1 /* zlib.h -- interface of the 'zlib' general purpose compression library
2   version 1.1.4, March 11th, 2002
3 
4   Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler
5 
6   This software is provided 'as-is', without any express or implied
7   warranty.  In no event will the authors be held liable for any damages
8   arising from the use of this software.
9 
10   Permission is granted to anyone to use this software for any purpose,
11   including commercial applications, and to alter it and redistribute it
12   freely, subject to the following restrictions:
13 
14   1. The origin of this software must not be misrepresented; you must not
15      claim that you wrote the original software. If you use this software
16      in a product, an acknowledgment in the product documentation would be
17      appreciated but is not required.
18   2. Altered source versions must be plainly marked as such, and must not be
19      misrepresented as being the original software.
20   3. This notice may not be removed or altered from any source distribution.
21 
22   Jean-loup Gailly        Mark Adler
23   jloup@gzip.org          madler@alumni.caltech.edu
24 
25 
26   The data format used by the zlib library is described by RFCs (Request for
27   Comments) 1950 to 1952 in the files ftp://ds.internic.net/rfc/rfc1950.txt
28   (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
29 */
30 
31 #ifndef _ZLIB_H
32 #define _ZLIB_H
33 
34 #include "zconf.h"
35 
36 #ifdef __cplusplus
37 extern "C" {
38 #endif
39 
40 #define ZLIB_VERSION "1.1.4"
41 
42 /*
43      The 'zlib' compression library provides in-memory compression and
44   decompression functions, including integrity checks of the uncompressed
45   data.  This version of the library supports only one compression method
46   (deflation) but other algorithms will be added later and will have the same
47   stream interface.
48 
49      Compression can be done in a single step if the buffers are large
50   enough (for example if an input file is mmap'ed), or can be done by
51   repeated calls of the compression function.  In the latter case, the
52   application must provide more input and/or consume the output
53   (providing more output space) before each call.
54 
55      The library also supports reading and writing files in gzip (.gz) format
56   with an interface similar to that of stdio.
57 
58      The library does not install any signal handler. The decoder checks
59   the consistency of the compressed data, so the library should never
60   crash even in case of corrupted input.
61 */
62 
63 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
64 typedef void   (*free_func)  OF((voidpf opaque, voidpf address));
65 
66 struct internal_state;
67 
68 typedef struct z_stream_s {
69     Bytef    *next_in;  /* next input byte */
70     uInt     avail_in;  /* number of bytes available at next_in */
71     uLong    total_in;  /* total nb of input bytes read so far */
72 
73     Bytef    *next_out; /* next output byte should be put there */
74     uInt     avail_out; /* remaining free space at next_out */
75     uLong    total_out; /* total nb of bytes output so far */
76 
77     char     *msg;      /* last error message, NULL if no error */
78     struct internal_state FAR *state; /* not visible by applications */
79 
80     alloc_func zalloc;  /* used to allocate the internal state */
81     free_func  zfree;   /* used to free the internal state */
82     voidpf     opaque;  /* private data object passed to zalloc and zfree */
83 
84     int     data_type;  /* best guess about the data type: ascii or binary */
85     uLong   adler;      /* adler32 value of the uncompressed data */
86     uLong   reserved;   /* reserved for future use */
87 } z_stream;
88 
89 typedef z_stream FAR *z_streamp;
90 
91 /*
92    The application must update next_in and avail_in when avail_in has
93    dropped to zero. It must update next_out and avail_out when avail_out
94    has dropped to zero. The application must initialize zalloc, zfree and
95    opaque before calling the init function. All other fields are set by the
96    compression library and must not be updated by the application.
97 
98    The opaque value provided by the application will be passed as the first
99    parameter for calls of zalloc and zfree. This can be useful for custom
100    memory management. The compression library attaches no meaning to the
101    opaque value.
102 
103    zalloc must return Z_NULL if there is not enough memory for the object.
104    If zlib is used in a multi-threaded application, zalloc and zfree must be
105    thread safe.
