xref: /netbsd-src/common/dist/zlib/zlib.h (revision 96c3282121aac2037abbd5952fd638784deb5ab1)
1 /*	$NetBSD: zlib.h,v 1.8 2024/09/22 19:12:27 christos Exp $	*/
2 
3 /* zlib.h -- interface of the 'zlib' general purpose compression library
4   version 1.3.1, January 22nd, 2024
5 
6   Copyright (C) 1995-2024 Jean-loup Gailly and Mark Adler
7 
8   This software is provided 'as-is', without any express or implied
9   warranty.  In no event will the authors be held liable for any damages
10   arising from the use of this software.
11 
12   Permission is granted to anyone to use this software for any purpose,
13   including commercial applications, and to alter it and redistribute it
14   freely, subject to the following restrictions:
15 
16   1. The origin of this software must not be misrepresented; you must not
17      claim that you wrote the original software. If you use this software
18      in a product, an acknowledgment in the product documentation would be
19      appreciated but is not required.
20   2. Altered source versions must be plainly marked as such, and must not be
21      misrepresented as being the original software.
22   3. This notice may not be removed or altered from any source distribution.
23 
24   Jean-loup Gailly        Mark Adler
25   jloup@gzip.org          madler@alumni.caltech.edu
26 
27 
28   The data format used by the zlib library is described by RFCs (Request for
29   Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
30   (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
31 */
32 
33 #ifndef ZLIB_H
34 #define ZLIB_H
35 
36 #include "zconf.h"
37 
38 #ifdef __cplusplus
39 extern "C" {
40 #endif
41 
42 #define ZLIB_VERSION "1.3.1"
43 #define ZLIB_VERNUM 0x1310
44 #define ZLIB_VER_MAJOR 1
45 #define ZLIB_VER_MINOR 3
46 #define ZLIB_VER_REVISION 1
47 #define ZLIB_VER_SUBREVISION 0
48 
49 /*
50     The 'zlib' compression library provides in-memory compression and
51   decompression functions, including integrity checks of the uncompressed data.
52   This version of the library supports only one compression method (deflation)
53   but other algorithms will be added later and will have the same stream
54   interface.
55 
56     Compression can be done in a single step if the buffers are large enough,
57   or can be done by repeated calls of the compression function.  In the latter
58   case, the application must provide more input and/or consume the output
59   (providing more output space) before each call.
60 
61     The compressed data format used by default by the in-memory functions is
62   the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
63   around a deflate stream, which is itself documented in RFC 1951.
64 
65     The library also supports reading and writing files in gzip (.gz) format
66   with an interface similar to that of stdio using the functions that start
67   with "gz".  The gzip format is different from the zlib format.  gzip is a
68   gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
69 
70     This library can optionally read and write gzip and raw deflate streams in
71   memory as well.
72 
73     The zlib format was designed to be compact and fast for use in memory
74   and on communications channels.  The gzip format was designed for single-
75   file compression on file systems, has a larger header than zlib to maintain
76   directory information, and uses a different, slower check method than zlib.
77 
78     The library does not install any signal handler.  The decoder checks
79   the consistency of the compressed data, so the library should never crash
80   even in the case of corrupted input.
81 */
82 
83 typedef voidpf (*alloc_func)(voidpf opaque, uInt items, uInt size);
84 typedef void   (*free_func)(voidpf opaque, voidpf address);
85 
86 struct internal_state;
87 
88 typedef struct z_stream_s {
89     z_const Bytef *next_in;     /* next input byte */
90     uInt     avail_in;  /* number of bytes available at next_in */
91     uLong    total_in;  /* total number of input bytes read so far */
92 
93     Bytef    *next_out; /* next output byte will go here */
94     uInt     avail_out; /* remaining free space at next_out */
95     uLong    total_out; /* total number of bytes output so far */
96 
97     z_const char *msg;  /* last error message, NULL if no error */
98     struct internal_state FAR *state; /* not visible by applications */
99 
100     alloc_func zalloc;  /* used to allocate the internal state */
101     free_func  zfree;   /* used to free the internal state */
102     voidpf     opaque;  /* private data object passed to zalloc and zfree */
103 
104     int     data_type;  /* best guess about the data type: binary or text
105                            for deflate, or the decoding state for inflate */
106     uLong   adler;      /* Adler-32 or CRC-32 value of the uncompressed data */
107     uLong   reserved;   /* reserved for future use */
108 } z_stream;
109 
110 typedef z_stream FAR *z_streamp;
111 
112 /*
113      gzip header information passed to and from zlib routines.  See RFC 1952
114   for more details on the meanings of these fields.
115 */
116 typedef struct gz_header_s {
117     int     text;       /* true if compressed data believed to be text */
118     uLong   time;       /* modification time */
119     int     xflags;     /* extra flags (not used when writing a gzip file) */
120     int     os;         /* operating system */
121     Bytef   *extra;     /* pointer to extra field or Z_NULL if none */
122     uInt    extra_len;  /* extra field length (valid if extra != Z_NULL) */
123     uInt    extra_max;  /* space at extra (only when reading header) */
124     Bytef   *name;      /* pointer to zero-terminated file name or Z_NULL */
125     uInt    name_max;   /* space at name (only when reading header) */
126     Bytef   *comment;   /* pointer to zero-terminated comment or Z_NULL */
127     uInt    comm_max;   /* space at comment (only when reading header) */
128     int     hcrc;       /* true if there was or will be a header crc */
129     int     done;       /* true when done reading gzip header (not used
130                            when writing a gzip file) */
131 } gz_header;
132 
133 typedef gz_header FAR *gz_headerp;
134 
135 /*
136      The application must update next_in and avail_in when avail_in has dropped
137    to zero.  It must update next_out and avail_out when avail_out has dropped
138    to zero.  The application must initialize zalloc, zfree and opaque before
139    calling the init function.  All other fields are set by the compression
140    library and must not be updated by the application.
141 
142      The opaque value provided by the application will be passed as the first
143    parameter for calls of zalloc and zfree.  This can be useful for custom
144    memory management.  The compression library attaches no meaning to the
145    opaque value.
146 
147      zalloc must return Z_NULL if there is not enough memory for the object.
148    If zlib is used in a multi-threaded application, zalloc and zfree must be
149    thread safe.  In that case, zlib is thread-safe.  When zalloc and zfree are
150    Z_NULL on entry to the initialization function, they are set to internal
151    routines that use the standard library functions malloc() and free().
152 
153      On 16-bit systems, the functions zalloc and zfree must be able to allocate
154    exactly 65536 bytes, but will not be required to allocate more than this if
155    the symbol MAXSEG_64K is defined (see zconf.h).  WARNING: On MSDOS, pointers
156    returned by zalloc for objects of exactly 65536 bytes *must* have their
157    offset normalized to zero.  The default allocation function provided by this
158    library ensures this (see zutil.c).  To reduce memory requirements and avoid
159    any allocation of 64K objects, at the expense of compression ratio, compile
160    the library with -DMAX_WBITS=14 (see zconf.h).
161 
162      The fields total_in and total_out can be used for statistics or progress
163    reports.  After compression, total_in holds the total size of the
164    uncompressed data and may be saved for use by the decompressor (particularly
165    if the decompressor wants to decompress everything in a single step).
166 */
167 
168                         /* constants */
169 
170 #define Z_NO_FLUSH      0
171 #define Z_PARTIAL_FLUSH 1
172 #define Z_SYNC_FLUSH    2
173 #define Z_FULL_FLUSH    3
174 #define Z_FINISH        4
175 #define Z_BLOCK         5
176 #define Z_TREES         6
177 /* Allowed flush values; see deflate() and inflate() below for details */
178 
179 #define Z_OK            0
180 #define Z_STREAM_END    1
181 #define Z_NEED_DICT     2
182 #define Z_ERRNO        (-1)
183 #define Z_STREAM_ERROR (-2)
184 #define Z_DATA_ERROR   (-3)
185 #define Z_MEM_ERROR    (-4)
186 #define Z_BUF_ERROR    (-5)
187 #define Z_VERSION_ERROR (-6)
188 /* Return codes for the compression/decompression functions. Negative values
189  * are errors, positive values are used for special but normal events.
190  */
191 
192 #define Z_NO_COMPRESSION         0
193 #define Z_BEST_SPEED             1
194 #define Z_BEST_COMPRESSION       9
195 #define Z_DEFAULT_COMPRESSION  (-1)
196 /* compression levels */
197 
198 #define Z_FILTERED            1
199 #define Z_HUFFMAN_ONLY        2
200 #define Z_RLE                 3
201 #define Z_FIXED               4
202 #define Z_DEFAULT_STRATEGY    0
203 /* compression strategy; see deflateInit2() below for details */
204 
205 #define Z_BINARY   0
206 #define Z_TEXT     1
207 #define Z_ASCII    Z_TEXT   /* for compatibility with 1.2.2 and earlier */
208 #define Z_UNKNOWN  2
209 /* Possible values of the data_type field for deflate() */
210 
211 #define Z_DEFLATED   8
212 /* The deflate compression method (the only one supported in this version) */
213 
214 #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
215 
216 #define zlib_version zlibVersion()
217 /* for compatibility with versions < 1.0.2 */
218 
219 
220                         /* basic functions */
221 
222 ZEXTERN const char * ZEXPORT zlibVersion(void);
223 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
224    If the first character differs, the library code actually used is not
225    compatible with the zlib.h header file used by the application.  This check
226    is automatically made by deflateInit and inflateInit.
227  */
228 
229 /*
230 ZEXTERN int ZEXPORT deflateInit(z_streamp strm, int level);
231 
232      Initializes the internal stream state for compression.  The fields
233    zalloc, zfree and opaque must be initialized before by the caller.  If
234    zalloc and zfree are set to Z_NULL, deflateInit updates them to use default
235    allocation functions.  total_in, total_out, adler, and msg are initialized.
236 
237      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
238    1 gives best speed, 9 gives best compression, 0 gives no compression at all
239    (the input data is simply copied a block at a time).  Z_DEFAULT_COMPRESSION
240    requests a default compromise between speed and compression (currently
241    equivalent to level 6).
242 
243      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
244    memory, Z_STREAM_ERROR if level is not a valid compression level, or
245    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
246    with the version assumed by the caller (ZLIB_VERSION).  msg is set to null
247    if there is no error message.  deflateInit does not perform any compression:
248    this will be done by deflate().
249 */
250 
251 
252 ZEXTERN int ZEXPORT deflate(z_streamp strm, int flush);
253 /*
254     deflate compresses as much data as possible, and stops when the input
255   buffer becomes empty or the output buffer becomes full.  It may introduce
256   some output latency (reading input without producing any output) except when
257   forced to flush.
258 
259     The detailed semantics are as follows.  deflate performs one or both of the
260   following actions:
261 
262   - Compress more input starting at next_in and update next_in and avail_in
263     accordingly.  If not all input can be processed (because there is not
264     enough room in the output buffer), next_in and avail_in are updated and
265     processing will resume at this point for the next call of deflate().
266 
267   - Generate more output starting at next_out and update next_out and avail_out
268     accordingly.  This action is forced if the parameter flush is non zero.
269     Forcing flush frequently degrades the compression ratio, so this parameter
270     should be set only when necessary.  Some output may be provided even if
271     flush is zero.
