| 1 | /* |
| 2 | * puff.c |
| 3 | * Copyright (C) 2002-2013 Mark Adler |
| 4 | * For conditions of distribution and use, see copyright notice in puff.h |
| 5 | * version 2.3, 21 Jan 2013 |
| 6 | * |
| 7 | * puff.c is a simple inflate written to be an unambiguous way to specify the |
| 8 | * deflate format. It is not written for speed but rather simplicity. As a |
| 9 | * side benefit, this code might actually be useful when small code is more |
| 10 | * important than speed, such as bootstrap applications. For typical deflate |
| 11 | * data, zlib's inflate() is about four times as fast as puff(). zlib's |
| 12 | * inflate compiles to around 20K on my machine, whereas puff.c compiles to |
| 13 | * around 4K on my machine (a PowerPC using GNU cc). If the faster decode() |
| 14 | * function here is used, then puff() is only twice as slow as zlib's |
| 15 | * inflate(). |
| 16 | * |
| 17 | * All dynamically allocated memory comes from the stack. The stack required |
| 18 | * is less than 2K bytes. This code is compatible with 16-bit int's and |
| 19 | * assumes that long's are at least 32 bits. puff.c uses the short data type, |
| 20 | * assumed to be 16 bits, for arrays in order to conserve memory. The code |
| 21 | * works whether integers are stored big endian or little endian. |
| 22 | * |
| 23 | * In the comments below are "Format notes" that describe the inflate process |
| 24 | * and document some of the less obvious aspects of the format. This source |
| 25 | * code is meant to supplement RFC 1951, which formally describes the deflate |
| 26 | * format: |
| 27 | * |
| 28 | * http://www.zlib.org/rfc-deflate.html |
| 29 | */ |
| 30 | |
| 31 | /* |
| 32 | * Change history: |
| 33 | * |
| 34 | * 1.0 10 Feb 2002 - First version |
| 35 | * 1.1 17 Feb 2002 - Clarifications of some comments and notes |
| 36 | * - Update puff() dest and source pointers on negative |
| 37 | * errors to facilitate debugging deflators |
| 38 | * - Remove longest from struct huffman -- not needed |
| 39 | * - Simplify offs[] index in construct() |
| 40 | * - Add input size and checking, using longjmp() to |
| 41 | * maintain easy readability |
| 42 | * - Use short data type for large arrays |
| 43 | * - Use pointers instead of long to specify source and |
| 44 | * destination sizes to avoid arbitrary 4 GB limits |
| 45 | * 1.2 17 Mar 2002 - Add faster version of decode(), doubles speed (!), |
| 46 | * but leave simple version for readabilty |
| 47 | * - Make sure invalid distances detected if pointers |
| 48 | * are 16 bits |
| 49 | * - Fix fixed codes table error |
| 50 | * - Provide a scanning mode for determining size of |
| 51 | * uncompressed data |
| 52 | * 1.3 20 Mar 2002 - Go back to lengths for puff() parameters [Gailly] |
| 53 | * - Add a puff.h file for the interface |
| 54 | * - Add braces in puff() for else do [Gailly] |
| 55 | * - Use indexes instead of pointers for readability |
| 56 | * 1.4 31 Mar 2002 - Simplify construct() code set check |
| 57 | * - Fix some comments |
| 58 | * - Add FIXLCODES #define |
| 59 | * 1.5 6 Apr 2002 - Minor comment fixes |
| 60 | * 1.6 7 Aug 2002 - Minor format changes |
| 61 | * 1.7 3 Mar 2003 - Added test code for distribution |
| 62 | * - Added zlib-like license |
| 63 | * 1.8 9 Jan 2004 - Added some comments on no distance codes case |
| 64 | * 1.9 21 Feb 2008 - Fix bug on 16-bit integer architectures [Pohland] |
| 65 | * - Catch missing end-of-block symbol error |
| 66 | * 2.0 25 Jul 2008 - Add #define to permit distance too far back |
| 67 | * - Add option in TEST code for puff to write the data |
| 68 | * - Add option in TEST code to skip input bytes |
| 69 | * - Allow TEST code to read from piped stdin |
| 70 | * 2.1 4 Apr 2010 - Avoid variable initialization for happier compilers |
| 71 | * - Avoid unsigned comparisons for even happier compilers |
| 72 | * 2.2 25 Apr 2010 - Fix bug in variable initializations [Oberhumer] |
| 73 | * - Add const where appropriate [Oberhumer] |
| 74 | * - Split if's and ?'s for coverage testing |
| 75 | * - Break out test code to separate file |
| 76 | * - Move NIL to puff.h |
| 77 | * - Allow incomplete code only if single code length is 1 |
| 78 | * - Add full code coverage test to Makefile |
| 79 | * 2.3 21 Jan 2013 - Check for invalid code length codes in dynamic blocks |
| 80 | */ |
| 81 | |
| 82 | #include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ |
| 83 | #include "puff.h" /* prototype for puff() */ |
| 84 | |
| 85 | #define local static /* for local function definitions */ |
| 86 | |
| 87 | /* |
| 88 | * Maximums for allocations and loops. It is not useful to change these -- |
| 89 | * they are fixed by the deflate format. |
| 90 | */ |
| 91 | #define MAXBITS 15 /* maximum bits in a code */ |
| 92 | #define MAXLCODES 286 /* maximum number of literal/length codes */ |
| 93 | #define MAXDCODES 30 /* maximum number of distance codes */ |
| 94 | #define MAXCODES (MAXLCODES+MAXDCODES) /* maximum codes lengths to read */ |
| 95 | #define FIXLCODES 288 /* number of fixed literal/length codes */ |
| 96 | |