106 
107    On 16-bit systems, the functions zalloc and zfree must be able to allocate
108    exactly 65536 bytes, but will not be required to allocate more than this
109    if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
110    pointers returned by zalloc for objects of exactly 65536 bytes *must*
111    have their offset normalized to zero. The default allocation function
112    provided by this library ensures this (see zutil.c). To reduce memory
113    requirements and avoid any allocation of 64K objects, at the expense of
114    compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
115 
116    The fields total_in and total_out can be used for statistics or
117    progress reports. After compression, total_in holds the total size of
118    the uncompressed data and may be saved for use in the decompressor
119    (particularly if the decompressor wants to decompress everything in
120    a single step).
121 */
122 
123                         /* constants */
124 
125 #define Z_NO_FLUSH      0
126 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
127 #define Z_SYNC_FLUSH    2
128 #define Z_FULL_FLUSH    3
129 #define Z_FINISH        4
130 /* Allowed flush values; see deflate() below for details */
131 
132 #define Z_OK            0
133 #define Z_STREAM_END    1
134 #define Z_NEED_DICT     2
135 #define Z_ERRNO        (-1)
136 #define Z_STREAM_ERROR (-2)
137 #define Z_DATA_ERROR   (-3)
138 #define Z_MEM_ERROR    (-4)
139 #define Z_BUF_ERROR    (-5)
140 #define Z_VERSION_ERROR (-6)
141 /* Return codes for the compression/decompression functions. Negative
142  * values are errors, positive values are used for special but normal events.
143  */
144 
145 #define Z_NO_COMPRESSION         0
146 #define Z_BEST_SPEED             1
147 #define Z_BEST_COMPRESSION       9
148 #define Z_DEFAULT_COMPRESSION  (-1)
149 /* compression levels */
150 
151 #define Z_FILTERED            1
152 #define Z_HUFFMAN_ONLY        2
153 #define Z_DEFAULT_STRATEGY    0
154 /* compression strategy; see deflateInit2() below for details */
155 
156 #define Z_BINARY   0
157 #define Z_ASCII    1
158 #define Z_UNKNOWN  2
159 /* Possible values of the data_type field */
160 
161 #define Z_DEFLATED   8
162 /* The deflate compression method (the only one supported in this version) */
163 
164 #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
165 
166 
167                         /* basic functions */
168 
169 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
170    If the first character differs, the library code actually used is
171    not compatible with the zlib.h header file used by the application.
172    This check is automatically made by deflateInit and inflateInit.
173  */
174 
175 /*
176 ZEXTERN(int)  deflateInit OF((z_streamp strm, int level));
177 
178      Initializes the internal stream state for compression. The fields
179    zalloc, zfree and opaque must be initialized before by the caller.
180    If zalloc and zfree are set to Z_NULL, deflateInit updates them to
181    use default allocation functions.
182 
183      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
184    1 gives best speed, 9 gives best compression, 0 gives no compression at
185    all (the input data is simply copied a block at a time).
186    Z_DEFAULT_COMPRESSION requests a default compromise between speed and
187    compression (currently equivalent to level 6).
188 
189      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
190    enough memory, Z_STREAM_ERROR if level is not a valid compression level,
191    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
192    with the version assumed by the caller (ZLIB_VERSION).
193    msg is set to null if there is no error message.  deflateInit does not
194    perform any compression: this will be done by deflate().
195 */
196 
197 
198 /*
199     deflate compresses as much data as possible, and stops when the input
200   buffer becomes empty or the output buffer becomes full. It may introduce some
201   output latency (reading input without producing any output) except when
202   forced to flush.
203 
204     The detailed semantics are as follows. deflate performs one or both of the
205   following actions:
206 
207   - Compress more input starting at next_in and update next_in and avail_in
208     accordingly. If not all input can be processed (because there is not
209     enough room in the output buffer), next_in and avail_in are updated and
210     processing will resume at this point for the next call of deflate().
