1 /* zlib.h -- interface of the 'zlib' general purpose compression library
2   version 1.2.7, May 2nd, 2012
3 
4   Copyright (C) 1995-2012 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 http://tools.ietf.org/html/rfc1950
28   (zlib format), rfc1951 (deflate format) and rfc1952 (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 "1.2.7"
41 #define ZLIB_VERNUM 0x1270
42 #define ZLIB_VER_MAJOR 1
43 #define ZLIB_VER_MINOR 2
44 #define ZLIB_VER_REVISION 7
45 #define ZLIB_VER_SUBREVISION 0
46 
47 /*
48     The 'zlib' compression library provides in-memory compression and
49   decompression functions, including integrity checks of the uncompressed data.
50   This version of the library supports only one compression method (deflation)
51   but other algorithms will be added later and will have the same stream
52   interface.
53 
54     Compression can be done in a single step if the buffers are large enough,
55   or can be done by repeated calls of the compression function.  In the latter
56   case, the application must provide more input and/or consume the output
57   (providing more output space) before each call.
58 
59     The compressed data format used by default by the in-memory functions is
60   the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
61   around a deflate stream, which is itself documented in RFC 1951.
62 
63     The library also supports reading and writing files in gzip (.gz) format
64   with an interface similar to that of stdio using the functions that start
65   with "gz".  The gzip format is different from the zlib format.  gzip is a
66   gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
67 
68     This library can optionally read and write gzip streams in memory as well.
69 
70     The zlib format was designed to be compact and fast for use in memory
71   and on communications channels.  The gzip format was designed for single-
72   file compression on file systems, has a larger header than zlib to maintain
73   directory information, and uses a different, slower check method than zlib.
74 
75     The library does not install any signal handler.  The decoder checks
76   the consistency of the compressed data, so the library should never crash
77   even in case of corrupted input.
78 */
79 
80 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
81 typedef void   (*free_func)  OF((voidpf opaque, voidpf address));
82 
83 struct internal_state;
84 
85 typedef struct z_stream_s {
86     z_const Bytef *next_in;     /* next input byte */
87     uInt     avail_in;  /* number of bytes available at next_in */
88     uLong    total_in;  /* total number of input bytes read so far */
89 
90     Bytef    *next_out; /* next output byte should be put there */
91     uInt     avail_out; /* remaining free space at next_out */
92     uLong    total_out; /* total number of bytes output so far */
93 
94     z_const char *msg;  /* last error message, NULL if no error */
95     struct internal_state FAR *state; /* not visible by applications */
96 
97     alloc_func zalloc;  /* used to allocate the internal state */
98     free_func  zfree;   /* used to free the internal state */
99     voidpf     opaque;  /* private data object passed to zalloc and zfree */
100 
101     int     data_type;  /* best guess about the data type: binary or text */
102     uLong   adler;      /* adler32 value of the uncompressed data */
103     uLong   reserved;   /* reserved for future use */
104 } z_stream;
105 
106 typedef z_stream FAR *z_streamp;
107 
108 /*
109      gzip header information passed to and from zlib routines.  See RFC 1952
110   for more details on the meanings of these fields.
111 */
112 typedef struct gz_header_s {
113     int     text;       /* true if compressed data believed to be text */
114     uLong   time;       /* modification time */
115     int     xflags;     /* extra flags (not used when writing a gzip file) */
116     int     os;         /* operating system */
117     Bytef   *extra;     /* pointer to extra field or Z_NULL if none */
118     uInt    extra_len;  /* extra field length (valid if extra != Z_NULL) */
119     uInt    extra_max;  /* space at extra (only when reading header) */
120     Bytef   *name;      /* pointer to zero-terminated file name or Z_NULL */
121     uInt    name_max;   /* space at name (only when reading header) */
122     Bytef   *comment;   /* pointer to zero-terminated comment or Z_NULL */
123     uInt    comm_max;   /* space at comment (only when reading header) */
124     int     hcrc;       /* true if there was or will be a header crc */
125     int     done;       /* true when done reading gzip header (not used
126                            when writing a gzip file) */
127 } gz_header;
128 
129 typedef gz_header FAR *gz_headerp;
130 
131 /*
132      The application must update next_in and avail_in when avail_in has dropped
133    to zero.  It must update next_out and avail_out when avail_out has dropped
134    to zero.  The application must initialize zalloc, zfree and opaque before
135    calling the init function.  All other fields are set by the compression
136    library and must not be updated by the application.
137 
138      The opaque value provided by the application will be passed as the first
139    parameter for calls of zalloc and zfree.  This can be useful for custom
140    memory management.  The compression library attaches no meaning to the
141    opaque value.
142 
143      zalloc must return Z_NULL if there is not enough memory for the object.
144    If zlib is used in a multi-threaded application, zalloc and zfree must be
145    thread safe.
146 
147      On 16-bit systems, the functions zalloc and zfree must be able to allocate
148    exactly 65536 bytes, but will not be required to allocate more than this if
149    the symbol MAXSEG_64K is defined (see zconf.h).  WARNING: On MSDOS, pointers
150    returned by zalloc for objects of exactly 65536 bytes *must* have their
151    offset normalized to zero.  The default allocation function provided by this
152    library ensures this (see zutil.c).  To reduce memory requirements and avoid
153    any allocation of 64K objects, at the expense of compression ratio, compile
154    the library with -DMAX_WBITS=14 (see zconf.h).
155 
156      The fields total_in and total_out can be used for statistics or progress
157    reports.  After compression, total_in holds the total size of the
158    uncompressed data and may be saved for use in the decompressor (particularly
159    if the decompressor wants to decompress everything in a single step).
160 */
161 
162                         /* constants */
163 
164 #define Z_NO_FLUSH      0
165 #define Z_PARTIAL_FLUSH 1
166 #define Z_SYNC_FLUSH    2
167 #define Z_FULL_FLUSH    3
168 #define Z_FINISH        4
169 #define Z_BLOCK         5
170 #define Z_TREES         6
171 /* Allowed flush values; see deflate() and inflate() below for details */
172 
173 #define Z_OK            0
174 #define Z_STREAM_END    1
175 #define Z_NEED_DICT     2
176 #define Z_ERRNO        (-1)
177 #define Z_STREAM_ERROR (-2)
178 #define Z_DATA_ERROR   (-3)
179 #define Z_MEM_ERROR    (-4)
180 #define Z_BUF_ERROR    (-5)
181 #define Z_VERSION_ERROR (-6)
182 /* Return codes for the compression/decompression functions. Negative values
183  * are errors, positive values are used for special but normal events.
184  */
185 
186 #define Z_NO_COMPRESSION         0
187 #define Z_BEST_SPEED             1
188 #define Z_BEST_COMPRESSION       9
189 #define Z_DEFAULT_COMPRESSION  (-1)
190 /* compression levels */
191 
192 #define Z_FILTERED            1
193 #define Z_HUFFMAN_ONLY        2
194 #define Z_RLE                 3
195 #define Z_FIXED               4
196 #define Z_DEFAULT_STRATEGY    0
197 /* compression strategy; see deflateInit2() below for details */
198 
199 #define Z_BINARY   0
200 #define Z_TEXT     1
201 #define Z_ASCII    Z_TEXT   /* for compatibility with 1.2.2 and earlier */
202 #define Z_UNKNOWN  2
203 /* Possible values of the data_type field (though see inflate()) */
204 
205 #define Z_DEFLATED   8
206 /* The deflate compression method (the only one supported in this version) */
207 
208 #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
209 
210 #define zlib_version zlibVersion()
211 /* for compatibility with versions < 1.0.2 */
212 
213 
214                         /* basic functions */
215 
216 ZEXTERN const char * ZEXPORT zlibVersion OF((void));
217 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
218    If the first character differs, the library code actually used is not
219    compatible with the zlib.h header file used by the application.  This check
220    is automatically made by deflateInit and inflateInit.
221  */
222 
223 /*
224 ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));
225 
226      Initializes the internal stream state for compression.  The fields
227    zalloc, zfree and opaque must be initialized before by the caller.  If
228    zalloc and zfree are set to Z_NULL, deflateInit updates them to use default
229    allocation functions.
230 
231      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
232    1 gives best speed, 9 gives best compression, 0 gives no compression at all
233    (the input data is simply copied a block at a time).  Z_DEFAULT_COMPRESSION
234    requests a default compromise between speed and compression (currently
235    equivalent to level 6).
236 
237      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
238    memory, Z_STREAM_ERROR if level is not a valid compression level, or
239    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
240    with the version assumed by the caller (ZLIB_VERSION).  msg is set to null
241    if there is no error message.  deflateInit does not perform any compression:
242    this will be done by deflate().
243 */
244 
245 
246 ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));
247 /*
248     deflate compresses as much data as possible, and stops when the input
249   buffer becomes empty or the output buffer becomes full.  It may introduce
250   some output latency (reading input without producing any output) except when
251   forced to flush.
252 
253     The detailed semantics are as follows.  deflate performs one or both of the
254   following actions:
255 
256   - Compress more input starting at next_in and update next_in and avail_in
257     accordingly.  If not all input can be processed (because there is not
258     enough room in the output buffer), next_in and avail_in are updated and
259     processing will resume at this point for the next call of deflate().
260 
261   - Provide more output starting at next_out and update next_out and avail_out
262     accordingly.  This action is forced if the parameter flush is non zero.
263     Forcing flush frequently degrades the compression ratio, so this parameter
264     should be set only when necessary (in interactive applications).  Some
265     output may be provided even if flush is not set.