| 97 | /* input and output state */ |
| 98 | struct state { |
| 99 | /* output state */ |
| 100 | unsigned char *out; /* output buffer */ |
| 101 | unsigned long outlen; /* available space at out */ |
| 102 | unsigned long outcnt; /* bytes written to out so far */ |
| 103 | |
| 104 | /* input state */ |
| 105 | const unsigned char *in; /* input buffer */ |
| 106 | unsigned long inlen; /* available input at in */ |
| 107 | unsigned long incnt; /* bytes read so far */ |
| 108 | int bitbuf; /* bit buffer */ |
| 109 | int bitcnt; /* number of bits in bit buffer */ |
| 110 | |
| 111 | /* input limit error return state for bits() and decode() */ |
| 112 | jmp_buf env; |
| 113 | }; |
| 114 | |
| 115 | /* |
| 116 | * Return need bits from the input stream. This always leaves less than |
| 117 | * eight bits in the buffer. bits() works properly for need == 0. |
| 118 | * |
| 119 | * Format notes: |
| 120 | * |
| 121 | * - Bits are stored in bytes from the least significant bit to the most |
| 122 | * significant bit. Therefore bits are dropped from the bottom of the bit |
| 123 | * buffer, using shift right, and new bytes are appended to the top of the |
| 124 | * bit buffer, using shift left. |
| 125 | */ |
| 126 | local int bits(struct state *s, int need) |
| 127 | { |
| 128 | long val; /* bit accumulator (can use up to 20 bits) */ |
| 129 | |
| 130 | /* load at least need bits into val */ |
| 131 | val = s->bitbuf; |
| 132 | while (s->bitcnt < need) { |
| 133 | if (s->incnt == s->inlen) |
| 134 | longjmp(s->env, 1); /* out of input */ |
| 135 | val |= (long)(s->in[s->incnt++]) << s->bitcnt; /* load eight bits */ |
| 136 | s->bitcnt += 8; |
| 137 | } |
| 138 | |
| 139 | /* drop need bits and update buffer, always zero to seven bits left */ |
| 140 | s->bitbuf = (int)(val >> need); |
| 141 | s->bitcnt -= need; |
| 142 | |
| 143 | /* return need bits, zeroing the bits above that */ |
| 144 | return (int)(val & ((1L << need) - 1)); |
| 145 | } |
| 146 | |
| 147 | /* |
| 148 | * Process a stored block. |
| 149 | * |
| 150 | * Format notes: |
| 151 | * |
| 152 | * - After the two-bit stored block type (00), the stored block length and |
| 153 | * stored bytes are byte-aligned for fast copying. Therefore any leftover |
| 154 | * bits in the byte that has the last bit of the type, as many as seven, are |
| 155 | * discarded. The value of the discarded bits are not defined and should not |
| 156 | * be checked against any expectation. |
| 157 | * |
| 158 | * - The second inverted copy of the stored block length does not have to be |
| 159 | * checked, but it's probably a good idea to do so anyway. |
| 160 | * |
| 161 | * - A stored block can have zero length. This is sometimes used to byte-align |
| 162 | * subsets of the compressed data for random access or partial recovery. |
| 163 | */ |
| 164 | local int stored(struct state *s) |
| 165 | { |
| 166 | unsigned len; /* length of stored block */ |
| 167 | |
| 168 | /* discard leftover bits from current byte (assumes s->bitcnt < 8) */ |
| 169 | s->bitbuf = 0; |
| 170 | s->bitcnt = 0; |
| 171 | |
| 172 | /* get length and check against its one's complement */ |
| 173 | if (s->incnt + 4 > s->inlen) |
| 174 | return 2; /* not enough input */ |
| 175 | len = s->in[s->incnt++]; |
| 176 | len |= s->in[s->incnt++] << 8; |
| 177 | if (s->in[s->incnt++] != (~len & 0xff) || |
| 178 | s->in[s->incnt++] != ((~len >> 8) & 0xff)) |
| 179 | return -2; /* didn't match complement! */ |
| 180 | |
| 181 | /* copy len bytes from in to out */ |
| 182 | if (s->incnt + len > s->inlen) |
| 183 | return 2; /* not enough input */ |
| 184 | if (s->out != NIL) { |
| 185 | if (s->outcnt + len > s->outlen) |
| 186 | return 1; /* not enough output space */ |
| 187 | while (len--) |
| 188 | s->out[s->outcnt++] = s->in[s->incnt++]; |
| 189 | } |
| 190 | else { /* just scanning */ |
| 191 | s->outcnt += len; |
| 192 | s->incnt += len; |
| 193 | } |
| 194 | |
| 195 | /* done with a valid stored block */ |
| 196 | return 0; |
| 197 | } |
| 198 | |
| 199 | /* |
| 200 | * Huffman code decoding tables. count[1..MAXBITS] is the number of symbols of |
| 201 | * each length, which for a canonical code are stepped through in order. |
| 202 | * symbol[] are the symbol values in canonical order, where the number of |
| 203 | * entries is the sum of the counts in count[]. The decoding process can be |
| 204 | * seen in the function decode() below. |
| 205 | */ |
| 206 | struct huffman { |
| 207 | short *count; /* number of symbols of each length */ |
| 208 | short *symbol; /* canonically ordered symbols */ |
| 209 | }; |
| 210 | |
| 211 | /* |
| 212 | * Decode a code from the stream s using huffman table h. Return the symbol or |
| 213 | * a negative value if there is an error. If all of the lengths are zero, i.e. |
| 214 | * an empty code, or if the code is incomplete and an invalid code is received, |
| 215 | * then -10 is returned after reading MAXBITS bits. |
| 216 | * |
| 217 | * Format notes: |
| 218 | * |
| 219 | * - The codes as stored in the compressed data are bit-reversed relative to |