211 
212   - Provide more output starting at next_out and update next_out and avail_out
213     accordingly. This action is forced if the parameter flush is non zero.
214     Forcing flush frequently degrades the compression ratio, so this parameter
215     should be set only when necessary (in interactive applications).
216     Some output may be provided even if flush is not set.
217 
218   Before the call of deflate(), the application should ensure that at least
219   one of the actions is possible, by providing more input and/or consuming
220   more output, and updating avail_in or avail_out accordingly; avail_out
221   should never be zero before the call. The application can consume the
222   compressed output when it wants, for example when the output buffer is full
223   (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
224   and with zero avail_out, it must be called again after making room in the
225   output buffer because there might be more output pending.
226 
227     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
228   flushed to the output buffer and the output is aligned on a byte boundary, so
229   that the decompressor can get all input data available so far. (In particular
230   avail_in is zero after the call if enough output space has been provided
231   before the call.)  Flushing may degrade compression for some compression
232   algorithms and so it should be used only when necessary.
233 
234     If flush is set to Z_FULL_FLUSH, all output is flushed as with
235   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
236   restart from this point if previous compressed data has been damaged or if
237   random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
238   the compression.
239 
240     If deflate returns with avail_out == 0, this function must be called again
241   with the same value of the flush parameter and more output space (updated
242   avail_out), until the flush is complete (deflate returns with non-zero
243   avail_out).
244 
245     If the parameter flush is set to Z_FINISH, pending input is processed,
246   pending output is flushed and deflate returns with Z_STREAM_END if there
247   was enough output space; if deflate returns with Z_OK, this function must be
248   called again with Z_FINISH and more output space (updated avail_out) but no
249   more input data, until it returns with Z_STREAM_END or an error. After
250   deflate has returned Z_STREAM_END, the only possible operations on the
251   stream are deflateReset or deflateEnd.
252 
253     Z_FINISH can be used immediately after deflateInit if all the compression
254   is to be done in a single step. In this case, avail_out must be at least
255   0.1% larger than avail_in plus 12 bytes.  If deflate does not return
256   Z_STREAM_END, then it must be called again as described above.
257 
258     deflate() sets strm->adler to the adler32 checksum of all input read
259   so far (that is, total_in bytes).
260 
261     deflate() may update data_type if it can make a good guess about
262   the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
263   binary. This field is only for information purposes and does not affect
264   the compression algorithm in any manner.
265 
266     deflate() returns Z_OK if some progress has been made (more input
267   processed or more output produced), Z_STREAM_END if all input has been
268   consumed and all output has been produced (only when flush is set to
269   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
270   if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
271   (for example avail_in or avail_out was zero).
272 */
273 
274 
275 /*
276      All dynamically allocated data structures for this stream are freed.
277    This function discards any unprocessed input and does not flush any
278    pending output.
279 
280      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
281    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
282    prematurely (some input or output was discarded). In the error case,
283    msg may be set but then points to a static string (which must not be
284    deallocated).
285 */
286 
287 
288 /*
289 ZEXTERN(int)  inflateInit OF((z_streamp strm));
290 
291      Initializes the internal stream state for decompression. The fields
292    next_in, avail_in, zalloc, zfree and opaque must be initialized before by
293    the caller. If next_in is not Z_NULL and avail_in is large enough (the exact
294    value depends on the compression method), inflateInit determines the
295    compression method from the zlib header and allocates all data structures
296    accordingly; otherwise the allocation will be deferred to the first call of
297    inflate.  If zalloc and zfree are set to Z_NULL, inflateInit updates them to
298    use default allocation functions.
299 
300      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
301    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
302    version assumed by the caller.  msg is set to null if there is no error
303    message. inflateInit does not perform any decompression apart from reading
304    the zlib header if present: this will be done by inflate().  (So next_in and
305    avail_in may be modified, but next_out and avail_out are unchanged.)