266 
267     Before the call of deflate(), the application should ensure that at least
268   one of the actions is possible, by providing more input and/or consuming more
269   output, and updating avail_in or avail_out accordingly; avail_out should
270   never be zero before the call.  The application can consume the compressed
271   output when it wants, for example when the output buffer is full (avail_out
272   == 0), or after each call of deflate().  If deflate returns Z_OK and with
273   zero avail_out, it must be called again after making room in the output
274   buffer because there might be more output pending.
275 
276     Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to
277   decide how much data to accumulate before producing output, in order to
278   maximize compression.
279 
280     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
281   flushed to the output buffer and the output is aligned on a byte boundary, so
282   that the decompressor can get all input data available so far.  (In
283   particular avail_in is zero after the call if enough output space has been
284   provided before the call.) Flushing may degrade compression for some
285   compression algorithms and so it should be used only when necessary.  This
286   completes the current deflate block and follows it with an empty stored block
287   that is three bits plus filler bits to the next byte, followed by four bytes
288   (00 00 ff ff).
289 
290     If flush is set to Z_PARTIAL_FLUSH, all pending output is flushed to the
291   output buffer, but the output is not aligned to a byte boundary.  All of the
292   input data so far will be available to the decompressor, as for Z_SYNC_FLUSH.
293   This completes the current deflate block and follows it with an empty fixed
294   codes block that is 10 bits long.  This assures that enough bytes are output
295   in order for the decompressor to finish the block before the empty fixed code
296   block.
297 
298     If flush is set to Z_BLOCK, a deflate block is completed and emitted, as
299   for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to
300   seven bits of the current block are held to be written as the next byte after
301   the next deflate block is completed.  In this case, the decompressor may not
302   be provided enough bits at this point in order to complete decompression of
303   the data provided so far to the compressor.  It may need to wait for the next
304   block to be emitted.  This is for advanced applications that need to control
305   the emission of deflate blocks.
306 
307     If flush is set to Z_FULL_FLUSH, all output is flushed as with
308   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
309   restart from this point if previous compressed data has been damaged or if
310   random access is desired.  Using Z_FULL_FLUSH too often can seriously degrade
311   compression.
312 
313     If deflate returns with avail_out == 0, this function must be called again
314   with the same value of the flush parameter and more output space (updated
315   avail_out), until the flush is complete (deflate returns with non-zero
316   avail_out).  In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
317   avail_out is greater than six to avoid repeated flush markers due to
318   avail_out == 0 on return.
319 
320     If the parameter flush is set to Z_FINISH, pending input is processed,
321   pending output is flushed and deflate returns with Z_STREAM_END if there was
322   enough output space; if deflate returns with Z_OK, this function must be
323   called again with Z_FINISH and more output space (updated avail_out) but no
324   more input data, until it returns with Z_STREAM_END or an error.  After
325   deflate has returned Z_STREAM_END, the only possible operations on the stream
326   are deflateReset or deflateEnd.
327 
328     Z_FINISH can be used immediately after deflateInit if all the compression
329   is to be done in a single step.  In this case, avail_out must be at least the
330   value returned by deflateBound (see below).  Then deflate is guaranteed to
331   return Z_STREAM_END.  If not enough output space is provided, deflate will
332   not return Z_STREAM_END, and it must be called again as described above.
333 
334     deflate() sets strm->adler to the adler32 checksum of all input read
335   so far (that is, total_in bytes).
336 
337     deflate() may update strm->data_type if it can make a good guess about
338   the input data type (Z_BINARY or Z_TEXT).  In doubt, the data is considered
339   binary.  This field is only for information purposes and does not affect the
340   compression algorithm in any manner.
341 
342     deflate() returns Z_OK if some progress has been made (more input
343   processed or more output produced), Z_STREAM_END if all input has been
344   consumed and all output has been produced (only when flush is set to
345   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
346   if next_in or next_out was Z_NULL), Z_BUF_ERROR if no progress is possible
347   (for example avail_in or avail_out was zero).  Note that Z_BUF_ERROR is not
348   fatal, and deflate() can be called again with more input and more output
349   space to continue compressing.
350 */
351 
352 
353 ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
354 /*
355      All dynamically allocated data structures for this stream are freed.
356    This function discards any unprocessed input and does not flush any pending
357    output.
358 
359      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
360    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
361    prematurely (some input or output was discarded).  In the error case, msg
362    may be set but then points to a static string (which must not be
363    deallocated).
364 */
365 
366 
367 /*
368 ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));
369 
370      Initializes the internal stream state for decompression.  The fields
371    next_in, avail_in, zalloc, zfree and opaque must be initialized before by
372    the caller.  If next_in is not Z_NULL and avail_in is large enough (the
373    exact value depends on the compression method), inflateInit determines the
374    compression method from the zlib header and allocates all data structures
375    accordingly; otherwise the allocation will be deferred to the first call of
376    inflate.  If zalloc and zfree are set to Z_NULL, inflateInit updates them to
377    use default allocation functions.
378 
379      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
380    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
381    version assumed by the caller, or Z_STREAM_ERROR if the parameters are
382    invalid, such as a null pointer to the structure.  msg is set to null if
383    there is no error message.  inflateInit does not perform any decompression
384    apart from possibly reading the zlib header if present: actual decompression
385    will be done by inflate().  (So next_in and avail_in may be modified, but
386    next_out and avail_out are unused and unchanged.) The current implementation
387    of inflateInit() does not process any header information -- that is deferred
388    until inflate() is called.
389 */
390 
391 
392 ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
393 /*
394     inflate decompresses as much data as possible, and stops when the input
395   buffer becomes empty or the output buffer becomes full.  It may introduce
396   some output latency (reading input without producing any output) except when
397   forced to flush.
398 
399   The detailed semantics are as follows.  inflate performs one or both of the
400   following actions:
401 
402   - Decompress more input starting at next_in and update next_in and avail_in
403     accordingly.  If not all input can be processed (because there is not
404     enough room in the output buffer), next_in is updated and processing will
405     resume at this point for the next call of inflate().
406 
407   - Provide more output starting at next_out and update next_out and avail_out
408     accordingly.  inflate() provides as much output as possible, until there is
409     no more input data or no more space in the output buffer (see below about
410     the flush parameter).
411 
412     Before the call of inflate(), the application should ensure that at least
413   one of the actions is possible, by providing more input and/or consuming more
414   output, and updating the next_* and avail_* values accordingly.  The
415   application can consume the uncompressed output when it wants, for example
416   when the output buffer is full (avail_out == 0), or after each call of
417   inflate().  If inflate returns Z_OK and with zero avail_out, it must be
418   called again after making room in the output buffer because there might be
419   more output pending.
420 
421     The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH, Z_FINISH,
422   Z_BLOCK, or Z_TREES.  Z_SYNC_FLUSH requests that inflate() flush as much
423   output as possible to the output buffer.  Z_BLOCK requests that inflate()
424   stop if and when it gets to the next deflate block boundary.  When decoding
425   the zlib or gzip format, this will cause inflate() to return immediately
426   after the header and before the first block.  When doing a raw inflate,
427   inflate() will go ahead and process the first block, and will return when it
428   gets to the end of that block, or when it runs out of data.
429 
430     The Z_BLOCK option assists in appending to or combining deflate streams.
431   Also to assist in this, on return inflate() will set strm->data_type to the
432   number of unused bits in the last byte taken from strm->next_in, plus 64 if
433   inflate() is currently decoding the last block in the deflate stream, plus
434   128 if inflate() returned immediately after decoding an end-of-block code or
435   decoding the complete header up to just before the first byte of the deflate
436   stream.  The end-of-block will not be indicated until all of the uncompressed
437   data from that block has been written to strm->next_out.  The number of
438   unused bits may in general be greater than seven, except when bit 7 of
439   data_type is set, in which case the number of unused bits will be less than
440   eight.  data_type is set as noted here every time inflate() returns for all
441   flush options, and so can be used to determine the amount of currently
442   consumed input in bits.
443 
444     The Z_TREES option behaves as Z_BLOCK does, but it also returns when the
445   end of each deflate block header is reached, before any actual data in that
446   block is decoded.  This allows the caller to determine the length of the
447   deflate block header for later use in random access within a deflate block.
448   256 is added to the value of strm->data_type when inflate() returns
449   immediately after reaching the end of the deflate block header.
450 
451     inflate() should normally be called until it returns Z_STREAM_END or an
452   error.  However if all decompression is to be performed in a single step (a
453   single call of inflate), the parameter flush should be set to Z_FINISH.  In
454   this case all pending input is processed and all pending output is flushed;
455   avail_out must be large enough to hold all of the uncompressed data for the
456   operation to complete.  (The size of the uncompressed data may have been
457   saved by the compressor for this purpose.) The use of Z_FINISH is not
458   required to perform an inflation in one step.  However it may be used to
459   inform inflate that a faster approach can be used for the single inflate()
460   call.  Z_FINISH also informs inflate to not maintain a sliding window if the
461   stream completes, which reduces inflate's memory footprint.  If the stream
462   does not complete, either because not all of the stream is provided or not
463   enough output space is provided, then a sliding window will be allocated and
464   inflate() can be called again to continue the operation as if Z_NO_FLUSH had
465   been used.
466 
467      In this implementation, inflate() always flushes as much output as
468   possible to the output buffer, and always uses the faster approach on the
469   first call.  So the effects of the flush parameter in this implementation are
470   on the return value of inflate() as noted below, when inflate() returns early
471   when Z_BLOCK or Z_TREES is used, and when inflate() avoids the allocation of
472   memory for a sliding window when Z_FINISH is used.
