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