306 */
307 
308 
309 ZEXTERN(int) inflate OF((z_streamp strm, int flush));
310 /*
311     inflate decompresses as much data as possible, and stops when the input
312   buffer becomes empty or the output buffer becomes full. It may some
313   introduce some output latency (reading input without producing any output)
314   except when forced to flush.
315 
316   The detailed semantics are as follows. inflate performs one or both of the
317   following actions:
318 
319   - Decompress more input starting at next_in and update next_in and avail_in
320     accordingly. If not all input can be processed (because there is not
321     enough room in the output buffer), next_in is updated and processing
322     will resume at this point for the next call of inflate().
323 
324   - Provide more output starting at next_out and update next_out and avail_out
325     accordingly.  inflate() provides as much output as possible, until there
326     is no more input data or no more space in the output buffer (see below
327     about the flush parameter).
328 
329   Before the call of inflate(), the application should ensure that at least
330   one of the actions is possible, by providing more input and/or consuming
331   more output, and updating the next_* and avail_* values accordingly.
332   The application can consume the uncompressed output when it wants, for
333   example when the output buffer is full (avail_out == 0), or after each
334   call of inflate(). If inflate returns Z_OK and with zero avail_out, it
335   must be called again after making room in the output buffer because there
336   might be more output pending.
337 
338     If the parameter flush is set to Z_SYNC_FLUSH, inflate flushes as much
339   output as possible to the output buffer. The flushing behavior of inflate is
340   not specified for values of the flush parameter other than Z_SYNC_FLUSH
341   and Z_FINISH, but the current implementation actually flushes as much output
342   as possible anyway.
343 
344     inflate() should normally be called until it returns Z_STREAM_END or an
345   error. However if all decompression is to be performed in a single step
346   (a single call of inflate), the parameter flush should be set to
347   Z_FINISH. In this case all pending input is processed and all pending
348   output is flushed; avail_out must be large enough to hold all the
349   uncompressed data. (The size of the uncompressed data may have been saved
350   by the compressor for this purpose.) The next operation on this stream must
351   be inflateEnd to deallocate the decompression state. The use of Z_FINISH
352   is never required, but can be used to inform inflate that a faster routine
353   may be used for the single inflate() call.
354 
355      If a preset dictionary is needed at this point (see inflateSetDictionary
356   below), inflate sets strm-adler to the adler32 checksum of the
357   dictionary chosen by the compressor and returns Z_NEED_DICT; otherwise
358   it sets strm->adler to the adler32 checksum of all output produced
359   so far (that is, total_out bytes) and returns Z_OK, Z_STREAM_END or
360   an error code as described below. At the end of the stream, inflate()
361   checks that its computed adler32 checksum is equal to that saved by the
362   compressor and returns Z_STREAM_END only if the checksum is correct.
363 
364     inflate() returns Z_OK if some progress has been made (more input processed
365   or more output produced), Z_STREAM_END if the end of the compressed data has
366   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
367   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
368   corrupted (input stream not conforming to the zlib format or incorrect
369   adler32 checksum), Z_STREAM_ERROR if the stream structure was inconsistent
370   (for example if next_in or next_out was NULL), Z_MEM_ERROR if there was not
371   enough memory, Z_BUF_ERROR if no progress is possible or if there was not
372   enough room in the output buffer when Z_FINISH is used. In the Z_DATA_ERROR
373   case, the application may then call inflateSync to look for a good
374   compression block.
375 */
376 
377 
378 ZEXTERN(int)  inflateEnd OF((z_streamp strm));
379 /*
380      All dynamically allocated data structures for this stream are freed.
381    This function discards any unprocessed input and does not flush any
382    pending output.
383 
384      inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
385    was inconsistent. In the error case, msg may be set but then points to a
386    static string (which must not be deallocated).
387 */
388 
389                         /* Advanced functions */
390 
391 /*
392     The following functions are needed only in some special applications.
393 */
394 
395 /*
396 ZEXTERN(int)  deflateInit2 OF((z_streamp strm,
397                                      int  level,
398                                      int  method,
399                                      int  windowBits,
400                                      int  memLevel,
401                                      int  strategy));
402 
403      This is another version of deflateInit with more compression options. The
404    fields next_in, zalloc, zfree and opaque must be initialized before by
405    the caller.