473 
474      If a preset dictionary is needed after this call (see inflateSetDictionary
475   below), inflate sets strm->adler to the Adler-32 checksum of the dictionary
476   chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
477   strm->adler to the Adler-32 checksum of all output produced so far (that is,
478   total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
479   below.  At the end of the stream, inflate() checks that its computed adler32
480   checksum is equal to that saved by the compressor and returns Z_STREAM_END
481   only if the checksum is correct.
482 
483     inflate() can decompress and check either zlib-wrapped or gzip-wrapped
484   deflate data.  The header type is detected automatically, if requested when
485   initializing with inflateInit2().  Any information contained in the gzip
486   header is not retained, so applications that need that information should
487   instead use raw inflate, see inflateInit2() below, or inflateBack() and
488   perform their own processing of the gzip header and trailer.  When processing
489   gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output
490   producted so far.  The CRC-32 is checked against the gzip trailer.
491 
492     inflate() returns Z_OK if some progress has been made (more input processed
493   or more output produced), Z_STREAM_END if the end of the compressed data has
494   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
495   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
496   corrupted (input stream not conforming to the zlib format or incorrect check
497   value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
498   next_in or next_out was Z_NULL), Z_MEM_ERROR if there was not enough memory,
499   Z_BUF_ERROR if no progress is possible or if there was not enough room in the
500   output buffer when Z_FINISH is used.  Note that Z_BUF_ERROR is not fatal, and
501   inflate() can be called again with more input and more output space to
502   continue decompressing.  If Z_DATA_ERROR is returned, the application may
503   then call inflateSync() to look for a good compression block if a partial
504   recovery of the data is desired.
505 */
506 
507 
508 ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));
509 /*
510      All dynamically allocated data structures for this stream are freed.
511    This function discards any unprocessed input and does not flush any pending
512    output.
513 
514      inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
515    was inconsistent.  In the error case, msg may be set but then points to a
516    static string (which must not be deallocated).
517 */
518 
519 
520                         /* Advanced functions */
521 
522 /*
523     The following functions are needed only in some special applications.
524 */
525 
526 /*
527 ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
528                                      int  level,
529                                      int  method,
530                                      int  windowBits,
531                                      int  memLevel,
532                                      int  strategy));
533 
534      This is another version of deflateInit with more compression options.  The
535    fields next_in, zalloc, zfree and opaque must be initialized before by the
536    caller.
537 
538      The method parameter is the compression method.  It must be Z_DEFLATED in
539    this version of the library.
540 
541      The windowBits parameter is the base two logarithm of the window size
542    (the size of the history buffer).  It should be in the range 8..15 for this
543    version of the library.  Larger values of this parameter result in better
544    compression at the expense of memory usage.  The default value is 15 if
545    deflateInit is used instead.
546 
547      windowBits can also be -8..-15 for raw deflate.  In this case, -windowBits
548    determines the window size.  deflate() will then generate raw deflate data
549    with no zlib header or trailer, and will not compute an adler32 check value.
550 
551      windowBits can also be greater than 15 for optional gzip encoding.  Add
552    16 to windowBits to write a simple gzip header and trailer around the
553    compressed data instead of a zlib wrapper.  The gzip header will have no
554    file name, no extra data, no comment, no modification time (set to zero), no
555    header crc, and the operating system will be set to 255 (unknown).  If a
556    gzip stream is being written, strm->adler is a crc32 instead of an adler32.
557 
558      The memLevel parameter specifies how much memory should be allocated
559    for the internal compression state.  memLevel=1 uses minimum memory but is
560    slow and reduces compression ratio; memLevel=9 uses maximum memory for
561    optimal speed.  The default value is 8.  See zconf.h for total memory usage
562    as a function of windowBits and memLevel.
563 
564      The strategy parameter is used to tune the compression algorithm.  Use the
565    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
566    filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
567    string match), or Z_RLE to limit match distances to one (run-length
568    encoding).  Filtered data consists mostly of small values with a somewhat
569    random distribution.  In this case, the compression algorithm is tuned to
570    compress them better.  The effect of Z_FILTERED is to force more Huffman
571    coding and less string matching; it is somewhat intermediate between
572    Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY.  Z_RLE is designed to be almost as
573    fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data.  The
574    strategy parameter only affects the compression ratio but not the
575    correctness of the compressed output even if it is not set appropriately.
576    Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler
577    decoder for special applications.
578 
579      deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
580    memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid
581    method), or Z_VERSION_ERROR if the zlib library version (zlib_version) is
582    incompatible with the version assumed by the caller (ZLIB_VERSION).  msg is
583    set to null if there is no error message.  deflateInit2 does not perform any
584    compression: this will be done by deflate().
585 */
586 
587 ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,
588                                              const Bytef *dictionary,
589                                              uInt  dictLength));
590 /*
591      Initializes the compression dictionary from the given byte sequence
592    without producing any compressed output.  When using the zlib format, this
593    function must be called immediately after deflateInit, deflateInit2 or
594    deflateReset, and before any call of deflate.  When doing raw deflate, this
595    function must be called either before any call of deflate, or immediately
596    after the completion of a deflate block, i.e. after all input has been
597    consumed and all output has been delivered when using any of the flush
598    options Z_BLOCK, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH, or Z_FULL_FLUSH.  The
599    compressor and decompressor must use exactly the same dictionary (see
600    inflateSetDictionary).
601 
602      The dictionary should consist of strings (byte sequences) that are likely
603    to be encountered later in the data to be compressed, with the most commonly
604    used strings preferably put towards the end of the dictionary.  Using a
605    dictionary is most useful when the data to be compressed is short and can be
606    predicted with good accuracy; the data can then be compressed better than
607    with the default empty dictionary.
608 
609      Depending on the size of the compression data structures selected by
610    deflateInit or deflateInit2, a part of the dictionary may in effect be
611    discarded, for example if the dictionary is larger than the window size
612    provided in deflateInit or deflateInit2.  Thus the strings most likely to be
613    useful should be put at the end of the dictionary, not at the front.  In
614    addition, the current implementation of deflate will use at most the window
615    size minus 262 bytes of the provided dictionary.
616 
617      Upon return of this function, strm->adler is set to the adler32 value
618    of the dictionary; the decompressor may later use this value to determine
619    which dictionary has been used by the compressor.  (The adler32 value
620    applies to the whole dictionary even if only a subset of the dictionary is
621    actually used by the compressor.) If a raw deflate was requested, then the
622    adler32 value is not computed and strm->adler is not set.
623 
624      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
625    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
626    inconsistent (for example if deflate has already been called for this stream
627    or if not at a block boundary for raw deflate).  deflateSetDictionary does
628    not perform any compression: this will be done by deflate().
629 */
630 
631 ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,
632                                     z_streamp source));
633 /*
634      Sets the destination stream as a complete copy of the source stream.
635 
636      This function can be useful when several compression strategies will be
637    tried, for example when there are several ways of pre-processing the input
638    data with a filter.  The streams that will be discarded should then be freed
639    by calling deflateEnd.  Note that deflateCopy duplicates the internal
640    compression state which can be quite large, so this strategy is slow and can
641    consume lots of memory.
642 
643      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
644    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
645    (such as zalloc being Z_NULL).  msg is left unchanged in both source and
646    destination.
647 */
648 
649 ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
650 /*
651      This function is equivalent to deflateEnd followed by deflateInit,
652    but does not free and reallocate all the internal compression state.  The
653    stream will keep the same compression level and any other attributes that
654    may have been set by deflateInit2.
655 
656      deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
657    stream state was inconsistent (such as zalloc or state being Z_NULL).
658 */
659 
660 ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
661                                       int level,
662                                       int strategy));
663 /*
664      Dynamically update the compression level and compression strategy.  The
665    interpretation of level and strategy is as in deflateInit2.  This can be
666    used to switch between compression and straight copy of the input data, or
667    to switch to a different kind of input data requiring a different strategy.
668    If the compression level is changed, the input available so far is
669    compressed with the old level (and may be flushed); the new level will take
670    effect only at the next call of deflate().
671 
672      Before the call of deflateParams, the stream state must be set as for
673    a call of deflate(), since the currently available input may have to be
674    compressed and flushed.  In particular, strm->avail_out must be non-zero.
675 
676      deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
677    stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR if
678    strm->avail_out was zero.
679 */
680 
681 ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm,
682                                     int good_length,
683                                     int max_lazy,
684                                     int nice_length,
685                                     int max_chain));
686 /*
687      Fine tune deflate's internal compression parameters.  This should only be
688    used by someone who understands the algorithm used by zlib's deflate for
689    searching for the best matching string, and even then only by the most
690    fanatic optimizer trying to squeeze out the last compressed bit for their
691    specific input data.  Read the deflate.c source code for the meaning of the
692    max_lazy, good_length, nice_length, and max_chain parameters.
693 
694      deflateTune() can be called after deflateInit() or deflateInit2(), and
695    returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.
696  */
697 
698 ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,
699                                        uLong sourceLen));
700 /*
701      deflateBound() returns an upper bound on the compressed size after
702    deflation of sourceLen bytes.  It must be called after deflateInit() or
703    deflateInit2(), and after deflateSetHeader(), if used.  This would be used
704    to allocate an output buffer for deflation in a single pass, and so would be
705    called before deflate().  If that first deflate() call is provided the
706    sourceLen input bytes, an output buffer allocated to the size returned by
707    deflateBound(), and the flush value Z_FINISH, then deflate() is guaranteed
708    to return Z_STREAM_END.  Note that it is possible for the compressed size to
709    be larger than the value returned by deflateBound() if flush options other
710    than Z_FINISH or Z_NO_FLUSH are used.
