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/src/zlib/zlib.h

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  1/* zlib.h -- interface of the 'zlib' general purpose compression library
  2  version 1.2.8, April 28th, 2013
  3
  4  Copyright (C) 1995-2013 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
 37extern "C" {
 38#endif
 39
 40#define ZLIB_VERSION "1.2.8"
 41#define ZLIB_VERNUM 0x1280
 42#define ZLIB_VER_MAJOR 1
 43#define ZLIB_VER_MINOR 2
 44#define ZLIB_VER_REVISION 8
 45#define ZLIB_VER_SUBREVISION 0
 46
 47/*
 48    The 'zlib' compression library provides in-memory compression and
 49  decompression functions, including integrity checks of the uncompressed data.
 50  This version of the library supports only one compression method (deflation)
 51  but other algorithms will be added later and will have the same stream
 52  interface.
 53
 54    Compression can be done in a single step if the buffers are large enough,
 55  or can be done by repeated calls of the compression function.  In the latter
 56  case, the application must provide more input and/or consume the output
 57  (providing more output space) before each call.
 58
 59    The compressed data format used by default by the in-memory functions is
 60  the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
 61  around a deflate stream, which is itself documented in RFC 1951.
 62
 63    The library also supports reading and writing files in gzip (.gz) format
 64  with an interface similar to that of stdio using the functions that start
 65  with "gz".  The gzip format is different from the zlib format.  gzip is a
 66  gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
 67
 68    This library can optionally read and write gzip streams in memory as well.
 69
 70    The zlib format was designed to be compact and fast for use in memory
 71  and on communications channels.  The gzip format was designed for single-
 72  file compression on file systems, has a larger header than zlib to maintain
 73  directory information, and uses a different, slower check method than zlib.
 74
 75    The library does not install any signal handler.  The decoder checks
 76  the consistency of the compressed data, so the library should never crash
 77  even in case of corrupted input.
 78*/
 79
 80typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
 81typedef void   (*free_func)  OF((voidpf opaque, voidpf address));
 82
 83struct internal_state;
 84
 85typedef struct z_stream_s {
 86    z_const Bytef *next_in;     /* next input byte */
 87    uInt     avail_in;  /* number of bytes available at next_in */
 88    uLong    total_in;  /* total number of input bytes read so far */
 89
 90    Bytef    *next_out; /* next output byte should be put there */
 91    uInt     avail_out; /* remaining free space at next_out */
 92    uLong    total_out; /* total number of bytes output so far */
 93
 94    z_const char *msg;  /* last error message, NULL if no error */
 95    struct internal_state FAR *state; /* not visible by applications */
 96
 97    alloc_func zalloc;  /* used to allocate the internal state */
 98    free_func  zfree;   /* used to free the internal state */
 99    voidpf     opaque;  /* private data object passed to zalloc and zfree */
100
101    int     data_type;  /* best guess about the data type: binary or text */
102    uLong   adler;      /* adler32 value of the uncompressed data */
103    uLong   reserved;   /* reserved for future use */
104} z_stream;
105
106typedef z_stream FAR *z_streamp;
107
108/*
109     gzip header information passed to and from zlib routines.  See RFC 1952
110  for more details on the meanings of these fields.
111*/
112typedef struct gz_header_s {
113    int     text;       /* true if compressed data believed to be text */
114    uLong   time;       /* modification time */
115    int     xflags;     /* extra flags (not used when writing a gzip file) */
116    int     os;         /* operating system */
117    Bytef   *extra;     /* pointer to extra field or Z_NULL if none */
118    uInt    extra_len;  /* extra field length (valid if extra != Z_NULL) */
119    uInt    extra_max;  /* space at extra (only when reading header) */
120    Bytef   *name;      /* pointer to zero-terminated file name or Z_NULL */
121    uInt    name_max;   /* space at name (only when reading header) */
122    Bytef   *comment;   /* pointer to zero-terminated comment or Z_NULL */
123    uInt    comm_max;   /* space at comment (only when reading header) */
124    int     hcrc;       /* true if there was or will be a header crc */
125    int     done;       /* true when done reading gzip header (not used
126                           when writing a gzip file) */
127} gz_header;
128
129typedef gz_header FAR *gz_headerp;
130
131/*
132     The application must update next_in and avail_in when avail_in has dropped
133   to zero.  It must update next_out and avail_out when avail_out has dropped
134   to zero.  The application must initialize zalloc, zfree and opaque before
135   calling the init function.  All other fields are set by the compression
136   library and must not be updated by the application.
