of four and a length of |
| 278 | * twelve copies the last four bytes three times. A simple forward copy |
| 279 | * ignoring whether the length is greater than the distance or not implements |
| 280 | * this correctly. |
| 281 | */ |
| 282 | local int decomp(struct state *s) |
| 283 | { |
| 284 | int lit; /* true if literals are coded */ |
| 285 | int dict; /* log2(dictionary size) - 6 */ |
| 286 | int symbol; /* decoded symbol, extra bits for distance */ |
| 287 | int len; /* length for copy */ |
| 288 | unsigned dist; /* distance for copy */ |
| 289 | int copy; /* copy counter */ |
| 290 | unsigned char *from, *to; /* copy pointers */ |
| 291 | static int virgin = 1; /* build tables once */ |
| 292 | static short litcnt[MAXBITS+1], litsym[256]; /* litcode memory */ |
| 293 | static short lencnt[MAXBITS+1], lensym[16]; /* lencode memory */ |
| 294 | static short distcnt[MAXBITS+1], distsym[64]; /* distcode memory */ |
| 295 | static struct huffman litcode = {litcnt, litsym}; /* length code */ |
| 296 | static struct huffman lencode = {lencnt, lensym}; /* length code */ |
| 297 | static struct huffman distcode = {distcnt, distsym};/* distance code */ |
| 298 | /* bit lengths of literal codes */ |
| 299 | static const unsigned char litlen[] = { |
| 300 | 11, 124, 8, 7, 28, 7, 188, 13, 76, 4, 10, 8, 12, 10, 12, 10, 8, 23, 8, |
| 301 | 9, 7, 6, 7, 8, 7, 6, 55, 8, 23, 24, 12, 11, 7, 9, 11, 12, 6, 7, 22, 5, |
| 302 | 7, 24, 6, 11, 9, 6, 7, 22, 7, 11, 38, 7, 9, 8, 25, 11, 8, 11, 9, 12, |
| 303 | 8, 12, 5, 38, 5, 38, 5, 11, 7, 5, 6, 21, 6, 10, 53, 8, 7, 24, 10, 27, |
| 304 | 44, 253, 253, 253, 252, 252, 252, 13, 12, 45, 12, 45, 12, 61, 12, 45, |
| 305 | 44, 173}; |
| 306 | /* bit lengths of length codes 0..15 */ |
| 307 | static const unsigned char lenlen[] = {2, 35, 36, 53, 38, 23}; |
| 308 | /* bit lengths of distance codes 0..63 */ |
| 309 | static const unsigned char distlen[] = {2, 20, 53, 230, 247, 151, 248}; |
| 310 | static const short base[16] = { /* base for length codes */ |
| 311 | 3, 2, 4, 5, 6, 7, 8, 9, 10, 12, 16, 24, 40, 72, 136, 264}; |
| 312 | static const char extra[16] = { /* extra bits for length codes */ |
| 313 | 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8}; |
| 314 | |
| 315 | /* set up decoding tables (once--might not be thread-safe) */ |
| 316 | if (virgin) { |
| 317 | construct(&litcode, litlen, sizeof(litlen)); |
| 318 | construct(&lencode, lenlen, sizeof(lenlen)); |
| 319 | construct(&distcode, distlen, sizeof(distlen)); |
| 320 | virgin = 0; |
| 321 | } |
| 322 | |
| 323 | /* read header */ |
| 324 | lit = bits(s, 8); |
| 325 | if (lit > 1) return -1; |
| 326 | dict = bits(s, 8); |
| 327 | if (dict < 4 || dict > 6) return -2; |
| 328 | |
| 329 | /* decode literals and length/distance pairs */ |
| 330 | do { |
| 331 | if (bits(s, 1)) { |
| 332 | /* get length */ |
| 333 | symbol = decode(s, &lencode); |
| 334 | len = base[symbol] + bits(s, extra[symbol]); |
| 335 | if (len == 519) break; /* end code */ |
| 336 | |
| 337 | /* get distance */ |
| 338 | symbol = len == 2 ? 2 : dict; |
| 339 | dist = decode(s, &distcode) << symbol; |
| 340 | dist += bits(s, symbol); |
| 341 | dist++; |
| 342 | if (s->first && dist > s->next) |
| 343 | return -3; /* distance too far back */ |
| 344 | |
| 345 | /* copy length bytes from distance bytes back */ |
| 346 | do { |
| 347 | to = s->out + s->next; |
| 348 | from = to - dist; |
| 349 | copy = MAXWIN; |
| 350 | if (s->next < dist) { |
