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zlib.h
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1 /* zlib.h -- interface of the 'zlib' general purpose compression library
2 
3  Copyright (C) 1995-2005 Jean-loup Gailly and Mark Adler
4 
5  This software is provided 'as-is', without any express or implied
6  warranty. In no event will the authors be held liable for any damages
7  arising from the use of this software.
8 
9  Permission is granted to anyone to use this software for any purpose,
10  including commercial applications, and to alter it and redistribute it
11  freely, subject to the following restrictions:
12 
13  1. The origin of this software must not be misrepresented; you must not
14  claim that you wrote the original software. If you use this software
15  in a product, an acknowledgment in the product documentation would be
16  appreciated but is not required.
17  2. Altered source versions must be plainly marked as such, and must not be
18  misrepresented as being the original software.
19  3. This notice may not be removed or altered from any source distribution.
20 
21  Jean-loup Gailly Mark Adler
23 
24 
25  The data format used by the zlib library is described by RFCs (Request for
26  Comments) 1950 to 1952 in the files http://www.ietf.org/rfc/rfc1950.txt
27  (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
28 */
29 
30 #ifndef _ZLIB_H
31 #define _ZLIB_H
32 
33 #include <linux/zconf.h>
34 
35 /* zlib deflate based on ZLIB_VERSION "1.1.3" */
36 /* zlib inflate based on ZLIB_VERSION "1.2.3" */
37 
38 /*
39  This is a modified version of zlib for use inside the Linux kernel.
40  The main changes are to perform all memory allocation in advance.
41 
42  Inflation Changes:
43  * Z_PACKET_FLUSH is added and used by ppp_deflate. Before returning
44  this checks there is no more input data available and the next data
45  is a STORED block. It also resets the mode to be read for the next
46  data, all as per PPP requirements.
47  * Addition of zlib_inflateIncomp which copies incompressible data into
48  the history window and adjusts the accoutning without calling
49  zlib_inflate itself to inflate the data.
50 */
51 
52 /*
53  The 'zlib' compression library provides in-memory compression and
54  decompression functions, including integrity checks of the uncompressed
55  data. This version of the library supports only one compression method
56  (deflation) but other algorithms will be added later and will have the same
57  stream interface.
58 
59  Compression can be done in a single step if the buffers are large
60  enough (for example if an input file is mmap'ed), or can be done by
61  repeated calls of the compression function. In the latter case, the
62  application must provide more input and/or consume the output
63  (providing more output space) before each call.
64 
65  The compressed data format used by default by the in-memory functions is
66  the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
67  around a deflate stream, which is itself documented in RFC 1951.
68 
69  The library also supports reading and writing files in gzip (.gz) format
70  with an interface similar to that of stdio.
71 
72  The zlib format was designed to be compact and fast for use in memory
73  and on communications channels. The gzip format was designed for single-
74  file compression on file systems, has a larger header than zlib to maintain
75  directory information, and uses a different, slower check method than zlib.
76 
77  The library does not install any signal handler. The decoder checks
78  the consistency of the compressed data, so the library should never
79  crash even in case of corrupted input.
80 */
81 
82 struct internal_state;
83 
84 typedef struct z_stream_s {
85  const Byte *next_in; /* next input byte */
86  uInt avail_in; /* number of bytes available at next_in */
87  uLong total_in; /* total nb of input bytes read so far */
88 
89  Byte *next_out; /* next output byte should be put there */
90  uInt avail_out; /* remaining free space at next_out */
91  uLong total_out; /* total nb of bytes output so far */
92 
93  char *msg; /* last error message, NULL if no error */
94  struct internal_state *state; /* not visible by applications */
95 
96  void *workspace; /* memory allocated for this stream */
97 
98  int data_type; /* best guess about the data type: ascii or binary */
99  uLong adler; /* adler32 value of the uncompressed data */
100  uLong reserved; /* reserved for future use */
101 } z_stream;
102 
104 
105 /*
106  The application must update next_in and avail_in when avail_in has
107  dropped to zero. It must update next_out and avail_out when avail_out
108  has dropped to zero. The application must initialize zalloc, zfree and
109  opaque before calling the init function. All other fields are set by the
110  compression library and must not be updated by the application.