272 
273     Before the call of deflate(), the application should ensure that at least
274   one of the actions is possible, by providing more input and/or consuming more
275   output, and updating avail_in or avail_out accordingly; avail_out should
276   never be zero before the call.  The application can consume the compressed
277   output when it wants, for example when the output buffer is full (avail_out
278   == 0), or after each call of deflate().  If deflate returns Z_OK and with
279   zero avail_out, it must be called again after making room in the output
280   buffer because there might be more output pending. See deflatePending(),
281   which can be used if desired to determine whether or not there is more output
282   in that case.
283 
284     Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to
285   decide how much data to accumulate before producing output, in order to
286   maximize compression.
287 
288     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
289   flushed to the output buffer and the output is aligned on a byte boundary, so
290   that the decompressor can get all input data available so far.  (In
291   particular avail_in is zero after the call if enough output space has been
292   provided before the call.) Flushing may degrade compression for some
293   compression algorithms and so it should be used only when necessary.  This
294   completes the current deflate block and follows it with an empty stored block
295   that is three bits plus filler bits to the next byte, followed by four bytes
296   (00 00 ff ff).
297 
298     If flush is set to Z_PARTIAL_FLUSH, all pending output is flushed to the
299   output buffer, but the output is not aligned to a byte boundary.  All of the
300   input data so far will be available to the decompressor, as for Z_SYNC_FLUSH.
301   This completes the current deflate block and follows it with an empty fixed
302   codes block that is 10 bits long.  This assures that enough bytes are output
303   in order for the decompressor to finish the block before the empty fixed
304   codes block.
305 
306     If flush is set to Z_BLOCK, a deflate block is completed and emitted, as
307   for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to
308   seven bits of the current block are held to be written as the next byte after
309   the next deflate block is completed.  In this case, the decompressor may not
310   be provided enough bits at this point in order to complete decompression of
311   the data provided so far to the compressor.  It may need to wait for the next
312   block to be emitted.  This is for advanced applications that need to control
313   the emission of deflate blocks.
314 
315     If flush is set to Z_FULL_FLUSH, all output is flushed as with
316   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
317   restart from this point if previous compressed data has been damaged or if
318   random access is desired.  Using Z_FULL_FLUSH too often can seriously degrade
319   compression.
320 
321     If deflate returns with avail_out == 0, this function must be called again
322   with the same value of the flush parameter and more output space (updated
323   avail_out), until the flush is complete (deflate returns with non-zero
324   avail_out).  In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
325   avail_out is greater than six when the flush marker begins, in order to avoid
326   repeated flush markers upon calling deflate() again when avail_out == 0.
327 
328     If the parameter flush is set to Z_FINISH, pending input is processed,
329   pending output is flushed and deflate returns with Z_STREAM_END if there was
330   enough output space.  If deflate returns with Z_OK or Z_BUF_ERROR, this
331   function must be called again with Z_FINISH and more output space (updated
332   avail_out) but no more input data, until it returns with Z_STREAM_END or an
333   error.  After deflate has returned Z_STREAM_END, the only possible operations
334   on the stream are deflateReset or deflateEnd.
335 
336     Z_FINISH can be used in the first deflate call after deflateInit if all the
337   compression is to be done in a single step.  In order to complete in one
338   call, avail_out must be at least the value returned by deflateBound (see
339   below).  Then deflate is guaranteed to return Z_STREAM_END.  If not enough
340   output space is provided, deflate will not return Z_STREAM_END, and it must
341   be called again as described above.
342 
343     deflate() sets strm->adler to the Adler-32 checksum of all input read
344   so far (that is, total_in bytes).  If a gzip stream is being generated, then
345   strm->adler will be the CRC-32 checksum of the input read so far.  (See
346   deflateInit2 below.)
347 
348     deflate() may update strm->data_type if it can make a good guess about
349   the input data type (Z_BINARY or Z_TEXT).  If in doubt, the data is
350   considered binary.  This field is only for information purposes and does not
351   affect the compression algorithm in any manner.
352 
353     deflate() returns Z_OK if some progress has been made (more input
354   processed or more output produced), Z_STREAM_END if all input has been
355   consumed and all output has been produced (only when flush is set to
356   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
357   if next_in or next_out was Z_NULL or the state was inadvertently written over
358   by the application), or Z_BUF_ERROR if no progress is possible (for example
359   avail_in or avail_out was zero).  Note that Z_BUF_ERROR is not fatal, and
360   deflate() can be called again with more input and more output space to
361   continue compressing.
362 */
363 
364 
365 ZEXTERN int ZEXPORT deflateEnd(z_streamp strm);
366 /*
367      All dynamically allocated data structures for this stream are freed.
368    This function discards any unprocessed input and does not flush any pending
369    output.
370 
371      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
372    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
373    prematurely (some input or output was discarded).  In the error case, msg
374    may be set but then points to a static string (which must not be
375    deallocated).
376 */
377 
378 
379 /*
380 ZEXTERN int ZEXPORT inflateInit(z_streamp strm);
381 
382      Initializes the internal stream state for decompression.  The fields
383    next_in, avail_in, zalloc, zfree and opaque must be initialized before by
384    the caller.  In the current version of inflate, the provided input is not
385    read or consumed.  The allocation of a sliding window will be deferred to
386    the first call of inflate (if the decompression does not complete on the
387    first call).  If zalloc and zfree are set to Z_NULL, inflateInit updates
388    them to use default allocation functions.  total_in, total_out, adler, and
389    msg are initialized.
390 
391      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
392    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
393    version assumed by the caller, or Z_STREAM_ERROR if the parameters are
394    invalid, such as a null pointer to the structure.  msg is set to null if
395    there is no error message.  inflateInit does not perform any decompression.
396    Actual decompression will be done by inflate().  So next_in, and avail_in,
397    next_out, and avail_out are unused and unchanged.  The current
398    implementation of inflateInit() does not process any header information --
399    that is deferred until inflate() is called.
400 */
401 
402 
403 ZEXTERN int ZEXPORT inflate(z_streamp strm, int flush);
404 /*
405     inflate decompresses as much data as possible, and stops when the input
406   buffer becomes empty or the output buffer becomes full.  It may introduce
407   some output latency (reading input without producing any output) except when
408   forced to flush.
409 
410   The detailed semantics are as follows.  inflate performs one or both of the
411   following actions:
412 
413   - Decompress more input starting at next_in and update next_in and avail_in
414     accordingly.  If not all input can be processed (because there is not
415     enough room in the output buffer), then next_in and avail_in are updated
416     accordingly, and processing will resume at this point for the next call of
417     inflate().
418 
419   - Generate more output starting at next_out and update next_out and avail_out
420     accordingly.  inflate() provides as much output as possible, until there is
421     no more input data or no more space in the output buffer (see below about
422     the flush parameter).
423 
424     Before the call of inflate(), the application should ensure that at least
425   one of the actions is possible, by providing more input and/or consuming more
426   output, and updating the next_* and avail_* values accordingly.  If the
427   caller of inflate() does not provide both available input and available
428   output space, it is possible that there will be no progress made.  The
429   application can consume the uncompressed output when it wants, for example
430   when the output buffer is full (avail_out == 0), or after each call of
431   inflate().  If inflate returns Z_OK and with zero avail_out, it must be
432   called again after making room in the output buffer because there might be
433   more output pending.
434 
435     The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH, Z_FINISH,
436   Z_BLOCK, or Z_TREES.  Z_SYNC_FLUSH requests that inflate() flush as much
437   output as possible to the output buffer.  Z_BLOCK requests that inflate()
438   stop if and when it gets to the next deflate block boundary.  When decoding
439   the zlib or gzip format, this will cause inflate() to return immediately
440   after the header and before the first block.  When doing a raw inflate,
441   inflate() will go ahead and process the first block, and will return when it
442   gets to the end of that block, or when it runs out of data.
443 
444     The Z_BLOCK option assists in appending to or combining deflate streams.
445   To assist in this, on return inflate() always sets strm->data_type to the
446   number of unused bits in the last byte taken from strm->next_in, plus 64 if
447   inflate() is currently decoding the last block in the deflate stream, plus
448   128 if inflate() returned immediately after decoding an end-of-block code or
449   decoding the complete header up to just before the first byte of the deflate
450   stream.  The end-of-block will not be indicated until all of the uncompressed
451   data from that block has been written to strm->next_out.  The number of
452   unused bits may in general be greater than seven, except when bit 7 of
453   data_type is set, in which case the number of unused bits will be less than
454   eight.  data_type is set as noted here every time inflate() returns for all
455   flush options, and so can be used to determine the amount of currently
456   consumed input in bits.
457 
458     The Z_TREES option behaves as Z_BLOCK does, but it also returns when the
459   end of each deflate block header is reached, before any actual data in that
460   block is decoded.  This allows the caller to determine the length of the
461   deflate block header for later use in random access within a deflate block.
462   256 is added to the value of strm->data_type when inflate() returns
463   immediately after reaching the end of the deflate block header.
464 
465     inflate() should normally be called until it returns Z_STREAM_END or an
466   error.  However if all decompression is to be performed in a single step (a
467   single call of inflate), the parameter flush should be set to Z_FINISH.  In
468   this case all pending input is processed and all pending output is flushed;
469   avail_out must be large enough to hold all of the uncompressed data for the
470   operation to complete.  (The size of the uncompressed data may have been
471   saved by the compressor for this purpose.)  The use of Z_FINISH is not
472   required to perform an inflation in one step.  However it may be used to
473   inform inflate that a faster approach can be used for the single inflate()
474   call.  Z_FINISH also informs inflate to not maintain a sliding window if the
475   stream completes, which reduces inflate's memory footprint.  If the stream
476   does not complete, either because not all of the stream is provided or not
477   enough output space is provided, then a sliding window will be allocated and
478   inflate() can be called again to continue the operation as if Z_NO_FLUSH had
479   been used.
480 
481      In this implementation, inflate() always flushes as much output as
482   possible to the output buffer, and always uses the faster approach on the
483   first call.  So the effects of the flush parameter in this implementation are
484   on the return value of inflate() as noted below, when inflate() returns early
485   when Z_BLOCK or Z_TREES is used, and when inflate() avoids the allocation of
486   memory for a sliding window when Z_FINISH is used.
487 
488      If a preset dictionary is needed after this call (see inflateSetDictionary
489   below), inflate sets strm->adler to the Adler-32 checksum of the dictionary
490   chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
491   strm->adler to the Adler-32 checksum of all output produced so far (that is,
492   total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
493   below.  At the end of the stream, inflate() checks that its computed Adler-32
494   checksum is equal to that saved by the compressor and returns Z_STREAM_END
495   only if the checksum is correct.
496 
497     inflate() can decompress and check either zlib-wrapped or gzip-wrapped
498   deflate data.  The header type is detected automatically, if requested when
499   initializing with inflateInit2().  Any information contained in the gzip
500   header is not retained unless inflateGetHeader() is used.  When processing
501   gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output
502   produced so far.  The CRC-32 is checked against the gzip trailer, as is the
503   uncompressed length, modulo 2^32.