406 
407      The method parameter is the compression method. It must be Z_DEFLATED in
408    this version of the library.
409 
410      The windowBits parameter is the base two logarithm of the window size
411    (the size of the history buffer).  It should be in the range 8..15 for this
412    version of the library. Larger values of this parameter result in better
413    compression at the expense of memory usage. The default value is 15 if
414    deflateInit is used instead.
415 
416      The memLevel parameter specifies how much memory should be allocated
417    for the internal compression state. memLevel=1 uses minimum memory but
418    is slow and reduces compression ratio; memLevel=9 uses maximum memory
419    for optimal speed. The default value is 8. See zconf.h for total memory
420    usage as a function of windowBits and memLevel.
421 
422      The strategy parameter is used to tune the compression algorithm. Use the
423    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
424    filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
425    string match).  Filtered data consists mostly of small values with a
426    somewhat random distribution. In this case, the compression algorithm is
427    tuned to compress them better. The effect of Z_FILTERED is to force more
428    Huffman coding and less string matching; it is somewhat intermediate
429    between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affects
430    the compression ratio but not the correctness of the compressed output even
431    if it is not set appropriately.
432 
433       deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
434    memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
435    method). msg is set to null if there is no error message.  deflateInit2 does
436    not perform any compression: this will be done by deflate().
437 */
438 
439 /*
440      Initializes the compression dictionary from the given byte sequence
441    without producing any compressed output. This function must be called
442    immediately after deflateInit, deflateInit2 or deflateReset, before any
443    call of deflate. The compressor and decompressor must use exactly the same
444    dictionary (see inflateSetDictionary).
445 
446      The dictionary should consist of strings (byte sequences) that are likely
447    to be encountered later in the data to be compressed, with the most commonly
448    used strings preferably put towards the end of the dictionary. Using a
449    dictionary is most useful when the data to be compressed is short and can be
450    predicted with good accuracy; the data can then be compressed better than
451    with the default empty dictionary.
452 
453      Depending on the size of the compression data structures selected by
454    deflateInit or deflateInit2, a part of the dictionary may in effect be
455    discarded, for example if the dictionary is larger than the window size in
456    deflate or deflate2. Thus the strings most likely to be useful should be
457    put at the end of the dictionary, not at the front.
458 
459      Upon return of this function, strm->adler is set to the Adler32 value
460    of the dictionary; the decompressor may later use this value to determine
461    which dictionary has been used by the compressor. (The Adler32 value
462    applies to the whole dictionary even if only a subset of the dictionary is
463    actually used by the compressor.)
464 
465      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
466    parameter is invalid (such as NULL dictionary) or the stream state is
467    inconsistent (for example if deflate has already been called for this stream
468    or if the compression method is bsort). deflateSetDictionary does not
469    perform any compression: this will be done by deflate().
470 */
471 
472 /*
473      Sets the destination stream as a complete copy of the source stream.
474 
475      This function can be useful when several compression strategies will be
476    tried, for example when there are several ways of pre-processing the input
477    data with a filter. The streams that will be discarded should then be freed
478    by calling deflateEnd.  Note that deflateCopy duplicates the internal
479    compression state which can be quite large, so this strategy is slow and
480    can consume lots of memory.
481 
482      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
483    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
484    (such as zalloc being NULL). msg is left unchanged in both source and
485    destination.
486 */
487 
488 /*
489      This function is equivalent to deflateEnd followed by deflateInit,
490    but does not free and reallocate all the internal compression state.
491    The stream will keep the same compression level and any other attributes
492    that may have been set by deflateInit2.
493 
494       deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
495    stream state was inconsistent (such as zalloc or state being NULL).