111 
112  The opaque value provided by the application will be passed as the first
113  parameter for calls of zalloc and zfree. This can be useful for custom
114  memory management. The compression library attaches no meaning to the
115  opaque value.
116 
117  zalloc must return NULL if there is not enough memory for the object.
118  If zlib is used in a multi-threaded application, zalloc and zfree must be
119  thread safe.
120 
121  On 16-bit systems, the functions zalloc and zfree must be able to allocate
122  exactly 65536 bytes, but will not be required to allocate more than this
123  if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
124  pointers returned by zalloc for objects of exactly 65536 bytes *must*
125  have their offset normalized to zero. The default allocation function
126  provided by this library ensures this (see zutil.c). To reduce memory
127  requirements and avoid any allocation of 64K objects, at the expense of
128  compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
129 
130  The fields total_in and total_out can be used for statistics or
131  progress reports. After compression, total_in holds the total size of
132  the uncompressed data and may be saved for use in the decompressor
133  (particularly if the decompressor wants to decompress everything in
134  a single step).
135 */
136 
137  /* constants */
138 
139 #define Z_NO_FLUSH 0
140 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
141 #define Z_PACKET_FLUSH 2
142 #define Z_SYNC_FLUSH 3
143 #define Z_FULL_FLUSH 4
144 #define Z_FINISH 5
145 #define Z_BLOCK 6 /* Only for inflate at present */
146 /* Allowed flush values; see deflate() and inflate() below for details */
147 
148 #define Z_OK 0
149 #define Z_STREAM_END 1
150 #define Z_NEED_DICT 2
151 #define Z_ERRNO (-1)
152 #define Z_STREAM_ERROR (-2)
153 #define Z_DATA_ERROR (-3)
154 #define Z_MEM_ERROR (-4)
155 #define Z_BUF_ERROR (-5)
156 #define Z_VERSION_ERROR (-6)
157 /* Return codes for the compression/decompression functions. Negative
158  * values are errors, positive values are used for special but normal events.
159  */
160 
161 #define Z_NO_COMPRESSION 0
162 #define Z_BEST_SPEED 1
163 #define Z_BEST_COMPRESSION 9
164 #define Z_DEFAULT_COMPRESSION (-1)
165 /* compression levels */
166 
167 #define Z_FILTERED 1
168 #define Z_HUFFMAN_ONLY 2
169 #define Z_DEFAULT_STRATEGY 0
170 /* compression strategy; see deflateInit2() below for details */
171 
172 #define Z_BINARY 0
173 #define Z_ASCII 1
174 #define Z_UNKNOWN 2
175 /* Possible values of the data_type field */
176 
177 #define Z_DEFLATED 8
178 /* The deflate compression method (the only one supported in this version) */
179 
180  /* basic functions */
181 
182 extern int zlib_deflate_workspacesize (int windowBits, int memLevel);
183 /*
184  Returns the number of bytes that needs to be allocated for a per-
185  stream workspace with the specified parameters. A pointer to this
186  number of bytes should be returned in stream->workspace before
187  you call zlib_deflateInit() or zlib_deflateInit2(). If you call
188  zlib_deflateInit(), specify windowBits = MAX_WBITS and memLevel =
189  MAX_MEM_LEVEL here. If you call zlib_deflateInit2(), the windowBits
190  and memLevel parameters passed to zlib_deflateInit2() must not
191  exceed those passed here.
192 */
193 
194 /*
195 extern int deflateInit (z_streamp strm, int level);
196 
197  Initializes the internal stream state for compression. The fields
198  zalloc, zfree and opaque must be initialized before by the caller.
199  If zalloc and zfree are set to NULL, deflateInit updates them to
200  use default allocation functions.
201 
202  The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
203  1 gives best speed, 9 gives best compression, 0 gives no compression at
204  all (the input data is simply copied a block at a time).
205  Z_DEFAULT_COMPRESSION requests a default compromise between speed and
206  compression (currently equivalent to level 6).
207 
208  deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
209  enough memory, Z_STREAM_ERROR if level is not a valid compression level,
210  Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
211  with the version assumed by the caller (ZLIB_VERSION).