504 
505     inflate() returns Z_OK if some progress has been made (more input processed
506   or more output produced), Z_STREAM_END if the end of the compressed data has
507   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
508   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
509   corrupted (input stream not conforming to the zlib format or incorrect check
510   value, in which case strm->msg points to a string with a more specific
511   error), Z_STREAM_ERROR if the stream structure was inconsistent (for example
512   next_in or next_out was Z_NULL, or the state was inadvertently written over
513   by the application), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR
514   if no progress was possible or if there was not enough room in the output
515   buffer when Z_FINISH is used.  Note that Z_BUF_ERROR is not fatal, and
516   inflate() can be called again with more input and more output space to
517   continue decompressing.  If Z_DATA_ERROR is returned, the application may
518   then call inflateSync() to look for a good compression block if a partial
519   recovery of the data is to be attempted.
520 */
521 
522 
523 ZEXTERN int ZEXPORT inflateEnd(z_streamp strm);
524 /*
525      All dynamically allocated data structures for this stream are freed.
526    This function discards any unprocessed input and does not flush any pending
527    output.
528 
529      inflateEnd returns Z_OK if success, or Z_STREAM_ERROR if the stream state
530    was inconsistent.
531 */
532 
533 
534                         /* Advanced functions */
535 
536 /*
537     The following functions are needed only in some special applications.
538 */
539 
540 /*
541 ZEXTERN int ZEXPORT deflateInit2(z_streamp strm,
542                                  int level,
543                                  int method,
544                                  int windowBits,
545                                  int memLevel,
546                                  int strategy);
547 
548      This is another version of deflateInit with more compression options.  The
549    fields zalloc, zfree and opaque must be initialized before by the caller.
550 
551      The method parameter is the compression method.  It must be Z_DEFLATED in
552    this version of the library.
553 
554      The windowBits parameter is the base two logarithm of the window size
555    (the size of the history buffer).  It should be in the range 8..15 for this
556    version of the library.  Larger values of this parameter result in better
557    compression at the expense of memory usage.  The default value is 15 if
558    deflateInit is used instead.
559 
560      For the current implementation of deflate(), a windowBits value of 8 (a
561    window size of 256 bytes) is not supported.  As a result, a request for 8
562    will result in 9 (a 512-byte window).  In that case, providing 8 to
563    inflateInit2() will result in an error when the zlib header with 9 is
564    checked against the initialization of inflate().  The remedy is to not use 8
565    with deflateInit2() with this initialization, or at least in that case use 9
566    with inflateInit2().
567 
568      windowBits can also be -8..-15 for raw deflate.  In this case, -windowBits
569    determines the window size.  deflate() will then generate raw deflate data
570    with no zlib header or trailer, and will not compute a check value.
571 
572      windowBits can also be greater than 15 for optional gzip encoding.  Add
573    16 to windowBits to write a simple gzip header and trailer around the
574    compressed data instead of a zlib wrapper.  The gzip header will have no
575    file name, no extra data, no comment, no modification time (set to zero), no
576    header crc, and the operating system will be set to the appropriate value,
577    if the operating system was determined at compile time.  If a gzip stream is
578    being written, strm->adler is a CRC-32 instead of an Adler-32.
579 
580      For raw deflate or gzip encoding, a request for a 256-byte window is
581    rejected as invalid, since only the zlib header provides a means of
582    transmitting the window size to the decompressor.
583 
584      The memLevel parameter specifies how much memory should be allocated
585    for the internal compression state.  memLevel=1 uses minimum memory but is
586    slow and reduces compression ratio; memLevel=9 uses maximum memory for
587    optimal speed.  The default value is 8.  See zconf.h for total memory usage
588    as a function of windowBits and memLevel.
589 
590      The strategy parameter is used to tune the compression algorithm.  Use the
591    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
592    filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
593    string match), or Z_RLE to limit match distances to one (run-length
594    encoding).  Filtered data consists mostly of small values with a somewhat
595    random distribution.  In this case, the compression algorithm is tuned to
596    compress them better.  The effect of Z_FILTERED is to force more Huffman
597    coding and less string matching; it is somewhat intermediate between
598    Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY.  Z_RLE is designed to be almost as
599    fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data.  The
600    strategy parameter only affects the compression ratio but not the
601    correctness of the compressed output even if it is not set appropriately.
602    Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler
603    decoder for special applications.
604 
605      deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
606    memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid
607    method), or Z_VERSION_ERROR if the zlib library version (zlib_version) is
608    incompatible with the version assumed by the caller (ZLIB_VERSION).  msg is
609    set to null if there is no error message.  deflateInit2 does not perform any
610    compression: this will be done by deflate().
611 */
612 
613 ZEXTERN int ZEXPORT deflateSetDictionary(z_streamp strm,
614                                          const Bytef *dictionary,
615                                          uInt  dictLength);
616 /*
617      Initializes the compression dictionary from the given byte sequence
618    without producing any compressed output.  When using the zlib format, this
619    function must be called immediately after deflateInit, deflateInit2 or
620    deflateReset, and before any call of deflate.  When doing raw deflate, this
621    function must be called either before any call of deflate, or immediately
622    after the completion of a deflate block, i.e. after all input has been
623    consumed and all output has been delivered when using any of the flush
624    options Z_BLOCK, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH, or Z_FULL_FLUSH.  The
625    compressor and decompressor must use exactly the same dictionary (see
626    inflateSetDictionary).
627 
628      The dictionary should consist of strings (byte sequences) that are likely
629    to be encountered later in the data to be compressed, with the most commonly
630    used strings preferably put towards the end of the dictionary.  Using a
631    dictionary is most useful when the data to be compressed is short and can be
632    predicted with good accuracy; the data can then be compressed better than
633    with the default empty dictionary.
634 
635      Depending on the size of the compression data structures selected by
636    deflateInit or deflateInit2, a part of the dictionary may in effect be
637    discarded, for example if the dictionary is larger than the window size
638    provided in deflateInit or deflateInit2.  Thus the strings most likely to be
639    useful should be put at the end of the dictionary, not at the front.  In
640    addition, the current implementation of deflate will use at most the window
641    size minus 262 bytes of the provided dictionary.
642 
643      Upon return of this function, strm->adler is set to the Adler-32 value
644    of the dictionary; the decompressor may later use this value to determine
645    which dictionary has been used by the compressor.  (The Adler-32 value
646    applies to the whole dictionary even if only a subset of the dictionary is
647    actually used by the compressor.) If a raw deflate was requested, then the
648    Adler-32 value is not computed and strm->adler is not set.
649 
650      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
651    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
652    inconsistent (for example if deflate has already been called for this stream
653    or if not at a block boundary for raw deflate).  deflateSetDictionary does
654    not perform any compression: this will be done by deflate().
655 */
656 
657 ZEXTERN int ZEXPORT deflateGetDictionary(z_streamp strm,
658                                          Bytef *dictionary,
659                                          uInt  *dictLength);
660 /*
661      Returns the sliding dictionary being maintained by deflate.  dictLength is
662    set to the number of bytes in the dictionary, and that many bytes are copied
663    to dictionary.  dictionary must have enough space, where 32768 bytes is
664    always enough.  If deflateGetDictionary() is called with dictionary equal to
665    Z_NULL, then only the dictionary length is returned, and nothing is copied.
666    Similarly, if dictLength is Z_NULL, then it is not set.
667 
668      deflateGetDictionary() may return a length less than the window size, even
669    when more than the window size in input has been provided. It may return up
670    to 258 bytes less in that case, due to how zlib's implementation of deflate
671    manages the sliding window and lookahead for matches, where matches can be
672    up to 258 bytes long. If the application needs the last window-size bytes of
673    input, then that would need to be saved by the application outside of zlib.
674 
675      deflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the
676    stream state is inconsistent.
677 */
678 
679 ZEXTERN int ZEXPORT deflateCopy(z_streamp dest,
680                                 z_streamp source);
681 /*
682      Sets the destination stream as a complete copy of the source stream.
683 
684      This function can be useful when several compression strategies will be
685    tried, for example when there are several ways of pre-processing the input
686    data with a filter.  The streams that will be discarded should then be freed
687    by calling deflateEnd.  Note that deflateCopy duplicates the internal
688    compression state which can be quite large, so this strategy is slow and can
689    consume lots of memory.
690 
691      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
692    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
693    (such as zalloc being Z_NULL).  msg is left unchanged in both source and
694    destination.
695 */
696 
697 ZEXTERN int ZEXPORT deflateReset(z_streamp strm);
698 /*
699      This function is equivalent to deflateEnd followed by deflateInit, but
700    does not free and reallocate the internal compression state.  The stream
701    will leave the compression level and any other attributes that may have been
702    set unchanged.  total_in, total_out, adler, and msg are initialized.
703 
704      deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
705    stream state was inconsistent (such as zalloc or state being Z_NULL).
706 */
707 
708 ZEXTERN int ZEXPORT deflateParams(z_streamp strm,
709                                   int level,
710                                   int strategy);
711 /*
712      Dynamically update the compression level and compression strategy.  The
713    interpretation of level and strategy is as in deflateInit2().  This can be
714    used to switch between compression and straight copy of the input data, or
715    to switch to a different kind of input data requiring a different strategy.
716    If the compression approach (which is a function of the level) or the
717    strategy is changed, and if there have been any deflate() calls since the
718    state was initialized or reset, then the input available so far is
719    compressed with the old level and strategy using deflate(strm, Z_BLOCK).
720    There are three approaches for the compression levels 0, 1..3, and 4..9
721    respectively.  The new level and strategy will take effect at the next call
722    of deflate().
723 
724      If a deflate(strm, Z_BLOCK) is performed by deflateParams(), and it does
725    not have enough output space to complete, then the parameter change will not
726    take effect.  In this case, deflateParams() can be called again with the
727    same parameters and more output space to try again.
728 
729      In order to assure a change in the parameters on the first try, the
730    deflate stream should be flushed using deflate() with Z_BLOCK or other flush
731    request until strm.avail_out is not zero, before calling deflateParams().
732    Then no more input data should be provided before the deflateParams() call.
733    If this is done, the old level and strategy will be applied to the data
734    compressed before deflateParams(), and the new level and strategy will be
735    applied to the data compressed after deflateParams().
736 
737      deflateParams returns Z_OK on success, Z_STREAM_ERROR if the source stream
738    state was inconsistent or if a parameter was invalid, or Z_BUF_ERROR if
739    there was not enough output space to complete the compression of the
740    available input data before a change in the strategy or approach.  Note that
741    in the case of a Z_BUF_ERROR, the parameters are not changed.  A return
742    value of Z_BUF_ERROR is not fatal, in which case deflateParams() can be
743    retried with more output space.
744 */
745 
746 ZEXTERN int ZEXPORT deflateTune(z_streamp strm,
747                                 int good_length,
748                                 int max_lazy,
749                                 int nice_length,
750                                 int max_chain);
751 /*
752      Fine tune deflate's internal compression parameters.  This should only be
753    used by someone who understands the algorithm used by zlib's deflate for
754    searching for the best matching string, and even then only by the most
755    fanatic optimizer trying to squeeze out the last compressed bit for their
756    specific input data.  Read the deflate.c source code for the meaning of the
757    max_lazy, good_length, nice_length, and max_chain parameters.
758 
759      deflateTune() can be called after deflateInit() or deflateInit2(), and
760    returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.
