xref: /freebsd/sys/contrib/zlib/zlib.h (revision c93b6e5fa24ba172ab271432c6692f9cc604e15a)
1 /* zlib.h -- interface of the 'zlib' general purpose compression library
2   version 1.2.11, January 15th, 2017
3 
4   Copyright (C) 1995-2017 Jean-loup Gailly and Mark Adler
5 
6   This software is provided 'as-is', without any express or implied
7   warranty.  In no event will the authors be held liable for any damages
8   arising from the use of this software.
9 
10   Permission is granted to anyone to use this software for any purpose,
11   including commercial applications, and to alter it and redistribute it
12   freely, subject to the following restrictions:
13 
14   1. The origin of this software must not be misrepresented; you must not
15      claim that you wrote the original software. If you use this software
16      in a product, an acknowledgment in the product documentation would be
17      appreciated but is not required.
18   2. Altered source versions must be plainly marked as such, and must not be
19      misrepresented as being the original software.
20   3. This notice may not be removed or altered from any source distribution.
21 
22   Jean-loup Gailly        Mark Adler
23   jloup@gzip.org          madler@alumni.caltech.edu
24 
25 
26   The data format used by the zlib library is described by RFCs (Request for
27   Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
28   (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
29 */
30 
31 #ifndef ZLIB_H
32 #define ZLIB_H
33 
34 #include "zconf.h"
35 
36 #ifdef __cplusplus
37 extern "C" {
38 #endif
39 
40 #define ZLIB_VERSION "1.2.11"
41 #define ZLIB_VERNUM 0x12b0
42 #define ZLIB_VER_MAJOR 1
43 #define ZLIB_VER_MINOR 2
44 #define ZLIB_VER_REVISION 11
45 #define ZLIB_VER_SUBREVISION 0
46 
47 /*
48     The 'zlib' compression library provides in-memory compression and
49   decompression functions, including integrity checks of the uncompressed data.
50   This version of the library supports only one compression method (deflation)
51   but other algorithms will be added later and will have the same stream
52   interface.
53 
54     Compression can be done in a single step if the buffers are large enough,
55   or can be done by repeated calls of the compression function.  In the latter
56   case, the application must provide more input and/or consume the output
57   (providing more output space) before each call.
58 
59     The compressed data format used by default by the in-memory functions is
60   the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
61   around a deflate stream, which is itself documented in RFC 1951.
62 
63     The library also supports reading and writing files in gzip (.gz) format
64   with an interface similar to that of stdio using the functions that start
65   with "gz".  The gzip format is different from the zlib format.  gzip is a
66   gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
67 
68     This library can optionally read and write gzip and raw deflate streams in
69   memory as well.
70 
71     The zlib format was designed to be compact and fast for use in memory
72   and on communications channels.  The gzip format was designed for single-
73   file compression on file systems, has a larger header than zlib to maintain
74   directory information, and uses a different, slower check method than zlib.
75 
76     The library does not install any signal handler.  The decoder checks
77   the consistency of the compressed data, so the library should never crash
78   even in the case of corrupted input.
79 */
80 
81 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
82 typedef void   (*free_func)  OF((voidpf opaque, voidpf address));
83 
84 struct internal_state;
85 
86 typedef struct z_stream_s {
87     z_const Bytef *next_in;     /* next input byte */
88     uInt     avail_in;  /* number of bytes available at next_in */
89     uLong    total_in;  /* total number of input bytes read so far */
90 
91     Bytef    *next_out; /* next output byte will go here */
92     uInt     avail_out; /* remaining free space at next_out */
93     uLong    total_out; /* total number of bytes output so far */
94 
95     z_const char *msg;  /* last error message, NULL if no error */
96     struct internal_state FAR *state; /* not visible by applications */
97 
98     alloc_func zalloc;  /* used to allocate the internal state */
99     free_func  zfree;   /* used to free the internal state */
100     voidpf     opaque;  /* private data object passed to zalloc and zfree */
101 
102     int     data_type;  /* best guess about the data type: binary or text
103                            for deflate, or the decoding state for inflate */
104     uLong   adler;      /* Adler-32 or CRC-32 value of the uncompressed data */
105     uLong   reserved;   /* reserved for future use */
106 } z_stream;
107 
108 typedef z_stream FAR *z_streamp;
109 
110 /*
111      gzip header information passed to and from zlib routines.  See RFC 1952
112   for more details on the meanings of these fields.
113 */
114 typedef struct gz_header_s {
115     int     text;       /* true if compressed data believed to be text */
116     uLong   time;       /* modification time */
117     int     xflags;     /* extra flags (not used when writing a gzip file) */
118     int     os;         /* operating system */
119     Bytef   *extra;     /* pointer to extra field or Z_NULL if none */
120     uInt    extra_len;  /* extra field length (valid if extra != Z_NULL) */
121     uInt    extra_max;  /* space at extra (only when reading header) */
122     Bytef   *name;      /* pointer to zero-terminated file name or Z_NULL */
123     uInt    name_max;   /* space at name (only when reading header) */
124     Bytef   *comment;   /* pointer to zero-terminated comment or Z_NULL */
125     uInt    comm_max;   /* space at comment (only when reading header) */
126     int     hcrc;       /* true if there was or will be a header crc */
127     int     done;       /* true when done reading gzip header (not used
128                            when writing a gzip file) */
129 } gz_header;
130 
131 typedef gz_header FAR *gz_headerp;
132 
133 /*
134      The application must update next_in and avail_in when avail_in has dropped
135    to zero.  It must update next_out and avail_out when avail_out has dropped
136    to zero.  The application must initialize zalloc, zfree and opaque before
137    calling the init function.  All other fields are set by the compression
138    library and must not be updated by the application.
139 
140      The opaque value provided by the application will be passed as the first
141    parameter for calls of zalloc and zfree.  This can be useful for custom
142    memory management.  The compression library attaches no meaning to the
143    opaque value.
144 
145      zalloc must return Z_NULL if there is not enough memory for the object.
146    If zlib is used in a multi-threaded application, zalloc and zfree must be
147    thread safe.  In that case, zlib is thread-safe.  When zalloc and zfree are
148    Z_NULL on entry to the initialization function, they are set to internal
149    routines that use the standard library functions malloc() and free().
150 
151      On 16-bit systems, the functions zalloc and zfree must be able to allocate
152    exactly 65536 bytes, but will not be required to allocate more than this if
153    the symbol MAXSEG_64K is defined (see zconf.h).  WARNING: On MSDOS, pointers
154    returned by zalloc for objects of exactly 65536 bytes *must* have their
155    offset normalized to zero.  The default allocation function provided by this
156    library ensures this (see zutil.c).  To reduce memory requirements and avoid
157    any allocation of 64K objects, at the expense of compression ratio, compile
158    the library with -DMAX_WBITS=14 (see zconf.h).
159 
160      The fields total_in and total_out can be used for statistics or progress
161    reports.  After compression, total_in holds the total size of the
162    uncompressed data and may be saved for use by the decompressor (particularly
163    if the decompressor wants to decompress everything in a single step).
164 */
165 
166                         /* constants */
167 
168 #define Z_NO_FLUSH      0
169 #define Z_PARTIAL_FLUSH 1
170 #define Z_SYNC_FLUSH    2
171 #define Z_FULL_FLUSH    3
172 #define Z_FINISH        4
173 #define Z_BLOCK         5
174 #define Z_TREES         6
175 /* Allowed flush values; see deflate() and inflate() below for details */
176 
177 #define Z_OK            0
178 #define Z_STREAM_END    1
179 #define Z_NEED_DICT     2
180 #define Z_ERRNO        (-1)
181 #define Z_STREAM_ERROR (-2)
182 #define Z_DATA_ERROR   (-3)
183 #define Z_MEM_ERROR    (-4)
184 #define Z_BUF_ERROR    (-5)
185 #define Z_VERSION_ERROR (-6)
186 /* Return codes for the compression/decompression functions. Negative values
187  * are errors, positive values are used for special but normal events.
188  */
189 
190 #define Z_NO_COMPRESSION         0
191 #define Z_BEST_SPEED             1
192 #define Z_BEST_COMPRESSION       9
193 #define Z_DEFAULT_COMPRESSION  (-1)
194 /* compression levels */
195 
196 #define Z_FILTERED            1
197 #define Z_HUFFMAN_ONLY        2
198 #define Z_RLE                 3
199 #define Z_FIXED               4
200 #define Z_DEFAULT_STRATEGY    0
201 /* compression strategy; see deflateInit2() below for details */
202 
203 #define Z_BINARY   0
204 #define Z_TEXT     1
205 #define Z_ASCII    Z_TEXT   /* for compatibility with 1.2.2 and earlier */
206 #define Z_UNKNOWN  2
207 /* Possible values of the data_type field for deflate() */
208 
209 #define Z_DEFLATED   8
210 /* The deflate compression method (the only one supported in this version) */
211 
212 #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
213 
214 #define zlib_version zlibVersion()
215 /* for compatibility with versions < 1.0.2 */
216 
217 
218                         /* basic functions */
219 
220 ZEXTERN const char * ZEXPORT zlibVersion OF((void));
221 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
222    If the first character differs, the library code actually used is not
223    compatible with the zlib.h header file used by the application.  This check
224    is automatically made by deflateInit and inflateInit.
225  */
226 
227 /*
228 ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));
229 
230      Initializes the internal stream state for compression.  The fields
231    zalloc, zfree and opaque must be initialized before by the caller.  If
232    zalloc and zfree are set to Z_NULL, deflateInit updates them to use default
233    allocation functions.
234 
235      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
236    1 gives best speed, 9 gives best compression, 0 gives no compression at all
237    (the input data is simply copied a block at a time).  Z_DEFAULT_COMPRESSION
238    requests a default compromise between speed and compression (currently
239    equivalent to level 6).
240 
241      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
242    memory, Z_STREAM_ERROR if level is not a valid compression level, or
243    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
244    with the version assumed by the caller (ZLIB_VERSION).  msg is set to null
245    if there is no error message.  deflateInit does not perform any compression:
246    this will be done by deflate().
247 */
248 
249 
250 ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));
251 /*
252     deflate compresses as much data as possible, and stops when the input
253   buffer becomes empty or the output buffer becomes full.  It may introduce
254   some output latency (reading input without producing any output) except when
255   forced to flush.
256 
257     The detailed semantics are as follows.  deflate performs one or both of the
258   following actions:
259 
260   - Compress more input starting at next_in and update next_in and avail_in
261     accordingly.  If not all input can be processed (because there is not
262     enough room in the output buffer), next_in and avail_in are updated and
263     processing will resume at this point for the next call of deflate().
264 
265   - Generate more output starting at next_out and update next_out and avail_out
266     accordingly.  This action is forced if the parameter flush is non zero.
267     Forcing flush frequently degrades the compression ratio, so this parameter
268     should be set only when necessary.  Some output may be provided even if
269     flush is zero.