212  msg is set to null if there is no error message. deflateInit does not
213  perform any compression: this will be done by deflate().
214 */
215 
216 
217 extern int zlib_deflate (z_streamp strm, int flush);
218 /*
219  deflate compresses as much data as possible, and stops when the input
220  buffer becomes empty or the output buffer becomes full. It may introduce some
221  output latency (reading input without producing any output) except when
222  forced to flush.
223 
224  The detailed semantics are as follows. deflate performs one or both of the
225  following actions:
226 
227  - Compress more input starting at next_in and update next_in and avail_in
228  accordingly. If not all input can be processed (because there is not
229  enough room in the output buffer), next_in and avail_in are updated and
230  processing will resume at this point for the next call of deflate().
231 
232  - Provide more output starting at next_out and update next_out and avail_out
233  accordingly. This action is forced if the parameter flush is non zero.
234  Forcing flush frequently degrades the compression ratio, so this parameter
235  should be set only when necessary (in interactive applications).
236  Some output may be provided even if flush is not set.
237 
238  Before the call of deflate(), the application should ensure that at least
239  one of the actions is possible, by providing more input and/or consuming
240  more output, and updating avail_in or avail_out accordingly; avail_out
241  should never be zero before the call. The application can consume the
242  compressed output when it wants, for example when the output buffer is full
243  (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
244  and with zero avail_out, it must be called again after making room in the
245  output buffer because there might be more output pending.
246 
247  If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
248  flushed to the output buffer and the output is aligned on a byte boundary, so
249  that the decompressor can get all input data available so far. (In particular
250  avail_in is zero after the call if enough output space has been provided
251  before the call.) Flushing may degrade compression for some compression
252  algorithms and so it should be used only when necessary.
253 
254  If flush is set to Z_FULL_FLUSH, all output is flushed as with
255  Z_SYNC_FLUSH, and the compression state is reset so that decompression can
256  restart from this point if previous compressed data has been damaged or if
257  random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
258  the compression.
259 
260  If deflate returns with avail_out == 0, this function must be called again
261  with the same value of the flush parameter and more output space (updated
262  avail_out), until the flush is complete (deflate returns with non-zero
263  avail_out).
264 
265  If the parameter flush is set to Z_FINISH, pending input is processed,
266  pending output is flushed and deflate returns with Z_STREAM_END if there
267  was enough output space; if deflate returns with Z_OK, this function must be
268  called again with Z_FINISH and more output space (updated avail_out) but no
269  more input data, until it returns with Z_STREAM_END or an error. After
270  deflate has returned Z_STREAM_END, the only possible operations on the
271  stream are deflateReset or deflateEnd.
272 
273  Z_FINISH can be used immediately after deflateInit if all the compression
274  is to be done in a single step. In this case, avail_out must be at least
275  0.1% larger than avail_in plus 12 bytes. If deflate does not return
276  Z_STREAM_END, then it must be called again as described above.
277 
278  deflate() sets strm->adler to the adler32 checksum of all input read
279  so far (that is, total_in bytes).
280 
281  deflate() may update data_type if it can make a good guess about
282  the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
283  binary. This field is only for information purposes and does not affect
284  the compression algorithm in any manner.
285 
286  deflate() returns Z_OK if some progress has been made (more input
287  processed or more output produced), Z_STREAM_END if all input has been
288  consumed and all output has been produced (only when flush is set to
289  Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
290  if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
291  (for example avail_in or avail_out was zero).
292 */
293 
294 
295 extern int zlib_deflateEnd (z_streamp strm);
296 /*
297  All dynamically allocated data structures for this stream are freed.
298  This function discards any unprocessed input and does not flush any
299  pending output.
300 
301  deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
302  stream state was inconsistent, Z_DATA_ERROR if the stream was freed
303  prematurely (some input or output was discarded). In the error case,
304  msg may be set but then points to a static string (which must not be
305  deallocated).
306 */
307 
308 
309 extern int zlib_inflate_workspacesize (void);
310 /*
311  Returns the number of bytes that needs to be allocated for a per-
312  stream workspace. A pointer to this number of bytes should be
313  returned in stream->workspace before calling zlib_inflateInit().