711 */
712 
713 ZEXTERN int ZEXPORT deflatePending OF((z_streamp strm,
714                                        unsigned *pending,
715                                        int *bits));
716 /*
717      deflatePending() returns the number of bytes and bits of output that have
718    been generated, but not yet provided in the available output.  The bytes not
719    provided would be due to the available output space having being consumed.
720    The number of bits of output not provided are between 0 and 7, where they
721    await more bits to join them in order to fill out a full byte.  If pending
722    or bits are Z_NULL, then those values are not set.
723 
724      deflatePending returns Z_OK if success, or Z_STREAM_ERROR if the source
725    stream state was inconsistent.
726  */
727 
728 ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,
729                                      int bits,
730                                      int value));
731 /*
732      deflatePrime() inserts bits in the deflate output stream.  The intent
733    is that this function is used to start off the deflate output with the bits
734    leftover from a previous deflate stream when appending to it.  As such, this
735    function can only be used for raw deflate, and must be used before the first
736    deflate() call after a deflateInit2() or deflateReset().  bits must be less
737    than or equal to 16, and that many of the least significant bits of value
738    will be inserted in the output.
739 
740      deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough
741    room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the
742    source stream state was inconsistent.
743 */
744 
745 ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm,
746                                          gz_headerp head));
747 /*
748      deflateSetHeader() provides gzip header information for when a gzip
749    stream is requested by deflateInit2().  deflateSetHeader() may be called
750    after deflateInit2() or deflateReset() and before the first call of
751    deflate().  The text, time, os, extra field, name, and comment information
752    in the provided gz_header structure are written to the gzip header (xflag is
753    ignored -- the extra flags are set according to the compression level).  The
754    caller must assure that, if not Z_NULL, name and comment are terminated with
755    a zero byte, and that if extra is not Z_NULL, that extra_len bytes are
756    available there.  If hcrc is true, a gzip header crc is included.  Note that
757    the current versions of the command-line version of gzip (up through version
758    1.3.x) do not support header crc's, and will report that it is a "multi-part
759    gzip file" and give up.
760 
761      If deflateSetHeader is not used, the default gzip header has text false,
762    the time set to zero, and os set to 255, with no extra, name, or comment
763    fields.  The gzip header is returned to the default state by deflateReset().
764 
765      deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
766    stream state was inconsistent.
767 */
768 
769 /*
770 ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
771                                      int  windowBits));
772 
773      This is another version of inflateInit with an extra parameter.  The
774    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
775    before by the caller.
776 
777      The windowBits parameter is the base two logarithm of the maximum window
778    size (the size of the history buffer).  It should be in the range 8..15 for
779    this version of the library.  The default value is 15 if inflateInit is used
780    instead.  windowBits must be greater than or equal to the windowBits value
781    provided to deflateInit2() while compressing, or it must be equal to 15 if
782    deflateInit2() was not used.  If a compressed stream with a larger window
783    size is given as input, inflate() will return with the error code
784    Z_DATA_ERROR instead of trying to allocate a larger window.
785 
786      windowBits can also be zero to request that inflate use the window size in
787    the zlib header of the compressed stream.
788 
789      windowBits can also be -8..-15 for raw inflate.  In this case, -windowBits
790    determines the window size.  inflate() will then process raw deflate data,
791    not looking for a zlib or gzip header, not generating a check value, and not
792    looking for any check values for comparison at the end of the stream.  This
793    is for use with other formats that use the deflate compressed data format
794    such as zip.  Those formats provide their own check values.  If a custom
795    format is developed using the raw deflate format for compressed data, it is
796    recommended that a check value such as an adler32 or a crc32 be applied to
797    the uncompressed data as is done in the zlib, gzip, and zip formats.  For
798    most applications, the zlib format should be used as is.  Note that comments
799    above on the use in deflateInit2() applies to the magnitude of windowBits.
800 
801      windowBits can also be greater than 15 for optional gzip decoding.  Add
802    32 to windowBits to enable zlib and gzip decoding with automatic header
803    detection, or add 16 to decode only the gzip format (the zlib format will
804    return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is a
805    crc32 instead of an adler32.
806 
807      inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
808    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
809    version assumed by the caller, or Z_STREAM_ERROR if the parameters are
810    invalid, such as a null pointer to the structure.  msg is set to null if
811    there is no error message.  inflateInit2 does not perform any decompression
812    apart from possibly reading the zlib header if present: actual decompression
813    will be done by inflate().  (So next_in and avail_in may be modified, but
814    next_out and avail_out are unused and unchanged.) The current implementation
815    of inflateInit2() does not process any header information -- that is
816    deferred until inflate() is called.
817 */
818 
819 ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,
820                                              const Bytef *dictionary,
821                                              uInt  dictLength));
822 /*
823      Initializes the decompression dictionary from the given uncompressed byte
824    sequence.  This function must be called immediately after a call of inflate,
825    if that call returned Z_NEED_DICT.  The dictionary chosen by the compressor
826    can be determined from the adler32 value returned by that call of inflate.
827    The compressor and decompressor must use exactly the same dictionary (see
828    deflateSetDictionary).  For raw inflate, this function can be called at any
829    time to set the dictionary.  If the provided dictionary is smaller than the
830    window and there is already data in the window, then the provided dictionary
831    will amend what's there.  The application must insure that the dictionary
832    that was used for compression is provided.
833 
834      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
835    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
836    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
837    expected one (incorrect adler32 value).  inflateSetDictionary does not
838    perform any decompression: this will be done by subsequent calls of
839    inflate().
840 */
841 
842 ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
843 /*
844      Skips invalid compressed data until a possible full flush point (see above
845    for the description of deflate with Z_FULL_FLUSH) can be found, or until all
846    available input is skipped.  No output is provided.
847 
848      inflateSync searches for a 00 00 FF FF pattern in the compressed data.
849    All full flush points have this pattern, but not all occurences of this
850    pattern are full flush points.
851 
852      inflateSync returns Z_OK if a possible full flush point has been found,
853    Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point
854    has been found, or Z_STREAM_ERROR if the stream structure was inconsistent.
855    In the success case, the application may save the current current value of
856    total_in which indicates where valid compressed data was found.  In the
857    error case, the application may repeatedly call inflateSync, providing more
858    input each time, until success or end of the input data.
859 */
860 
861 ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,
862                                     z_streamp source));
863 /*
864      Sets the destination stream as a complete copy of the source stream.
865 
866      This function can be useful when randomly accessing a large stream.  The
867    first pass through the stream can periodically record the inflate state,
868    allowing restarting inflate at those points when randomly accessing the
869    stream.
870 
871      inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
872    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
873    (such as zalloc being Z_NULL).  msg is left unchanged in both source and
874    destination.
875 */
876 
877 ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
878 /*
879      This function is equivalent to inflateEnd followed by inflateInit,
880    but does not free and reallocate all the internal decompression state.  The
881    stream will keep attributes that may have been set by inflateInit2.
882 
883      inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
884    stream state was inconsistent (such as zalloc or state being Z_NULL).
885 */
886 
887 ZEXTERN int ZEXPORT inflateReset2 OF((z_streamp strm,
888                                       int windowBits));
889 /*
890      This function is the same as inflateReset, but it also permits changing
891    the wrap and window size requests.  The windowBits parameter is interpreted
892    the same as it is for inflateInit2.
893 
894      inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source
895    stream state was inconsistent (such as zalloc or state being Z_NULL), or if
896    the windowBits parameter is invalid.
897 */
898 
899 ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm,
900                                      int bits,
901                                      int value));
902 /*
903      This function inserts bits in the inflate input stream.  The intent is
904    that this function is used to start inflating at a bit position in the
905    middle of a byte.  The provided bits will be used before any bytes are used
906    from next_in.  This function should only be used with raw inflate, and
907    should be used before the first inflate() call after inflateInit2() or
908    inflateReset().  bits must be less than or equal to 16, and that many of the
909    least significant bits of value will be inserted in the input.
910 
911      If bits is negative, then the input stream bit buffer is emptied.  Then
912    inflatePrime() can be called again to put bits in the buffer.  This is used
913    to clear out bits leftover after feeding inflate a block description prior
914    to feeding inflate codes.
915 
916      inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
917    stream state was inconsistent.
918 */
919 
920 ZEXTERN long ZEXPORT inflateMark OF((z_streamp strm));
921 /*
922      This function returns two values, one in the lower 16 bits of the return
923    value, and the other in the remaining upper bits, obtained by shifting the
924    return value down 16 bits.  If the upper value is -1 and the lower value is
925    zero, then inflate() is currently decoding information outside of a block.
926    If the upper value is -1 and the lower value is non-zero, then inflate is in
927    the middle of a stored block, with the lower value equaling the number of
928    bytes from the input remaining to copy.  If the upper value is not -1, then
929    it is the number of bits back from the current bit position in the input of
930    the code (literal or length/distance pair) currently being processed.  In
931    that case the lower value is the number of bytes already emitted for that
932    code.
933 
934      A code is being processed if inflate is waiting for more input to complete
935    decoding of the code, or if it has completed decoding but is waiting for
936    more output space to write the literal or match data.
937 
938      inflateMark() is used to mark locations in the input data for random
939    access, which may be at bit positions, and to note those cases where the
940    output of a code may span boundaries of random access blocks.  The current
941    location in the input stream can be determined from avail_in and data_type
942    as noted in the description for the Z_BLOCK flush parameter for inflate.