496 */
497 
498 /*
499      Dynamically update the compression level and compression strategy.  The
500    interpretation of level and strategy is as in deflateInit2.  This can be
501    used to switch between compression and straight copy of the input data, or
502    to switch to a different kind of input data requiring a different
503    strategy. If the compression level is changed, the input available so far
504    is compressed with the old level (and may be flushed); the new level will
505    take effect only at the next call of deflate().
506 
507      Before the call of deflateParams, the stream state must be set as for
508    a call of deflate(), since the currently available input may have to
509    be compressed and flushed. In particular, strm->avail_out must be non-zero.
510 
511      deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
512    stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
513    if strm->avail_out was zero.
514 */
515 
516 /*
517 ZEXTERN(int)  inflateInit2 OF((z_streamp strm,
518                                      int  windowBits));
519 
520      This is another version of inflateInit with an extra parameter. The
521    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
522    before by the caller.
523 
524      The windowBits parameter is the base two logarithm of the maximum window
525    size (the size of the history buffer).  It should be in the range 8..15 for
526    this version of the library. The default value is 15 if inflateInit is used
527    instead. If a compressed stream with a larger window size is given as
528    input, inflate() will return with the error code Z_DATA_ERROR instead of
529    trying to allocate a larger window.
530 
531       inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
532    memory, Z_STREAM_ERROR if a parameter is invalid (such as a negative
533    memLevel). msg is set to null if there is no error message.  inflateInit2
534    does not perform any decompression apart from reading the zlib header if
535    present: this will be done by inflate(). (So next_in and avail_in may be
536    modified, but next_out and avail_out are unchanged.)
537 */
538 
539 /*
540      Initializes the decompression dictionary from the given uncompressed byte
541    sequence. This function must be called immediately after a call of inflate
542    if this call returned Z_NEED_DICT. The dictionary chosen by the compressor
543    can be determined from the Adler32 value returned by this call of
544    inflate. The compressor and decompressor must use exactly the same
545    dictionary (see deflateSetDictionary).
546 
547      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
548    parameter is invalid (such as NULL dictionary) or the stream state is
549    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
550    expected one (incorrect Adler32 value). inflateSetDictionary does not
551    perform any decompression: this will be done by subsequent calls of
552    inflate().
553 */
554 
555 /*
556     Skips invalid compressed data until a full flush point (see above the
557   description of deflate with Z_FULL_FLUSH) can be found, or until all
558   available input is skipped. No output is provided.
559 
560     inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
561   if no more input was provided, Z_DATA_ERROR if no flush point has been found,
562   or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
563   case, the application may save the current current value of total_in which
564   indicates where valid compressed data was found. In the error case, the
565   application may repeatedly call inflateSync, providing more input each time,
566   until success or end of the input data.
567 */
568 
569 ZEXTERN(int)  inflateReset OF((z_streamp strm));
570 /*
571      This function is equivalent to inflateEnd followed by inflateInit,
572    but does not free and reallocate all the internal decompression state.
573    The stream will keep attributes that may have been set by inflateInit2.
574 
575       inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
576    stream state was inconsistent (such as zalloc or state being NULL).
577 */
578 
579 
580                         /* utility functions */
581 
582 /*
583      The following utility functions are implemented on top of the
584    basic stream-oriented functions. To simplify the interface, some
585    default options are assumed (compression level and memory usage,
586    standard memory allocation functions). The source code of these
587    utility functions can easily be modified if you need special options.
588 */
589 
590 /*
591      Compresses the source buffer into the destination buffer.  sourceLen is
592    the byte length of the source buffer. Upon entry, destLen is the total
593    size of the destination buffer, which must be at least 0.1% larger than
594    sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the
595    compressed buffer.
596      This function can be used to compress a whole file at once if the
597    input file is mmap'ed.
598      compress returns Z_OK if success, Z_MEM_ERROR if there was not
599    enough memory, Z_BUF_ERROR if there was not enough room in the output
600    buffer.