314 */
315 
316 /*
317 extern int zlib_inflateInit (z_streamp strm);
318 
319  Initializes the internal stream state for decompression. The fields
320  next_in, avail_in, and workspace must be initialized before by
321  the caller. If next_in is not NULL and avail_in is large enough (the exact
322  value depends on the compression method), inflateInit determines the
323  compression method from the zlib header and allocates all data structures
324  accordingly; otherwise the allocation will be deferred to the first call of
325  inflate. If zalloc and zfree are set to NULL, inflateInit updates them to
326  use default allocation functions.
327 
328  inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
329  memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
330  version assumed by the caller. msg is set to null if there is no error
331  message. inflateInit does not perform any decompression apart from reading
332  the zlib header if present: this will be done by inflate(). (So next_in and
333  avail_in may be modified, but next_out and avail_out are unchanged.)
334 */
335 
336 
337 extern int zlib_inflate (z_streamp strm, int flush);
338 /*
339  inflate decompresses as much data as possible, and stops when the input
340  buffer becomes empty or the output buffer becomes full. It may introduce
341  some output latency (reading input without producing any output) except when
342  forced to flush.
343 
344  The detailed semantics are as follows. inflate performs one or both of the
345  following actions:
346 
347  - Decompress more input starting at next_in and update next_in and avail_in
348  accordingly. If not all input can be processed (because there is not
349  enough room in the output buffer), next_in is updated and processing
350  will resume at this point for the next call of inflate().
351 
352  - Provide more output starting at next_out and update next_out and avail_out
353  accordingly. inflate() provides as much output as possible, until there
354  is no more input data or no more space in the output buffer (see below
355  about the flush parameter).
356 
357  Before the call of inflate(), the application should ensure that at least
358  one of the actions is possible, by providing more input and/or consuming
359  more output, and updating the next_* and avail_* values accordingly.
360  The application can consume the uncompressed output when it wants, for
361  example when the output buffer is full (avail_out == 0), or after each
362  call of inflate(). If inflate returns Z_OK and with zero avail_out, it
363  must be called again after making room in the output buffer because there
364  might be more output pending.
365 
366  The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
367  Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush as much
368  output as possible to the output buffer. Z_BLOCK requests that inflate() stop
369  if and when it gets to the next deflate block boundary. When decoding the
370  zlib or gzip format, this will cause inflate() to return immediately after
371  the header and before the first block. When doing a raw inflate, inflate()
372  will go ahead and process the first block, and will return when it gets to
373  the end of that block, or when it runs out of data.
374 
375  The Z_BLOCK option assists in appending to or combining deflate streams.
376  Also to assist in this, on return inflate() will set strm->data_type to the
377  number of unused bits in the last byte taken from strm->next_in, plus 64
378  if inflate() is currently decoding the last block in the deflate stream,
379  plus 128 if inflate() returned immediately after decoding an end-of-block
380  code or decoding the complete header up to just before the first byte of the
381  deflate stream. The end-of-block will not be indicated until all of the
382  uncompressed data from that block has been written to strm->next_out. The
383  number of unused bits may in general be greater than seven, except when
384  bit 7 of data_type is set, in which case the number of unused bits will be
385  less than eight.
386 
387  inflate() should normally be called until it returns Z_STREAM_END or an
388  error. However if all decompression is to be performed in a single step
389  (a single call of inflate), the parameter flush should be set to
390  Z_FINISH. In this case all pending input is processed and all pending
391  output is flushed; avail_out must be large enough to hold all the
392  uncompressed data. (The size of the uncompressed data may have been saved
393  by the compressor for this purpose.) The next operation on this stream must
394  be inflateEnd to deallocate the decompression state. The use of Z_FINISH
395  is never required, but can be used to inform inflate that a faster approach
396  may be used for the single inflate() call.
397 
398  In this implementation, inflate() always flushes as much output as
399  possible to the output buffer, and always uses the faster approach on the
400  first call. So the only effect of the flush parameter in this implementation
401  is on the return value of inflate(), as noted below, or when it returns early
402  because Z_BLOCK is used.