270 
271     Before the call of deflate(), the application should ensure that at least
272   one of the actions is possible, by providing more input and/or consuming more
273   output, and updating avail_in or avail_out accordingly; avail_out should
274   never be zero before the call.  The application can consume the compressed
275   output when it wants, for example when the output buffer is full (avail_out
276   == 0), or after each call of deflate().  If deflate returns Z_OK and with
277   zero avail_out, it must be called again after making room in the output
278   buffer because there might be more output pending. See deflatePending(),
279   which can be used if desired to determine whether or not there is more ouput
280   in that case.
281 
282     Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to
283   decide how much data to accumulate before producing output, in order to
284   maximize compression.
285 
286     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
287   flushed to the output buffer and the output is aligned on a byte boundary, so
288   that the decompressor can get all input data available so far.  (In
289   particular avail_in is zero after the call if enough output space has been
290   provided before the call.) Flushing may degrade compression for some
291   compression algorithms and so it should be used only when necessary.  This
292   completes the current deflate block and follows it with an empty stored block
293   that is three bits plus filler bits to the next byte, followed by four bytes
294   (00 00 ff ff).
295 
296     If flush is set to Z_PARTIAL_FLUSH, all pending output is flushed to the
297   output buffer, but the output is not aligned to a byte boundary.  All of the
298   input data so far will be available to the decompressor, as for Z_SYNC_FLUSH.
299   This completes the current deflate block and follows it with an empty fixed
300   codes block that is 10 bits long.  This assures that enough bytes are output
301   in order for the decompressor to finish the block before the empty fixed
302   codes block.
303 
304     If flush is set to Z_BLOCK, a deflate block is completed and emitted, as
305   for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to
306   seven bits of the current block are held to be written as the next byte after
307   the next deflate block is completed.  In this case, the decompressor may not
308   be provided enough bits at this point in order to complete decompression of
309   the data provided so far to the compressor.  It may need to wait for the next
310   block to be emitted.  This is for advanced applications that need to control
311   the emission of deflate blocks.
312 
313     If flush is set to Z_FULL_FLUSH, all output is flushed as with
314   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
315   restart from this point if previous compressed data has been damaged or if
316   random access is desired.  Using Z_FULL_FLUSH too often can seriously degrade
317   compression.
318 
319     If deflate returns with avail_out == 0, this function must be called again
320   with the same value of the flush parameter and more output space (updated
321   avail_out), until the flush is complete (deflate returns with non-zero
322   avail_out).  In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
323   avail_out is greater than six to avoid repeated flush markers due to
324   avail_out == 0 on return.
325 
326     If the parameter flush is set to Z_FINISH, pending input is processed,
327   pending output is flushed and deflate returns with Z_STREAM_END if there was
328   enough output space.  If deflate returns with Z_OK or Z_BUF_ERROR, this
329   function must be called again with Z_FINISH and more output space (updated
330   avail_out) but no more input data, until it returns with Z_STREAM_END or an
331   error.  After deflate has returned Z_STREAM_END, the only possible operations
332   on the stream are deflateReset or deflateEnd.
333 
334     Z_FINISH can be used in the first deflate call after deflateInit if all the
335   compression is to be done in a single step.  In order to complete in one
336   call, avail_out must be at least the value returned by deflateBound (see
337   below).  Then deflate is guaranteed to return Z_STREAM_END.  If not enough
338   output space is provided, deflate will not return Z_STREAM_END, and it must
339   be called again as described above.
340 
341     deflate() sets strm->adler to the Adler-32 checksum of all input read
342   so far (that is, total_in bytes).  If a gzip stream is being generated, then
343   strm->adler will be the CRC-32 checksum of the input read so far.  (See
344   deflateInit2 below.)
345 
346     deflate() may update strm->data_type if it can make a good guess about
347   the input data type (Z_BINARY or Z_TEXT).  If in doubt, the data is
348   considered binary.  This field is only for information purposes and does not
349   affect the compression algorithm in any manner.
350 
351     deflate() returns Z_OK if some progress has been made (more input
352   processed or more output produced), Z_STREAM_END if all input has been
353   consumed and all output has been produced (only when flush is set to
354   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
355   if next_in or next_out was Z_NULL or the state was inadvertently written over
356   by the application), or Z_BUF_ERROR if no progress is possible (for example
357   avail_in or avail_out was zero).  Note that Z_BUF_ERROR is not fatal, and
358   deflate() can be called again with more input and more output space to
359   continue compressing.
360 */
361 
362 
363 ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
364 /*
365      All dynamically allocated data structures for this stream are freed.
366    This function discards any unprocessed input and does not flush any pending
367    output.
368 
369      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
370    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
371    prematurely (some input or output was discarded).  In the error case, msg
372    may be set but then points to a static string (which must not be
373    deallocated).
374 */
375 
376 
377 /*
378 ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));
379 
380      Initializes the internal stream state for decompression.  The fields
381    next_in, avail_in, zalloc, zfree and opaque must be initialized before by
382    the caller.  In the current version of inflate, the provided input is not
383    read or consumed.  The allocation of a sliding window will be deferred to
384    the first call of inflate (if the decompression does not complete on the
385    first call).  If zalloc and zfree are set to Z_NULL, inflateInit updates
386    them to use default allocation functions.
387 
388      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
389    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
390    version assumed by the caller, or Z_STREAM_ERROR if the parameters are
391    invalid, such as a null pointer to the structure.  msg is set to null if
392    there is no error message.  inflateInit does not perform any decompression.
393    Actual decompression will be done by inflate().  So next_in, and avail_in,
394    next_out, and avail_out are unused and unchanged.  The current
395    implementation of inflateInit() does not process any header information --
396    that is deferred until inflate() is called.
397 */
398 
399 
400 ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
401 /*
402     inflate decompresses as much data as possible, and stops when the input
403   buffer becomes empty or the output buffer becomes full.  It may introduce
404   some output latency (reading input without producing any output) except when
405   forced to flush.
406 
407   The detailed semantics are as follows.  inflate performs one or both of the
408   following actions:
409 
410   - Decompress more input starting at next_in and update next_in and avail_in
411     accordingly.  If not all input can be processed (because there is not
412     enough room in the output buffer), then next_in and avail_in are updated
413     accordingly, and processing will resume at this point for the next call of
414     inflate().
415 
416   - Generate more output starting at next_out and update next_out and avail_out
417     accordingly.  inflate() provides as much output as possible, until there is
418     no more input data or no more space in the output buffer (see below about
419     the flush parameter).
420 
421     Before the call of inflate(), the application should ensure that at least
422   one of the actions is possible, by providing more input and/or consuming more
423   output, and updating the next_* and avail_* values accordingly.  If the
424   caller of inflate() does not provide both available input and available
425   output space, it is possible that there will be no progress made.  The
426   application can consume the uncompressed output when it wants, for example
427   when the output buffer is full (avail_out == 0), or after each call of
428   inflate().  If inflate returns Z_OK and with zero avail_out, it must be
429   called again after making room in the output buffer because there might be
430   more output pending.
431 
432     The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH, Z_FINISH,
433   Z_BLOCK, or Z_TREES.  Z_SYNC_FLUSH requests that inflate() flush as much
434   output as possible to the output buffer.  Z_BLOCK requests that inflate()
435   stop if and when it gets to the next deflate block boundary.  When decoding
436   the zlib or gzip format, this will cause inflate() to return immediately
437   after the header and before the first block.  When doing a raw inflate,
438   inflate() will go ahead and process the first block, and will return when it
439   gets to the end of that block, or when it runs out of data.
440 
441     The Z_BLOCK option assists in appending to or combining deflate streams.
442   To assist in this, on return inflate() always sets strm->data_type to the
443   number of unused bits in the last byte taken from strm->next_in, plus 64 if
444   inflate() is currently decoding the last block in the deflate stream, plus
445   128 if inflate() returned immediately after decoding an end-of-block code or
446   decoding the complete header up to just before the first byte of the deflate
447   stream.  The end-of-block will not be indicated until all of the uncompressed
448   data from that block has been written to strm->next_out.  The number of
449   unused bits may in general be greater than seven, except when bit 7 of
450   data_type is set, in which case the number of unused bits will be less than
451   eight.  data_type is set as noted here every time inflate() returns for all
452   flush options, and so can be used to determine the amount of currently
453   consumed input in bits.
454 
455     The Z_TREES option behaves as Z_BLOCK does, but it also returns when the
456   end of each deflate block header is reached, before any actual data in that
457   block is decoded.  This allows the caller to determine the length of the
458   deflate block header for later use in random access within a deflate block.
459   256 is added to the value of strm->data_type when inflate() returns
460   immediately after reaching the end of the deflate block header.
461 
462     inflate() should normally be called until it returns Z_STREAM_END or an
463   error.  However if all decompression is to be performed in a single step (a
464   single call of inflate), the parameter flush should be set to Z_FINISH.  In
465   this case all pending input is processed and all pending output is flushed;
466   avail_out must be large enough to hold all of the uncompressed data for the
467   operation to complete.  (The size of the uncompressed data may have been
468   saved by the compressor for this purpose.)  The use of Z_FINISH is not
469   required to perform an inflation in one step.  However it may be used to
470   inform inflate that a faster approach can be used for the single inflate()
471   call.  Z_FINISH also informs inflate to not maintain a sliding window if the
472   stream completes, which reduces inflate's memory footprint.  If the stream
473   does not complete, either because not all of the stream is provided or not
474   enough output space is provided, then a sliding window will be allocated and
475   inflate() can be called again to continue the operation as if Z_NO_FLUSH had
476   been used.
477 
478      In this implementation, inflate() always flushes as much output as
479   possible to the output buffer, and always uses the faster approach on the
480   first call.  So the effects of the flush parameter in this implementation are
481   on the return value of inflate() as noted below, when inflate() returns early
482   when Z_BLOCK or Z_TREES is used, and when inflate() avoids the allocation of
483   memory for a sliding window when Z_FINISH is used.
484 
485      If a preset dictionary is needed after this call (see inflateSetDictionary
486   below), inflate sets strm->adler to the Adler-32 checksum of the dictionary
487   chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
488   strm->adler to the Adler-32 checksum of all output produced so far (that is,
489   total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
490   below.  At the end of the stream, inflate() checks that its computed Adler-32
491   checksum is equal to that saved by the compressor and returns Z_STREAM_END
492   only if the checksum is correct.
493 
494     inflate() can decompress and check either zlib-wrapped or gzip-wrapped
495   deflate data.  The header type is detected automatically, if requested when
496   initializing with inflateInit2().  Any information contained in the gzip
497   header is not retained unless inflateGetHeader() is used.  When processing
498   gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output
499   produced so far.  The CRC-32 is checked against the gzip trailer, as is the
500   uncompressed length, modulo 2^32.