943 
944      inflateMark returns the value noted above or -1 << 16 if the provided
945    source stream state was inconsistent.
946 */
947 
948 ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm,
949                                          gz_headerp head));
950 /*
951      inflateGetHeader() requests that gzip header information be stored in the
952    provided gz_header structure.  inflateGetHeader() may be called after
953    inflateInit2() or inflateReset(), and before the first call of inflate().
954    As inflate() processes the gzip stream, head->done is zero until the header
955    is completed, at which time head->done is set to one.  If a zlib stream is
956    being decoded, then head->done is set to -1 to indicate that there will be
957    no gzip header information forthcoming.  Note that Z_BLOCK or Z_TREES can be
958    used to force inflate() to return immediately after header processing is
959    complete and before any actual data is decompressed.
960 
961      The text, time, xflags, and os fields are filled in with the gzip header
962    contents.  hcrc is set to true if there is a header CRC.  (The header CRC
963    was valid if done is set to one.) If extra is not Z_NULL, then extra_max
964    contains the maximum number of bytes to write to extra.  Once done is true,
965    extra_len contains the actual extra field length, and extra contains the
966    extra field, or that field truncated if extra_max is less than extra_len.
967    If name is not Z_NULL, then up to name_max characters are written there,
968    terminated with a zero unless the length is greater than name_max.  If
969    comment is not Z_NULL, then up to comm_max characters are written there,
970    terminated with a zero unless the length is greater than comm_max.  When any
971    of extra, name, or comment are not Z_NULL and the respective field is not
972    present in the header, then that field is set to Z_NULL to signal its
973    absence.  This allows the use of deflateSetHeader() with the returned
974    structure to duplicate the header.  However if those fields are set to
975    allocated memory, then the application will need to save those pointers
976    elsewhere so that they can be eventually freed.
977 
978      If inflateGetHeader is not used, then the header information is simply
979    discarded.  The header is always checked for validity, including the header
980    CRC if present.  inflateReset() will reset the process to discard the header
981    information.  The application would need to call inflateGetHeader() again to
982    retrieve the header from the next gzip stream.
983 
984      inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
985    stream state was inconsistent.
986 */
987 
988 /*
989 ZEXTERN int ZEXPORT inflateBackInit OF((z_streamp strm, int windowBits,
990                                         unsigned char FAR *window));
991 
992      Initialize the internal stream state for decompression using inflateBack()
993    calls.  The fields zalloc, zfree and opaque in strm must be initialized
994    before the call.  If zalloc and zfree are Z_NULL, then the default library-
995    derived memory allocation routines are used.  windowBits is the base two
996    logarithm of the window size, in the range 8..15.  window is a caller
997    supplied buffer of that size.  Except for special applications where it is
998    assured that deflate was used with small window sizes, windowBits must be 15
999    and a 32K byte window must be supplied to be able to decompress general
1000    deflate streams.
1001 
1002      See inflateBack() for the usage of these routines.
1003 
1004      inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
1005    the parameters are invalid, Z_MEM_ERROR if the internal state could not be
1006    allocated, or Z_VERSION_ERROR if the version of the library does not match
1007    the version of the header file.
1008 */
1009 
1010 typedef unsigned (*in_func) OF((void FAR *, unsigned char FAR * FAR *));
1011 typedef int (*out_func) OF((void FAR *, unsigned char FAR *, unsigned));
1012 
1013 ZEXTERN int ZEXPORT inflateBack OF((z_streamp strm,
1014                                     in_func in, void FAR *in_desc,
1015                                     out_func out, void FAR *out_desc));
1016 /*
1017      inflateBack() does a raw inflate with a single call using a call-back
1018    interface for input and output.  This is more efficient than inflate() for
1019    file i/o applications in that it avoids copying between the output and the
1020    sliding window by simply making the window itself the output buffer.  This
1021    function trusts the application to not change the output buffer passed by
1022    the output function, at least until inflateBack() returns.
1023 
1024      inflateBackInit() must be called first to allocate the internal state
1025    and to initialize the state with the user-provided window buffer.
1026    inflateBack() may then be used multiple times to inflate a complete, raw
1027    deflate stream with each call.  inflateBackEnd() is then called to free the
1028    allocated state.
1029 
1030      A raw deflate stream is one with no zlib or gzip header or trailer.
1031    This routine would normally be used in a utility that reads zip or gzip
1032    files and writes out uncompressed files.  The utility would decode the
1033    header and process the trailer on its own, hence this routine expects only
1034    the raw deflate stream to decompress.  This is different from the normal
1035    behavior of inflate(), which expects either a zlib or gzip header and
1036    trailer around the deflate stream.
1037 
1038      inflateBack() uses two subroutines supplied by the caller that are then
1039    called by inflateBack() for input and output.  inflateBack() calls those
1040    routines until it reads a complete deflate stream and writes out all of the
1041    uncompressed data, or until it encounters an error.  The function's
1042    parameters and return types are defined above in the in_func and out_func
1043    typedefs.  inflateBack() will call in(in_desc, &buf) which should return the
1044    number of bytes of provided input, and a pointer to that input in buf.  If
1045    there is no input available, in() must return zero--buf is ignored in that
1046    case--and inflateBack() will return a buffer error.  inflateBack() will call
1047    out(out_desc, buf, len) to write the uncompressed data buf[0..len-1].  out()
1048    should return zero on success, or non-zero on failure.  If out() returns
1049    non-zero, inflateBack() will return with an error.  Neither in() nor out()
1050    are permitted to change the contents of the window provided to
1051    inflateBackInit(), which is also the buffer that out() uses to write from.
1052    The length written by out() will be at most the window size.  Any non-zero
1053    amount of input may be provided by in().
1054 
1055      For convenience, inflateBack() can be provided input on the first call by
1056    setting strm->next_in and strm->avail_in.  If that input is exhausted, then
1057    in() will be called.  Therefore strm->next_in must be initialized before
1058    calling inflateBack().  If strm->next_in is Z_NULL, then in() will be called
1059    immediately for input.  If strm->next_in is not Z_NULL, then strm->avail_in
1060    must also be initialized, and then if strm->avail_in is not zero, input will
1061    initially be taken from strm->next_in[0 ..  strm->avail_in - 1].
1062 
1063      The in_desc and out_desc parameters of inflateBack() is passed as the
1064    first parameter of in() and out() respectively when they are called.  These
1065    descriptors can be optionally used to pass any information that the caller-
1066    supplied in() and out() functions need to do their job.
1067 
1068      On return, inflateBack() will set strm->next_in and strm->avail_in to
1069    pass back any unused input that was provided by the last in() call.  The
1070    return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR
1071    if in() or out() returned an error, Z_DATA_ERROR if there was a format error
1072    in the deflate stream (in which case strm->msg is set to indicate the nature
1073    of the error), or Z_STREAM_ERROR if the stream was not properly initialized.
1074    In the case of Z_BUF_ERROR, an input or output error can be distinguished
1075    using strm->next_in which will be Z_NULL only if in() returned an error.  If
1076    strm->next_in is not Z_NULL, then the Z_BUF_ERROR was due to out() returning
1077    non-zero.  (in() will always be called before out(), so strm->next_in is
1078    assured to be defined if out() returns non-zero.) Note that inflateBack()
1079    cannot return Z_OK.
1080 */
1081 
1082 ZEXTERN int ZEXPORT inflateBackEnd OF((z_streamp strm));
1083 /*
1084      All memory allocated by inflateBackInit() is freed.
1085 
1086      inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream
1087    state was inconsistent.
1088 */
1089 
1090 ZEXTERN uLong ZEXPORT zlibCompileFlags OF((void));
1091 /* Return flags indicating compile-time options.
1092 
1093     Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
1094      1.0: size of uInt
1095      3.2: size of uLong
1096      5.4: size of voidpf (pointer)
1097      7.6: size of z_off_t
1098 
1099     Compiler, assembler, and debug options:
1100      8: DEBUG
1101      9: ASMV or ASMINF -- use ASM code
1102      10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
1103      11: 0 (reserved)
1104 
1105     One-time table building (smaller code, but not thread-safe if true):
1106      12: BUILDFIXED -- build static block decoding tables when needed
1107      13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
1108      14,15: 0 (reserved)
1109 
1110     Library content (indicates missing functionality):
1111      16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
1112                           deflate code when not needed)
1113      17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect
1114                     and decode gzip streams (to avoid linking crc code)
1115      18-19: 0 (reserved)
1116 
1117     Operation variations (changes in library functionality):
1118      20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
1119      21: FASTEST -- deflate algorithm with only one, lowest compression level
1120      22,23: 0 (reserved)
1121 
1122     The sprintf variant used by gzprintf (zero is best):
1123      24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
1124      25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
1125      26: 0 = returns value, 1 = void -- 1 means inferred string length returned
1126 
1127     Remainder:
1128      27-31: 0 (reserved)
1129  */
1130 
1131 #ifndef Z_SOLO
1132 
1133                         /* utility functions */
1134 
1135 /*
1136      The following utility functions are implemented on top of the basic
1137    stream-oriented functions.  To simplify the interface, some default options
1138    are assumed (compression level and memory usage, standard memory allocation
1139    functions).  The source code of these utility functions can be modified if
1140    you need special options.