403 
404  If a preset dictionary is needed after this call (see inflateSetDictionary
405  below), inflate sets strm->adler to the adler32 checksum of the dictionary
406  chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
407  strm->adler to the adler32 checksum of all output produced so far (that is,
408  total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
409  below. At the end of the stream, inflate() checks that its computed adler32
410  checksum is equal to that saved by the compressor and returns Z_STREAM_END
411  only if the checksum is correct.
412 
413  inflate() will decompress and check either zlib-wrapped or gzip-wrapped
414  deflate data. The header type is detected automatically. Any information
415  contained in the gzip header is not retained, so applications that need that
416  information should instead use raw inflate, see inflateInit2() below, or
417  inflateBack() and perform their own processing of the gzip header and
418  trailer.
419 
420  inflate() returns Z_OK if some progress has been made (more input processed
421  or more output produced), Z_STREAM_END if the end of the compressed data has
422  been reached and all uncompressed output has been produced, Z_NEED_DICT if a
423  preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
424  corrupted (input stream not conforming to the zlib format or incorrect check
425  value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
426  if next_in or next_out was NULL), Z_MEM_ERROR if there was not enough memory,
427  Z_BUF_ERROR if no progress is possible or if there was not enough room in the
428  output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
429  inflate() can be called again with more input and more output space to
430  continue decompressing. If Z_DATA_ERROR is returned, the application may then
431  call inflateSync() to look for a good compression block if a partial recovery
432  of the data is desired.
433 */
434 
435 
436 extern int zlib_inflateEnd (z_streamp strm);
437 /*
438  All dynamically allocated data structures for this stream are freed.
439  This function discards any unprocessed input and does not flush any
440  pending output.
441 
442  inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
443  was inconsistent. In the error case, msg may be set but then points to a
444  static string (which must not be deallocated).
445 */
446 
447  /* Advanced functions */
448 
449 /*
450  The following functions are needed only in some special applications.
451 */
452 
453 /*
454 extern int deflateInit2 (z_streamp strm,
455  int level,
456  int method,
457  int windowBits,
458  int memLevel,
459  int strategy);
460 
461  This is another version of deflateInit with more compression options. The
462  fields next_in, zalloc, zfree and opaque must be initialized before by
463  the caller.
464 
465  The method parameter is the compression method. It must be Z_DEFLATED in
466  this version of the library.
467 
468  The windowBits parameter is the base two logarithm of the window size
469  (the size of the history buffer). It should be in the range 8..15 for this
470  version of the library. Larger values of this parameter result in better
471  compression at the expense of memory usage. The default value is 15 if
472  deflateInit is used instead.
473 
474  The memLevel parameter specifies how much memory should be allocated
475  for the internal compression state. memLevel=1 uses minimum memory but
476  is slow and reduces compression ratio; memLevel=9 uses maximum memory
477  for optimal speed. The default value is 8. See zconf.h for total memory
478  usage as a function of windowBits and memLevel.
479 
480  The strategy parameter is used to tune the compression algorithm. Use the
481  value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
482  filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
483  string match). Filtered data consists mostly of small values with a
484  somewhat random distribution. In this case, the compression algorithm is
485  tuned to compress them better. The effect of Z_FILTERED is to force more
486  Huffman coding and less string matching; it is somewhat intermediate
487  between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affects
488  the compression ratio but not the correctness of the compressed output even
489  if it is not set appropriately.
490 
491  deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
492  memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
493  method). msg is set to null if there is no error message. deflateInit2 does
494  not perform any compression: this will be done by deflate().
495 */
496 
497 #if 0
498 extern int zlib_deflateSetDictionary (z_streamp strm,
499  const Byte *dictionary,
500  uInt dictLength);
501 #endif
502 /*
503  Initializes the compression dictionary from the given byte sequence
504  without producing any compressed output. This function must be called
505  immediately after deflateInit, deflateInit2 or deflateReset, before any
506  call of deflate. The compressor and decompressor must use exactly the same
507  dictionary (see inflateSetDictionary).
508 
509  The dictionary should consist of strings (byte sequences) that are likely
510  to be encountered later in the data to be compressed, with the most commonly
511  used strings preferably put towards the end of the dictionary. Using a
512  dictionary is most useful when the data to be compressed is short and can be
513  predicted with good accuracy; the data can then be compressed better than
514  with the default empty dictionary.