137
138     The opaque value provided by the application will be passed as the first
139   parameter for calls of zalloc and zfree.  This can be useful for custom
140   memory management.  The compression library attaches no meaning to the
141   opaque value.
142
143     zalloc must return Z_NULL if there is not enough memory for the object.
144   If zlib is used in a multi-threaded application, zalloc and zfree must be
145   thread safe.
146
147     On 16-bit systems, the functions zalloc and zfree must be able to allocate
148   exactly 65536 bytes, but will not be required to allocate more than this if
149   the symbol MAXSEG_64K is defined (see zconf.h).  WARNING: On MSDOS, pointers
150   returned by zalloc for objects of exactly 65536 bytes *must* have their
151   offset normalized to zero.  The default allocation function provided by this
152   library ensures this (see zutil.c).  To reduce memory requirements and avoid
153   any allocation of 64K objects, at the expense of compression ratio, compile
154   the library with -DMAX_WBITS=14 (see zconf.h).
155
156     The fields total_in and total_out can be used for statistics or progress
157   reports.  After compression, total_in holds the total size of the
158   uncompressed data and may be saved for use in the decompressor (particularly
159   if the decompressor wants to decompress everything in a single step).
160*/
161
162                        /* constants */
163
164#define Z_NO_FLUSH      0
165#define Z_PARTIAL_FLUSH 1
166#define Z_SYNC_FLUSH    2
167#define Z_FULL_FLUSH    3
168#define Z_FINISH        4
169#define Z_BLOCK         5
170#define Z_TREES         6
171/* Allowed flush values; see deflate() and inflate() below for details */
172
173#define Z_OK            0
174#define Z_STREAM_END    1
175#define Z_NEED_DICT     2
176#define Z_ERRNO        (-1)
177#define Z_STREAM_ERROR (-2)
178#define Z_DATA_ERROR   (-3)
179#define Z_MEM_ERROR    (-4)
180#define Z_BUF_ERROR    (-5)
181#define Z_VERSION_ERROR (-6)
182/* Return codes for the compression/decompression functions. Negative values
183 * are errors, positive values are used for special but normal events.
184 */
185
186#define Z_NO_COMPRESSION         0
187#define Z_BEST_SPEED             1
188#define Z_BEST_COMPRESSION       9
189#define Z_DEFAULT_COMPRESSION  (-1)
190/* compression levels */
191
192#define Z_FILTERED            1
193#define Z_HUFFMAN_ONLY        2
194#define Z_RLE                 3
195#define Z_FIXED               4
196#define Z_DEFAULT_STRATEGY    0
197/* compression strategy; see deflateInit2() below for details */
198
199#define Z_BINARY   0
200#define Z_TEXT     1
201#define Z_ASCII    Z_TEXT   /* for compatibility with 1.2.2 and earlier */
202#define Z_UNKNOWN  2
203/* Possible values of the data_type field (though see inflate()) */
204
205#define Z_DEFLATED   8
206/* The deflate compression method (the only one supported in this version) */
207
208#define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
209
210#define zlib_version zlibVersion()
211/* for compatibility with versions < 1.0.2 */
212
213
214                        /* basic functions */
215
216ZEXTERN const char * ZEXPORT zlibVersion OF((void));
217/* The application can compare zlibVersion and ZLIB_VERSION for consistency.
218   If the first character differs, the library code actually used is not
219   compatible with the zlib.h header file used by the application.  This check
220   is automatically made by deflateInit and inflateInit.
221 */
222
223/*
224ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));
225
226     Initializes the internal stream state for compression.  The fields
227   zalloc, zfree and opaque must be initialized before by the caller.  If
228   zalloc and zfree are set to Z_NULL, deflateInit updates them to use default
229   allocation functions.
230
231     The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
232   1 gives best speed, 9 gives best compression, 0 gives no compression at all
233   (the input data is simply copied a block at a time).  Z_DEFAULT_COMPRESSION
234   requests a default compromise between speed and compression (currently
235   equivalent to level 6).
236
237     deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
238   memory, Z_STREAM_ERROR if level is not a valid compression level, or
239   Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
240   with the version assumed by the caller (ZLIB_VERSION).  msg is set to null
241   if there is no error message.  deflateInit does not perform any compression:
242   this will be done by deflate().
243*/
244
245
246ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));
247/*
248    deflate compresses as much data as possible, and stops when the input
249  buffer becomes empty or the output buffer becomes full.  It may introduce
250  some output latency (reading input without producing any output) except when
251  forced to flush.