1141 */
1142 
1143 ZEXTERN int ZEXPORT compress OF((Bytef *dest,   uLongf *destLen,
1144                                  const Bytef *source, uLong sourceLen));
1145 /*
1146      Compresses the source buffer into the destination buffer.  sourceLen is
1147    the byte length of the source buffer.  Upon entry, destLen is the total size
1148    of the destination buffer, which must be at least the value returned by
1149    compressBound(sourceLen).  Upon exit, destLen is the actual size of the
1150    compressed buffer.
1151 
1152      compress returns Z_OK if success, Z_MEM_ERROR if there was not
1153    enough memory, Z_BUF_ERROR if there was not enough room in the output
1154    buffer.
1155 */
1156 
1157 ZEXTERN int ZEXPORT compress2 OF((Bytef *dest,   uLongf *destLen,
1158                                   const Bytef *source, uLong sourceLen,
1159                                   int level));
1160 /*
1161      Compresses the source buffer into the destination buffer.  The level
1162    parameter has the same meaning as in deflateInit.  sourceLen is the byte
1163    length of the source buffer.  Upon entry, destLen is the total size of the
1164    destination buffer, which must be at least the value returned by
1165    compressBound(sourceLen).  Upon exit, destLen is the actual size of the
1166    compressed buffer.
1167 
1168      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
1169    memory, Z_BUF_ERROR if there was not enough room in the output buffer,
1170    Z_STREAM_ERROR if the level parameter is invalid.
1171 */
1172 
1173 ZEXTERN uLong ZEXPORT compressBound OF((uLong sourceLen));
1174 /*
1175      compressBound() returns an upper bound on the compressed size after
1176    compress() or compress2() on sourceLen bytes.  It would be used before a
1177    compress() or compress2() call to allocate the destination buffer.
1178 */
1179 
1180 ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen,
1181                                    const Bytef *source, uLong sourceLen));
1182 /*
1183      Decompresses the source buffer into the destination buffer.  sourceLen is
1184    the byte length of the source buffer.  Upon entry, destLen is the total size
1185    of the destination buffer, which must be large enough to hold the entire
1186    uncompressed data.  (The size of the uncompressed data must have been saved
1187    previously by the compressor and transmitted to the decompressor by some
1188    mechanism outside the scope of this compression library.) Upon exit, destLen
1189    is the actual size of the uncompressed buffer.
1190 
1191      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
1192    enough memory, Z_BUF_ERROR if there was not enough room in the output
1193    buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.  In
1194    the case where there is not enough room, uncompress() will fill the output
1195    buffer with the uncompressed data up to that point.
1196 */
1197 
1198                         /* gzip file access functions */
1199 
1200 /*
1201      This library supports reading and writing files in gzip (.gz) format with
1202    an interface similar to that of stdio, using the functions that start with
1203    "gz".  The gzip format is different from the zlib format.  gzip is a gzip
1204    wrapper, documented in RFC 1952, wrapped around a deflate stream.
1205 */
1206 
1207 typedef struct gzFile_s *gzFile;    /* semi-opaque gzip file descriptor */
1208 
1209 /*
1210 ZEXTERN gzFile ZEXPORT gzopen OF((const char *path, const char *mode));
1211 
1212      Opens a gzip (.gz) file for reading or writing.  The mode parameter is as
1213    in fopen ("rb" or "wb") but can also include a compression level ("wb9") or
1214    a strategy: 'f' for filtered data as in "wb6f", 'h' for Huffman-only
1215    compression as in "wb1h", 'R' for run-length encoding as in "wb1R", or 'F'
1216    for fixed code compression as in "wb9F".  (See the description of
1217    deflateInit2 for more information about the strategy parameter.)  'T' will
1218    request transparent writing or appending with no compression and not using
1219    the gzip format.
1220 
1221      "a" can be used instead of "w" to request that the gzip stream that will
1222    be written be appended to the file.  "+" will result in an error, since
1223    reading and writing to the same gzip file is not supported.  The addition of
1224    "x" when writing will create the file exclusively, which fails if the file
1225    already exists.  On systems that support it, the addition of "e" when
1226    reading or writing will set the flag to close the file on an execve() call.
1227 
1228      These functions, as well as gzip, will read and decode a sequence of gzip
1229    streams in a file.  The append function of gzopen() can be used to create
1230    such a file.  (Also see gzflush() for another way to do this.)  When
1231    appending, gzopen does not test whether the file begins with a gzip stream,
1232    nor does it look for the end of the gzip streams to begin appending.  gzopen
1233    will simply append a gzip stream to the existing file.
1234 
1235      gzopen can be used to read a file which is not in gzip format; in this
1236    case gzread will directly read from the file without decompression.  When
1237    reading, this will be detected automatically by looking for the magic two-
1238    byte gzip header.
1239 
1240      gzopen returns NULL if the file could not be opened, if there was
1241    insufficient memory to allocate the gzFile state, or if an invalid mode was
1242    specified (an 'r', 'w', or 'a' was not provided, or '+' was provided).
1243    errno can be checked to determine if the reason gzopen failed was that the
1244    file could not be opened.
1245 */
1246 
1247 ZEXTERN gzFile ZEXPORT gzdopen OF((int fd, const char *mode));
1248 /*
1249      gzdopen associates a gzFile with the file descriptor fd.  File descriptors
1250    are obtained from calls like open, dup, creat, pipe or fileno (if the file
1251    has been previously opened with fopen).  The mode parameter is as in gzopen.
1252 
1253      The next call of gzclose on the returned gzFile will also close the file
1254    descriptor fd, just like fclose(fdopen(fd, mode)) closes the file descriptor
1255    fd.  If you want to keep fd open, use fd = dup(fd_keep); gz = gzdopen(fd,
1256    mode);.  The duplicated descriptor should be saved to avoid a leak, since
1257    gzdopen does not close fd if it fails.  If you are using fileno() to get the
1258    file descriptor from a FILE *, then you will have to use dup() to avoid
1259    double-close()ing the file descriptor.  Both gzclose() and fclose() will
1260    close the associated file descriptor, so they need to have different file
1261    descriptors.
1262 
1263      gzdopen returns NULL if there was insufficient memory to allocate the
1264    gzFile state, if an invalid mode was specified (an 'r', 'w', or 'a' was not
1265    provided, or '+' was provided), or if fd is -1.  The file descriptor is not
1266    used until the next gz* read, write, seek, or close operation, so gzdopen
1267    will not detect if fd is invalid (unless fd is -1).
1268 */
1269 
1270 ZEXTERN int ZEXPORT gzbuffer OF((gzFile file, unsigned size));
1271 /*
1272      Set the internal buffer size used by this library's functions.  The
1273    default buffer size is 8192 bytes.  This function must be called after
1274    gzopen() or gzdopen(), and before any other calls that read or write the
1275    file.  The buffer memory allocation is always deferred to the first read or
1276    write.  Two buffers are allocated, either both of the specified size when
1277    writing, or one of the specified size and the other twice that size when
1278    reading.  A larger buffer size of, for example, 64K or 128K bytes will
1279    noticeably increase the speed of decompression (reading).
1280 
1281      The new buffer size also affects the maximum length for gzprintf().
1282 
1283      gzbuffer() returns 0 on success, or -1 on failure, such as being called
1284    too late.
1285 */
1286 
1287 ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
1288 /*
1289      Dynamically update the compression level or strategy.  See the description
1290    of deflateInit2 for the meaning of these parameters.
1291 
1292      gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not
1293    opened for writing.
1294 */
1295 
1296 ZEXTERN int ZEXPORT gzread OF((gzFile file, voidp buf, unsigned len));
1297 /*
1298      Reads the given number of uncompressed bytes from the compressed file.  If
1299    the input file is not in gzip format, gzread copies the given number of
1300    bytes into the buffer directly from the file.
1301 
1302      After reaching the end of a gzip stream in the input, gzread will continue
1303    to read, looking for another gzip stream.  Any number of gzip streams may be
1304    concatenated in the input file, and will all be decompressed by gzread().
1305    If something other than a gzip stream is encountered after a gzip stream,
1306    that remaining trailing garbage is ignored (and no error is returned).
1307 
1308      gzread can be used to read a gzip file that is being concurrently written.
1309    Upon reaching the end of the input, gzread will return with the available
1310    data.  If the error code returned by gzerror is Z_OK or Z_BUF_ERROR, then
1311    gzclearerr can be used to clear the end of file indicator in order to permit
1312    gzread to be tried again.  Z_OK indicates that a gzip stream was completed
1313    on the last gzread.  Z_BUF_ERROR indicates that the input file ended in the
1314    middle of a gzip stream.  Note that gzread does not return -1 in the event
1315    of an incomplete gzip stream.  This error is deferred until gzclose(), which
1316    will return Z_BUF_ERROR if the last gzread ended in the middle of a gzip
1317    stream.  Alternatively, gzerror can be used before gzclose to detect this
1318    case.
1319 
1320      gzread returns the number of uncompressed bytes actually read, less than
1321    len for end of file, or -1 for error.
1322 */
1323 
1324 ZEXTERN int ZEXPORT gzwrite OF((gzFile file,
1325                                 voidpc buf, unsigned len));
1326 /*
1327      Writes the given number of uncompressed bytes into the compressed file.
1328    gzwrite returns the number of uncompressed bytes written or 0 in case of
1329    error.