| 351 | from += copy; |
| 352 | copy = dist; |
| 353 | } |
| 354 | copy -= s->next; |
| 355 | if (copy > len) copy = len; |
| 356 | len -= copy; |
| 357 | s->next += copy; |
| 358 | do { |
| 359 | *to++ = *from++; |
| 360 | } while (--copy); |
| 361 | if (s->next == MAXWIN) { |
| 362 | if (s->outfun(s->outhow, s->out, s->next)) return 1; |
| 363 | s->next = 0; |
| 364 | s->first = 0; |
| 365 | } |
| 366 | } while (len != 0); |
| 367 | } |
| 368 | else { |
| 369 | /* get literal and write it */ |
| 370 | symbol = lit ? decode(s, &litcode) : bits(s, 8); |
| 371 | s->out[s->next++] = symbol; |
| 372 | if (s->next == MAXWIN) { |
| 373 | if (s->outfun(s->outhow, s->out, s->next)) return 1; |
| 374 | s->next = 0; |
| 375 | s->first = 0; |
| 376 | } |
| 377 | } |
| 378 | } while (1); |
| 379 | return 0; |
| 380 | } |
| 381 | |
| 382 | /* See comments in blast.h */ |
| 383 | int blast(blast_in infun, void *inhow, blast_out outfun, void *outhow, |
| 384 | unsigned *left, unsigned char **in) |
| 385 | { |
| 386 | struct state s; /* input/output state */ |
| 387 | int err; /* return value */ |
| 388 | |
| 389 | /* initialize input state */ |
| 390 | s.infun = infun; |
| 391 | s.inhow = inhow; |
| 392 | if (left != NULL && *left) { |
| 393 | s.left = *left; |
| 394 | s.in = *in; |
| 395 | } |
| 396 | else |
| 397 | s.left = 0; |
| 398 | s.bitbuf = 0; |
| 399 | s.bitcnt = 0; |
| 400 | |
| 401 | /* initialize output state */ |
| 402 | s.outfun = outfun; |
| 403 | s.outhow = outhow; |
| 404 | s.next = 0; |
| 405 | s.first = 1; |
| 406 | |
| 407 | /* return if bits() or decode() tries to read past available input */ |
| 408 | if (setjmp(s.env) != 0) /* if came back here via longjmp(), */ |
| 409 | err = 2; /* then skip decomp(), return error */ |
| 410 | else |
| 411 | err = decomp(&s); /* decompress */ |
| 412 | |
| 413 | /* return unused input */ |
| 414 | if (left != NULL) |
| 415 | *left = s.left; |
| 416 | if (in != NULL) |
| 417 | *in = s.left ? s.in : NULL; |
| 418 | |
| 419 | /* write any leftover output and update the error code if needed */ |
| 420 | if (err != 1 && s.next && s.outfun(s.outhow, s.out, s.next) && err == 0) |
| 421 | err = 1; |
| 422 | return err; |
| 423 | } |
| 424 | |
| 425 | #ifdef TEST |
| 426 | /* Example of how to use blast() */ |
| 427 | #include <stdio.h> |
| 428 | #include <stdlib.h> |
| 429 | |
| 430 | #define CHUNK 16384 |
| 431 | |
| 432 | local unsigned inf(void *how, unsigned char **buf) |
| 433 | { |
| 434 | static unsigned char hold[CHUNK]; |
| 435 | |
| 436 | *buf = hold; |
| 437 | return fread(hold, 1, CHUNK, (FILE *)how); |
| 438 | } |
| 439 | |
| 440 | local int outf(void *how, unsigned char *buf, unsigned len) |
| 441 | { |
| 442 | return fwrite(buf, 1, len, (FILE *)how) != len; |
| 443 | } |
| 444 | |
| 445 | /* Decompress a PKWare Compression Library stream from stdin to stdout */ |
| 446 | int main(void) |
| 447 | { |
| 448 | int ret; |
| 449 | unsigned left; |
| 450 | |
| 451 | /* decompress to stdout */ |
| 452 | left = 0; |
| 453 | ret = blast(inf, stdin, outf, stdout, &left, NULL); |
| 454 | if (ret != 0) |
| 455 | fprintf(stderr, "blast error: %d\n", ret); |
| 456 | |
| 457 | /* count any leftover bytes */ |
| 458 | while (getchar() != EOF) |
| 459 | left++; |
| 460 | if (left) |
| 461 | fprintf(stderr, "blast warning: %u unused bytes of input\n", left); |
| 462 | |
| 463 | /* return blast() error code */ |
| 464 | return ret; |
| 465 | } |
| 466 | #endif |