| 220 | * a simple integer ordering of codes of the same lengths. Hence below the |
| 221 | * bits are pulled from the compressed data one at a time and used to |
| 222 | * build the code value reversed from what is in the stream in order to |
| 223 | * permit simple integer comparisons for decoding. A table-based decoding |
| 224 | * scheme (as used in zlib) does not need to do this reversal. |
| 225 | * |
| 226 | * - The first code for the shortest length is all zeros. Subsequent codes of |
| 227 | * the same length are simply integer increments of the previous code. When |
| 228 | * moving up a length, a zero bit is appended to the code. For a complete |
| 229 | * code, the last code of the longest length will be all ones. |
| 230 | * |
| 231 | * - Incomplete codes are handled by this decoder, since they are permitted |
| 232 | * in the deflate format. See the format notes for fixed() and dynamic(). |
| 233 | */ |
| 234 | #ifdef SLOW |
| 235 | local int decode(struct state *s, const struct huffman *h) |
| 236 | { |
| 237 | int len; /* current number of bits in code */ |
| 238 | int code; /* len bits being decoded */ |
| 239 | int first; /* first code of length len */ |
| 240 | int count; /* number of codes of length len */ |
| 241 | int index; /* index of first code of length len in symbol table */ |
| 242 | |
| 243 | code = first = index = 0; |
| 244 | for (len = 1; len <= MAXBITS; len++) { |
| 245 | code |= bits(s, 1); /* get next bit */ |
| 246 | count = h->count[len]; |
| 247 | if (code - count < first) /* if length len, return symbol */ |
| 248 | return h->symbol[index + (code - first)]; |
| 249 | index += count; /* else update for next length */ |
| 250 | first += count; |
| 251 | first <<= 1; |
| 252 | code <<= 1; |
| 253 | } |
| 254 | return -10; /* ran out of codes */ |
| 255 | } |
| 256 | |
| 257 | /* |
| 258 | * A faster version of decode() for real applications of this code. It's not |
| 259 | * as readable, but it makes puff() twice as fast. And it only makes the code |
| 260 | * a few percent larger. |
| 261 | */ |
| 262 | #else /* !SLOW */ |
| 263 | local int decode(struct state *s, const struct huffman *h) |
| 264 | { |
| 265 | int len; /* current number of bits in code */ |
| 266 | int code; /* len bits being decoded */ |
| 267 | int first; /* first code of length len */ |
| 268 | int count; /* number of codes of length len */ |
| 269 | int index; /* index of first code of length len in symbol table */ |
| 270 | int bitbuf; /* bits from stream */ |
| 271 | int left; /* bits left in next or left to process */ |
| 272 | short *next; /* next number of codes */ |
| 273 | |
| 274 | bitbuf = s->bitbuf; |
| 275 | left = s->bitcnt; |
| 276 | code = first = index = 0; |
| 277 | len = 1; |
| 278 | next = h->count + 1; |
| 279 | while (1) { |
| 280 | while (left--) { |
| 281 | code |= bitbuf & 1; |
| 282 | bitbuf >>= 1; |
| 283 | count = *next++; |
| 284 | if (code - count < first) { /* if length len, return symbol */ |
| 285 | s->bitbuf = bitbuf; |
| 286 | s->bitcnt = (s->bitcnt - len) & 7; |
| 287 | return h->symbol[index + (code - first)]; |
| 288 | } |
| 289 | index += count; /* else update for next length */ |
| 290 | first += count; |
| 291 | first <<= 1; |
| 292 | code <<= 1; |
| 293 | len++; |
| 294 | } |
| 295 | left = (MAXBITS+1) - len; |
| 296 | if (left == 0) |
| 297 | break; |
| 298 | if (s->incnt == s->inlen) |
| 299 | longjmp(s->env, 1); /* out of input */ |
| 300 | bitbuf = s->in[s->incnt++]; |
| 301 | if (left > 8) |
| 302 | left = 8; |
| 303 | } |
| 304 | return -10; /* ran out of codes */ |
| 305 | } |
| 306 | #endif /* SLOW */ |
| 307 | |
| 308 | /* |
| 309 | * Given the list of code lengths length[0..n-1] representing a canonical |
| 310 | * Huffman code for n symbols, construct the tables required to decode those |
| 311 | * codes. Those tables are the number of codes of each length, and the symbols |
| 312 | * sorted by length, retaining their original order within each length. The |
| 313 | * return value is zero for a complete code set, negative for an over- |
| 314 | * subscribed code set, and positive for an incomplete code set. The tables |
| 315 | * can be used if the return value is zero or positive, but they cannot be used |
| 316 | * if the return value is negative. If the return value is zero, it is not |
| 317 | * possible for decode() using that table to return an error--any stream of |
| 318 | * enough bits will resolve to a symbol. If the return value is positive, then |
| 319 | * it is possible for decode() using that table to return an error for received |
| 320 | * codes past the end of the incomplete lengths. |
| 321 | * |
| 322 | * Not used by decode(), but used for error checking, h->count[0] is the number |
| 323 | * of the n symbols not in the code. So n - h->count[0] is the number of |
| 324 | * codes. This is useful for checking for incomplete codes that have more than |
| 325 | * one symbol, which is an error in a dynamic block. |
| 326 | * |
| 327 | * Assumption: for all i in 0..n-1, 0 <= length[i] <= MAXBITS |