501 
502     inflate() returns Z_OK if some progress has been made (more input processed
503   or more output produced), Z_STREAM_END if the end of the compressed data has
504   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
505   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
506   corrupted (input stream not conforming to the zlib format or incorrect check
507   value, in which case strm->msg points to a string with a more specific
508   error), Z_STREAM_ERROR if the stream structure was inconsistent (for example
509   next_in or next_out was Z_NULL, or the state was inadvertently written over
510   by the application), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR
511   if no progress was possible or if there was not enough room in the output
512   buffer when Z_FINISH is used.  Note that Z_BUF_ERROR is not fatal, and
513   inflate() can be called again with more input and more output space to
514   continue decompressing.  If Z_DATA_ERROR is returned, the application may
515   then call inflateSync() to look for a good compression block if a partial
516   recovery of the data is to be attempted.
517 */
518 
519 
520 ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));
521 /*
522      All dynamically allocated data structures for this stream are freed.
523    This function discards any unprocessed input and does not flush any pending
524    output.
525 
526      inflateEnd returns Z_OK if success, or Z_STREAM_ERROR if the stream state
527    was inconsistent.
528 */
529 
530 
531                         /* Advanced functions */
532 
533 /*
534     The following functions are needed only in some special applications.
535 */
536 
537 /*
538 ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
539                                      int  level,
540                                      int  method,
541                                      int  windowBits,
542                                      int  memLevel,
543                                      int  strategy));
544 
545      This is another version of deflateInit with more compression options.  The
546    fields next_in, zalloc, zfree and opaque must be initialized before by the
547    caller.
548 
549      The method parameter is the compression method.  It must be Z_DEFLATED in
550    this version of the library.
551 
552      The windowBits parameter is the base two logarithm of the window size
553    (the size of the history buffer).  It should be in the range 8..15 for this
554    version of the library.  Larger values of this parameter result in better
555    compression at the expense of memory usage.  The default value is 15 if
556    deflateInit is used instead.
557 
558      For the current implementation of deflate(), a windowBits value of 8 (a
559    window size of 256 bytes) is not supported.  As a result, a request for 8
560    will result in 9 (a 512-byte window).  In that case, providing 8 to
561    inflateInit2() will result in an error when the zlib header with 9 is
562    checked against the initialization of inflate().  The remedy is to not use 8
563    with deflateInit2() with this initialization, or at least in that case use 9
564    with inflateInit2().
565 
566      windowBits can also be -8..-15 for raw deflate.  In this case, -windowBits
567    determines the window size.  deflate() will then generate raw deflate data
568    with no zlib header or trailer, and will not compute a check value.
569 
570      windowBits can also be greater than 15 for optional gzip encoding.  Add
571    16 to windowBits to write a simple gzip header and trailer around the
572    compressed data instead of a zlib wrapper.  The gzip header will have no
573    file name, no extra data, no comment, no modification time (set to zero), no
574    header crc, and the operating system will be set to the appropriate value,
575    if the operating system was determined at compile time.  If a gzip stream is
576    being written, strm->adler is a CRC-32 instead of an Adler-32.
577 
578      For raw deflate or gzip encoding, a request for a 256-byte window is
579    rejected as invalid, since only the zlib header provides a means of
580    transmitting the window size to the decompressor.
581 
582      The memLevel parameter specifies how much memory should be allocated
583    for the internal compression state.  memLevel=1 uses minimum memory but is
584    slow and reduces compression ratio; memLevel=9 uses maximum memory for
585    optimal speed.  The default value is 8.  See zconf.h for total memory usage
586    as a function of windowBits and memLevel.
587 
588      The strategy parameter is used to tune the compression algorithm.  Use the
589    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
590    filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
591    string match), or Z_RLE to limit match distances to one (run-length
592    encoding).  Filtered data consists mostly of small values with a somewhat
593    random distribution.  In this case, the compression algorithm is tuned to
594    compress them better.  The effect of Z_FILTERED is to force more Huffman
595    coding and less string matching; it is somewhat intermediate between
596    Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY.  Z_RLE is designed to be almost as
597    fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data.  The
598    strategy parameter only affects the compression ratio but not the
599    correctness of the compressed output even if it is not set appropriately.
600    Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler
601    decoder for special applications.
602 
603      deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
604    memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid
605    method), or Z_VERSION_ERROR if the zlib library version (zlib_version) is
606    incompatible with the version assumed by the caller (ZLIB_VERSION).  msg is
607    set to null if there is no error message.  deflateInit2 does not perform any
608    compression: this will be done by deflate().
609 */
610 
611 ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,
612                                              const Bytef *dictionary,
613                                              uInt  dictLength));
614 /*
615      Initializes the compression dictionary from the given byte sequence
616    without producing any compressed output.  When using the zlib format, this
617    function must be called immediately after deflateInit, deflateInit2 or
618    deflateReset, and before any call of deflate.  When doing raw deflate, this
619    function must be called either before any call of deflate, or immediately
620    after the completion of a deflate block, i.e. after all input has been
621    consumed and all output has been delivered when using any of the flush
622    options Z_BLOCK, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH, or Z_FULL_FLUSH.  The
623    compressor and decompressor must use exactly the same dictionary (see
624    inflateSetDictionary).
625 
626      The dictionary should consist of strings (byte sequences) that are likely
627    to be encountered later in the data to be compressed, with the most commonly
628    used strings preferably put towards the end of the dictionary.  Using a
629    dictionary is most useful when the data to be compressed is short and can be
630    predicted with good accuracy; the data can then be compressed better than
631    with the default empty dictionary.
632 
633      Depending on the size of the compression data structures selected by
634    deflateInit or deflateInit2, a part of the dictionary may in effect be
635    discarded, for example if the dictionary is larger than the window size
636    provided in deflateInit or deflateInit2.  Thus the strings most likely to be
637    useful should be put at the end of the dictionary, not at the front.  In
638    addition, the current implementation of deflate will use at most the window
639    size minus 262 bytes of the provided dictionary.
640 
641      Upon return of this function, strm->adler is set to the Adler-32 value
642    of the dictionary; the decompressor may later use this value to determine
643    which dictionary has been used by the compressor.  (The Adler-32 value
644    applies to the whole dictionary even if only a subset of the dictionary is
645    actually used by the compressor.) If a raw deflate was requested, then the
646    Adler-32 value is not computed and strm->adler is not set.
647 
648      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
649    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
650    inconsistent (for example if deflate has already been called for this stream
651    or if not at a block boundary for raw deflate).  deflateSetDictionary does
652    not perform any compression: this will be done by deflate().
653 */
654 
655 ZEXTERN int ZEXPORT deflateGetDictionary OF((z_streamp strm,
656                                              Bytef *dictionary,
657                                              uInt  *dictLength));
658 /*
659      Returns the sliding dictionary being maintained by deflate.  dictLength is
660    set to the number of bytes in the dictionary, and that many bytes are copied
661    to dictionary.  dictionary must have enough space, where 32768 bytes is
662    always enough.  If deflateGetDictionary() is called with dictionary equal to
663    Z_NULL, then only the dictionary length is returned, and nothing is copied.
664    Similary, if dictLength is Z_NULL, then it is not set.
665 
666      deflateGetDictionary() may return a length less than the window size, even
667    when more than the window size in input has been provided. It may return up
668    to 258 bytes less in that case, due to how zlib's implementation of deflate
669    manages the sliding window and lookahead for matches, where matches can be
670    up to 258 bytes long. If the application needs the last window-size bytes of
671    input, then that would need to be saved by the application outside of zlib.
672 
673      deflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the
674    stream state is inconsistent.
675 */
676 
677 ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,
678                                     z_streamp source));
679 /*
680      Sets the destination stream as a complete copy of the source stream.
681 
682      This function can be useful when several compression strategies will be
683    tried, for example when there are several ways of pre-processing the input
684    data with a filter.  The streams that will be discarded should then be freed
685    by calling deflateEnd.  Note that deflateCopy duplicates the internal
686    compression state which can be quite large, so this strategy is slow and can
687    consume lots of memory.
688 
689      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
690    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
691    (such as zalloc being Z_NULL).  msg is left unchanged in both source and
692    destination.
693 */
694 
695 ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
696 /*
697      This function is equivalent to deflateEnd followed by deflateInit, but
698    does not free and reallocate the internal compression state.  The stream
699    will leave the compression level and any other attributes that may have been
700    set unchanged.
701 
702      deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
703    stream state was inconsistent (such as zalloc or state being Z_NULL).
704 */
705 
706 ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
707                                       int level,
708                                       int strategy));
709 /*
710      Dynamically update the compression level and compression strategy.  The
711    interpretation of level and strategy is as in deflateInit2().  This can be
712    used to switch between compression and straight copy of the input data, or
713    to switch to a different kind of input data requiring a different strategy.
714    If the compression approach (which is a function of the level) or the
715    strategy is changed, and if there have been any deflate() calls since the
716    state was initialized or reset, then the input available so far is
717    compressed with the old level and strategy using deflate(strm, Z_BLOCK).
718    There are three approaches for the compression levels 0, 1..3, and 4..9
719    respectively.  The new level and strategy will take effect at the next call
720    of deflate().
721 
722      If a deflate(strm, Z_BLOCK) is performed by deflateParams(), and it does
723    not have enough output space to complete, then the parameter change will not
724    take effect.  In this case, deflateParams() can be called again with the
725    same parameters and more output space to try again.
726 
727      In order to assure a change in the parameters on the first try, the
728    deflate stream should be flushed using deflate() with Z_BLOCK or other flush
729    request until strm.avail_out is not zero, before calling deflateParams().
730    Then no more input data should be provided before the deflateParams() call.
731    If this is done, the old level and strategy will be applied to the data
732    compressed before deflateParams(), and the new level and strategy will be
733    applied to the the data compressed after deflateParams().
734 
735      deflateParams returns Z_OK on success, Z_STREAM_ERROR if the source stream
736    state was inconsistent or if a parameter was invalid, or Z_BUF_ERROR if
737    there was not enough output space to complete the compression of the
738    available input data before a change in the strategy or approach.  Note that
739    in the case of a Z_BUF_ERROR, the parameters are not changed.  A return
740    value of Z_BUF_ERROR is not fatal, in which case deflateParams() can be
741    retried with more output space.
742 */
743 
744 ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm,
745                                     int good_length,
746                                     int max_lazy,
747                                     int nice_length,
748                                     int max_chain));
749 /*
750      Fine tune deflate's internal compression parameters.  This should only be
751    used by someone who understands the algorithm used by zlib's deflate for
752    searching for the best matching string, and even then only by the most
753    fanatic optimizer trying to squeeze out the last compressed bit for their
754    specific input data.  Read the deflate.c source code for the meaning of the
755    max_lazy, good_length, nice_length, and max_chain parameters.
756 
757      deflateTune() can be called after deflateInit() or deflateInit2(), and
758    returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.