601 */
602 
603 /*
604      Compresses the source buffer into the destination buffer. The level
605    parameter has the same meaning as in deflateInit.  sourceLen is the byte
606    length of the source buffer. Upon entry, destLen is the total size of the
607    destination buffer, which must be at least 0.1% larger than sourceLen plus
608    12 bytes. Upon exit, destLen is the actual size of the compressed buffer.
609 
610      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
611    memory, Z_BUF_ERROR if there was not enough room in the output buffer,
612    Z_STREAM_ERROR if the level parameter is invalid.
613 */
614 
615 /*
616      Decompresses the source buffer into the destination buffer.  sourceLen is
617    the byte length of the source buffer. Upon entry, destLen is the total
618    size of the destination buffer, which must be large enough to hold the
619    entire uncompressed data. (The size of the uncompressed data must have
620    been saved previously by the compressor and transmitted to the decompressor
621    by some mechanism outside the scope of this compression library.)
622    Upon exit, destLen is the actual size of the compressed buffer.
623      This function can be used to decompress a whole file at once if the
624    input file is mmap'ed.
625 
626      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
627    enough memory, Z_BUF_ERROR if there was not enough room in the output
628    buffer, or Z_DATA_ERROR if the input data was corrupted.
629 */
630 
631 
632 /*
633      Opens a gzip (.gz) file for reading or writing. The mode parameter
634    is as in fopen ("rb" or "wb") but can also include a compression level
635    ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
636    Huffman only compression as in "wb1h". (See the description
637    of deflateInit2 for more information about the strategy parameter.)
638 
639      gzopen can be used to read a file which is not in gzip format; in this
640    case gzread will directly read from the file without decompression.
641 
642      gzopen returns NULL if the file could not be opened or if there was
643    insufficient memory to allocate the (de)compression state; errno
644    can be checked to distinguish the two cases (if errno is zero, the
645    zlib error is Z_MEM_ERROR).  */
646 
647 /*
648      gzdopen() associates a gzFile with the file descriptor fd.  File
649    descriptors are obtained from calls like open, dup, creat, pipe or
650    fileno (in the file has been previously opened with fopen).
651    The mode parameter is as in gzopen.
652      The next call of gzclose on the returned gzFile will also close the
653    file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
654    descriptor fd. If you want to keep fd open, use gzdopen(dup(fd), mode).
655      gzdopen returns NULL if there was insufficient memory to allocate
656    the (de)compression state.
657 */
658 
659 /*
660      Dynamically update the compression level or strategy. See the description
661    of deflateInit2 for the meaning of these parameters.
662      gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not
663    opened for writing.
664 */
665 
666 /*
667      Reads the given number of uncompressed bytes from the compressed file.
668    If the input file was not in gzip format, gzread copies the given number
669    of bytes into the buffer.
670      gzread returns the number of uncompressed bytes actually read (0 for
671    end of file, -1 for error). */
672 
673 /*
674      Writes the given number of uncompressed bytes into the compressed file.
675    gzwrite returns the number of uncompressed bytes actually written
676    (0 in case of error).
677 */
678 
679 /*
680      Converts, formats, and writes the args to the compressed file under
681    control of the format string, as in fprintf. gzprintf returns the number of
682    uncompressed bytes actually written (0 in case of error).
683 */
684 
685 /*
686       Writes the given null-terminated string to the compressed file, excluding
687    the terminating null character.
688       gzputs returns the number of characters written, or -1 in case of error.
689 */
690 
691 /*
692       Reads bytes from the compressed file until len-1 characters are read, or
693    a newline character is read and transferred to buf, or an end-of-file
694    condition is encountered.  The string is then terminated with a null
695    character.
696       gzgets returns buf, or Z_NULL in case of error.
697 */
698 
699 /*
700       Writes c, converted to an unsigned char, into the compressed file.
701    gzputc returns the value that was written, or -1 in case of error.
702 */
703 
704 /*
705       Reads one byte from the compressed file. gzgetc returns this byte
706    or -1 in case of end of file or error.