| 328 | * This is assured by the construction of the length arrays in dynamic() and |
| 329 | * fixed() and is not verified by construct(). |
| 330 | * |
| 331 | * Format notes: |
| 332 | * |
| 333 | * - Permitted and expected examples of incomplete codes are one of the fixed |
| 334 | * codes and any code with a single symbol which in deflate is coded as one |
| 335 | * bit instead of zero bits. See the format notes for fixed() and dynamic(). |
| 336 | * |
| 337 | * - Within a given code length, the symbols are kept in ascending order for |
| 338 | * the code bits definition. |
| 339 | */ |
| 340 | local int construct(struct huffman *h, const short *length, int n) |
| 341 | { |
| 342 | int symbol; /* current symbol when stepping through length[] */ |
| 343 | int len; /* current length when stepping through h->count[] */ |
| 344 | int left; /* number of possible codes left of current length */ |
| 345 | short offs[MAXBITS+1]; /* offsets in symbol table for each length */ |
| 346 | |
| 347 | /* count number of codes of each length */ |
| 348 | for (len = 0; len <= MAXBITS; len++) |
| 349 | h->count[len] = 0; |
| 350 | for (symbol = 0; symbol < n; symbol++) |
| 351 | (h->count[length[symbol]])++; /* assumes lengths are within bounds */ |
| 352 | if (h->count[0] == n) /* no codes! */ |
| 353 | return 0; /* complete, but decode() will fail */ |
| 354 | |
| 355 | /* check for an over-subscribed or incomplete set of lengths */ |
| 356 | left = 1; /* one possible code of zero length */ |
| 357 | for (len = 1; len <= MAXBITS; len++) { |
| 358 | left <<= 1; /* one more bit, double codes left */ |
| 359 | left -= h->count[len]; /* deduct count from possible codes */ |
| 360 | if (left < 0) |
| 361 | return left; /* over-subscribed--return negative */ |
| 362 | } /* left > 0 means incomplete */ |
| 363 | |
| 364 | /* generate offsets into symbol table for each length for sorting */ |
| 365 | offs[1] = 0; |
| 366 | for (len = 1; len < MAXBITS; len++) |
| 367 | offs[len + 1] = offs[len] + h->count[len]; |
| 368 | |
| 369 | /* |
| 370 | * put symbols in table sorted by length, by symbol order within each |
| 371 | * length |
| 372 | */ |
| 373 | for (symbol = 0; symbol < n; symbol++) |
| 374 | if (length[symbol] != 0) |
| 375 | h->symbol[offs[length[symbol]]++] = symbol; |
| 376 | |
| 377 | /* return zero for complete set, positive for incomplete set */ |
| 378 | return left; |
| 379 | } |
| 380 | |
| 381 | /* |
| 382 | * Decode literal/length and distance codes until an end-of-block code. |
| 383 | * |
| 384 | * Format notes: |
| 385 | * |
| 386 | * - Compressed data that is after the block type if fixed or after the code |
| 387 | * description if dynamic is a combination of literals and length/distance |
| 388 | * pairs terminated by and end-of-block code. Literals are simply Huffman |
| 389 | * coded bytes. A length/distance pair is a coded length followed by a |
| 390 | * coded distance to represent a string that occurs earlier in the |
| 391 | * uncompressed data that occurs again at the current location. |
| 392 | * |
| 393 | * - Literals, lengths, and the end-of-block code are combined into a single |
| 394 | * code of up to 286 symbols. They are 256 literals (0..255), 29 length |
| 395 | * symbols (257..285), and the end-of-block symbol (256). |
| 396 | * |
| 397 | * - There are 256 possible lengths (3..258), and so 29 symbols are not enough |
| 398 | * to represent all of those. Lengths 3..10 and 258 are in fact represented |
| 399 | * by just a length symbol. Lengths 11..257 are represented as a symbol and |
| 400 | * some number of extra bits that are added as an integer to the base length |
| 401 | * of the length symbol. The number of extra bits is determined by the base |
| 402 | * length symbol. These are in the static arrays below, lens[] for the base |
| 403 | * lengths and lext[] for the corresponding number of extra bits. |
| 404 | * |
| 405 | * - The reason that 258 gets its own symbol is that the longest length is used |
| 406 | * often in highly redundant files. Note that 258 can also be coded as the |
| 407 | * base value 227 plus the maximum extra value of 31. While a good deflate |
| 408 | * should never do this, it is not an error, and should be decoded properly. |
| 409 | * |
| 410 | * - If a length is decoded, including its extra bits if any, then it is |
| 411 | * followed a distance code. There are up to 30 distance symbols. Again |
| 412 | * there are many more possible distances (1..32768), so extra bits are added |
| 413 | * to a base value represented by the symbol. The distances 1..4 get their |
| 414 | * own symbol, but the rest require extra bits. The base distances and |
| 415 | * corresponding number of extra bits are below in the static arrays dist[] |
| 416 | * and dext[]. |
| 417 | * |
| 418 | * - Literal bytes are simply written to the output. A length/distance pair is |
| 419 | * an instruction to copy previously uncompressed bytes to the output. The |
| 420 | * copy is from distance bytes back in the output stream, copying for length |
| 421 | * bytes. |
| 422 | * |