759  */
760 
761 ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,
762                                        uLong sourceLen));
763 /*
764      deflateBound() returns an upper bound on the compressed size after
765    deflation of sourceLen bytes.  It must be called after deflateInit() or
766    deflateInit2(), and after deflateSetHeader(), if used.  This would be used
767    to allocate an output buffer for deflation in a single pass, and so would be
768    called before deflate().  If that first deflate() call is provided the
769    sourceLen input bytes, an output buffer allocated to the size returned by
770    deflateBound(), and the flush value Z_FINISH, then deflate() is guaranteed
771    to return Z_STREAM_END.  Note that it is possible for the compressed size to
772    be larger than the value returned by deflateBound() if flush options other
773    than Z_FINISH or Z_NO_FLUSH are used.
774 */
775 
776 ZEXTERN int ZEXPORT deflatePending OF((z_streamp strm,
777                                        unsigned *pending,
778                                        int *bits));
779 /*
780      deflatePending() returns the number of bytes and bits of output that have
781    been generated, but not yet provided in the available output.  The bytes not
782    provided would be due to the available output space having being consumed.
783    The number of bits of output not provided are between 0 and 7, where they
784    await more bits to join them in order to fill out a full byte.  If pending
785    or bits are Z_NULL, then those values are not set.
786 
787      deflatePending returns Z_OK if success, or Z_STREAM_ERROR if the source
788    stream state was inconsistent.
789  */
790 
791 ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,
792                                      int bits,
793                                      int value));
794 /*
795      deflatePrime() inserts bits in the deflate output stream.  The intent
796    is that this function is used to start off the deflate output with the bits
797    leftover from a previous deflate stream when appending to it.  As such, this
798    function can only be used for raw deflate, and must be used before the first
799    deflate() call after a deflateInit2() or deflateReset().  bits must be less
800    than or equal to 16, and that many of the least significant bits of value
801    will be inserted in the output.
802 
803      deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough
804    room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the
805    source stream state was inconsistent.
806 */
807 
808 ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm,
809                                          gz_headerp head));
810 /*
811      deflateSetHeader() provides gzip header information for when a gzip
812    stream is requested by deflateInit2().  deflateSetHeader() may be called
813    after deflateInit2() or deflateReset() and before the first call of
814    deflate().  The text, time, os, extra field, name, and comment information
815    in the provided gz_header structure are written to the gzip header (xflag is
816    ignored -- the extra flags are set according to the compression level).  The
817    caller must assure that, if not Z_NULL, name and comment are terminated with
818    a zero byte, and that if extra is not Z_NULL, that extra_len bytes are
819    available there.  If hcrc is true, a gzip header crc is included.  Note that
820    the current versions of the command-line version of gzip (up through version
821    1.3.x) do not support header crc's, and will report that it is a "multi-part
822    gzip file" and give up.
823 
824      If deflateSetHeader is not used, the default gzip header has text false,
825    the time set to zero, and os set to 255, with no extra, name, or comment
826    fields.  The gzip header is returned to the default state by deflateReset().
827 
828      deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
829    stream state was inconsistent.
830 */
831 
832 /*
833 ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
834                                      int  windowBits));
835 
836      This is another version of inflateInit with an extra parameter.  The
837    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
838    before by the caller.
839 
840      The windowBits parameter is the base two logarithm of the maximum window
841    size (the size of the history buffer).  It should be in the range 8..15 for
842    this version of the library.  The default value is 15 if inflateInit is used
843    instead.  windowBits must be greater than or equal to the windowBits value
844    provided to deflateInit2() while compressing, or it must be equal to 15 if
845    deflateInit2() was not used.  If a compressed stream with a larger window
846    size is given as input, inflate() will return with the error code
847    Z_DATA_ERROR instead of trying to allocate a larger window.
848 
849      windowBits can also be zero to request that inflate use the window size in
850    the zlib header of the compressed stream.
851 
852      windowBits can also be -8..-15 for raw inflate.  In this case, -windowBits
853    determines the window size.  inflate() will then process raw deflate data,
854    not looking for a zlib or gzip header, not generating a check value, and not
855    looking for any check values for comparison at the end of the stream.  This
856    is for use with other formats that use the deflate compressed data format
857    such as zip.  Those formats provide their own check values.  If a custom
858    format is developed using the raw deflate format for compressed data, it is
859    recommended that a check value such as an Adler-32 or a CRC-32 be applied to
860    the uncompressed data as is done in the zlib, gzip, and zip formats.  For
861    most applications, the zlib format should be used as is.  Note that comments
862    above on the use in deflateInit2() applies to the magnitude of windowBits.
863 
864      windowBits can also be greater than 15 for optional gzip decoding.  Add
865    32 to windowBits to enable zlib and gzip decoding with automatic header
866    detection, or add 16 to decode only the gzip format (the zlib format will
867    return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is a
868    CRC-32 instead of an Adler-32.  Unlike the gunzip utility and gzread() (see
869    below), inflate() will not automatically decode concatenated gzip streams.
870    inflate() will return Z_STREAM_END at the end of the gzip stream.  The state
871    would need to be reset to continue decoding a subsequent gzip stream.
872 
873      inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
874    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
875    version assumed by the caller, or Z_STREAM_ERROR if the parameters are
876    invalid, such as a null pointer to the structure.  msg is set to null if
877    there is no error message.  inflateInit2 does not perform any decompression
878    apart from possibly reading the zlib header if present: actual decompression
879    will be done by inflate().  (So next_in and avail_in may be modified, but
880    next_out and avail_out are unused and unchanged.) The current implementation
881    of inflateInit2() does not process any header information -- that is
882    deferred until inflate() is called.
883 */
884 
885 ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,
886                                              const Bytef *dictionary,
887                                              uInt  dictLength));
888 /*
889      Initializes the decompression dictionary from the given uncompressed byte
890    sequence.  This function must be called immediately after a call of inflate,
891    if that call returned Z_NEED_DICT.  The dictionary chosen by the compressor
892    can be determined from the Adler-32 value returned by that call of inflate.
893    The compressor and decompressor must use exactly the same dictionary (see
894    deflateSetDictionary).  For raw inflate, this function can be called at any
895    time to set the dictionary.  If the provided dictionary is smaller than the
896    window and there is already data in the window, then the provided dictionary
897    will amend what's there.  The application must insure that the dictionary
898    that was used for compression is provided.
899 
900      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
901    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
902    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
903    expected one (incorrect Adler-32 value).  inflateSetDictionary does not
904    perform any decompression: this will be done by subsequent calls of
905    inflate().
906 */
907 
908 ZEXTERN int ZEXPORT inflateGetDictionary OF((z_streamp strm,
909                                              Bytef *dictionary,
910                                              uInt  *dictLength));
911 /*
912      Returns the sliding dictionary being maintained by inflate.  dictLength is
913    set to the number of bytes in the dictionary, and that many bytes are copied
914    to dictionary.  dictionary must have enough space, where 32768 bytes is
915    always enough.  If inflateGetDictionary() is called with dictionary equal to
916    Z_NULL, then only the dictionary length is returned, and nothing is copied.
917    Similary, if dictLength is Z_NULL, then it is not set.
918 
919      inflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the
920    stream state is inconsistent.
921 */
922 
923 ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
924 /*
925      Skips invalid compressed data until a possible full flush point (see above
926    for the description of deflate with Z_FULL_FLUSH) can be found, or until all
927    available input is skipped.  No output is provided.
928 
929      inflateSync searches for a 00 00 FF FF pattern in the compressed data.
930    All full flush points have this pattern, but not all occurrences of this
931    pattern are full flush points.
932 
933      inflateSync returns Z_OK if a possible full flush point has been found,
934    Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point
935    has been found, or Z_STREAM_ERROR if the stream structure was inconsistent.
936    In the success case, the application may save the current current value of
937    total_in which indicates where valid compressed data was found.  In the
938    error case, the application may repeatedly call inflateSync, providing more
939    input each time, until success or end of the input data.
940 */
941 
942 ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,
943                                     z_streamp source));
944 /*
945      Sets the destination stream as a complete copy of the source stream.
946 
947      This function can be useful when randomly accessing a large stream.  The
948    first pass through the stream can periodically record the inflate state,
949    allowing restarting inflate at those points when randomly accessing the
950    stream.
951 
952      inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
953    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
954    (such as zalloc being Z_NULL).  msg is left unchanged in both source and
955    destination.
956 */
957 
958 ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
959 /*
960      This function is equivalent to inflateEnd followed by inflateInit,
961    but does not free and reallocate the internal decompression state.  The
962    stream will keep attributes that may have been set by inflateInit2.
963 
964      inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
965    stream state was inconsistent (such as zalloc or state being Z_NULL).
966 */
967 
968 ZEXTERN int ZEXPORT inflateReset2 OF((z_streamp strm,
969                                       int windowBits));
970 /*
971      This function is the same as inflateReset, but it also permits changing
972    the wrap and window size requests.  The windowBits parameter is interpreted
973    the same as it is for inflateInit2.  If the window size is changed, then the
974    memory allocated for the window is freed, and the window will be reallocated
975    by inflate() if needed.
976 
977      inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source
978    stream state was inconsistent (such as zalloc or state being Z_NULL), or if
979    the windowBits parameter is invalid.
980 */
981 
982 ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm,
983                                      int bits,
984                                      int value));
985 /*
986      This function inserts bits in the inflate input stream.  The intent is
987    that this function is used to start inflating at a bit position in the
988    middle of a byte.  The provided bits will be used before any bytes are used
989    from next_in.  This function should only be used with raw inflate, and
990    should be used before the first inflate() call after inflateInit2() or
991    inflateReset().  bits must be less than or equal to 16, and that many of the
992    least significant bits of value will be inserted in the input.
993 
994      If bits is negative, then the input stream bit buffer is emptied.  Then
995    inflatePrime() can be called again to put bits in the buffer.  This is used
996    to clear out bits leftover after feeding inflate a block description prior
997    to feeding inflate codes.
998 
999      inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
1000    stream state was inconsistent.
1001 */
1002 
1003 ZEXTERN long ZEXPORT inflateMark OF((z_streamp strm));
1004 /*
1005      This function returns two values, one in the lower 16 bits of the return
1006    value, and the other in the remaining upper bits, obtained by shifting the
1007    return value down 16 bits.  If the upper value is -1 and the lower value is
1008    zero, then inflate() is currently decoding information outside of a block.
1009    If the upper value is -1 and the lower value is non-zero, then inflate is in
1010    the middle of a stored block, with the lower value equaling the number of
1011    bytes from the input remaining to copy.  If the upper value is not -1, then
1012    it is the number of bits back from the current bit position in the input of
1013    the code (literal or length/distance pair) currently being processed.  In
1014    that case the lower value is the number of bytes already emitted for that
1015    code.