761  */
762 
763 ZEXTERN uLong ZEXPORT deflateBound(z_streamp strm,
764                                    uLong sourceLen);
765 /*
766      deflateBound() returns an upper bound on the compressed size after
767    deflation of sourceLen bytes.  It must be called after deflateInit() or
768    deflateInit2(), and after deflateSetHeader(), if used.  This would be used
769    to allocate an output buffer for deflation in a single pass, and so would be
770    called before deflate().  If that first deflate() call is provided the
771    sourceLen input bytes, an output buffer allocated to the size returned by
772    deflateBound(), and the flush value Z_FINISH, then deflate() is guaranteed
773    to return Z_STREAM_END.  Note that it is possible for the compressed size to
774    be larger than the value returned by deflateBound() if flush options other
775    than Z_FINISH or Z_NO_FLUSH are used.
776 */
777 
778 ZEXTERN int ZEXPORT deflatePending(z_streamp strm,
779                                    unsigned *pending,
780                                    int *bits);
781 /*
782      deflatePending() returns the number of bytes and bits of output that have
783    been generated, but not yet provided in the available output.  The bytes not
784    provided would be due to the available output space having being consumed.
785    The number of bits of output not provided are between 0 and 7, where they
786    await more bits to join them in order to fill out a full byte.  If pending
787    or bits are Z_NULL, then those values are not set.
788 
789      deflatePending returns Z_OK if success, or Z_STREAM_ERROR if the source
790    stream state was inconsistent.
791  */
792 
793 ZEXTERN int ZEXPORT deflatePrime(z_streamp strm,
794                                  int bits,
795                                  int value);
796 /*
797      deflatePrime() inserts bits in the deflate output stream.  The intent
798    is that this function is used to start off the deflate output with the bits
799    leftover from a previous deflate stream when appending to it.  As such, this
800    function can only be used for raw deflate, and must be used before the first
801    deflate() call after a deflateInit2() or deflateReset().  bits must be less
802    than or equal to 16, and that many of the least significant bits of value
803    will be inserted in the output.
804 
805      deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough
806    room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the
807    source stream state was inconsistent.
808 */
809 
810 ZEXTERN int ZEXPORT deflateSetHeader(z_streamp strm,
811                                      gz_headerp head);
812 /*
813      deflateSetHeader() provides gzip header information for when a gzip
814    stream is requested by deflateInit2().  deflateSetHeader() may be called
815    after deflateInit2() or deflateReset() and before the first call of
816    deflate().  The text, time, os, extra field, name, and comment information
817    in the provided gz_header structure are written to the gzip header (xflag is
818    ignored -- the extra flags are set according to the compression level).  The
819    caller must assure that, if not Z_NULL, name and comment are terminated with
820    a zero byte, and that if extra is not Z_NULL, that extra_len bytes are
821    available there.  If hcrc is true, a gzip header crc is included.  Note that
822    the current versions of the command-line version of gzip (up through version
823    1.3.x) do not support header crc's, and will report that it is a "multi-part
824    gzip file" and give up.
825 
826      If deflateSetHeader is not used, the default gzip header has text false,
827    the time set to zero, and os set to the current operating system, with no
828    extra, name, or comment fields.  The gzip header is returned to the default
829    state by deflateReset().
830 
831      deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
832    stream state was inconsistent.
833 */
834 
835 /*
836 ZEXTERN int ZEXPORT inflateInit2(z_streamp strm,
837                                  int windowBits);
838 
839      This is another version of inflateInit with an extra parameter.  The
840    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
841    before by the caller.
842 
843      The windowBits parameter is the base two logarithm of the maximum window
844    size (the size of the history buffer).  It should be in the range 8..15 for
845    this version of the library.  The default value is 15 if inflateInit is used
846    instead.  windowBits must be greater than or equal to the windowBits value
847    provided to deflateInit2() while compressing, or it must be equal to 15 if
848    deflateInit2() was not used.  If a compressed stream with a larger window
849    size is given as input, inflate() will return with the error code
850    Z_DATA_ERROR instead of trying to allocate a larger window.
851 
852      windowBits can also be zero to request that inflate use the window size in
853    the zlib header of the compressed stream.
854 
855      windowBits can also be -8..-15 for raw inflate.  In this case, -windowBits
856    determines the window size.  inflate() will then process raw deflate data,
857    not looking for a zlib or gzip header, not generating a check value, and not
858    looking for any check values for comparison at the end of the stream.  This
859    is for use with other formats that use the deflate compressed data format
860    such as zip.  Those formats provide their own check values.  If a custom
861    format is developed using the raw deflate format for compressed data, it is
862    recommended that a check value such as an Adler-32 or a CRC-32 be applied to
863    the uncompressed data as is done in the zlib, gzip, and zip formats.  For
864    most applications, the zlib format should be used as is.  Note that comments
865    above on the use in deflateInit2() applies to the magnitude of windowBits.
866 
867      windowBits can also be greater than 15 for optional gzip decoding.  Add
868    32 to windowBits to enable zlib and gzip decoding with automatic header
869    detection, or add 16 to decode only the gzip format (the zlib format will
870    return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is a
871    CRC-32 instead of an Adler-32.  Unlike the gunzip utility and gzread() (see
872    below), inflate() will *not* automatically decode concatenated gzip members.
873    inflate() will return Z_STREAM_END at the end of the gzip member.  The state
874    would need to be reset to continue decoding a subsequent gzip member.  This
875    *must* be done if there is more data after a gzip member, in order for the
876    decompression to be compliant with the gzip standard (RFC 1952).
877 
878      inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
879    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
880    version assumed by the caller, or Z_STREAM_ERROR if the parameters are
881    invalid, such as a null pointer to the structure.  msg is set to null if
882    there is no error message.  inflateInit2 does not perform any decompression
883    apart from possibly reading the zlib header if present: actual decompression
884    will be done by inflate().  (So next_in and avail_in may be modified, but
885    next_out and avail_out are unused and unchanged.) The current implementation
886    of inflateInit2() does not process any header information -- that is
887    deferred until inflate() is called.
888 */
889 
890 ZEXTERN int ZEXPORT inflateSetDictionary(z_streamp strm,
891                                          const Bytef *dictionary,
892                                          uInt  dictLength);
893 /*
894      Initializes the decompression dictionary from the given uncompressed byte
895    sequence.  This function must be called immediately after a call of inflate,
896    if that call returned Z_NEED_DICT.  The dictionary chosen by the compressor
897    can be determined from the Adler-32 value returned by that call of inflate.
898    The compressor and decompressor must use exactly the same dictionary (see
899    deflateSetDictionary).  For raw inflate, this function can be called at any
900    time to set the dictionary.  If the provided dictionary is smaller than the
901    window and there is already data in the window, then the provided dictionary
902    will amend what's there.  The application must insure that the dictionary
903    that was used for compression is provided.
904 
905      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
906    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
907    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
908    expected one (incorrect Adler-32 value).  inflateSetDictionary does not
909    perform any decompression: this will be done by subsequent calls of
910    inflate().
911 */
912 
913 ZEXTERN int ZEXPORT inflateGetDictionary(z_streamp strm,
914                                          Bytef *dictionary,
915                                          uInt  *dictLength);
916 /*
917      Returns the sliding dictionary being maintained by inflate.  dictLength is
918    set to the number of bytes in the dictionary, and that many bytes are copied
919    to dictionary.  dictionary must have enough space, where 32768 bytes is
920    always enough.  If inflateGetDictionary() is called with dictionary equal to
921    Z_NULL, then only the dictionary length is returned, and nothing is copied.
922    Similarly, if dictLength is Z_NULL, then it is not set.
923 
924      inflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the
925    stream state is inconsistent.
926 */
927 
928 ZEXTERN int ZEXPORT inflateSync(z_streamp strm);
929 /*
930      Skips invalid compressed data until a possible full flush point (see above
931    for the description of deflate with Z_FULL_FLUSH) can be found, or until all
932    available input is skipped.  No output is provided.
933 
934      inflateSync searches for a 00 00 FF FF pattern in the compressed data.
935    All full flush points have this pattern, but not all occurrences of this
936    pattern are full flush points.
937 
938      inflateSync returns Z_OK if a possible full flush point has been found,
939    Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point
940    has been found, or Z_STREAM_ERROR if the stream structure was inconsistent.
941    In the success case, the application may save the current value of total_in
942    which indicates where valid compressed data was found.  In the error case,
943    the application may repeatedly call inflateSync, providing more input each
944    time, until success or end of the input data.
945 */
946 
947 ZEXTERN int ZEXPORT inflateCopy(z_streamp dest,
948                                 z_streamp source);
949 /*
950      Sets the destination stream as a complete copy of the source stream.
951 
952      This function can be useful when randomly accessing a large stream.  The
953    first pass through the stream can periodically record the inflate state,
954    allowing restarting inflate at those points when randomly accessing the
955    stream.
956 
957      inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
958    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
959    (such as zalloc being Z_NULL).  msg is left unchanged in both source and
960    destination.
961 */
962 
963 ZEXTERN int ZEXPORT inflateReset(z_streamp strm);
964 /*
965      This function is equivalent to inflateEnd followed by inflateInit,
966    but does not free and reallocate the internal decompression state.  The
967    stream will keep attributes that may have been set by inflateInit2.
968    total_in, total_out, adler, and msg are initialized.
969 
970      inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
971    stream state was inconsistent (such as zalloc or state being Z_NULL).
972 */
973 
974 ZEXTERN int ZEXPORT inflateReset2(z_streamp strm,
975                                   int windowBits);
976 /*
977      This function is the same as inflateReset, but it also permits changing
978    the wrap and window size requests.  The windowBits parameter is interpreted
979    the same as it is for inflateInit2.  If the window size is changed, then the
980    memory allocated for the window is freed, and the window will be reallocated
981    by inflate() if needed.
982 
983      inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source
984    stream state was inconsistent (such as zalloc or state being Z_NULL), or if
985    the windowBits parameter is invalid.
986 */
987 
988 ZEXTERN int ZEXPORT inflatePrime(z_streamp strm,
989                                  int bits,
990                                  int value);
991 /*
992      This function inserts bits in the inflate input stream.  The intent is
993    that this function is used to start inflating at a bit position in the
994    middle of a byte.  The provided bits will be used before any bytes are used
995    from next_in.  This function should only be used with raw inflate, and
996    should be used before the first inflate() call after inflateInit2() or
997    inflateReset().  bits must be less than or equal to 16, and that many of the
998    least significant bits of value will be inserted in the input.
999 
1000      If bits is negative, then the input stream bit buffer is emptied.  Then
1001    inflatePrime() can be called again to put bits in the buffer.  This is used
1002    to clear out bits leftover after feeding inflate a block description prior
1003    to feeding inflate codes.
1004 
1005      inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
1006    stream state was inconsistent.
1007 */
1008 
1009 ZEXTERN long ZEXPORT inflateMark(z_streamp strm);
1010 /*
1011      This function returns two values, one in the lower 16 bits of the return
1012    value, and the other in the remaining upper bits, obtained by shifting the
1013    return value down 16 bits.  If the upper value is -1 and the lower value is
1014    zero, then inflate() is currently decoding information outside of a block.
1015    If the upper value is -1 and the lower value is non-zero, then inflate is in
1016    the middle of a stored block, with the lower value equaling the number of
1017    bytes from the input remaining to copy.  If the upper value is not -1, then
1018    it is the number of bits back from the current bit position in the input of
1019    the code (literal or length/distance pair) currently being processed.  In
1020    that case the lower value is the number of bytes already emitted for that
1021    code.