515 
516  Depending on the size of the compression data structures selected by
517  deflateInit or deflateInit2, a part of the dictionary may in effect be
518  discarded, for example if the dictionary is larger than the window size in
519  deflate or deflate2. Thus the strings most likely to be useful should be
520  put at the end of the dictionary, not at the front.
521 
522  Upon return of this function, strm->adler is set to the Adler32 value
523  of the dictionary; the decompressor may later use this value to determine
524  which dictionary has been used by the compressor. (The Adler32 value
525  applies to the whole dictionary even if only a subset of the dictionary is
526  actually used by the compressor.)
527 
528  deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
529  parameter is invalid (such as NULL dictionary) or the stream state is
530  inconsistent (for example if deflate has already been called for this stream
531  or if the compression method is bsort). deflateSetDictionary does not
532  perform any compression: this will be done by deflate().
533 */
534 
535 #if 0
536 extern int zlib_deflateCopy (z_streamp dest, z_streamp source);
537 #endif
538 
539 /*
540  Sets the destination stream as a complete copy of the source stream.
541 
542  This function can be useful when several compression strategies will be
543  tried, for example when there are several ways of pre-processing the input
544  data with a filter. The streams that will be discarded should then be freed
545  by calling deflateEnd. Note that deflateCopy duplicates the internal
546  compression state which can be quite large, so this strategy is slow and
547  can consume lots of memory.
548 
549  deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
550  enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
551  (such as zalloc being NULL). msg is left unchanged in both source and
552  destination.
553 */
554 
555 extern int zlib_deflateReset (z_streamp strm);
556 /*
557  This function is equivalent to deflateEnd followed by deflateInit,
558  but does not free and reallocate all the internal compression state.
559  The stream will keep the same compression level and any other attributes
560  that may have been set by deflateInit2.
561 
562  deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
563  stream state was inconsistent (such as zalloc or state being NULL).
564 */
565 
566 static inline unsigned long deflateBound(unsigned long s)
567 {
568  return s + ((s + 7) >> 3) + ((s + 63) >> 6) + 11;
569 }
570 
571 #if 0
572 extern int zlib_deflateParams (z_streamp strm, int level, int strategy);
573 #endif
574 /*
575  Dynamically update the compression level and compression strategy. The
576  interpretation of level and strategy is as in deflateInit2. This can be
577  used to switch between compression and straight copy of the input data, or
578  to switch to a different kind of input data requiring a different
579  strategy. If the compression level is changed, the input available so far
580  is compressed with the old level (and may be flushed); the new level will
581  take effect only at the next call of deflate().
582 
583  Before the call of deflateParams, the stream state must be set as for
584  a call of deflate(), since the currently available input may have to
585  be compressed and flushed. In particular, strm->avail_out must be non-zero.
586 
587  deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
588  stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
589  if strm->avail_out was zero.
590 */
591 
592 /*
593 extern int inflateInit2 (z_streamp strm, int windowBits);
594 
595  This is another version of inflateInit with an extra parameter. The
596  fields next_in, avail_in, zalloc, zfree and opaque must be initialized
597  before by the caller.
598 
599  The windowBits parameter is the base two logarithm of the maximum window
600  size (the size of the history buffer). It should be in the range 8..15 for
601  this version of the library. The default value is 15 if inflateInit is used
602  instead. windowBits must be greater than or equal to the windowBits value
603  provided to deflateInit2() while compressing, or it must be equal to 15 if
604  deflateInit2() was not used. If a compressed stream with a larger window
605  size is given as input, inflate() will return with the error code
606  Z_DATA_ERROR instead of trying to allocate a larger window.
607 
608  windowBits can also be -8..-15 for raw inflate. In this case, -windowBits
609  determines the window size. inflate() will then process raw deflate data,
610  not looking for a zlib or gzip header, not generating a check value, and not
611  looking for any check values for comparison at the end of the stream. This
612  is for use with other formats that use the deflate compressed data format
613  such as zip. Those formats provide their own check values. If a custom
614  format is developed using the raw deflate format for compressed data, it is
615  recommended that a check value such as an adler32 or a crc32 be applied to
616  the uncompressed data as is done in the zlib, gzip, and zip formats. For
617  most applications, the zlib format should be used as is. Note that comments
618  above on the use in deflateInit2() applies to the magnitude of windowBits.