252
253    The detailed semantics are as follows.  deflate performs one or both of the
254  following actions:
255
256  - Compress more input starting at next_in and update next_in and avail_in
257    accordingly.  If not all input can be processed (because there is not
258    enough room in the output buffer), next_in and avail_in are updated and
259    processing will resume at this point for the next call of deflate().
260
261  - Provide more output starting at next_out and update next_out and avail_out
262    accordingly.  This action is forced if the parameter flush is non zero.
263    Forcing flush frequently degrades the compression ratio, so this parameter
264    should be set only when necessary (in interactive applications).  Some
265    output may be provided even if flush is not set.
266
267    Before the call of deflate(), the application should ensure that at least
268  one of the actions is possible, by providing more input and/or consuming more
269  output, and updating avail_in or avail_out accordingly; avail_out should
270  never be zero before the call.  The application can consume the compressed
271  output when it wants, for example when the output buffer is full (avail_out
272  == 0), or after each call of deflate().  If deflate returns Z_OK and with
273  zero avail_out, it must be called again after making room in the output
274  buffer because there might be more output pending.
275
276    Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to
277  decide how much data to accumulate before producing output, in order to
278  maximize compression.
279
280    If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
281  flushed to the output buffer and the output is aligned on a byte boundary, so
282  that the decompressor can get all input data available so far.  (In
283  particular avail_in is zero after the call if enough output space has been
284  provided before the call.) Flushing may degrade compression for some
285  compression algorithms and so it should be used only when necessary.  This
286  completes the current deflate block and follows it with an empty stored block
287  that is three bits plus filler bits to the next byte, followed by four bytes
288  (00 00 ff ff).
289
290    If flush is set to Z_PARTIAL_FLUSH, all pending output is flushed to the
291  output buffer, but the output is not aligned to a byte boundary.  All of the
292  input data so far will be available to the decompressor, as for Z_SYNC_FLUSH.
293  This completes the current deflate block and follows it with an empty fixed
294  codes block that is 10 bits long.  This assures that enough bytes are output
295  in order for the decompressor to finish the block before the empty fixed code
296  block.
297
298    If flush is set to Z_BLOCK, a deflate block is completed and emitted, as
299  for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to
300  seven bits of the current block are held to be written as the next byte after
301  the next deflate block is completed.  In this case, the decompressor may not
302  be provided enough bits at this point in order to complete decompression of
303  the data provided so far to the compressor.  It may need to wait for the next
304  block to be emitted.  This is for advanced applications that need to control
305  the emission of deflate blocks.
306
307    If flush is set to Z_FULL_FLUSH, all output is flushed as with
308  Z_SYNC_FLUSH, and the compression state is reset so that decompression can
309  restart from this point if previous compressed data has been damaged or if
310  random access is desired.  Using Z_FULL_FLUSH too often can seriously degrade
311  compression.
312
313    If deflate returns with avail_out == 0, this function must be called again
314  with the same value of the flush parameter and more output space (updated
315  avail_out), until the flush is complete (deflate returns with non-zero
316  avail_out).  In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
317  avail_out is greater than six to avoid repeated flush markers due to
318  avail_out == 0 on return.
319
320    If the parameter flush is set to Z_FINISH, pending input is processed,
321  pending output is flushed and deflate returns with Z_STREAM_END if there was
322  enough output space; if deflate returns with Z_OK, this function must be
323  called again with Z_FINISH and more output space (updated avail_out) but no
324  more input data, until it returns with Z_STREAM_END or an error.  After
325  deflate has returned Z_STREAM_END, the only possible operations on the stream
326  are deflateReset or deflateEnd.
327
328    Z_FINISH can be used immediately after deflateInit if all the compression
329  is to be done in a single step.  In this case, avail_out must be at least the
330  value returned by deflateBound (see below).  Then deflate is guaranteed to
331  return Z_STREAM_END.  If not enough output space is provided, deflate will
332  not return Z_STREAM_END, and it must be called again as described above.
333
334    deflate() sets strm->adler to the adler32 checksum of all input read
335  so far (that is, total_in bytes).
336
337    deflate() may update strm->data_type if it can make a good guess about
338  the input data type (Z_BINARY or Z_TEXT).  In doubt, the data is considered
339  binary.  This field is only for information purposes and does not affect the
340  compression algorithm in any manner.
341
342    deflate() returns Z_OK if some progress has been made (more input
343  processed or more output produced), Z_STREAM_END if all input has been
344  consumed and all output has been produced (only when flush is set to
345  Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
346  if next_in or next_out was Z_NULL), Z_BUF_ERROR if no progress is possible
347  (for example avail_in or avail_out was zero).  Note that Z_BUF_ERROR is not
348  fatal, and deflate() can be called again with more input and more output
349  space to continue compressing.