| 423 | * - Distances pointing before the beginning of the output data are not |
| 424 | * permitted. |
| 425 | * |
| 426 | * - Overlapped copies, where the length is greater than the distance, are |
| 427 | * allowed and common. For example, a distance of one and a length of 258 |
| 428 | * simply copies the last byte 258 times. A distance of four and a length of |
| 429 | * twelve copies the last four bytes three times. A simple forward copy |
| 430 | * ignoring whether the length is greater than the distance or not implements |
| 431 | * this correctly. You should not use memcpy() since its behavior is not |
| 432 | * defined for overlapped arrays. You should not use memmove() or bcopy() |
| 433 | * since though their behavior -is- defined for overlapping arrays, it is |
| 434 | * defined to do the wrong thing in this case. |
| 435 | */ |
| 436 | local int codes(struct state *s, |
| 437 | const struct huffman *lencode, |
| 438 | const struct huffman *distcode) |
| 439 | { |
| 440 | int symbol; /* decoded symbol */ |
| 441 | int len; /* length for copy */ |
| 442 | unsigned dist; /* distance for copy */ |
| 443 | static const short lens[29] = { /* Size base for length codes 257..285 */ |
| 444 | 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, |
| 445 | 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258}; |
| 446 | static const short lext[29] = { /* Extra bits for length codes 257..285 */ |
| 447 | 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, |
| 448 | 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0}; |
| 449 | static const short dists[30] = { /* Offset base for distance codes 0..29 */ |
| 450 | 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, |
| 451 | 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, |
| 452 | 8193, 12289, 16385, 24577}; |
| 453 | static const short dext[30] = { /* Extra bits for distance codes 0..29 */ |
| 454 | 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, |
| 455 | 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, |
| 456 | 12, 12, 13, 13}; |
| 457 | |
| 458 | /* decode literals and length/distance pairs */ |
| 459 | do { |
| 460 | symbol = decode(s, lencode); |
| 461 | if (symbol < 0) |
| 462 | return symbol; /* invalid symbol */ |
| 463 | if (symbol < 256) { /* literal: symbol is the byte */ |
| 464 | /* write out the literal */ |
| 465 | if (s->out != NIL) { |
| 466 | if (s->outcnt == s->outlen) |
| 467 | return 1; |
| 468 | s->out[s->outcnt] = symbol; |
| 469 | } |
| 470 | s->outcnt++; |
| 471 | } |
| 472 | else if (symbol > 256) { /* length */ |
| 473 | /* get and compute length */ |
| 474 | symbol -= 257; |
| 475 | if (symbol >= 29) |
| 476 | return -10; /* invalid fixed code */ |
| 477 | len = lens[symbol] + bits(s, lext[symbol]); |
| 478 | |
| 479 | /* get and check distance */ |
| 480 | symbol = decode(s, distcode); |
| 481 | if (symbol < 0) |
| 482 | return symbol; /* invalid symbol */ |
| 483 | dist = dists[symbol] + bits(s, dext[symbol]); |
| 484 | #ifndef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR |
| 485 | if (dist > s->outcnt) |
| 486 | return -11; /* distance too far back */ |
| 487 | #endif |
| 488 | |
| 489 | /* copy length bytes from distance bytes back */ |
| 490 | if (s->out != NIL) { |
| 491 | if (s->outcnt + len > s->outlen) |
| 492 | return 1; |
| 493 | while (len--) { |
| 494 | s->out[s->outcnt] = |
| 495 | #ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR |
| 496 | dist > s->outcnt ? |
| 497 | 0 : |
| 498 | #endif |
| 499 | s->out[s->outcnt - dist]; |
| 500 | s->outcnt++; |
| 501 | } |
| 502 | } |
| 503 | else |
| 504 | s->outcnt += len; |
| 505 | } |
| 506 | } while (symbol != 256); /* end of block symbol */ |
| 507 | |
| 508 | /* done with a valid fixed or dynamic block */ |
| 509 | return 0; |
| 510 | } |
| 511 | |
| 512 | /* |
| 513 | * Process a fixed codes block. |
| 514 | * |
| 515 | * Format notes: |
| 516 | * |
| 517 | * - This block type can be useful for compressing small amounts of data for |
| 518 | * which the size of the code descriptions in a dynamic block exceeds the |
| 519 | * benefit of custom codes for that block. For fixed codes, no bits are |
| 520 | * spent on code descriptions. Instead the code lengths for literal/length |
| 521 | * codes and distance codes are fixed. The specific lengths for each symbol |
| 522 | * can be seen in the "for" loops below. |
| 523 | * |
| 524 | * - The literal/length code is complete, but has two symbols that are invalid |
| 525 | * and should result in an error if received. This cannot be implemented |
| 526 | * simply as an incomplete code since those two symbols are in the "middle" |
| 527 | * of the code. They are eight bits long and the longest literal/length\ |
| 528 | * code is nine bits. Therefore the code must be constructed with those |
| 529 | * symbols, and the invalid symbols must be detected after decoding. |
| 530 | * |
| 531 | * - The fixed distance codes also have two invalid symbols that should result |
| 532 | * in an error if received. Since all of the distance codes are the same |