707 */
708 
709 /*
710      Flushes all pending output into the compressed file. The parameter
711    flush is as in the deflate() function. The return value is the zlib
712    error number (see function gzerror below). gzflush returns Z_OK if
713    the flush parameter is Z_FINISH and all output could be flushed.
714      gzflush should be called only when strictly necessary because it can
715    degrade compression.
716 */
717 
718 /*
719       Sets the starting position for the next gzread or gzwrite on the
720    given compressed file. The offset represents a number of bytes in the
721    uncompressed data stream. The whence parameter is defined as in lseek(2);
722    the value SEEK_END is not supported.
723      If the file is opened for reading, this function is emulated but can be
724    extremely slow. If the file is opened for writing, only forward seeks are
725    supported; gzseek then compresses a sequence of zeroes up to the new
726    starting position.
727 
728       gzseek returns the resulting offset location as measured in bytes from
729    the beginning of the uncompressed stream, or -1 in case of error, in
730    particular if the file is opened for writing and the new starting position
731    would be before the current position.
732 */
733 
734 /*
735      Rewinds the given file. This function is supported only for reading.
736 
737    gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
738 */
739 
740 /*
741      Returns the starting position for the next gzread or gzwrite on the
742    given compressed file. This position represents a number of bytes in the
743    uncompressed data stream.
744 
745    gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
746 */
747 
748 /*
749      Returns 1 when EOF has previously been detected reading the given
750    input stream, otherwise zero.
751 */
752 
753 /*
754      Flushes all pending output if necessary, closes the compressed file
755    and deallocates all the (de)compression state. The return value is the zlib
756    error number (see function gzerror below).
757 */
758 
759 /*
760      Returns the error message for the last error which occurred on the
761    given compressed file. errnum is set to zlib error number. If an
762    error occurred in the file system and not in the compression library,
763    errnum is set to Z_ERRNO and the application may consult errno
764    to get the exact error code.
765 */
766 
767                         /* checksum functions */
768 
769 /*
770      These functions are not related to compression but are exported
771    anyway because they might be useful in applications using the
772    compression library.
773 */
774 
775 ZEXTERN(uLong)  adler32 OF((uLong adler, const Bytef *buf, uInt len));
776 
777 /*
778      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
779    return the updated checksum. If buf is NULL, this function returns
780    the required initial value for the checksum.
781    An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
782    much faster. Usage example:
783 
784      uLong adler = adler32(0L, Z_NULL, 0);
785 
786      while (read_buffer(buffer, length) != EOF) {
787        adler = adler32(adler, buffer, length);
788      }
789      if (adler != original_adler) error();
790 */
791 
792 /*
793      Update a running crc with the bytes buf[0..len-1] and return the updated
794    crc. If buf is NULL, this function returns the required initial value
795    for the crc. Pre- and post-conditioning (one's complement) is performed
796    within this function so it shouldn't be done by the application.
797    Usage example:
798 
799      uLong crc = crc32(0L, Z_NULL, 0);
800 
801      while (read_buffer(buffer, length) != EOF) {
802        crc = crc32(crc, buffer, length);
803      }
804      if (crc != original_crc) error();
805 */
806 
807 
808                         /* various hacks, don't look :) */
809 
810 /* deflateInit and inflateInit are macros to allow checking the zlib version
811  * and the compiler's view of z_stream:
812  */
813 ZEXTERN(int)  inflateInit2_ OF((z_streamp strm, int  windowBits,
814                                       const char *version, int stream_size));
815 #define deflateInit(strm, level) \
816         deflateInit_((strm), (level),       ZLIB_VERSION, sizeof(z_stream))
817 #define inflateInit(strm) \
818         inflateInit_((strm),                ZLIB_VERSION, sizeof(z_stream))
819 #define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
820         deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
821                       (strategy),           ZLIB_VERSION, sizeof(z_stream))
822 #define inflateInit2(strm, windowBits) \
823         inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
824 
825 
826 #ifdef __cplusplus
827 }
828 #endif
829 
830 #endif /* _ZLIB_H */
831