1330 */
1331 
1332 ZEXTERN int ZEXPORTVA gzprintf Z_ARG((gzFile file, const char *format, ...));
1333 /*
1334      Converts, formats, and writes the arguments to the compressed file under
1335    control of the format string, as in fprintf.  gzprintf returns the number of
1336    uncompressed bytes actually written, or 0 in case of error.  The number of
1337    uncompressed bytes written is limited to 8191, or one less than the buffer
1338    size given to gzbuffer().  The caller should assure that this limit is not
1339    exceeded.  If it is exceeded, then gzprintf() will return an error (0) with
1340    nothing written.  In this case, there may also be a buffer overflow with
1341    unpredictable consequences, which is possible only if zlib was compiled with
1342    the insecure functions sprintf() or vsprintf() because the secure snprintf()
1343    or vsnprintf() functions were not available.  This can be determined using
1344    zlibCompileFlags().
1345 */
1346 
1347 ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char *s));
1348 /*
1349      Writes the given null-terminated string to the compressed file, excluding
1350    the terminating null character.
1351 
1352      gzputs returns the number of characters written, or -1 in case of error.
1353 */
1354 
1355 ZEXTERN char * ZEXPORT gzgets OF((gzFile file, char *buf, int len));
1356 /*
1357      Reads bytes from the compressed file until len-1 characters are read, or a
1358    newline character is read and transferred to buf, or an end-of-file
1359    condition is encountered.  If any characters are read or if len == 1, the
1360    string is terminated with a null character.  If no characters are read due
1361    to an end-of-file or len < 1, then the buffer is left untouched.
1362 
1363      gzgets returns buf which is a null-terminated string, or it returns NULL
1364    for end-of-file or in case of error.  If there was an error, the contents at
1365    buf are indeterminate.
1366 */
1367 
1368 ZEXTERN int ZEXPORT gzputc OF((gzFile file, int c));
1369 /*
1370      Writes c, converted to an unsigned char, into the compressed file.  gzputc
1371    returns the value that was written, or -1 in case of error.
1372 */
1373 
1374 ZEXTERN int ZEXPORT gzgetc OF((gzFile file));
1375 /*
1376      Reads one byte from the compressed file.  gzgetc returns this byte or -1
1377    in case of end of file or error.  This is implemented as a macro for speed.
1378    As such, it does not do all of the checking the other functions do.  I.e.
1379    it does not check to see if file is NULL, nor whether the structure file
1380    points to has been clobbered or not.
1381 */
1382 
1383 ZEXTERN int ZEXPORT gzungetc OF((int c, gzFile file));
1384 /*
1385      Push one character back onto the stream to be read as the first character
1386    on the next read.  At least one character of push-back is allowed.
1387    gzungetc() returns the character pushed, or -1 on failure.  gzungetc() will
1388    fail if c is -1, and may fail if a character has been pushed but not read
1389    yet.  If gzungetc is used immediately after gzopen or gzdopen, at least the
1390    output buffer size of pushed characters is allowed.  (See gzbuffer above.)
1391    The pushed character will be discarded if the stream is repositioned with
1392    gzseek() or gzrewind().
1393 */
1394 
1395 ZEXTERN int ZEXPORT gzflush OF((gzFile file, int flush));
1396 /*
1397      Flushes all pending output into the compressed file.  The parameter flush
1398    is as in the deflate() function.  The return value is the zlib error number
1399    (see function gzerror below).  gzflush is only permitted when writing.
1400 
1401      If the flush parameter is Z_FINISH, the remaining data is written and the
1402    gzip stream is completed in the output.  If gzwrite() is called again, a new
1403    gzip stream will be started in the output.  gzread() is able to read such
1404    concatented gzip streams.
1405 
1406      gzflush should be called only when strictly necessary because it will
1407    degrade compression if called too often.
1408 */
1409 
1410 /*
1411 ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile file,
1412                                    z_off_t offset, int whence));
1413 
1414      Sets the starting position for the next gzread or gzwrite on the given
1415    compressed file.  The offset represents a number of bytes in the
1416    uncompressed data stream.  The whence parameter is defined as in lseek(2);
1417    the value SEEK_END is not supported.
1418 
1419      If the file is opened for reading, this function is emulated but can be
1420    extremely slow.  If the file is opened for writing, only forward seeks are
1421    supported; gzseek then compresses a sequence of zeroes up to the new
1422    starting position.
1423 
1424      gzseek returns the resulting offset location as measured in bytes from
1425    the beginning of the uncompressed stream, or -1 in case of error, in
1426    particular if the file is opened for writing and the new starting position
1427    would be before the current position.
1428 */
1429 
1430 ZEXTERN int ZEXPORT    gzrewind OF((gzFile file));
1431 /*
1432      Rewinds the given file. This function is supported only for reading.
1433 
1434      gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
1435 */
1436 
1437 /*
1438 ZEXTERN z_off_t ZEXPORT    gztell OF((gzFile file));
1439 
1440      Returns the starting position for the next gzread or gzwrite on the given
1441    compressed file.  This position represents a number of bytes in the
1442    uncompressed data stream, and is zero when starting, even if appending or
1443    reading a gzip stream from the middle of a file using gzdopen().
1444 
1445      gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
1446 */
1447 
1448 /*
1449 ZEXTERN z_off_t ZEXPORT gzoffset OF((gzFile file));
1450 
1451      Returns the current offset in the file being read or written.  This offset
1452    includes the count of bytes that precede the gzip stream, for example when
1453    appending or when using gzdopen() for reading.  When reading, the offset
1454    does not include as yet unused buffered input.  This information can be used
1455    for a progress indicator.  On error, gzoffset() returns -1.
1456 */
1457 
1458 ZEXTERN int ZEXPORT gzeof OF((gzFile file));
1459 /*
1460      Returns true (1) if the end-of-file indicator has been set while reading,
1461    false (0) otherwise.  Note that the end-of-file indicator is set only if the
1462    read tried to go past the end of the input, but came up short.  Therefore,
1463    just like feof(), gzeof() may return false even if there is no more data to
1464    read, in the event that the last read request was for the exact number of
1465    bytes remaining in the input file.  This will happen if the input file size
1466    is an exact multiple of the buffer size.
1467 
1468      If gzeof() returns true, then the read functions will return no more data,
1469    unless the end-of-file indicator is reset by gzclearerr() and the input file
1470    has grown since the previous end of file was detected.
1471 */
1472 
1473 ZEXTERN int ZEXPORT gzdirect OF((gzFile file));
1474 /*
1475      Returns true (1) if file is being copied directly while reading, or false
1476    (0) if file is a gzip stream being decompressed.
1477 
1478      If the input file is empty, gzdirect() will return true, since the input
1479    does not contain a gzip stream.
1480 
1481      If gzdirect() is used immediately after gzopen() or gzdopen() it will
1482    cause buffers to be allocated to allow reading the file to determine if it
1483    is a gzip file.  Therefore if gzbuffer() is used, it should be called before
1484    gzdirect().
1485 
1486      When writing, gzdirect() returns true (1) if transparent writing was
1487    requested ("wT" for the gzopen() mode), or false (0) otherwise.  (Note:
1488    gzdirect() is not needed when writing.  Transparent writing must be
1489    explicitly requested, so the application already knows the answer.  When
1490    linking statically, using gzdirect() will include all of the zlib code for
1491    gzip file reading and decompression, which may not be desired.)
1492 */
1493 
1494 ZEXTERN int ZEXPORT    gzclose OF((gzFile file));
1495 /*
1496      Flushes all pending output if necessary, closes the compressed file and
1497    deallocates the (de)compression state.  Note that once file is closed, you
1498    cannot call gzerror with file, since its structures have been deallocated.
1499    gzclose must not be called more than once on the same file, just as free
1500    must not be called more than once on the same allocation.
1501 
1502      gzclose will return Z_STREAM_ERROR if file is not valid, Z_ERRNO on a
1503    file operation error, Z_MEM_ERROR if out of memory, Z_BUF_ERROR if the
1504    last read ended in the middle of a gzip stream, or Z_OK on success.
1505 */
1506 
1507 ZEXTERN int ZEXPORT gzclose_r OF((gzFile file));
1508 ZEXTERN int ZEXPORT gzclose_w OF((gzFile file));
1509 /*
1510      Same as gzclose(), but gzclose_r() is only for use when reading, and
1511    gzclose_w() is only for use when writing or appending.  The advantage to
1512    using these instead of gzclose() is that they avoid linking in zlib
1513    compression or decompression code that is not used when only reading or only
1514    writing respectively.  If gzclose() is used, then both compression and
1515    decompression code will be included the application when linking to a static
1516    zlib library.
1517 */
1518 
1519 ZEXTERN const char * ZEXPORT gzerror OF((gzFile file, int *errnum));
1520 /*
1521      Returns the error message for the last error which occurred on the given
1522    compressed file.  errnum is set to zlib error number.  If an error occurred
1523    in the file system and not in the compression library, errnum is set to
1524    Z_ERRNO and the application may consult errno to get the exact error code.
1525 
1526      The application must not modify the returned string.  Future calls to
1527    this function may invalidate the previously returned string.  If file is
1528    closed, then the string previously returned by gzerror will no longer be
1529    available.
1530 
1531      gzerror() should be used to distinguish errors from end-of-file for those
1532    functions above that do not distinguish those cases in their return values.
1533 */
1534 
1535 ZEXTERN void ZEXPORT gzclearerr OF((gzFile file));
1536 /*
1537      Clears the error and end-of-file flags for file.  This is analogous to the
1538    clearerr() function in stdio.  This is useful for continuing to read a gzip
1539    file that is being written concurrently.
1540 */
1541 
1542 #endif /* !Z_SOLO */
1543 
1544                         /* checksum functions */
1545 
1546 /*
1547      These functions are not related to compression but are exported
1548    anyway because they might be useful in applications using the compression
1549    library.