| 533 | * length, this can be implemented as an incomplete code. Then the invalid |
| 534 | * codes are detected while decoding. |
| 535 | */ |
| 536 | local int fixed(struct state *s) |
| 537 | { |
| 538 | static int virgin = 1; |
| 539 | static short lencnt[MAXBITS+1], lensym[FIXLCODES]; |
| 540 | static short distcnt[MAXBITS+1], distsym[MAXDCODES]; |
| 541 | static struct huffman lencode, distcode; |
| 542 | |
| 543 | /* build fixed huffman tables if first call (may not be thread safe) */ |
| 544 | if (virgin) { |
| 545 | int symbol; |
| 546 | short lengths[FIXLCODES]; |
| 547 | |
| 548 | /* construct lencode and distcode */ |
| 549 | lencode.count = lencnt; |
| 550 | lencode.symbol = lensym; |
| 551 | distcode.count = distcnt; |
| 552 | distcode.symbol = distsym; |
| 553 | |
| 554 | /* literal/length table */ |
| 555 | for (symbol = 0; symbol < 144; symbol++) |
| 556 | lengths[symbol] = 8; |
| 557 | for (; symbol < 256; symbol++) |
| 558 | lengths[symbol] = 9; |
| 559 | for (; symbol < 280; symbol++) |
| 560 | lengths[symbol] = 7; |
| 561 | for (; symbol < FIXLCODES; symbol++) |
| 562 | lengths[symbol] = 8; |
| 563 | construct(&lencode, lengths, FIXLCODES); |
| 564 | |
| 565 | /* distance table */ |
| 566 | for (symbol = 0; symbol < MAXDCODES; symbol++) |
| 567 | lengths[symbol] = 5; |
| 568 | construct(&distcode, lengths, MAXDCODES); |
| 569 | |
| 570 | /* do this just once */ |
| 571 | virgin = 0; |
| 572 | } |
| 573 | |
| 574 | /* decode data until end-of-block code */ |
| 575 | return codes(s, &lencode, &distcode); |
| 576 | } |
| 577 | |
| 578 | /* |
| 579 | * Process a dynamic codes block. |
| 580 | * |
| 581 | * Format notes: |
| 582 | * |
| 583 | * - A dynamic block starts with a description of the literal/length and |
| 584 | * distance codes for that block. New dynamic blocks allow the compressor to |
| 585 | * rapidly adapt to changing data with new codes optimized for that data. |
| 586 | * |
| 587 | * - The codes used by the deflate format are "canonical", which means that |
| 588 | * the actual bits of the codes are generated in an unambiguous way simply |
| 589 | * from the number of bits in each code. Therefore the code descriptions |
| 590 | * are simply a list of code lengths for each symbol. |
| 591 | * |
| 592 | * - The code lengths are stored in order for the symbols, so lengths are |
| 593 | * provided for each of the literal/length symbols, and for each of the |
| 594 | * distance symbols. |
| 595 | * |
| 596 | * - If a symbol is not used in the block, this is represented by a zero as |
| 597 | * as the code length. This does not mean a zero-length code, but rather |
| 598 | * that no code should be created for this symbol. There is no way in the |
| 599 | * deflate format to represent a zero-length code. |
| 600 | * |
| 601 | * - The maximum number of bits in a code is 15, so the possible lengths for |
| 602 | * any code are 1..15. |
| 603 | * |
| 604 | * - The fact that a length of zero is not permitted for a code has an |
| 605 | * interesting consequence. Normally if only one symbol is used for a given |
| 606 | * code, then in fact that code could be represented with zero bits. However |
| 607 | * in deflate, that code has to be at least one bit. So for example, if |
| 608 | * only a single distance base symbol appears in a block, then it will be |
| 609 | * represented by a single code of length one, in particular one 0 bit. This |
| 610 | * is an incomplete code, since if a 1 bit is received, it has no meaning, |
| 611 | * and should result in an error. So incomplete distance codes of one symbol |
| 612 | * should be permitted, and the receipt of invalid codes should be handled. |
| 613 | * |
| 614 | * - It is also possible to have a single literal/length code, but that code |
| 615 | * must be the end-of-block code, since every dynamic block has one. This |
| 616 | * is not the most efficient way to create an empty block (an empty fixed |
| 617 | * block is fewer bits), but it is allowed by the format. So incomplete |
| 618 | * literal/length codes of one symbol should also be permitted. |
| 619 | * |
| 620 | * - If there are only literal codes and no lengths, then there are no distance |
| 621 | * codes. This is represented by one distance code with zero bits. |
| 622 | * |
| 623 | * - The list of up to 286 length/literal lengths and up to 30 distance lengths |
| 624 | * are themselves compressed using Huffman codes and run-length encoding. In |
| 625 | * the list of code lengths, a 0 symbol means no code, a 1..15 symbol means |
| 626 | * that length, and the symbols 16, 17, and 18 are run-length instructions. |
| 627 | * Each of 16, 17, and 18 are follwed by extra bits to define the length of |
| 628 | * the run. 16 copies the last length 3 to 6 times. 17 represents 3 to 10 |
| 629 | * zero lengths, and 18 represents 11 to 138 zero lengths. Unused symbols |
| 630 | * are common, hence the special coding for zero lengths. |
| 631 | * |
| 632 | * - The symbols for 0..18 are Huffman coded, and so that code must be |