1016 
1017      A code is being processed if inflate is waiting for more input to complete
1018    decoding of the code, or if it has completed decoding but is waiting for
1019    more output space to write the literal or match data.
1020 
1021      inflateMark() is used to mark locations in the input data for random
1022    access, which may be at bit positions, and to note those cases where the
1023    output of a code may span boundaries of random access blocks.  The current
1024    location in the input stream can be determined from avail_in and data_type
1025    as noted in the description for the Z_BLOCK flush parameter for inflate.
1026 
1027      inflateMark returns the value noted above, or -65536 if the provided
1028    source stream state was inconsistent.
1029 */
1030 
1031 ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm,
1032                                          gz_headerp head));
1033 /*
1034      inflateGetHeader() requests that gzip header information be stored in the
1035    provided gz_header structure.  inflateGetHeader() may be called after
1036    inflateInit2() or inflateReset(), and before the first call of inflate().
1037    As inflate() processes the gzip stream, head->done is zero until the header
1038    is completed, at which time head->done is set to one.  If a zlib stream is
1039    being decoded, then head->done is set to -1 to indicate that there will be
1040    no gzip header information forthcoming.  Note that Z_BLOCK or Z_TREES can be
1041    used to force inflate() to return immediately after header processing is
1042    complete and before any actual data is decompressed.
1043 
1044      The text, time, xflags, and os fields are filled in with the gzip header
1045    contents.  hcrc is set to true if there is a header CRC.  (The header CRC
1046    was valid if done is set to one.) If extra is not Z_NULL, then extra_max
1047    contains the maximum number of bytes to write to extra.  Once done is true,
1048    extra_len contains the actual extra field length, and extra contains the
1049    extra field, or that field truncated if extra_max is less than extra_len.
1050    If name is not Z_NULL, then up to name_max characters are written there,
1051    terminated with a zero unless the length is greater than name_max.  If
1052    comment is not Z_NULL, then up to comm_max characters are written there,
1053    terminated with a zero unless the length is greater than comm_max.  When any
1054    of extra, name, or comment are not Z_NULL and the respective field is not
1055    present in the header, then that field is set to Z_NULL to signal its
1056    absence.  This allows the use of deflateSetHeader() with the returned
1057    structure to duplicate the header.  However if those fields are set to
1058    allocated memory, then the application will need to save those pointers
1059    elsewhere so that they can be eventually freed.
1060 
1061      If inflateGetHeader is not used, then the header information is simply
1062    discarded.  The header is always checked for validity, including the header
1063    CRC if present.  inflateReset() will reset the process to discard the header
1064    information.  The application would need to call inflateGetHeader() again to
1065    retrieve the header from the next gzip stream.
1066 
1067      inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
1068    stream state was inconsistent.
1069 */
1070 
1071 /*
1072 ZEXTERN int ZEXPORT inflateBackInit OF((z_streamp strm, int windowBits,
1073                                         unsigned char FAR *window));
1074 
1075      Initialize the internal stream state for decompression using inflateBack()
1076    calls.  The fields zalloc, zfree and opaque in strm must be initialized
1077    before the call.  If zalloc and zfree are Z_NULL, then the default library-
1078    derived memory allocation routines are used.  windowBits is the base two
1079    logarithm of the window size, in the range 8..15.  window is a caller
1080    supplied buffer of that size.  Except for special applications where it is
1081    assured that deflate was used with small window sizes, windowBits must be 15
1082    and a 32K byte window must be supplied to be able to decompress general
1083    deflate streams.
1084 
1085      See inflateBack() for the usage of these routines.
1086 
1087      inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
1088    the parameters are invalid, Z_MEM_ERROR if the internal state could not be
1089    allocated, or Z_VERSION_ERROR if the version of the library does not match
1090    the version of the header file.
1091 */
1092 
1093 typedef unsigned (*in_func) OF((void FAR *,
1094                                 z_const unsigned char FAR * FAR *));
1095 typedef int (*out_func) OF((void FAR *, unsigned char FAR *, unsigned));
1096 
1097 ZEXTERN int ZEXPORT inflateBack OF((z_streamp strm,
1098                                     in_func in, void FAR *in_desc,
1099                                     out_func out, void FAR *out_desc));
1100 /*
1101      inflateBack() does a raw inflate with a single call using a call-back
1102    interface for input and output.  This is potentially more efficient than
1103    inflate() for file i/o applications, in that it avoids copying between the
1104    output and the sliding window by simply making the window itself the output
1105    buffer.  inflate() can be faster on modern CPUs when used with large
1106    buffers.  inflateBack() trusts the application to not change the output
1107    buffer passed by the output function, at least until inflateBack() returns.
1108 
1109      inflateBackInit() must be called first to allocate the internal state
1110    and to initialize the state with the user-provided window buffer.
1111    inflateBack() may then be used multiple times to inflate a complete, raw
1112    deflate stream with each call.  inflateBackEnd() is then called to free the
1113    allocated state.
1114 
1115      A raw deflate stream is one with no zlib or gzip header or trailer.
1116    This routine would normally be used in a utility that reads zip or gzip
1117    files and writes out uncompressed files.  The utility would decode the
1118    header and process the trailer on its own, hence this routine expects only
1119    the raw deflate stream to decompress.  This is different from the default
1120    behavior of inflate(), which expects a zlib header and trailer around the
1121    deflate stream.
1122 
1123      inflateBack() uses two subroutines supplied by the caller that are then
1124    called by inflateBack() for input and output.  inflateBack() calls those
1125    routines until it reads a complete deflate stream and writes out all of the
1126    uncompressed data, or until it encounters an error.  The function's
1127    parameters and return types are defined above in the in_func and out_func
1128    typedefs.  inflateBack() will call in(in_desc, &buf) which should return the
1129    number of bytes of provided input, and a pointer to that input in buf.  If
1130    there is no input available, in() must return zero -- buf is ignored in that
1131    case -- and inflateBack() will return a buffer error.  inflateBack() will
1132    call out(out_desc, buf, len) to write the uncompressed data buf[0..len-1].
1133    out() should return zero on success, or non-zero on failure.  If out()
1134    returns non-zero, inflateBack() will return with an error.  Neither in() nor
1135    out() are permitted to change the contents of the window provided to
1136    inflateBackInit(), which is also the buffer that out() uses to write from.
1137    The length written by out() will be at most the window size.  Any non-zero
1138    amount of input may be provided by in().
1139 
1140      For convenience, inflateBack() can be provided input on the first call by
1141    setting strm->next_in and strm->avail_in.  If that input is exhausted, then
1142    in() will be called.  Therefore strm->next_in must be initialized before
1143    calling inflateBack().  If strm->next_in is Z_NULL, then in() will be called
1144    immediately for input.  If strm->next_in is not Z_NULL, then strm->avail_in
1145    must also be initialized, and then if strm->avail_in is not zero, input will
1146    initially be taken from strm->next_in[0 ..  strm->avail_in - 1].
1147 
1148      The in_desc and out_desc parameters of inflateBack() is passed as the
1149    first parameter of in() and out() respectively when they are called.  These
1150    descriptors can be optionally used to pass any information that the caller-
1151    supplied in() and out() functions need to do their job.
1152 
1153      On return, inflateBack() will set strm->next_in and strm->avail_in to
1154    pass back any unused input that was provided by the last in() call.  The
1155    return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR
1156    if in() or out() returned an error, Z_DATA_ERROR if there was a format error
1157    in the deflate stream (in which case strm->msg is set to indicate the nature
1158    of the error), or Z_STREAM_ERROR if the stream was not properly initialized.
1159    In the case of Z_BUF_ERROR, an input or output error can be distinguished
1160    using strm->next_in which will be Z_NULL only if in() returned an error.  If
1161    strm->next_in is not Z_NULL, then the Z_BUF_ERROR was due to out() returning
1162    non-zero.  (in() will always be called before out(), so strm->next_in is
1163    assured to be defined if out() returns non-zero.)  Note that inflateBack()
1164    cannot return Z_OK.
1165 */
1166 
1167 ZEXTERN int ZEXPORT inflateBackEnd OF((z_streamp strm));
1168 /*
1169      All memory allocated by inflateBackInit() is freed.
1170 
1171      inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream
1172    state was inconsistent.
1173 */
1174 
1175 ZEXTERN uLong ZEXPORT zlibCompileFlags OF((void));
1176 /* Return flags indicating compile-time options.
1177 
1178     Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
1179      1.0: size of uInt
1180      3.2: size of uLong
1181      5.4: size of voidpf (pointer)
1182      7.6: size of z_off_t
1183 
1184     Compiler, assembler, and debug options:
1185      8: ZLIB_DEBUG
1186      9: ASMV or ASMINF -- use ASM code
1187      10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
1188      11: 0 (reserved)
1189 
1190     One-time table building (smaller code, but not thread-safe if true):
1191      12: BUILDFIXED -- build static block decoding tables when needed
1192      13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
1193      14,15: 0 (reserved)
1194 
1195     Library content (indicates missing functionality):
1196      16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
1197                           deflate code when not needed)
1198      17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect
1199                     and decode gzip streams (to avoid linking crc code)
1200      18-19: 0 (reserved)
1201 
1202     Operation variations (changes in library functionality):
1203      20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
1204      21: FASTEST -- deflate algorithm with only one, lowest compression level
1205      22,23: 0 (reserved)
1206 
1207     The sprintf variant used by gzprintf (zero is best):
1208      24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
1209      25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
1210      26: 0 = returns value, 1 = void -- 1 means inferred string length returned
1211 
1212     Remainder:
1213      27-31: 0 (reserved)
1214  */
1215 
1216 #ifndef Z_SOLO
1217 
1218                         /* utility functions */
1219 
1220 /*
1221      The following utility functions are implemented on top of the basic
1222    stream-oriented functions.  To simplify the interface, some default options
1223    are assumed (compression level and memory usage, standard memory allocation
1224    functions).  The source code of these utility functions can be modified if
1225    you need special options.
1226 */
1227 
1228 ZEXTERN int ZEXPORT compress OF((Bytef *dest,   uLongf *destLen,
1229                                  const Bytef *source, uLong sourceLen));
1230 /*
1231      Compresses the source buffer into the destination buffer.  sourceLen is
1232    the byte length of the source buffer.  Upon entry, destLen is the total size
1233    of the destination buffer, which must be at least the value returned by
1234    compressBound(sourceLen).  Upon exit, destLen is the actual size of the
1235    compressed data.  compress() is equivalent to compress2() with a level
1236    parameter of Z_DEFAULT_COMPRESSION.
1237 
1238      compress returns Z_OK if success, Z_MEM_ERROR if there was not
1239    enough memory, Z_BUF_ERROR if there was not enough room in the output
1240    buffer.