1022 
1023      A code is being processed if inflate is waiting for more input to complete
1024    decoding of the code, or if it has completed decoding but is waiting for
1025    more output space to write the literal or match data.
1026 
1027      inflateMark() is used to mark locations in the input data for random
1028    access, which may be at bit positions, and to note those cases where the
1029    output of a code may span boundaries of random access blocks.  The current
1030    location in the input stream can be determined from avail_in and data_type
1031    as noted in the description for the Z_BLOCK flush parameter for inflate.
1032 
1033      inflateMark returns the value noted above, or -65536 if the provided
1034    source stream state was inconsistent.
1035 */
1036 
1037 ZEXTERN int ZEXPORT inflateGetHeader(z_streamp strm,
1038                                      gz_headerp head);
1039 /*
1040      inflateGetHeader() requests that gzip header information be stored in the
1041    provided gz_header structure.  inflateGetHeader() may be called after
1042    inflateInit2() or inflateReset(), and before the first call of inflate().
1043    As inflate() processes the gzip stream, head->done is zero until the header
1044    is completed, at which time head->done is set to one.  If a zlib stream is
1045    being decoded, then head->done is set to -1 to indicate that there will be
1046    no gzip header information forthcoming.  Note that Z_BLOCK or Z_TREES can be
1047    used to force inflate() to return immediately after header processing is
1048    complete and before any actual data is decompressed.
1049 
1050      The text, time, xflags, and os fields are filled in with the gzip header
1051    contents.  hcrc is set to true if there is a header CRC.  (The header CRC
1052    was valid if done is set to one.) If extra is not Z_NULL, then extra_max
1053    contains the maximum number of bytes to write to extra.  Once done is true,
1054    extra_len contains the actual extra field length, and extra contains the
1055    extra field, or that field truncated if extra_max is less than extra_len.
1056    If name is not Z_NULL, then up to name_max characters are written there,
1057    terminated with a zero unless the length is greater than name_max.  If
1058    comment is not Z_NULL, then up to comm_max characters are written there,
1059    terminated with a zero unless the length is greater than comm_max.  When any
1060    of extra, name, or comment are not Z_NULL and the respective field is not
1061    present in the header, then that field is set to Z_NULL to signal its
1062    absence.  This allows the use of deflateSetHeader() with the returned
1063    structure to duplicate the header.  However if those fields are set to
1064    allocated memory, then the application will need to save those pointers
1065    elsewhere so that they can be eventually freed.
1066 
1067      If inflateGetHeader is not used, then the header information is simply
1068    discarded.  The header is always checked for validity, including the header
1069    CRC if present.  inflateReset() will reset the process to discard the header
1070    information.  The application would need to call inflateGetHeader() again to
1071    retrieve the header from the next gzip stream.
1072 
1073      inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
1074    stream state was inconsistent.
1075 */
1076 
1077 /*
1078 ZEXTERN int ZEXPORT inflateBackInit(z_streamp strm, int windowBits,
1079                                     unsigned char FAR *window);
1080 
1081      Initialize the internal stream state for decompression using inflateBack()
1082    calls.  The fields zalloc, zfree and opaque in strm must be initialized
1083    before the call.  If zalloc and zfree are Z_NULL, then the default library-
1084    derived memory allocation routines are used.  windowBits is the base two
1085    logarithm of the window size, in the range 8..15.  window is a caller
1086    supplied buffer of that size.  Except for special applications where it is
1087    assured that deflate was used with small window sizes, windowBits must be 15
1088    and a 32K byte window must be supplied to be able to decompress general
1089    deflate streams.
1090 
1091      See inflateBack() for the usage of these routines.
1092 
1093      inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
1094    the parameters are invalid, Z_MEM_ERROR if the internal state could not be
1095    allocated, or Z_VERSION_ERROR if the version of the library does not match
1096    the version of the header file.
1097 */
1098 
1099 typedef unsigned (*in_func)(void FAR *,
1100                             z_const unsigned char FAR * FAR *);
1101 typedef int (*out_func)(void FAR *, unsigned char FAR *, unsigned);
1102 
1103 ZEXTERN int ZEXPORT inflateBack(z_streamp strm,
1104                                 in_func in, void FAR *in_desc,
1105                                 out_func out, void FAR *out_desc);
1106 /*
1107      inflateBack() does a raw inflate with a single call using a call-back
1108    interface for input and output.  This is potentially more efficient than
1109    inflate() for file i/o applications, in that it avoids copying between the
1110    output and the sliding window by simply making the window itself the output
1111    buffer.  inflate() can be faster on modern CPUs when used with large
1112    buffers.  inflateBack() trusts the application to not change the output
1113    buffer passed by the output function, at least until inflateBack() returns.
1114 
1115      inflateBackInit() must be called first to allocate the internal state
1116    and to initialize the state with the user-provided window buffer.
1117    inflateBack() may then be used multiple times to inflate a complete, raw
1118    deflate stream with each call.  inflateBackEnd() is then called to free the
1119    allocated state.
1120 
1121      A raw deflate stream is one with no zlib or gzip header or trailer.
1122    This routine would normally be used in a utility that reads zip or gzip
1123    files and writes out uncompressed files.  The utility would decode the
1124    header and process the trailer on its own, hence this routine expects only
1125    the raw deflate stream to decompress.  This is different from the default
1126    behavior of inflate(), which expects a zlib header and trailer around the
1127    deflate stream.
1128 
1129      inflateBack() uses two subroutines supplied by the caller that are then
1130    called by inflateBack() for input and output.  inflateBack() calls those
1131    routines until it reads a complete deflate stream and writes out all of the
1132    uncompressed data, or until it encounters an error.  The function's
1133    parameters and return types are defined above in the in_func and out_func
1134    typedefs.  inflateBack() will call in(in_desc, &buf) which should return the
1135    number of bytes of provided input, and a pointer to that input in buf.  If
1136    there is no input available, in() must return zero -- buf is ignored in that
1137    case -- and inflateBack() will return a buffer error.  inflateBack() will
1138    call out(out_desc, buf, len) to write the uncompressed data buf[0..len-1].
1139    out() should return zero on success, or non-zero on failure.  If out()
1140    returns non-zero, inflateBack() will return with an error.  Neither in() nor
1141    out() are permitted to change the contents of the window provided to
1142    inflateBackInit(), which is also the buffer that out() uses to write from.
1143    The length written by out() will be at most the window size.  Any non-zero
1144    amount of input may be provided by in().
1145 
1146      For convenience, inflateBack() can be provided input on the first call by
1147    setting strm->next_in and strm->avail_in.  If that input is exhausted, then
1148    in() will be called.  Therefore strm->next_in must be initialized before
1149    calling inflateBack().  If strm->next_in is Z_NULL, then in() will be called
1150    immediately for input.  If strm->next_in is not Z_NULL, then strm->avail_in
1151    must also be initialized, and then if strm->avail_in is not zero, input will
1152    initially be taken from strm->next_in[0 ..  strm->avail_in - 1].
1153 
1154      The in_desc and out_desc parameters of inflateBack() is passed as the
1155    first parameter of in() and out() respectively when they are called.  These
1156    descriptors can be optionally used to pass any information that the caller-
1157    supplied in() and out() functions need to do their job.
1158 
1159      On return, inflateBack() will set strm->next_in and strm->avail_in to
1160    pass back any unused input that was provided by the last in() call.  The
1161    return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR
1162    if in() or out() returned an error, Z_DATA_ERROR if there was a format error
1163    in the deflate stream (in which case strm->msg is set to indicate the nature
1164    of the error), or Z_STREAM_ERROR if the stream was not properly initialized.
1165    In the case of Z_BUF_ERROR, an input or output error can be distinguished
1166    using strm->next_in which will be Z_NULL only if in() returned an error.  If
1167    strm->next_in is not Z_NULL, then the Z_BUF_ERROR was due to out() returning
1168    non-zero.  (in() will always be called before out(), so strm->next_in is
1169    assured to be defined if out() returns non-zero.)  Note that inflateBack()
1170    cannot return Z_OK.
1171 */
1172 
1173 ZEXTERN int ZEXPORT inflateBackEnd(z_streamp strm);
1174 /*
1175      All memory allocated by inflateBackInit() is freed.
1176 
1177      inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream
1178    state was inconsistent.
1179 */
1180 
1181 ZEXTERN uLong ZEXPORT zlibCompileFlags(void);
1182 /* Return flags indicating compile-time options.
1183 
1184     Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
1185      1.0: size of uInt
1186      3.2: size of uLong
1187      5.4: size of voidpf (pointer)
1188      7.6: size of z_off_t
1189 
1190     Compiler, assembler, and debug options:
1191      8: ZLIB_DEBUG
1192      9: ASMV or ASMINF -- use ASM code
1193      10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
1194      11: 0 (reserved)
1195 
1196     One-time table building (smaller code, but not thread-safe if true):
1197      12: BUILDFIXED -- build static block decoding tables when needed
1198      13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
1199      14,15: 0 (reserved)
1200 
1201     Library content (indicates missing functionality):
1202      16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
1203                           deflate code when not needed)
1204      17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect
1205                     and decode gzip streams (to avoid linking crc code)
1206      18-19: 0 (reserved)
1207 
1208     Operation variations (changes in library functionality):
1209      20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
1210      21: FASTEST -- deflate algorithm with only one, lowest compression level
1211      22,23: 0 (reserved)
1212 
1213     The sprintf variant used by gzprintf (zero is best):
1214      24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
1215      25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
1216      26: 0 = returns value, 1 = void -- 1 means inferred string length returned
1217 
1218     Remainder:
1219      27-31: 0 (reserved)
1220  */
1221 
1222 #ifndef Z_SOLO
1223 
1224                         /* utility functions */
1225 
1226 /*
1227      The following utility functions are implemented on top of the basic
1228    stream-oriented functions.  To simplify the interface, some default options
1229    are assumed (compression level and memory usage, standard memory allocation
1230    functions).  The source code of these utility functions can be modified if
1231    you need special options.
1232 */
1233 
1234 ZEXTERN int ZEXPORT compress(Bytef *dest,   uLongf *destLen,
1235                              const Bytef *source, uLong sourceLen);
1236 /*
1237      Compresses the source buffer into the destination buffer.  sourceLen is
1238    the byte length of the source buffer.  Upon entry, destLen is the total size
1239    of the destination buffer, which must be at least the value returned by
1240    compressBound(sourceLen).  Upon exit, destLen is the actual size of the
1241    compressed data.  compress() is equivalent to compress2() with a level
1242    parameter of Z_DEFAULT_COMPRESSION.
1243 
1244      compress returns Z_OK if success, Z_MEM_ERROR if there was not
1245    enough memory, Z_BUF_ERROR if there was not enough room in the output
1246    buffer.
1247 */
1248 
1249 ZEXTERN int ZEXPORT compress2(Bytef *dest,   uLongf *destLen,
1250                               const Bytef *source, uLong sourceLen,
1251                               int level);
1252 /*
1253      Compresses the source buffer into the destination buffer.  The level
1254    parameter has the same meaning as in deflateInit.  sourceLen is the byte
1255    length of the source buffer.  Upon entry, destLen is the total size of the
1256    destination buffer, which must be at least the value returned by
1257    compressBound(sourceLen).  Upon exit, destLen is the actual size of the
1258    compressed data.
