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puff.c
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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 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 }
GLenum GLuint GLenum GLsizei length
#define MAXBITS
Definition: puff.c:91
for(n=1;n< outline->n_points;n++)
Definition: ftbbox.c:593
#define MAXDCODES
Definition: puff.c:93
#define MAXCODES
Definition: puff.c:94
local int construct(struct huffman *h, const short *length, int n)
Definition: puff.c:340
GLfloat GLfloat GLfloat GLfloat h
int puff(unsigned char *dest, unsigned long *destlen, const unsigned char *source, unsigned long *sourcelen)
Definition: puff.c:793
GLuint GLdouble GLdouble GLint GLint order
GLsizei GLsizei GLchar * source
#define NIL
Definition: puff.h:29
local int decode(struct state *s, const struct huffman *h)
Definition: puff.c:263
GLenum GLsizei len
GLint left
local int out(void *out_desc, unsigned char *buf, unsigned len)
Definition: gun.c:131
#define local
Definition: puff.c:85
typedef long(ZCALLBACK *tell_file_func) OF((voidpf opaque
GLuint GLfloat * val
GLdouble n
const GLint * first
#define MAXLCODES
Definition: puff.c:92
GLenum type
typedef int
Definition: png.h:978
local int dynamic(struct state *s)
Definition: puff.c:665
GLuint in
GLdouble s
GLuint index
GLsizei GLenum GLenum GLuint GLenum GLsizei * lengths
GLuint GLuint GLsizei count
local int bits(struct state *s, int need)
Definition: puff.c:126
local int stored(struct state *s)
Definition: puff.c:164
local int codes(struct state *s, const struct huffman *lencode, const struct huffman *distcode)
Definition: puff.c:436
local int * code
Definition: enough.c:174
#define FIXLCODES
Definition: puff.c:95
local int fixed(struct state *s)
Definition: puff.c:536