350*/
351
352
353ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
354/*
355     All dynamically allocated data structures for this stream are freed.
356   This function discards any unprocessed input and does not flush any pending
357   output.
358
359     deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
360   stream state was inconsistent, Z_DATA_ERROR if the stream was freed
361   prematurely (some input or output was discarded).  In the error case, msg
362   may be set but then points to a static string (which must not be
363   deallocated).
364*/
365
366
367/*
368ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));
369
370     Initializes the internal stream state for decompression.  The fields
371   next_in, avail_in, zalloc, zfree and opaque must be initialized before by
372   the caller.  If next_in is not Z_NULL and avail_in is large enough (the
373   exact value depends on the compression method), inflateInit determines the
374   compression method from the zlib header and allocates all data structures
375   accordingly; otherwise the allocation will be deferred to the first call of
376   inflate.  If zalloc and zfree are set to Z_NULL, inflateInit updates them to
377   use default allocation functions.
378
379     inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
380   memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
381   version assumed by the caller, or Z_STREAM_ERROR if the parameters are
382   invalid, such as a null pointer to the structure.  msg is set to null if
383   there is no error message.  inflateInit does not perform any decompression
384   apart from possibly reading the zlib header if present: actual decompression
385   will be done by inflate().  (So next_in and avail_in may be modified, but
386   next_out and avail_out are unused and unchanged.) The current implementation
387   of inflateInit() does not process any header information -- that is deferred
388   until inflate() is called.
389*/
390
391
392ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
393/*
394    inflate decompresses as much data as possible, and stops when the input
395  buffer becomes empty or the output buffer becomes full.  It may introduce
396  some output latency (reading input without producing any output) except when
397  forced to flush.
398
399  The detailed semantics are as follows.  inflate performs one or both of the
400  following actions:
401
402  - Decompress more input starting at next_in and update next_in and avail_in
403    accordingly.  If not all input can be processed (because there is not
404    enough room in the output buffer), next_in is updated and processing will
405    resume at this point for the next call of inflate().
406
407  - Provide more output starting at next_out and update next_out and avail_out
408    accordingly.  inflate() provides as much output as possible, until there is
409    no more input data or no more space in the output buffer (see below about
410    the flush parameter).
411
412    Before the call of inflate(), the application should ensure that at least
413  one of the actions is possible, by providing more input and/or consuming more
414  output, and updating the next_* and avail_* values accordingly.  The
415  application can consume the uncompressed output when it wants, for example
416  when the output buffer is full (avail_out == 0), or after each call of
417  inflate().  If inflate returns Z_OK and with zero avail_out, it must be
418  called again after making room in the output buffer because there might be
419  more output pending.
420
421    The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH, Z_FINISH,
422  Z_BLOCK, or Z_TREES.  Z_SYNC_FLUSH requests that inflate() flush as much
423  output as possible to the output buffer.  Z_BLOCK requests that inflate()
424  stop if and when it gets to the next deflate block boundary.  When decoding
425  the zlib or gzip format, this will cause inflate() to return immediately
426  after the header and before the first block.  When doing a raw inflate,
427  inflate() will go ahead and process the first block, and will return when it
428  gets to the end of that block, or when it runs out of data.
429
430    The Z_BLOCK option assists in appending to or combining deflate streams.
431  Also to assist in this, on return inflate() will set strm->data_type to the
432  number of unused bits in the last byte taken from strm->next_in, plus 64 if
433  inflate() is currently decoding the last block in the deflate stream, plus
434  128 if inflate() returned immediately after decoding an end-of-block code or
435  decoding the complete header up to just before the first byte of the deflate
436  stream.  The end-of-block will not be indicated until all of the uncompressed
437  data from that block has been written to strm->next_out.  The number of
438  unused bits may in general be greater than seven, except when bit 7 of
439  data_type is set, in which case the number of unused bits will be less than
440  eight.  data_type is set as noted here every time inflate() returns for all
441  flush options, and so can be used to determine the amount of currently
442  consumed input in bits.
443
444    The Z_TREES option behaves as Z_BLOCK does, but it also returns when the
445  end of each deflate block header is reached, before any actual data in that
446  block is decoded.  This allows the caller to determine the length of the
447  deflate block header for later use in random access within a deflate block.
448  256 is added to the value of strm->data_type when inflate() returns
449  immediately after reaching the end of the deflate block header.