| 633 | * described first. This is simply a sequence of up to 19 three-bit values |
| 634 | * representing no code (0) or the code length for that symbol (1..7). |
| 635 | * |
| 636 | * - A dynamic block starts with three fixed-size counts from which is computed |
| 637 | * the number of literal/length code lengths, the number of distance code |
| 638 | * lengths, and the number of code length code lengths (ok, you come up with |
| 639 | * a better name!) in the code descriptions. For the literal/length and |
| 640 | * distance codes, lengths after those provided are considered zero, i.e. no |
| 641 | * code. The code length code lengths are received in a permuted order (see |
| 642 | * the order[] array below) to make a short code length code length list more |
| 643 | * likely. As it turns out, very short and very long codes are less likely |
| 644 | * to be seen in a dynamic code description, hence what may appear initially |
| 645 | * to be a peculiar ordering. |
| 646 | * |
| 647 | * - Given the number of literal/length code lengths (nlen) and distance code |
| 648 | * lengths (ndist), then they are treated as one long list of nlen + ndist |
| 649 | * code lengths. Therefore run-length coding can and often does cross the |
| 650 | * boundary between the two sets of lengths. |
| 651 | * |
| 652 | * - So to summarize, the code description at the start of a dynamic block is |
| 653 | * three counts for the number of code lengths for the literal/length codes, |
| 654 | * the distance codes, and the code length codes. This is followed by the |
| 655 | * code length code lengths, three bits each. This is used to construct the |
| 656 | * code length code which is used to read the remainder of the lengths. Then |
| 657 | * the literal/length code lengths and distance lengths are read as a single |
| 658 | * set of lengths using the code length codes. Codes are constructed from |
| 659 | * the resulting two sets of lengths, and then finally you can start |
| 660 | * decoding actual compressed data in the block. |
| 661 | * |
| 662 | * - For reference, a "typical" size for the code description in a dynamic |
| 663 | * block is around 80 bytes. |
| 664 | */ |
| 665 | local int dynamic(struct state *s) |
| 666 | { |
| 667 | int nlen, ndist, ncode; /* number of lengths in descriptor */ |
| 668 | int index; /* index of lengths[] */ |
| 669 | int err; /* construct() return value */ |
| 670 | short lengths[MAXCODES]; /* descriptor code lengths */ |
| 671 | short lencnt[MAXBITS+1], lensym[MAXLCODES]; /* lencode memory */ |
| 672 | short distcnt[MAXBITS+1], distsym[MAXDCODES]; /* distcode memory */ |
| 673 | struct huffman lencode, distcode; /* length and distance codes */ |
| 674 | static const short order[19] = /* permutation of code length codes */ |
| 675 | {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}; |
| 676 | |
| 677 | /* construct lencode and distcode */ |
| 678 | lencode.count = lencnt; |
| 679 | lencode.symbol = lensym; |
| 680 | distcode.count = distcnt; |
| 681 | distcode.symbol = distsym; |
| 682 | |
| 683 | /* get number of lengths in each table, check lengths */ |
| 684 | nlen = bits(s, 5) + 257; |
| 685 | ndist = bits(s, 5) + 1; |
| 686 | ncode = bits(s, 4) + 4; |
| 687 | if (nlen > MAXLCODES || ndist > MAXDCODES) |
| 688 | return -3; /* bad counts */ |
| 689 | |
| 690 | /* read code length code lengths (really), missing lengths are zero */ |
| 691 | for (index = 0; index < ncode; index++) |
| 692 | lengths[order[index]] = bits(s, 3); |
| 693 | for (; index < 19; index++) |
| 694 | lengths[order[index]] = 0; |
| 695 | |
| 696 | /* build huffman table for code lengths codes (use lencode temporarily) */ |
| 697 | err = construct(&lencode, lengths, 19); |
| 698 | if (err != 0) /* require complete code set here */ |
| 699 | return -4; |
| 700 | |
| 701 | /* read length/literal and distance code length tables */ |
| 702 | index = 0; |
| 703 | while (index < nlen + ndist) { |
| 704 | int symbol; /* decoded value */ |
| 705 | int len; /* last length to repeat */ |
| 706 | |
| 707 | symbol = decode(s, &lencode); |
| 708 | if (symbol < 0) |
| 709 | return symbol; /* invalid symbol */ |
| 710 | if (symbol < 16) /* length in 0..15 */ |
| 711 | lengths[index++] = symbol; |
| 712 | else { /* repeat instruction */ |
| 713 | len = 0; /* assume repeating zeros */ |
| 714 | if (symbol == 16) { /* repeat last length 3..6 times */ |
| 715 | if (index == 0) |
| 716 | return -5; /* no last length! */ |
| 717 | len = lengths[index - 1]; /* last length */ |
| 718 | symbol = 3 + bits(s, 2); |
| 719 | } |
| 720 | else if (symbol == 17) /* repeat zero 3..10 times */ |
| 721 | symbol = 3 + bits(s, 3); |
| 722 | else /* == 18, repeat zero 11..138 times */ |
| 723 | symbol = 11 + bits(s, 7); |
| 724 | if (index + symbol > nlen + ndist) |
| 725 | return -6; /* too many lengths! */ |
| 726 | while (symbol--) /* repeat last or zero symbol times */ |
| 727 | lengths[index++] = len; |
| 728 | } |
| 729 | } |
| 730 | |
| 731 | /* check for end-of-block code -- there better be one! */ |
| 732 | if (lengths[256] == 0) |
| 733 | return -9; |