1550 */
1551 
1552 ZEXTERN uLong ZEXPORT adler32 OF((uLong adler, const Bytef *buf, uInt len));
1553 /*
1554      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
1555    return the updated checksum.  If buf is Z_NULL, this function returns the
1556    required initial value for the checksum.
1557 
1558      An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
1559    much faster.
1560 
1561    Usage example:
1562 
1563      uLong adler = adler32(0L, Z_NULL, 0);
1564 
1565      while (read_buffer(buffer, length) != EOF) {
1566        adler = adler32(adler, buffer, length);
1567      }
1568      if (adler != original_adler) error();
1569 */
1570 
1571 /*
1572 ZEXTERN uLong ZEXPORT adler32_combine OF((uLong adler1, uLong adler2,
1573                                           z_off_t len2));
1574 
1575      Combine two Adler-32 checksums into one.  For two sequences of bytes, seq1
1576    and seq2 with lengths len1 and len2, Adler-32 checksums were calculated for
1577    each, adler1 and adler2.  adler32_combine() returns the Adler-32 checksum of
1578    seq1 and seq2 concatenated, requiring only adler1, adler2, and len2.  Note
1579    that the z_off_t type (like off_t) is a signed integer.  If len2 is
1580    negative, the result has no meaning or utility.
1581 */
1582 
1583 ZEXTERN uLong ZEXPORT crc32   OF((uLong crc, const Bytef *buf, uInt len));
1584 /*
1585      Update a running CRC-32 with the bytes buf[0..len-1] and return the
1586    updated CRC-32.  If buf is Z_NULL, this function returns the required
1587    initial value for the crc.  Pre- and post-conditioning (one's complement) is
1588    performed within this function so it shouldn't be done by the application.
1589 
1590    Usage example:
1591 
1592      uLong crc = crc32(0L, Z_NULL, 0);
1593 
1594      while (read_buffer(buffer, length) != EOF) {
1595        crc = crc32(crc, buffer, length);
1596      }
1597      if (crc != original_crc) error();
1598 */
1599 
1600 /*
1601 ZEXTERN uLong ZEXPORT crc32_combine OF((uLong crc1, uLong crc2, z_off_t len2));
1602 
1603      Combine two CRC-32 check values into one.  For two sequences of bytes,
1604    seq1 and seq2 with lengths len1 and len2, CRC-32 check values were
1605    calculated for each, crc1 and crc2.  crc32_combine() returns the CRC-32
1606    check value of seq1 and seq2 concatenated, requiring only crc1, crc2, and
1607    len2.
1608 */
1609 
1610 
1611                         /* various hacks, don't look :) */
1612 
1613 /* deflateInit and inflateInit are macros to allow checking the zlib version
1614  * and the compiler's view of z_stream:
1615  */
1616 ZEXTERN int ZEXPORT deflateInit_ OF((z_streamp strm, int level,
1617                                      const char *version, int stream_size));
1618 ZEXTERN int ZEXPORT inflateInit_ OF((z_streamp strm,
1619                                      const char *version, int stream_size));
1620 ZEXTERN int ZEXPORT deflateInit2_ OF((z_streamp strm, int  level, int  method,
1621                                       int windowBits, int memLevel,
1622                                       int strategy, const char *version,
1623                                       int stream_size));
1624 ZEXTERN int ZEXPORT inflateInit2_ OF((z_streamp strm, int  windowBits,
1625                                       const char *version, int stream_size));
1626 ZEXTERN int ZEXPORT inflateBackInit_ OF((z_streamp strm, int windowBits,
1627                                          unsigned char FAR *window,
1628                                          const char *version,
1629                                          int stream_size));
1630 #define deflateInit(strm, level) \
1631         deflateInit_((strm), (level), ZLIB_VERSION, (int)sizeof(z_stream))
1632 #define inflateInit(strm) \
1633         inflateInit_((strm), ZLIB_VERSION, (int)sizeof(z_stream))
1634 #define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
1635         deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
1636                       (strategy), ZLIB_VERSION, (int)sizeof(z_stream))
1637 #define inflateInit2(strm, windowBits) \
1638         inflateInit2_((strm), (windowBits), ZLIB_VERSION, \
1639                       (int)sizeof(z_stream))
1640 #define inflateBackInit(strm, windowBits, window) \
1641         inflateBackInit_((strm), (windowBits), (window), \
1642                       ZLIB_VERSION, (int)sizeof(z_stream))
1643 
1644 #ifndef Z_SOLO
1645 
1646 /* gzgetc() macro and its supporting function and exposed data structure.  Note
1647  * that the real internal state is much larger than the exposed structure.
1648  * This abbreviated structure exposes just enough for the gzgetc() macro.  The
1649  * user should not mess with these exposed elements, since their names or
1650  * behavior could change in the future, perhaps even capriciously.  They can
1651  * only be used by the gzgetc() macro.  You have been warned.
1652  */
1653 struct gzFile_s {
1654     unsigned have;
1655     unsigned char *next;
1656     z_off64_t pos;
1657 };
1658 ZEXTERN int ZEXPORT gzgetc_ OF((gzFile file));  /* backward compatibility */
1659 #ifdef Z_PREFIX_SET
1660 #  undef z_gzgetc
1661 #  define z_gzgetc(g) \
1662           ((g)->have ? ((g)->have--, (g)->pos++, *((g)->next)++) : gzgetc(g))
1663 #else
1664 #  define gzgetc(g) \
1665           ((g)->have ? ((g)->have--, (g)->pos++, *((g)->next)++) : gzgetc(g))
1666 #endif
1667 
1668 /* provide 64-bit offset functions if _LARGEFILE64_SOURCE defined, and/or
1669  * change the regular functions to 64 bits if _FILE_OFFSET_BITS is 64 (if
1670  * both are true, the application gets the *64 functions, and the regular
1671  * functions are changed to 64 bits) -- in case these are set on systems
1672  * without large file support, _LFS64_LARGEFILE must also be true
1673  */
1674 #ifdef Z_LARGE64
1675    ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
1676    ZEXTERN z_off64_t ZEXPORT gzseek64 OF((gzFile, z_off64_t, int));
1677    ZEXTERN z_off64_t ZEXPORT gztell64 OF((gzFile));
1678    ZEXTERN z_off64_t ZEXPORT gzoffset64 OF((gzFile));
1679    ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off64_t));
1680    ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off64_t));
1681 #endif
1682 
1683 #if !defined(ZLIB_INTERNAL) && defined(Z_WANT64)
1684 #  ifdef Z_PREFIX_SET
1685 #    define z_gzopen z_gzopen64
1686 #    define z_gzseek z_gzseek64
1687 #    define z_gztell z_gztell64
1688 #    define z_gzoffset z_gzoffset64
1689 #    define z_adler32_combine z_adler32_combine64
1690 #    define z_crc32_combine z_crc32_combine64
1691 #  else
1692 #    define gzopen gzopen64
1693 #    define gzseek gzseek64
1694 #    define gztell gztell64
1695 #    define gzoffset gzoffset64
1696 #    define adler32_combine adler32_combine64
1697 #    define crc32_combine crc32_combine64
1698 #  endif
1699 #  ifndef Z_LARGE64
1700      ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
1701      ZEXTERN z_off_t ZEXPORT gzseek64 OF((gzFile, z_off_t, int));
1702      ZEXTERN z_off_t ZEXPORT gztell64 OF((gzFile));
1703      ZEXTERN z_off_t ZEXPORT gzoffset64 OF((gzFile));
1704      ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off_t));
1705      ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off_t));
1706 #  endif
1707 #else
1708    ZEXTERN gzFile ZEXPORT gzopen OF((const char *, const char *));
1709    ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile, z_off_t, int));
1710    ZEXTERN z_off_t ZEXPORT gztell OF((gzFile));
1711    ZEXTERN z_off_t ZEXPORT gzoffset OF((gzFile));
1712    ZEXTERN uLong ZEXPORT adler32_combine OF((uLong, uLong, z_off_t));
1713    ZEXTERN uLong ZEXPORT crc32_combine OF((uLong, uLong, z_off_t));
1714 #endif
1715 
1716 #else /* Z_SOLO */
1717 
1718    ZEXTERN uLong ZEXPORT adler32_combine OF((uLong, uLong, z_off_t));
1719    ZEXTERN uLong ZEXPORT crc32_combine OF((uLong, uLong, z_off_t));
1720 
1721 #endif /* !Z_SOLO */
1722 
1723 /* hack for buggy compilers */
1724 #if !defined(ZUTIL_H) && !defined(NO_DUMMY_DECL)
1725     struct internal_state {int dummy;};
1726 #endif
1727 
1728 /* undocumented functions */
1729 ZEXTERN const char   * ZEXPORT zError           OF((int));
1730 ZEXTERN int            ZEXPORT inflateSyncPoint OF((z_streamp));
1731 ZEXTERN const z_crc_t FAR * ZEXPORT get_crc_table    OF((void));
1732 ZEXTERN int            ZEXPORT inflateUndermine OF((z_streamp, int));
1733 ZEXTERN int            ZEXPORT inflateResetKeep OF((z_streamp));
1734 ZEXTERN int            ZEXPORT deflateResetKeep OF((z_streamp));
1735 #if defined(_WIN32) && !defined(Z_SOLO)
1736 ZEXTERN gzFile         ZEXPORT gzopen_w OF((const wchar_t *path,
1737                                             const char *mode));
1738 #endif
1739 
1740 #ifdef __cplusplus
1741 }
1742 #endif
1743 
1744 #endif /* ZLIB_H */
1745