1241 */
1242 
1243 ZEXTERN int ZEXPORT compress2 OF((Bytef *dest,   uLongf *destLen,
1244                                   const Bytef *source, uLong sourceLen,
1245                                   int level));
1246 /*
1247      Compresses the source buffer into the destination buffer.  The level
1248    parameter has the same meaning as in deflateInit.  sourceLen is the byte
1249    length of the source buffer.  Upon entry, destLen is the total size of the
1250    destination buffer, which must be at least the value returned by
1251    compressBound(sourceLen).  Upon exit, destLen is the actual size of the
1252    compressed data.
1253 
1254      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
1255    memory, Z_BUF_ERROR if there was not enough room in the output buffer,
1256    Z_STREAM_ERROR if the level parameter is invalid.
1257 */
1258 
1259 ZEXTERN uLong ZEXPORT compressBound OF((uLong sourceLen));
1260 /*
1261      compressBound() returns an upper bound on the compressed size after
1262    compress() or compress2() on sourceLen bytes.  It would be used before a
1263    compress() or compress2() call to allocate the destination buffer.
1264 */
1265 
1266 ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen,
1267                                    const Bytef *source, uLong sourceLen));
1268 /*
1269      Decompresses the source buffer into the destination buffer.  sourceLen is
1270    the byte length of the source buffer.  Upon entry, destLen is the total size
1271    of the destination buffer, which must be large enough to hold the entire
1272    uncompressed data.  (The size of the uncompressed data must have been saved
1273    previously by the compressor and transmitted to the decompressor by some
1274    mechanism outside the scope of this compression library.) Upon exit, destLen
1275    is the actual size of the uncompressed data.
1276 
1277      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
1278    enough memory, Z_BUF_ERROR if there was not enough room in the output
1279    buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.  In
1280    the case where there is not enough room, uncompress() will fill the output
1281    buffer with the uncompressed data up to that point.
1282 */
1283 
1284 ZEXTERN int ZEXPORT uncompress2 OF((Bytef *dest,   uLongf *destLen,
1285                                     const Bytef *source, uLong *sourceLen));
1286 /*
1287      Same as uncompress, except that sourceLen is a pointer, where the
1288    length of the source is *sourceLen.  On return, *sourceLen is the number of
1289    source bytes consumed.
1290 */
1291 
1292                         /* gzip file access functions */
1293 
1294 /*
1295      This library supports reading and writing files in gzip (.gz) format with
1296    an interface similar to that of stdio, using the functions that start with
1297    "gz".  The gzip format is different from the zlib format.  gzip is a gzip
1298    wrapper, documented in RFC 1952, wrapped around a deflate stream.
1299 */
1300 
1301 typedef struct gzFile_s *gzFile;    /* semi-opaque gzip file descriptor */
1302 
1303 /*
1304 ZEXTERN gzFile ZEXPORT gzopen OF((const char *path, const char *mode));
1305 
1306      Opens a gzip (.gz) file for reading or writing.  The mode parameter is as
1307    in fopen ("rb" or "wb") but can also include a compression level ("wb9") or
1308    a strategy: 'f' for filtered data as in "wb6f", 'h' for Huffman-only
1309    compression as in "wb1h", 'R' for run-length encoding as in "wb1R", or 'F'
1310    for fixed code compression as in "wb9F".  (See the description of
1311    deflateInit2 for more information about the strategy parameter.)  'T' will
1312    request transparent writing or appending with no compression and not using
1313    the gzip format.
1314 
1315      "a" can be used instead of "w" to request that the gzip stream that will
1316    be written be appended to the file.  "+" will result in an error, since
1317    reading and writing to the same gzip file is not supported.  The addition of
1318    "x" when writing will create the file exclusively, which fails if the file
1319    already exists.  On systems that support it, the addition of "e" when
1320    reading or writing will set the flag to close the file on an execve() call.
1321 
1322      These functions, as well as gzip, will read and decode a sequence of gzip
1323    streams in a file.  The append function of gzopen() can be used to create
1324    such a file.  (Also see gzflush() for another way to do this.)  When
1325    appending, gzopen does not test whether the file begins with a gzip stream,
1326    nor does it look for the end of the gzip streams to begin appending.  gzopen
1327    will simply append a gzip stream to the existing file.
1328 
1329      gzopen can be used to read a file which is not in gzip format; in this
1330    case gzread will directly read from the file without decompression.  When
1331    reading, this will be detected automatically by looking for the magic two-
1332    byte gzip header.
1333 
1334      gzopen returns NULL if the file could not be opened, if there was
1335    insufficient memory to allocate the gzFile state, or if an invalid mode was
1336    specified (an 'r', 'w', or 'a' was not provided, or '+' was provided).
1337    errno can be checked to determine if the reason gzopen failed was that the
1338    file could not be opened.
1339 */
1340 
1341 ZEXTERN gzFile ZEXPORT gzdopen OF((int fd, const char *mode));
1342 /*
1343      gzdopen associates a gzFile with the file descriptor fd.  File descriptors
1344    are obtained from calls like open, dup, creat, pipe or fileno (if the file
1345    has been previously opened with fopen).  The mode parameter is as in gzopen.
1346 
1347      The next call of gzclose on the returned gzFile will also close the file
1348    descriptor fd, just like fclose(fdopen(fd, mode)) closes the file descriptor
1349    fd.  If you want to keep fd open, use fd = dup(fd_keep); gz = gzdopen(fd,
1350    mode);.  The duplicated descriptor should be saved to avoid a leak, since
1351    gzdopen does not close fd if it fails.  If you are using fileno() to get the
1352    file descriptor from a FILE *, then you will have to use dup() to avoid
1353    double-close()ing the file descriptor.  Both gzclose() and fclose() will
1354    close the associated file descriptor, so they need to have different file
1355    descriptors.
1356 
1357      gzdopen returns NULL if there was insufficient memory to allocate the
1358    gzFile state, if an invalid mode was specified (an 'r', 'w', or 'a' was not
1359    provided, or '+' was provided), or if fd is -1.  The file descriptor is not
1360    used until the next gz* read, write, seek, or close operation, so gzdopen
1361    will not detect if fd is invalid (unless fd is -1).
1362 */
1363 
1364 ZEXTERN int ZEXPORT gzbuffer OF((gzFile file, unsigned size));
1365 /*
1366      Set the internal buffer size used by this library's functions.  The
1367    default buffer size is 8192 bytes.  This function must be called after
1368    gzopen() or gzdopen(), and before any other calls that read or write the
1369    file.  The buffer memory allocation is always deferred to the first read or
1370    write.  Three times that size in buffer space is allocated.  A larger buffer
1371    size of, for example, 64K or 128K bytes will noticeably increase the speed
1372    of decompression (reading).
1373 
1374      The new buffer size also affects the maximum length for gzprintf().
1375 
1376      gzbuffer() returns 0 on success, or -1 on failure, such as being called
1377    too late.
1378 */
1379 
1380 ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
1381 /*
1382      Dynamically update the compression level or strategy.  See the description
1383    of deflateInit2 for the meaning of these parameters.  Previously provided
1384    data is flushed before the parameter change.
1385 
1386      gzsetparams returns Z_OK if success, Z_STREAM_ERROR if the file was not
1387    opened for writing, Z_ERRNO if there is an error writing the flushed data,
1388    or Z_MEM_ERROR if there is a memory allocation error.
1389 */
1390 
1391 ZEXTERN int ZEXPORT gzread OF((gzFile file, voidp buf, unsigned len));
1392 /*
1393      Reads the given number of uncompressed bytes from the compressed file.  If
1394    the input file is not in gzip format, gzread copies the given number of
1395    bytes into the buffer directly from the file.
1396 
1397      After reaching the end of a gzip stream in the input, gzread will continue
1398    to read, looking for another gzip stream.  Any number of gzip streams may be
1399    concatenated in the input file, and will all be decompressed by gzread().
1400    If something other than a gzip stream is encountered after a gzip stream,
1401    that remaining trailing garbage is ignored (and no error is returned).
1402 
1403      gzread can be used to read a gzip file that is being concurrently written.
1404    Upon reaching the end of the input, gzread will return with the available
1405    data.  If the error code returned by gzerror is Z_OK or Z_BUF_ERROR, then
1406    gzclearerr can be used to clear the end of file indicator in order to permit
1407    gzread to be tried again.  Z_OK indicates that a gzip stream was completed
1408    on the last gzread.  Z_BUF_ERROR indicates that the input file ended in the
1409    middle of a gzip stream.  Note that gzread does not return -1 in the event
1410    of an incomplete gzip stream.  This error is deferred until gzclose(), which
1411    will return Z_BUF_ERROR if the last gzread ended in the middle of a gzip
1412    stream.  Alternatively, gzerror can be used before gzclose to detect this
1413    case.
1414 
1415      gzread returns the number of uncompressed bytes actually read, less than
1416    len for end of file, or -1 for error.  If len is too large to fit in an int,
1417    then nothing is read, -1 is returned, and the error state is set to
1418    Z_STREAM_ERROR.
1419 */
1420 
1421 ZEXTERN z_size_t ZEXPORT gzfread OF((voidp buf, z_size_t size, z_size_t nitems,
1422                                      gzFile file));
1423 /*
1424      Read up to nitems items of size size from file to buf, otherwise operating
1425    as gzread() does.  This duplicates the interface of stdio's fread(), with
1426    size_t request and return types.  If the library defines size_t, then
1427    z_size_t is identical to size_t.  If not, then z_size_t is an unsigned
1428    integer type that can contain a pointer.
1429 
1430      gzfread() returns the number of full items read of size size, or zero if
1431    the end of the file was reached and a full item could not be read, or if
1432    there was an error.  gzerror() must be consulted if zero is returned in
1433    order to determine if there was an error.  If the multiplication of size and
1434    nitems overflows, i.e. the product does not fit in a z_size_t, then nothing
1435    is read, zero is returned, and the error state is set to Z_STREAM_ERROR.
1436 
1437      In the event that the end of file is reached and only a partial item is
1438    available at the end, i.e. the remaining uncompressed data length is not a
1439    multiple of size, then the final partial item is nevetheless read into buf
1440    and the end-of-file flag is set.  The length of the partial item read is not
1441    provided, but could be inferred from the result of gztell().  This behavior
1442    is the same as the behavior of fread() implementations in common libraries,
1443    but it prevents the direct use of gzfread() to read a concurrently written
1444    file, reseting and retrying on end-of-file, when size is not 1.
1445 */
1446 
1447 ZEXTERN int ZEXPORT gzwrite OF((gzFile file,
1448                                 voidpc buf, unsigned len));
1449 /*
1450      Writes the given number of uncompressed bytes into the compressed file.
1451    gzwrite returns the number of uncompressed bytes written or 0 in case of
1452    error.
1453 */
1454 
1455 ZEXTERN z_size_t ZEXPORT gzfwrite OF((voidpc buf, z_size_t size,
1456                                       z_size_t nitems, gzFile file));
1457 /*
1458      gzfwrite() writes nitems items of size size from buf to file, duplicating
1459    the interface of stdio's fwrite(), with size_t request and return types.  If
1460    the library defines size_t, then z_size_t is identical to size_t.  If not,
1461    then z_size_t is an unsigned integer type that can contain a pointer.