1259 
1260      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
1261    memory, Z_BUF_ERROR if there was not enough room in the output buffer,
1262    Z_STREAM_ERROR if the level parameter is invalid.
1263 */
1264 
1265 ZEXTERN uLong ZEXPORT compressBound(uLong sourceLen);
1266 /*
1267      compressBound() returns an upper bound on the compressed size after
1268    compress() or compress2() on sourceLen bytes.  It would be used before a
1269    compress() or compress2() call to allocate the destination buffer.
1270 */
1271 
1272 ZEXTERN int ZEXPORT uncompress(Bytef *dest,   uLongf *destLen,
1273                                const Bytef *source, uLong sourceLen);
1274 /*
1275      Decompresses the source buffer into the destination buffer.  sourceLen is
1276    the byte length of the source buffer.  Upon entry, destLen is the total size
1277    of the destination buffer, which must be large enough to hold the entire
1278    uncompressed data.  (The size of the uncompressed data must have been saved
1279    previously by the compressor and transmitted to the decompressor by some
1280    mechanism outside the scope of this compression library.) Upon exit, destLen
1281    is the actual size of the uncompressed data.
1282 
1283      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
1284    enough memory, Z_BUF_ERROR if there was not enough room in the output
1285    buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.  In
1286    the case where there is not enough room, uncompress() will fill the output
1287    buffer with the uncompressed data up to that point.
1288 */
1289 
1290 ZEXTERN int ZEXPORT uncompress2(Bytef *dest,   uLongf *destLen,
1291                                 const Bytef *source, uLong *sourceLen);
1292 /*
1293      Same as uncompress, except that sourceLen is a pointer, where the
1294    length of the source is *sourceLen.  On return, *sourceLen is the number of
1295    source bytes consumed.
1296 */
1297 
1298                         /* gzip file access functions */
1299 
1300 /*
1301      This library supports reading and writing files in gzip (.gz) format with
1302    an interface similar to that of stdio, using the functions that start with
1303    "gz".  The gzip format is different from the zlib format.  gzip is a gzip
1304    wrapper, documented in RFC 1952, wrapped around a deflate stream.
1305 */
1306 
1307 typedef struct gzFile_s *gzFile;    /* semi-opaque gzip file descriptor */
1308 
1309 /*
1310 ZEXTERN gzFile ZEXPORT gzopen(const char *path, const char *mode);
1311 
1312      Open the gzip (.gz) file at path for reading and decompressing, or
1313    compressing and writing.  The mode parameter is as in fopen ("rb" or "wb")
1314    but can also include a compression level ("wb9") or a strategy: 'f' for
1315    filtered data as in "wb6f", 'h' for Huffman-only compression as in "wb1h",
1316    'R' for run-length encoding as in "wb1R", or 'F' for fixed code compression
1317    as in "wb9F".  (See the description of deflateInit2 for more information
1318    about the strategy parameter.)  'T' will request transparent writing or
1319    appending with no compression and not using the gzip format.
1320 
1321      "a" can be used instead of "w" to request that the gzip stream that will
1322    be written be appended to the file.  "+" will result in an error, since
1323    reading and writing to the same gzip file is not supported.  The addition of
1324    "x" when writing will create the file exclusively, which fails if the file
1325    already exists.  On systems that support it, the addition of "e" when
1326    reading or writing will set the flag to close the file on an execve() call.
1327 
1328      These functions, as well as gzip, will read and decode a sequence of gzip
1329    streams in a file.  The append function of gzopen() can be used to create
1330    such a file.  (Also see gzflush() for another way to do this.)  When
1331    appending, gzopen does not test whether the file begins with a gzip stream,
1332    nor does it look for the end of the gzip streams to begin appending.  gzopen
1333    will simply append a gzip stream to the existing file.
1334 
1335      gzopen can be used to read a file which is not in gzip format; in this
1336    case gzread will directly read from the file without decompression.  When
1337    reading, this will be detected automatically by looking for the magic two-
1338    byte gzip header.
1339 
1340      gzopen returns NULL if the file could not be opened, if there was
1341    insufficient memory to allocate the gzFile state, or if an invalid mode was
1342    specified (an 'r', 'w', or 'a' was not provided, or '+' was provided).
1343    errno can be checked to determine if the reason gzopen failed was that the
1344    file could not be opened.
1345 */
1346 
1347 ZEXTERN gzFile ZEXPORT gzdopen(int fd, const char *mode);
1348 /*
1349      Associate a gzFile with the file descriptor fd.  File descriptors are
1350    obtained from calls like open, dup, creat, pipe or fileno (if the file has
1351    been previously opened with fopen).  The mode parameter is as in gzopen.
1352 
1353      The next call of gzclose on the returned gzFile will also close the file
1354    descriptor fd, just like fclose(fdopen(fd, mode)) closes the file descriptor
1355    fd.  If you want to keep fd open, use fd = dup(fd_keep); gz = gzdopen(fd,
1356    mode);.  The duplicated descriptor should be saved to avoid a leak, since
1357    gzdopen does not close fd if it fails.  If you are using fileno() to get the
1358    file descriptor from a FILE *, then you will have to use dup() to avoid
1359    double-close()ing the file descriptor.  Both gzclose() and fclose() will
1360    close the associated file descriptor, so they need to have different file
1361    descriptors.
1362 
1363      gzdopen returns NULL if there was insufficient memory to allocate the
1364    gzFile state, if an invalid mode was specified (an 'r', 'w', or 'a' was not
1365    provided, or '+' was provided), or if fd is -1.  The file descriptor is not
1366    used until the next gz* read, write, seek, or close operation, so gzdopen
1367    will not detect if fd is invalid (unless fd is -1).
1368 */
1369 
1370 ZEXTERN int ZEXPORT gzbuffer(gzFile file, unsigned size);
1371 /*
1372      Set the internal buffer size used by this library's functions for file to
1373    size.  The default buffer size is 8192 bytes.  This function must be called
1374    after gzopen() or gzdopen(), and before any other calls that read or write
1375    the file.  The buffer memory allocation is always deferred to the first read
1376    or write.  Three times that size in buffer space is allocated.  A larger
1377    buffer size of, for example, 64K or 128K bytes will noticeably increase the
1378    speed of decompression (reading).
1379 
1380      The new buffer size also affects the maximum length for gzprintf().
1381 
1382      gzbuffer() returns 0 on success, or -1 on failure, such as being called
1383    too late.
1384 */
1385 
1386 ZEXTERN int ZEXPORT gzsetparams(gzFile file, int level, int strategy);
1387 /*
1388      Dynamically update the compression level and strategy for file.  See the
1389    description of deflateInit2 for the meaning of these parameters. Previously
1390    provided data is flushed before applying the parameter changes.
1391 
1392      gzsetparams returns Z_OK if success, Z_STREAM_ERROR if the file was not
1393    opened for writing, Z_ERRNO if there is an error writing the flushed data,
1394    or Z_MEM_ERROR if there is a memory allocation error.
1395 */
1396 
1397 ZEXTERN int ZEXPORT gzread(gzFile file, voidp buf, unsigned len);
1398 /*
1399      Read and decompress up to len uncompressed bytes from file into buf.  If
1400    the input file is not in gzip format, gzread copies the given number of
1401    bytes into the buffer directly from the file.
1402 
1403      After reaching the end of a gzip stream in the input, gzread will continue
1404    to read, looking for another gzip stream.  Any number of gzip streams may be
1405    concatenated in the input file, and will all be decompressed by gzread().
1406    If something other than a gzip stream is encountered after a gzip stream,
1407    that remaining trailing garbage is ignored (and no error is returned).
1408 
1409      gzread can be used to read a gzip file that is being concurrently written.
1410    Upon reaching the end of the input, gzread will return with the available
1411    data.  If the error code returned by gzerror is Z_OK or Z_BUF_ERROR, then
1412    gzclearerr can be used to clear the end of file indicator in order to permit
1413    gzread to be tried again.  Z_OK indicates that a gzip stream was completed
1414    on the last gzread.  Z_BUF_ERROR indicates that the input file ended in the
1415    middle of a gzip stream.  Note that gzread does not return -1 in the event
1416    of an incomplete gzip stream.  This error is deferred until gzclose(), which
1417    will return Z_BUF_ERROR if the last gzread ended in the middle of a gzip
1418    stream.  Alternatively, gzerror can be used before gzclose to detect this
1419    case.
1420 
1421      gzread returns the number of uncompressed bytes actually read, less than
1422    len for end of file, or -1 for error.  If len is too large to fit in an int,
1423    then nothing is read, -1 is returned, and the error state is set to
1424    Z_STREAM_ERROR.
1425 */
1426 
1427 ZEXTERN z_size_t ZEXPORT gzfread(voidp buf, z_size_t size, z_size_t nitems,
1428                                  gzFile file);
1429 /*
1430      Read and decompress up to nitems items of size size from file into buf,
1431    otherwise operating as gzread() does.  This duplicates the interface of
1432    stdio's fread(), with size_t request and return types.  If the library
1433    defines size_t, then z_size_t is identical to size_t.  If not, then z_size_t
1434    is an unsigned integer type that can contain a pointer.
1435 
1436      gzfread() returns the number of full items read of size size, or zero if
1437    the end of the file was reached and a full item could not be read, or if
1438    there was an error.  gzerror() must be consulted if zero is returned in
1439    order to determine if there was an error.  If the multiplication of size and
1440    nitems overflows, i.e. the product does not fit in a z_size_t, then nothing
1441    is read, zero is returned, and the error state is set to Z_STREAM_ERROR.
1442 
1443      In the event that the end of file is reached and only a partial item is
1444    available at the end, i.e. the remaining uncompressed data length is not a
1445    multiple of size, then the final partial item is nevertheless read into buf
1446    and the end-of-file flag is set.  The length of the partial item read is not
1447    provided, but could be inferred from the result of gztell().  This behavior
1448    is the same as the behavior of fread() implementations in common libraries,
1449    but it prevents the direct use of gzfread() to read a concurrently written
1450    file, resetting and retrying on end-of-file, when size is not 1.
1451 */
1452 
1453 ZEXTERN int ZEXPORT gzwrite(gzFile file, voidpc buf, unsigned len);
1454 /*
1455      Compress and write the len uncompressed bytes at buf to file. gzwrite
1456    returns the number of uncompressed bytes written or 0 in case of error.
1457 */
1458 
1459 ZEXTERN z_size_t ZEXPORT gzfwrite(voidpc buf, z_size_t size,
1460                                   z_size_t nitems, gzFile file);
1461 /*
1462      Compress and write nitems items of size size from buf to file, duplicating
1463    the interface of stdio's fwrite(), with size_t request and return types.  If
1464    the library defines size_t, then z_size_t is identical to size_t.  If not,
1465    then z_size_t is an unsigned integer type that can contain a pointer.
1466 
1467      gzfwrite() returns the number of full items written of size size, or zero
1468    if there was an error.  If the multiplication of size and nitems overflows,
1469    i.e. the product does not fit in a z_size_t, then nothing is written, zero
1470    is returned, and the error state is set to Z_STREAM_ERROR.