619 
620  windowBits can also be greater than 15 for optional gzip decoding. Add
621  32 to windowBits to enable zlib and gzip decoding with automatic header
622  detection, or add 16 to decode only the gzip format (the zlib format will
623  return a Z_DATA_ERROR). If a gzip stream is being decoded, strm->adler is
624  a crc32 instead of an adler32.
625 
626  inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
627  memory, Z_STREAM_ERROR if a parameter is invalid (such as a null strm). msg
628  is set to null if there is no error message. inflateInit2 does not perform
629  any decompression apart from reading the zlib header if present: this will
630  be done by inflate(). (So next_in and avail_in may be modified, but next_out
631  and avail_out are unchanged.)
632 */
633 
634 extern int zlib_inflateSetDictionary (z_streamp strm,
635  const Byte *dictionary,
636  uInt dictLength);
637 /*
638  Initializes the decompression dictionary from the given uncompressed byte
639  sequence. This function must be called immediately after a call of inflate,
640  if that call returned Z_NEED_DICT. The dictionary chosen by the compressor
641  can be determined from the adler32 value returned by that call of inflate.
642  The compressor and decompressor must use exactly the same dictionary (see
643  deflateSetDictionary). For raw inflate, this function can be called
644  immediately after inflateInit2() or inflateReset() and before any call of
645  inflate() to set the dictionary. The application must insure that the
646  dictionary that was used for compression is provided.
647 
648  inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
649  parameter is invalid (such as NULL dictionary) or the stream state is
650  inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
651  expected one (incorrect adler32 value). inflateSetDictionary does not
652  perform any decompression: this will be done by subsequent calls of
653  inflate().
654 */
655 
656 #if 0
657 extern int zlib_inflateSync (z_streamp strm);
658 #endif
659 /*
660  Skips invalid compressed data until a full flush point (see above the
661  description of deflate with Z_FULL_FLUSH) can be found, or until all
662  available input is skipped. No output is provided.
663 
664  inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
665  if no more input was provided, Z_DATA_ERROR if no flush point has been found,
666  or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
667  case, the application may save the current current value of total_in which
668  indicates where valid compressed data was found. In the error case, the
669  application may repeatedly call inflateSync, providing more input each time,
670  until success or end of the input data.
671 */
672 
673 extern int zlib_inflateReset (z_streamp strm);
674 /*
675  This function is equivalent to inflateEnd followed by inflateInit,
676  but does not free and reallocate all the internal decompression state.
677  The stream will keep attributes that may have been set by inflateInit2.
678 
679  inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
680  stream state was inconsistent (such as zalloc or state being NULL).
681 */
682 
683 extern int zlib_inflateIncomp (z_stream *strm);
684 /*
685  This function adds the data at next_in (avail_in bytes) to the output
686  history without performing any output. There must be no pending output,
687  and the decompressor must be expecting to see the start of a block.
688  Calling this function is equivalent to decompressing a stored block
689  containing the data at next_in (except that the data is not output).
690 */
691 
692 #define zlib_deflateInit(strm, level) \
693  zlib_deflateInit2((strm), (level), Z_DEFLATED, MAX_WBITS, \
694  DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY)
695 #define zlib_inflateInit(strm) \
696  zlib_inflateInit2((strm), DEF_WBITS)
697 
698 extern int zlib_deflateInit2(z_streamp strm, int level, int method,
699  int windowBits, int memLevel,
700  int strategy);
701 extern int zlib_inflateInit2(z_streamp strm, int windowBits);
702 
703 #if !defined(_Z_UTIL_H) && !defined(NO_DUMMY_DECL)
704  struct internal_state {int dummy;}; /* hack for buggy compilers */
705 #endif
706 
707 /* Utility function: initialize zlib, unpack binary blob, clean up zlib,
708  * return len or negative error code. */
709 extern int zlib_inflate_blob(void *dst, unsigned dst_sz, const void *src, unsigned src_sz);
710 
711 #endif /* _ZLIB_H */