| 734 | |
| 735 | /* build huffman table for literal/length codes */ |
| 736 | err = construct(&lencode, lengths, nlen); |
| 737 | if (err && (err < 0 || nlen != lencode.count[0] + lencode.count[1])) |
| 738 | return -7; /* incomplete code ok only for single length 1 code */ |
| 739 | |
| 740 | /* build huffman table for distance codes */ |
| 741 | err = construct(&distcode, lengths + nlen, ndist); |
| 742 | if (err && (err < 0 || ndist != distcode.count[0] + distcode.count[1])) |
| 743 | return -8; /* incomplete code ok only for single length 1 code */ |
| 744 | |
| 745 | /* decode data until end-of-block code */ |
| 746 | return codes(s, &lencode, &distcode); |
| 747 | } |
| 748 | |
| 749 | /* |
| 750 | * Inflate source to dest. On return, destlen and sourcelen are updated to the |
| 751 | * size of the uncompressed data and the size of the deflate data respectively. |
| 752 | * On success, the return value of puff() is zero. If there is an error in the |
| 753 | * source data, i.e. it is not in the deflate format, then a negative value is |
| 754 | * returned. If there is not enough input available or there is not enough |
| 755 | * output space, then a positive error is returned. In that case, destlen and |
| 756 | * sourcelen are not updated to facilitate retrying from the beginning with the |
| 757 | * provision of more input data or more output space. In the case of invalid |
| 758 | * inflate data (a negative error), the dest and source pointers are updated to |
| 759 | * facilitate the debugging of deflators. |
| 760 | * |
| 761 | * puff() also has a mode to determine the size of the uncompressed output with |
| 762 | * no output written. For this dest must be (unsigned char *)0. In this case, |
| 763 | * the input value of *destlen is ignored, and on return *destlen is set to the |
| 764 | * size of the uncompressed output. |
| 765 | * |
| 766 | * The return codes are: |
| 767 | * |
| 768 | * 2: available inflate data did not terminate |
| 769 | * 1: output space exhausted before completing inflate |
| 770 | * 0: successful inflate |
| 771 | * -1: invalid block type (type == 3) |
| 772 | * -2: stored block length did not match one's complement |
| 773 | * -3: dynamic block code description: too many length or distance codes |
| 774 | * -4: dynamic block code description: code lengths codes incomplete |
| 775 | * -5: dynamic block code description: repeat lengths with no first length |
| 776 | * -6: dynamic block code description: repeat more than specified lengths |
| 777 | * -7: dynamic block code description: invalid literal/length code lengths |
| 778 | * -8: dynamic block code description: invalid distance code lengths |
| 779 | * -9: dynamic block code description: missing end-of-block code |
| 780 | * -10: invalid literal/length or distance code in fixed or dynamic block |
| 781 | * -11: distance is too far back in fixed or dynamic block |
| 782 | * |
| 783 | * Format notes: |
| 784 | * |
| 785 | * - Three bits are read for each block to determine the kind of block and |
| 786 | * whether or not it is the last block. Then the block is decoded and the |
| 787 | * process repeated if it was not the last block. |
| 788 | * |
| 789 | * - The leftover bits in the last byte of the deflate data after the last |
| 790 | * block (if it was a fixed or dynamic block) are undefined and have no |
| 791 | * expected values to check. |
| 792 | */ |
| 793 | int puff(unsigned char *dest, /* pointer to destination pointer */ |
| 794 | unsigned long *destlen, /* amount of output space */ |
| 795 | const unsigned char *source, /* pointer to source data pointer */ |
| 796 | unsigned long *sourcelen) /* amount of input available */ |
| 797 | { |
| 798 | struct state s; /* input/output state */ |
| 799 | int last, type; /* block information */ |
| 800 | int err; /* return value */ |
| 801 | |
| 802 | /* initialize output state */ |
| 803 | s.out = dest; |
| 804 | s.outlen = *destlen; /* ignored if dest is NIL */ |
| 805 | s.outcnt = 0; |
| 806 | |
| 807 | /* initialize input state */ |
| 808 | s.in = source; |
| 809 | s.inlen = *sourcelen; |
| 810 | s.incnt = 0; |
| 811 | s.bitbuf = 0; |
| 812 | s.bitcnt = 0; |
| 813 | |
| 814 | /* return if bits() or decode() tries to read past available input */ |
| 815 | if (setjmp(s.env) != 0) /* if came back here via longjmp() */ |
| 816 | err = 2; /* then skip do-loop, return error */ |
| 817 | else { |
| 818 | /* process blocks until last block or error */ |
| 819 | do { |
| 820 | last = bits(&s, 1); /* one if last block */ |
| 821 | type = bits(&s, 2); /* block type 0..3 */ |
| 822 | err = type == 0 ? |
| 823 | stored(&s) : |
| 824 | (type == 1 ? |
| 825 | fixed(&s) : |
| 826 | (type == 2 ? |
| 827 | dynamic(&s) : |
| 828 | -1)); /* type == 3, invalid */ |
| 829 | if (err != 0) |
| 830 | break; /* return with error */ |
| 831 | } while (!last); |
| 832 | } |
| 833 | |
| 834 | /* update the lengths and return */ |
| 835 | if (err <= 0) { |
| 836 | *destlen = s.outcnt; |
| 837 | *sourcelen = s.incnt; |
| 838 | } |
| 839 | return err; |
| 840 | } |