1471 */
1472 
1473 ZEXTERN int ZEXPORTVA gzprintf(gzFile file, const char *format, ...);
1474 /*
1475      Convert, format, compress, and write the arguments (...) to file under
1476    control of the string format, as in fprintf.  gzprintf returns the number of
1477    uncompressed bytes actually written, or a negative zlib error code in case
1478    of error.  The number of uncompressed bytes written is limited to 8191, or
1479    one less than the buffer size given to gzbuffer().  The caller should assure
1480    that this limit is not exceeded.  If it is exceeded, then gzprintf() will
1481    return an error (0) with nothing written.  In this case, there may also be a
1482    buffer overflow with unpredictable consequences, which is possible only if
1483    zlib was compiled with the insecure functions sprintf() or vsprintf(),
1484    because the secure snprintf() or vsnprintf() functions were not available.
1485    This can be determined using zlibCompileFlags().
1486 */
1487 
1488 ZEXTERN int ZEXPORT gzputs(gzFile file, const char *s);
1489 /*
1490      Compress and write the given null-terminated string s to file, excluding
1491    the terminating null character.
1492 
1493      gzputs returns the number of characters written, or -1 in case of error.
1494 */
1495 
1496 ZEXTERN char * ZEXPORT gzgets(gzFile file, char *buf, int len);
1497 /*
1498      Read and decompress bytes from file into buf, until len-1 characters are
1499    read, or until a newline character is read and transferred to buf, or an
1500    end-of-file condition is encountered.  If any characters are read or if len
1501    is one, the string is terminated with a null character.  If no characters
1502    are read due to an end-of-file or len is less than one, then the buffer is
1503    left untouched.
1504 
1505      gzgets returns buf which is a null-terminated string, or it returns NULL
1506    for end-of-file or in case of error.  If there was an error, the contents at
1507    buf are indeterminate.
1508 */
1509 
1510 ZEXTERN int ZEXPORT gzputc(gzFile file, int c);
1511 /*
1512      Compress and write c, converted to an unsigned char, into file.  gzputc
1513    returns the value that was written, or -1 in case of error.
1514 */
1515 
1516 ZEXTERN int ZEXPORT gzgetc(gzFile file);
1517 /*
1518      Read and decompress one byte from file.  gzgetc returns this byte or -1
1519    in case of end of file or error.  This is implemented as a macro for speed.
1520    As such, it does not do all of the checking the other functions do.  I.e.
1521    it does not check to see if file is NULL, nor whether the structure file
1522    points to has been clobbered or not.
1523 */
1524 
1525 ZEXTERN int ZEXPORT gzungetc(int c, gzFile file);
1526 /*
1527      Push c back onto the stream for file to be read as the first character on
1528    the next read.  At least one character of push-back is always allowed.
1529    gzungetc() returns the character pushed, or -1 on failure.  gzungetc() will
1530    fail if c is -1, and may fail if a character has been pushed but not read
1531    yet.  If gzungetc is used immediately after gzopen or gzdopen, at least the
1532    output buffer size of pushed characters is allowed.  (See gzbuffer above.)
1533    The pushed character will be discarded if the stream is repositioned with
1534    gzseek() or gzrewind().
1535 */
1536 
1537 ZEXTERN int ZEXPORT gzflush(gzFile file, int flush);
1538 /*
1539      Flush all pending output to file.  The parameter flush is as in the
1540    deflate() function.  The return value is the zlib error number (see function
1541    gzerror below).  gzflush is only permitted when writing.
1542 
1543      If the flush parameter is Z_FINISH, the remaining data is written and the
1544    gzip stream is completed in the output.  If gzwrite() is called again, a new
1545    gzip stream will be started in the output.  gzread() is able to read such
1546    concatenated gzip streams.
1547 
1548      gzflush should be called only when strictly necessary because it will
1549    degrade compression if called too often.
1550 */
1551 
1552 /*
1553 ZEXTERN z_off_t ZEXPORT gzseek(gzFile file,
1554                                z_off_t offset, int whence);
1555 
1556      Set the starting position to offset relative to whence for the next gzread
1557    or gzwrite on file.  The offset represents a number of bytes in the
1558    uncompressed data stream.  The whence parameter is defined as in lseek(2);
1559    the value SEEK_END is not supported.
1560 
1561      If the file is opened for reading, this function is emulated but can be
1562    extremely slow.  If the file is opened for writing, only forward seeks are
1563    supported; gzseek then compresses a sequence of zeroes up to the new
1564    starting position.
1565 
1566      gzseek returns the resulting offset location as measured in bytes from
1567    the beginning of the uncompressed stream, or -1 in case of error, in
1568    particular if the file is opened for writing and the new starting position
1569    would be before the current position.
1570 */
1571 
1572 ZEXTERN int ZEXPORT    gzrewind(gzFile file);
1573 /*
1574      Rewind file. This function is supported only for reading.
1575 
1576      gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET).
1577 */
1578 
1579 /*
1580 ZEXTERN z_off_t ZEXPORT    gztell(gzFile file);
1581 
1582      Return the starting position for the next gzread or gzwrite on file.
1583    This position represents a number of bytes in the uncompressed data stream,
1584    and is zero when starting, even if appending or reading a gzip stream from
1585    the middle of a file using gzdopen().
1586 
1587      gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
1588 */
1589 
1590 /*
1591 ZEXTERN z_off_t ZEXPORT gzoffset(gzFile file);
1592 
1593      Return the current compressed (actual) read or write offset of file.  This
1594    offset includes the count of bytes that precede the gzip stream, for example
1595    when appending or when using gzdopen() for reading.  When reading, the
1596    offset does not include as yet unused buffered input.  This information can
1597    be used for a progress indicator.  On error, gzoffset() returns -1.
1598 */
1599 
1600 ZEXTERN int ZEXPORT gzeof(gzFile file);
1601 /*
1602      Return true (1) if the end-of-file indicator for file has been set while
1603    reading, false (0) otherwise.  Note that the end-of-file indicator is set
1604    only if the read tried to go past the end of the input, but came up short.
1605    Therefore, just like feof(), gzeof() may return false even if there is no
1606    more data to read, in the event that the last read request was for the exact
1607    number of bytes remaining in the input file.  This will happen if the input
1608    file size is an exact multiple of the buffer size.
1609 
1610      If gzeof() returns true, then the read functions will return no more data,
1611    unless the end-of-file indicator is reset by gzclearerr() and the input file
1612    has grown since the previous end of file was detected.
1613 */
1614 
1615 ZEXTERN int ZEXPORT gzdirect(gzFile file);
1616 /*
1617      Return true (1) if file is being copied directly while reading, or false
1618    (0) if file is a gzip stream being decompressed.
1619 
1620      If the input file is empty, gzdirect() will return true, since the input
1621    does not contain a gzip stream.
1622 
1623      If gzdirect() is used immediately after gzopen() or gzdopen() it will
1624    cause buffers to be allocated to allow reading the file to determine if it
1625    is a gzip file.  Therefore if gzbuffer() is used, it should be called before
1626    gzdirect().
1627 
1628      When writing, gzdirect() returns true (1) if transparent writing was
1629    requested ("wT" for the gzopen() mode), or false (0) otherwise.  (Note:
1630    gzdirect() is not needed when writing.  Transparent writing must be
1631    explicitly requested, so the application already knows the answer.  When
1632    linking statically, using gzdirect() will include all of the zlib code for
1633    gzip file reading and decompression, which may not be desired.)
1634 */
1635 
1636 ZEXTERN int ZEXPORT    gzclose(gzFile file);
1637 /*
1638      Flush all pending output for file, if necessary, close file and
1639    deallocate the (de)compression state.  Note that once file is closed, you
1640    cannot call gzerror with file, since its structures have been deallocated.
1641    gzclose must not be called more than once on the same file, just as free
1642    must not be called more than once on the same allocation.
1643 
1644      gzclose will return Z_STREAM_ERROR if file is not valid, Z_ERRNO on a
1645    file operation error, Z_MEM_ERROR if out of memory, Z_BUF_ERROR if the
1646    last read ended in the middle of a gzip stream, or Z_OK on success.
1647 */
1648 
1649 ZEXTERN int ZEXPORT gzclose_r(gzFile file);
1650 ZEXTERN int ZEXPORT gzclose_w(gzFile file);
1651 /*
1652      Same as gzclose(), but gzclose_r() is only for use when reading, and
1653    gzclose_w() is only for use when writing or appending.  The advantage to
1654    using these instead of gzclose() is that they avoid linking in zlib
1655    compression or decompression code that is not used when only reading or only
1656    writing respectively.  If gzclose() is used, then both compression and
1657    decompression code will be included the application when linking to a static
1658    zlib library.
1659 */
1660 
1661 ZEXTERN const char * ZEXPORT gzerror(gzFile file, int *errnum);
1662 /*
1663      Return the error message for the last error which occurred on file.
1664    errnum is set to zlib error number.  If an error occurred in the file system
1665    and not in the compression library, errnum is set to Z_ERRNO and the
1666    application may consult errno to get the exact error code.
1667 
1668      The application must not modify the returned string.  Future calls to
1669    this function may invalidate the previously returned string.  If file is
1670    closed, then the string previously returned by gzerror will no longer be
1671    available.
1672 
1673      gzerror() should be used to distinguish errors from end-of-file for those
1674    functions above that do not distinguish those cases in their return values.
1675 */
1676 
1677 ZEXTERN void ZEXPORT gzclearerr(gzFile file);
1678 /*
1679      Clear the error and end-of-file flags for file.  This is analogous to the
1680    clearerr() function in stdio.  This is useful for continuing to read a gzip
1681    file that is being written concurrently.
1682 */
1683 
1684 #endif /* !Z_SOLO */
1685 
1686                         /* checksum functions */
1687 
1688 /*
1689      These functions are not related to compression but are exported
1690    anyway because they might be useful in applications using the compression
1691    library.
1692 */
1693 
1694 ZEXTERN uLong ZEXPORT adler32(uLong adler, const Bytef *buf, uInt len);
1695 /*
1696      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
1697    return the updated checksum. An Adler-32 value is in the range of a 32-bit
1698    unsigned integer. If buf is Z_NULL, this function returns the required
1699    initial value for the checksum.
1700 
1701      An Adler-32 checksum is almost as reliable as a CRC-32 but can be computed
1702    much faster.
1703 
1704    Usage example:
1705 
1706      uLong adler = adler32(0L, Z_NULL, 0);
1707 
1708      while (read_buffer(buffer, length) != EOF) {
1709        adler = adler32(adler, buffer, length);
1710      }
1711      if (adler != original_adler) error();
1712 */
1713 
1714 ZEXTERN uLong ZEXPORT adler32_z(uLong adler, const Bytef *buf,
1715                                 z_size_t len);
1716 /*
1717      Same as adler32(), but with a size_t length.
1718 */
1719 
1720 /*
1721 ZEXTERN uLong ZEXPORT adler32_combine(uLong adler1, uLong adler2,
1722                                       z_off_t len2);
1723 
1724      Combine two Adler-32 checksums into one.  For two sequences of bytes, seq1
1725    and seq2 with lengths len1 and len2, Adler-32 checksums were calculated for
1726    each, adler1 and adler2.  adler32_combine() returns the Adler-32 checksum of
1727    seq1 and seq2 concatenated, requiring only adler1, adler2, and len2.  Note
1728    that the z_off_t type (like off_t) is a signed integer.  If len2 is
1729    negative, the result has no meaning or utility.