1462 
1463      gzfwrite() returns the number of full items written of size size, or zero
1464    if there was an error.  If the multiplication of size and nitems overflows,
1465    i.e. the product does not fit in a z_size_t, then nothing is written, zero
1466    is returned, and the error state is set to Z_STREAM_ERROR.
1467 */
1468 
1469 ZEXTERN int ZEXPORTVA gzprintf Z_ARG((gzFile file, const char *format, ...));
1470 /*
1471      Converts, formats, and writes the arguments to the compressed file under
1472    control of the format string, as in fprintf.  gzprintf returns the number of
1473    uncompressed bytes actually written, or a negative zlib error code in case
1474    of error.  The number of uncompressed bytes written is limited to 8191, or
1475    one less than the buffer size given to gzbuffer().  The caller should assure
1476    that this limit is not exceeded.  If it is exceeded, then gzprintf() will
1477    return an error (0) with nothing written.  In this case, there may also be a
1478    buffer overflow with unpredictable consequences, which is possible only if
1479    zlib was compiled with the insecure functions sprintf() or vsprintf()
1480    because the secure snprintf() or vsnprintf() functions were not available.
1481    This can be determined using zlibCompileFlags().
1482 */
1483 
1484 ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char *s));
1485 /*
1486      Writes the given null-terminated string to the compressed file, excluding
1487    the terminating null character.
1488 
1489      gzputs returns the number of characters written, or -1 in case of error.
1490 */
1491 
1492 ZEXTERN char * ZEXPORT gzgets OF((gzFile file, char *buf, int len));
1493 /*
1494      Reads bytes from the compressed file until len-1 characters are read, or a
1495    newline character is read and transferred to buf, or an end-of-file
1496    condition is encountered.  If any characters are read or if len == 1, the
1497    string is terminated with a null character.  If no characters are read due
1498    to an end-of-file or len < 1, then the buffer is left untouched.
1499 
1500      gzgets returns buf which is a null-terminated string, or it returns NULL
1501    for end-of-file or in case of error.  If there was an error, the contents at
1502    buf are indeterminate.
1503 */
1504 
1505 ZEXTERN int ZEXPORT gzputc OF((gzFile file, int c));
1506 /*
1507      Writes c, converted to an unsigned char, into the compressed file.  gzputc
1508    returns the value that was written, or -1 in case of error.
1509 */
1510 
1511 ZEXTERN int ZEXPORT gzgetc OF((gzFile file));
1512 /*
1513      Reads one byte from the compressed file.  gzgetc returns this byte or -1
1514    in case of end of file or error.  This is implemented as a macro for speed.
1515    As such, it does not do all of the checking the other functions do.  I.e.
1516    it does not check to see if file is NULL, nor whether the structure file
1517    points to has been clobbered or not.
1518 */
1519 
1520 ZEXTERN int ZEXPORT gzungetc OF((int c, gzFile file));
1521 /*
1522      Push one character back onto the stream to be read as the first character
1523    on the next read.  At least one character of push-back is allowed.
1524    gzungetc() returns the character pushed, or -1 on failure.  gzungetc() will
1525    fail if c is -1, and may fail if a character has been pushed but not read
1526    yet.  If gzungetc is used immediately after gzopen or gzdopen, at least the
1527    output buffer size of pushed characters is allowed.  (See gzbuffer above.)
1528    The pushed character will be discarded if the stream is repositioned with
1529    gzseek() or gzrewind().
1530 */
1531 
1532 ZEXTERN int ZEXPORT gzflush OF((gzFile file, int flush));
1533 /*
1534      Flushes all pending output into the compressed file.  The parameter flush
1535    is as in the deflate() function.  The return value is the zlib error number
1536    (see function gzerror below).  gzflush is only permitted when writing.
1537 
1538      If the flush parameter is Z_FINISH, the remaining data is written and the
1539    gzip stream is completed in the output.  If gzwrite() is called again, a new
1540    gzip stream will be started in the output.  gzread() is able to read such
1541    concatenated gzip streams.
1542 
1543      gzflush should be called only when strictly necessary because it will
1544    degrade compression if called too often.
1545 */
1546 
1547 /*
1548 ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile file,
1549                                    z_off_t offset, int whence));
1550 
1551      Sets the starting position for the next gzread or gzwrite on the given
1552    compressed file.  The offset represents a number of bytes in the
1553    uncompressed data stream.  The whence parameter is defined as in lseek(2);
1554    the value SEEK_END is not supported.
1555 
1556      If the file is opened for reading, this function is emulated but can be
1557    extremely slow.  If the file is opened for writing, only forward seeks are
1558    supported; gzseek then compresses a sequence of zeroes up to the new
1559    starting position.
1560 
1561      gzseek returns the resulting offset location as measured in bytes from
1562    the beginning of the uncompressed stream, or -1 in case of error, in
1563    particular if the file is opened for writing and the new starting position
1564    would be before the current position.
1565 */
1566 
1567 ZEXTERN int ZEXPORT    gzrewind OF((gzFile file));
1568 /*
1569      Rewinds the given file. This function is supported only for reading.
1570 
1571      gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
1572 */
1573 
1574 /*
1575 ZEXTERN z_off_t ZEXPORT    gztell OF((gzFile file));
1576 
1577      Returns the starting position for the next gzread or gzwrite on the given
1578    compressed file.  This position represents a number of bytes in the
1579    uncompressed data stream, and is zero when starting, even if appending or
1580    reading a gzip stream from the middle of a file using gzdopen().
1581 
1582      gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
1583 */
1584 
1585 /*
1586 ZEXTERN z_off_t ZEXPORT gzoffset OF((gzFile file));
1587 
1588      Returns the current offset in the file being read or written.  This offset
1589    includes the count of bytes that precede the gzip stream, for example when
1590    appending or when using gzdopen() for reading.  When reading, the offset
1591    does not include as yet unused buffered input.  This information can be used
1592    for a progress indicator.  On error, gzoffset() returns -1.
1593 */
1594 
1595 ZEXTERN int ZEXPORT gzeof OF((gzFile file));
1596 /*
1597      Returns true (1) if the end-of-file indicator has been set while reading,
1598    false (0) otherwise.  Note that the end-of-file indicator is set only if the
1599    read tried to go past the end of the input, but came up short.  Therefore,
1600    just like feof(), gzeof() may return false even if there is no more data to
1601    read, in the event that the last read request was for the exact number of
1602    bytes remaining in the input file.  This will happen if the input file size
1603    is an exact multiple of the buffer size.
1604 
1605      If gzeof() returns true, then the read functions will return no more data,
1606    unless the end-of-file indicator is reset by gzclearerr() and the input file
1607    has grown since the previous end of file was detected.
1608 */
1609 
1610 ZEXTERN int ZEXPORT gzdirect OF((gzFile file));
1611 /*
1612      Returns true (1) if file is being copied directly while reading, or false
1613    (0) if file is a gzip stream being decompressed.
1614 
1615      If the input file is empty, gzdirect() will return true, since the input
1616    does not contain a gzip stream.
1617 
1618      If gzdirect() is used immediately after gzopen() or gzdopen() it will
1619    cause buffers to be allocated to allow reading the file to determine if it
1620    is a gzip file.  Therefore if gzbuffer() is used, it should be called before
1621    gzdirect().
1622 
1623      When writing, gzdirect() returns true (1) if transparent writing was
1624    requested ("wT" for the gzopen() mode), or false (0) otherwise.  (Note:
1625    gzdirect() is not needed when writing.  Transparent writing must be
1626    explicitly requested, so the application already knows the answer.  When
1627    linking statically, using gzdirect() will include all of the zlib code for
1628    gzip file reading and decompression, which may not be desired.)
1629 */
1630 
1631 ZEXTERN int ZEXPORT    gzclose OF((gzFile file));
1632 /*
1633      Flushes all pending output if necessary, closes the compressed file and
1634    deallocates the (de)compression state.  Note that once file is closed, you
1635    cannot call gzerror with file, since its structures have been deallocated.
1636    gzclose must not be called more than once on the same file, just as free
1637    must not be called more than once on the same allocation.
1638 
1639      gzclose will return Z_STREAM_ERROR if file is not valid, Z_ERRNO on a
1640    file operation error, Z_MEM_ERROR if out of memory, Z_BUF_ERROR if the
1641    last read ended in the middle of a gzip stream, or Z_OK on success.
1642 */
1643 
1644 ZEXTERN int ZEXPORT gzclose_r OF((gzFile file));
1645 ZEXTERN int ZEXPORT gzclose_w OF((gzFile file));
1646 /*
1647      Same as gzclose(), but gzclose_r() is only for use when reading, and
1648    gzclose_w() is only for use when writing or appending.  The advantage to
1649    using these instead of gzclose() is that they avoid linking in zlib
1650    compression or decompression code that is not used when only reading or only
1651    writing respectively.  If gzclose() is used, then both compression and
1652    decompression code will be included the application when linking to a static
1653    zlib library.
1654 */
1655 
1656 ZEXTERN const char * ZEXPORT gzerror OF((gzFile file, int *errnum));
1657 /*
1658      Returns the error message for the last error which occurred on the given
1659    compressed file.  errnum is set to zlib error number.  If an error occurred
1660    in the file system and not in the compression library, errnum is set to
1661    Z_ERRNO and the application may consult errno to get the exact error code.
1662 
1663      The application must not modify the returned string.  Future calls to
1664    this function may invalidate the previously returned string.  If file is
1665    closed, then the string previously returned by gzerror will no longer be
1666    available.
1667 
1668      gzerror() should be used to distinguish errors from end-of-file for those
1669    functions above that do not distinguish those cases in their return values.
1670 */
1671 
1672 ZEXTERN void ZEXPORT gzclearerr OF((gzFile file));
1673 /*
1674      Clears the error and end-of-file flags for file.  This is analogous to the
1675    clearerr() function in stdio.  This is useful for continuing to read a gzip
1676    file that is being written concurrently.
1677 */
1678 
1679 #endif /* !Z_SOLO */
1680 
1681                         /* checksum functions */
1682 
1683 /*
1684      These functions are not related to compression but are exported
1685    anyway because they might be useful in applications using the compression
1686    library.
1687 */
1688 
1689 ZEXTERN uLong ZEXPORT adler32 OF((uLong adler, const Bytef *buf, uInt len));
1690 /*
1691      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
1692    return the updated checksum.  If buf is Z_NULL, this function returns the
1693    required initial value for the checksum.
1694 
1695      An Adler-32 checksum is almost as reliable as a CRC-32 but can be computed
1696    much faster.