1730 */
1731 
1732 #if !defined(_KERNEL) && !defined(_STANDALONE)
1733 ZEXTERN uLong ZEXPORT crc32(uLong crc, const Bytef *buf, uInt len);
1734 #endif
1735 /*
1736      Update a running CRC-32 with the bytes buf[0..len-1] and return the
1737    updated CRC-32. A CRC-32 value is in the range of a 32-bit unsigned integer.
1738    If buf is Z_NULL, this function returns the required initial value for the
1739    crc. Pre- and post-conditioning (one's complement) is performed within this
1740    function so it shouldn't be done by the application.
1741 
1742    Usage example:
1743 
1744      uLong crc = crc32(0L, Z_NULL, 0);
1745 
1746      while (read_buffer(buffer, length) != EOF) {
1747        crc = crc32(crc, buffer, length);
1748      }
1749      if (crc != original_crc) error();
1750 */
1751 
1752 ZEXTERN uLong ZEXPORT crc32_z(uLong crc, const Bytef *buf,
1753                               z_size_t len);
1754 /*
1755      Same as crc32(), but with a size_t length.
1756 */
1757 
1758 /*
1759 ZEXTERN uLong ZEXPORT crc32_combine(uLong crc1, uLong crc2, z_off_t len2);
1760 
1761      Combine two CRC-32 check values into one.  For two sequences of bytes,
1762    seq1 and seq2 with lengths len1 and len2, CRC-32 check values were
1763    calculated for each, crc1 and crc2.  crc32_combine() returns the CRC-32
1764    check value of seq1 and seq2 concatenated, requiring only crc1, crc2, and
1765    len2. len2 must be non-negative.
1766 */
1767 
1768 /*
1769 ZEXTERN uLong ZEXPORT crc32_combine_gen(z_off_t len2);
1770 
1771      Return the operator corresponding to length len2, to be used with
1772    crc32_combine_op(). len2 must be non-negative.
1773 */
1774 
1775 ZEXTERN uLong ZEXPORT crc32_combine_op(uLong crc1, uLong crc2, uLong op);
1776 /*
1777      Give the same result as crc32_combine(), using op in place of len2. op is
1778    is generated from len2 by crc32_combine_gen(). This will be faster than
1779    crc32_combine() if the generated op is used more than once.
1780 */
1781 
1782 
1783                         /* various hacks, don't look :) */
1784 
1785 /* deflateInit and inflateInit are macros to allow checking the zlib version
1786  * and the compiler's view of z_stream:
1787  */
1788 ZEXTERN int ZEXPORT deflateInit_(z_streamp strm, int level,
1789                                  const char *version, int stream_size);
1790 ZEXTERN int ZEXPORT inflateInit_(z_streamp strm,
1791                                  const char *version, int stream_size);
1792 ZEXTERN int ZEXPORT deflateInit2_(z_streamp strm, int  level, int  method,
1793                                   int windowBits, int memLevel,
1794                                   int strategy, const char *version,
1795                                   int stream_size);
1796 ZEXTERN int ZEXPORT inflateInit2_(z_streamp strm, int  windowBits,
1797                                   const char *version, int stream_size);
1798 ZEXTERN int ZEXPORT inflateBackInit_(z_streamp strm, int windowBits,
1799                                      unsigned char FAR *window,
1800                                      const char *version,
1801                                      int stream_size);
1802 #ifdef Z_PREFIX_SET
1803 #  define z_deflateInit(strm, level) \
1804           deflateInit_((strm), (level), ZLIB_VERSION, (int)sizeof(z_stream))
1805 #  define z_inflateInit(strm) \
1806           inflateInit_((strm), ZLIB_VERSION, (int)sizeof(z_stream))
1807 #  define z_deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
1808           deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
1809                         (strategy), ZLIB_VERSION, (int)sizeof(z_stream))
1810 #  define z_inflateInit2(strm, windowBits) \
1811           inflateInit2_((strm), (windowBits), ZLIB_VERSION, \
1812                         (int)sizeof(z_stream))
1813 #  define z_inflateBackInit(strm, windowBits, window) \
1814           inflateBackInit_((strm), (windowBits), (window), \
1815                            ZLIB_VERSION, (int)sizeof(z_stream))
1816 #else
1817 #  define deflateInit(strm, level) \
1818           deflateInit_((strm), (level), ZLIB_VERSION, (int)sizeof(z_stream))
1819 #  define inflateInit(strm) \
1820           inflateInit_((strm), ZLIB_VERSION, (int)sizeof(z_stream))
1821 #  define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
1822           deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
1823                         (strategy), ZLIB_VERSION, (int)sizeof(z_stream))
1824 #  define inflateInit2(strm, windowBits) \
1825           inflateInit2_((strm), (windowBits), ZLIB_VERSION, \
1826                         (int)sizeof(z_stream))
1827 #  define inflateBackInit(strm, windowBits, window) \
1828           inflateBackInit_((strm), (windowBits), (window), \
1829                            ZLIB_VERSION, (int)sizeof(z_stream))
1830 #endif
1831 
1832 #ifndef Z_SOLO
1833 
1834 /* gzgetc() macro and its supporting function and exposed data structure.  Note
1835  * that the real internal state is much larger than the exposed structure.
1836  * This abbreviated structure exposes just enough for the gzgetc() macro.  The
1837  * user should not mess with these exposed elements, since their names or
1838  * behavior could change in the future, perhaps even capriciously.  They can
1839  * only be used by the gzgetc() macro.  You have been warned.
1840  */
1841 struct gzFile_s {
1842     unsigned have;
1843     unsigned char *next;
1844     z_off64_t pos;
1845 };
1846 ZEXTERN int ZEXPORT gzgetc_(gzFile file);       /* backward compatibility */
1847 #ifdef Z_PREFIX_SET
1848 #  undef z_gzgetc
1849 #  define z_gzgetc(g) \
1850           ((g)->have ? ((g)->have--, (g)->pos++, *((g)->next)++) : (gzgetc)(g))
1851 #else
1852 #  define gzgetc(g) \
1853           ((g)->have ? ((g)->have--, (g)->pos++, *((g)->next)++) : (gzgetc)(g))
1854 #endif
1855 
1856 /* provide 64-bit offset functions if _LARGEFILE64_SOURCE defined, and/or
1857  * change the regular functions to 64 bits if _FILE_OFFSET_BITS is 64 (if
1858  * both are true, the application gets the *64 functions, and the regular
1859  * functions are changed to 64 bits) -- in case these are set on systems
1860  * without large file support, _LFS64_LARGEFILE must also be true
1861  */
1862 #ifdef Z_LARGE64
1863    ZEXTERN gzFile ZEXPORT gzopen64(const char *, const char *);
1864    ZEXTERN z_off64_t ZEXPORT gzseek64(gzFile, z_off64_t, int);
1865    ZEXTERN z_off64_t ZEXPORT gztell64(gzFile);
1866    ZEXTERN z_off64_t ZEXPORT gzoffset64(gzFile);
1867    ZEXTERN uLong ZEXPORT adler32_combine64(uLong, uLong, z_off64_t);
1868    ZEXTERN uLong ZEXPORT crc32_combine64(uLong, uLong, z_off64_t);
1869    ZEXTERN uLong ZEXPORT crc32_combine_gen64(z_off64_t);
1870 #endif
1871 
1872 #if !defined(ZLIB_INTERNAL) && defined(Z_WANT64)
1873 #  ifdef Z_PREFIX_SET
1874 #    define z_gzopen z_gzopen64
1875 #    define z_gzseek z_gzseek64
1876 #    define z_gztell z_gztell64
1877 #    define z_gzoffset z_gzoffset64
1878 #    define z_adler32_combine z_adler32_combine64
1879 #    define z_crc32_combine z_crc32_combine64
1880 #    define z_crc32_combine_gen z_crc32_combine_gen64
1881 #  else
1882 #    define gzopen gzopen64
1883 #    define gzseek gzseek64
1884 #    define gztell gztell64
1885 #    define gzoffset gzoffset64
1886 #    define adler32_combine adler32_combine64
1887 #    define crc32_combine crc32_combine64
1888 #    define crc32_combine_gen crc32_combine_gen64
1889 #  endif
1890 #  ifndef Z_LARGE64
1891      ZEXTERN gzFile ZEXPORT gzopen64(const char *, const char *);
1892      ZEXTERN z_off_t ZEXPORT gzseek64(gzFile, z_off_t, int);
1893      ZEXTERN z_off_t ZEXPORT gztell64(gzFile);
1894      ZEXTERN z_off_t ZEXPORT gzoffset64(gzFile);
1895      ZEXTERN uLong ZEXPORT adler32_combine64(uLong, uLong, z_off_t);
1896      ZEXTERN uLong ZEXPORT crc32_combine64(uLong, uLong, z_off_t);
1897      ZEXTERN uLong ZEXPORT crc32_combine_gen64(z_off_t);
1898 #  endif
1899 #else
1900    ZEXTERN gzFile ZEXPORT gzopen(const char *, const char *);
1901    ZEXTERN z_off_t ZEXPORT gzseek(gzFile, z_off_t, int);
1902    ZEXTERN z_off_t ZEXPORT gztell(gzFile);
1903    ZEXTERN z_off_t ZEXPORT gzoffset(gzFile);
1904    ZEXTERN uLong ZEXPORT adler32_combine(uLong, uLong, z_off_t);
1905    ZEXTERN uLong ZEXPORT crc32_combine(uLong, uLong, z_off_t);
1906    ZEXTERN uLong ZEXPORT crc32_combine_gen(z_off_t);
1907 #endif
1908 
1909 #else /* Z_SOLO */
1910 
1911    ZEXTERN uLong ZEXPORT adler32_combine(uLong, uLong, z_off_t);
1912    ZEXTERN uLong ZEXPORT crc32_combine(uLong, uLong, z_off_t);
1913    ZEXTERN uLong ZEXPORT crc32_combine_gen(z_off_t);
1914 
1915 #endif /* !Z_SOLO */
1916 
1917 /* undocumented functions */
1918 ZEXTERN const char   * ZEXPORT zError(int);
1919 ZEXTERN int            ZEXPORT inflateSyncPoint(z_streamp);
1920 ZEXTERN const z_crc_t FAR * ZEXPORT get_crc_table(void);
1921 ZEXTERN int            ZEXPORT inflateUndermine(z_streamp, int);
1922 ZEXTERN int            ZEXPORT inflateValidate(z_streamp, int);
1923 ZEXTERN unsigned long  ZEXPORT inflateCodesUsed(z_streamp);
1924 ZEXTERN int            ZEXPORT inflateResetKeep(z_streamp);
1925 ZEXTERN int            ZEXPORT deflateResetKeep(z_streamp);
1926 #if defined(_WIN32) && !defined(Z_SOLO)
1927 ZEXTERN gzFile         ZEXPORT gzopen_w(const wchar_t *path,
1928                                         const char *mode);
1929 #endif
1930 #if defined(STDC) || defined(Z_HAVE_STDARG_H)
1931 #  ifndef Z_SOLO
1932 ZEXTERN int            ZEXPORTVA gzvprintf(gzFile file,
1933                                            const char *format,
1934                                            va_list va);
1935 #  endif
1936 #endif
1937 
1938 #ifdef __cplusplus
1939 }
1940 #endif
1941 
1942 #endif /* ZLIB_H */
1943