1697 
1698    Usage example:
1699 
1700      uLong adler = adler32(0L, Z_NULL, 0);
1701 
1702      while (read_buffer(buffer, length) != EOF) {
1703        adler = adler32(adler, buffer, length);
1704      }
1705      if (adler != original_adler) error();
1706 */
1707 
1708 ZEXTERN uLong ZEXPORT adler32_z OF((uLong adler, const Bytef *buf,
1709                                     z_size_t len));
1710 /*
1711      Same as adler32(), but with a size_t length.
1712 */
1713 
1714 /*
1715 ZEXTERN uLong ZEXPORT adler32_combine OF((uLong adler1, uLong adler2,
1716                                           z_off_t len2));
1717 
1718      Combine two Adler-32 checksums into one.  For two sequences of bytes, seq1
1719    and seq2 with lengths len1 and len2, Adler-32 checksums were calculated for
1720    each, adler1 and adler2.  adler32_combine() returns the Adler-32 checksum of
1721    seq1 and seq2 concatenated, requiring only adler1, adler2, and len2.  Note
1722    that the z_off_t type (like off_t) is a signed integer.  If len2 is
1723    negative, the result has no meaning or utility.
1724 */
1725 
1726 ZEXTERN uLong ZEXPORT crc32   OF((uLong crc, const Bytef *buf, uInt len));
1727 /*
1728      Update a running CRC-32 with the bytes buf[0..len-1] and return the
1729    updated CRC-32.  If buf is Z_NULL, this function returns the required
1730    initial value for the crc.  Pre- and post-conditioning (one's complement) is
1731    performed within this function so it shouldn't be done by the application.
1732 
1733    Usage example:
1734 
1735      uLong crc = crc32(0L, Z_NULL, 0);
1736 
1737      while (read_buffer(buffer, length) != EOF) {
1738        crc = crc32(crc, buffer, length);
1739      }
1740      if (crc != original_crc) error();
1741 */
1742 
1743 ZEXTERN uLong ZEXPORT crc32_z OF((uLong adler, const Bytef *buf,
1744                                   z_size_t len));
1745 /*
1746      Same as crc32(), but with a size_t length.
1747 */
1748 
1749 /*
1750 ZEXTERN uLong ZEXPORT crc32_combine OF((uLong crc1, uLong crc2, z_off_t len2));
1751 
1752      Combine two CRC-32 check values into one.  For two sequences of bytes,
1753    seq1 and seq2 with lengths len1 and len2, CRC-32 check values were
1754    calculated for each, crc1 and crc2.  crc32_combine() returns the CRC-32
1755    check value of seq1 and seq2 concatenated, requiring only crc1, crc2, and
1756    len2.
1757 */
1758 
1759 
1760                         /* various hacks, don't look :) */
1761 
1762 /* deflateInit and inflateInit are macros to allow checking the zlib version
1763  * and the compiler's view of z_stream:
1764  */
1765 ZEXTERN int ZEXPORT deflateInit_ OF((z_streamp strm, int level,
1766                                      const char *version, int stream_size));
1767 ZEXTERN int ZEXPORT inflateInit_ OF((z_streamp strm,
1768                                      const char *version, int stream_size));
1769 ZEXTERN int ZEXPORT deflateInit2_ OF((z_streamp strm, int  level, int  method,
1770                                       int windowBits, int memLevel,
1771                                       int strategy, const char *version,
1772                                       int stream_size));
1773 ZEXTERN int ZEXPORT inflateInit2_ OF((z_streamp strm, int  windowBits,
1774                                       const char *version, int stream_size));
1775 ZEXTERN int ZEXPORT inflateBackInit_ OF((z_streamp strm, int windowBits,
1776                                          unsigned char FAR *window,
1777                                          const char *version,
1778                                          int stream_size));
1779 #ifdef Z_PREFIX_SET
1780 #  define z_deflateInit(strm, level) \
1781           deflateInit_((strm), (level), ZLIB_VERSION, (int)sizeof(z_stream))
1782 #  define z_inflateInit(strm) \
1783           inflateInit_((strm), ZLIB_VERSION, (int)sizeof(z_stream))
1784 #  define z_deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
1785           deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
1786                         (strategy), ZLIB_VERSION, (int)sizeof(z_stream))
1787 #  define z_inflateInit2(strm, windowBits) \
1788           inflateInit2_((strm), (windowBits), ZLIB_VERSION, \
1789                         (int)sizeof(z_stream))
1790 #  define z_inflateBackInit(strm, windowBits, window) \
1791           inflateBackInit_((strm), (windowBits), (window), \
1792                            ZLIB_VERSION, (int)sizeof(z_stream))
1793 #else
1794 #  define deflateInit(strm, level) \
1795           deflateInit_((strm), (level), ZLIB_VERSION, (int)sizeof(z_stream))
1796 #  define inflateInit(strm) \
1797           inflateInit_((strm), ZLIB_VERSION, (int)sizeof(z_stream))
1798 #  define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
1799           deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
1800                         (strategy), ZLIB_VERSION, (int)sizeof(z_stream))
1801 #  define inflateInit2(strm, windowBits) \
1802           inflateInit2_((strm), (windowBits), ZLIB_VERSION, \
1803                         (int)sizeof(z_stream))
1804 #  define inflateBackInit(strm, windowBits, window) \
1805           inflateBackInit_((strm), (windowBits), (window), \
1806                            ZLIB_VERSION, (int)sizeof(z_stream))
1807 #endif
1808 
1809 #ifndef Z_SOLO
1810 
1811 /* gzgetc() macro and its supporting function and exposed data structure.  Note
1812  * that the real internal state is much larger than the exposed structure.
1813  * This abbreviated structure exposes just enough for the gzgetc() macro.  The
1814  * user should not mess with these exposed elements, since their names or
1815  * behavior could change in the future, perhaps even capriciously.  They can
1816  * only be used by the gzgetc() macro.  You have been warned.
1817  */
1818 struct gzFile_s {
1819     unsigned have;
1820     unsigned char *next;
1821     z_off64_t pos;
1822 };
1823 ZEXTERN int ZEXPORT gzgetc_ OF((gzFile file));  /* backward compatibility */
1824 #ifdef Z_PREFIX_SET
1825 #  undef z_gzgetc
1826 #  define z_gzgetc(g) \
1827           ((g)->have ? ((g)->have--, (g)->pos++, *((g)->next)++) : (gzgetc)(g))
1828 #else
1829 #  define gzgetc(g) \
1830           ((g)->have ? ((g)->have--, (g)->pos++, *((g)->next)++) : (gzgetc)(g))
1831 #endif
1832 
1833 /* provide 64-bit offset functions if _LARGEFILE64_SOURCE defined, and/or
1834  * change the regular functions to 64 bits if _FILE_OFFSET_BITS is 64 (if
1835  * both are true, the application gets the *64 functions, and the regular
1836  * functions are changed to 64 bits) -- in case these are set on systems
1837  * without large file support, _LFS64_LARGEFILE must also be true
1838  */
1839 #ifdef Z_LARGE64
1840    ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
1841    ZEXTERN z_off64_t ZEXPORT gzseek64 OF((gzFile, z_off64_t, int));
1842    ZEXTERN z_off64_t ZEXPORT gztell64 OF((gzFile));
1843    ZEXTERN z_off64_t ZEXPORT gzoffset64 OF((gzFile));
1844    ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off64_t));
1845    ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off64_t));
1846 #endif
1847 
1848 #if !defined(ZLIB_INTERNAL) && defined(Z_WANT64)
1849 #  ifdef Z_PREFIX_SET
1850 #    define z_gzopen z_gzopen64
1851 #    define z_gzseek z_gzseek64
1852 #    define z_gztell z_gztell64
1853 #    define z_gzoffset z_gzoffset64
1854 #    define z_adler32_combine z_adler32_combine64
1855 #    define z_crc32_combine z_crc32_combine64
1856 #  else
1857 #    define gzopen gzopen64
1858 #    define gzseek gzseek64
1859 #    define gztell gztell64
1860 #    define gzoffset gzoffset64
1861 #    define adler32_combine adler32_combine64
1862 #    define crc32_combine crc32_combine64
1863 #  endif
1864 #  ifndef Z_LARGE64
1865      ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
1866      ZEXTERN z_off_t ZEXPORT gzseek64 OF((gzFile, z_off_t, int));
1867      ZEXTERN z_off_t ZEXPORT gztell64 OF((gzFile));
1868      ZEXTERN z_off_t ZEXPORT gzoffset64 OF((gzFile));
1869      ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off_t));
1870      ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off_t));
1871 #  endif
1872 #else
1873    ZEXTERN gzFile ZEXPORT gzopen OF((const char *, const char *));
1874    ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile, z_off_t, int));
1875    ZEXTERN z_off_t ZEXPORT gztell OF((gzFile));
1876    ZEXTERN z_off_t ZEXPORT gzoffset OF((gzFile));
1877    ZEXTERN uLong ZEXPORT adler32_combine OF((uLong, uLong, z_off_t));
1878    ZEXTERN uLong ZEXPORT crc32_combine OF((uLong, uLong, z_off_t));
1879 #endif
1880 
1881 #else /* Z_SOLO */
1882 
1883    ZEXTERN uLong ZEXPORT adler32_combine OF((uLong, uLong, z_off_t));
1884    ZEXTERN uLong ZEXPORT crc32_combine OF((uLong, uLong, z_off_t));
1885 
1886 #endif /* !Z_SOLO */
1887 
1888 /* undocumented functions */
1889 ZEXTERN const char   * ZEXPORT zError           OF((int));
1890 ZEXTERN int            ZEXPORT inflateSyncPoint OF((z_streamp));
1891 ZEXTERN const z_crc_t FAR * ZEXPORT get_crc_table    OF((void));
1892 ZEXTERN int            ZEXPORT inflateUndermine OF((z_streamp, int));
1893 ZEXTERN int            ZEXPORT inflateValidate OF((z_streamp, int));
1894 ZEXTERN unsigned long  ZEXPORT inflateCodesUsed OF ((z_streamp));
1895 ZEXTERN int            ZEXPORT inflateResetKeep OF((z_streamp));
1896 ZEXTERN int            ZEXPORT deflateResetKeep OF((z_streamp));
1897 #if (defined(_WIN32) || defined(__CYGWIN__)) && !defined(Z_SOLO)
1898 ZEXTERN gzFile         ZEXPORT gzopen_w OF((const wchar_t *path,
1899                                             const char *mode));
1900 #endif
1901 #if defined(STDC) || defined(Z_HAVE_STDARG_H)
1902 #  ifndef Z_SOLO
1903 ZEXTERN int            ZEXPORTVA gzvprintf Z_ARG((gzFile file,
1904                                                   const char *format,
1905                                                   va_list va));
1906 #  endif
1907 #endif
1908 
1909 #ifdef __cplusplus
1910 }
1911 #endif
1912 
1913 #endif /* ZLIB_H */
1914