450
451    inflate() should normally be called until it returns Z_STREAM_END or an
452  error.  However if all decompression is to be performed in a single step (a
453  single call of inflate), the parameter flush should be set to Z_FINISH.  In
454  this case all pending input is processed and all pending output is flushed;
455  avail_out must be large enough to hold all of the uncompressed data for the
456  operation to complete.  (The size of the uncompressed data may have been
457  saved by the compressor for this purpose.) The use of Z_FINISH is not
458  required to perform an inflation in one step.  However it may be used to
459  inform inflate that a faster approach can be used for the single inflate()
460  call.  Z_FINISH also informs inflate to not maintain a sliding window if the
461  stream completes, which reduces inflate's memory footprint.  If the stream
462  does not complete, either because not all of the stream is provided or not
463  enough output space is provided, then a sliding window will be allocated and
464  inflate() can be called again to continue the operation as if Z_NO_FLUSH had
465  been used.
466
467     In this implementation, inflate() always flushes as much output as
468  possible to the output buffer, and always uses the faster approach on the
469  first call.  So the effects of the flush parameter in this implementation are
470  on the return value of inflate() as noted below, when inflate() returns early
471  when Z_BLOCK or Z_TREES is used, and when inflate() avoids the allocation of
472  memory for a sliding window when Z_FINISH is used.
473
474     If a preset dictionary is needed after this call (see inflateSetDictionary
475  below), inflate sets strm->adler to the Adler-32 checksum of the dictionary
476  chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
477  strm->adler to the Adler-32 checksum of all output produced so far (that is,
478  total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
479  below.  At the end of the stream, inflate() checks that its computed adler32
480  checksum is equal to that saved by the compressor and returns Z_STREAM_END
481  only if the checksum is correct.
482
483    inflate() can decompress and check either zlib-wrapped or gzip-wrapped
484  deflate data.  The header type is detected automatically, if requested when
485  initializing with inflateInit2().  Any information contained in the gzip
486  header is not retained, so applications that need that information should
487  instead use raw inflate, see inflateInit2() below, or inflateBack() and
488  perform their own processing of the gzip header and trailer.  When processing
489  gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output
490  producted so far.  The CRC-32 is checked against the gzip trailer.
491
492    inflate() returns Z_OK if some progress has been made (more input processed
493  or more output produced), Z_STREAM_END if the end of the compressed data has
494  been reached and all uncompressed output has been produced, Z_NEED_DICT if a
495  preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
496  corrupted (input stream not conforming to the zlib format or incorrect check
497  value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
498  next_in or next_out was Z_NULL), Z_MEM_ERROR if there was not enough memory,
499  Z_BUF_ERROR if no progress is possible or if there was not enough room in the
500  output buffer when Z_FINISH is used.  Note that Z_BUF_ERROR is not fatal, and
501  inflate() can be called again with more input and more output space to
502  continue decompressing.  If Z_DATA_ERROR is returned, the application may
503  then call inflateSync() to look for a good compression block if a partial
504  recovery of the data is desired.
505*/
506
507
508ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));
509/*
510     All dynamically allocated data structures for this stream are freed.
511   This function discards any unprocessed input and does not flush any pending
512   output.
513
514     inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
515   was inconsistent.  In the error case, msg may be set but then points to a
516   static string (which must not be deallocated).
517*/
518
519
520                        /* Advanced functions */
521
522/*
523    The following functions are needed only in some special applications.
524*/
525
526/*
527ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
528                                     int  level,
529                                     int  method,
530                                     int  windowBits,
531                                     int  memLevel,
532                                     int  strategy));
533
534     This is another version of deflateInit with more compression options.  The
535   fields next_in, zalloc, zfree and opaque must be initialized before by the
536   caller.
537
538     The method parameter is the compression method.  It must be Z_DEFLATED in
539   this version of the library.
540
541     The windowBits parameter is the base two logarithm of the window size
542   (the size of the history buffer).  It should be in the range 8..15 for this
543   version of the library.  Larger values of this parameter result in better
544   compression at the expense of memory usage.  The default value is 15 if
545   deflateInit is used instead.
546
547     windowBits can also be -8..-15 for raw deflate.  In this case, -windowBits
548   determines the window size.  deflate() will then generate raw deflate data
549   with no zlib header or trailer, and will not compute an adler32 check value.
550
551     windowBits can also be greater than 15 for optional gzip encoding.  Add
552   16 to windowBits to write a simple gzip header and trailer around the
553   compressed data instead of a zlib wrapper.  The gzip header will have no
554   file name, no extra data, no comment, no modification time (set to zero), no
555   header crc, and the operating system will be set to 255 (unknown).  If a
556   gzip stream is being written, strm->adler is a crc32 instead of an adler32.
557
558     The memLevel parameter specifies how much memory should be allocated
559   for the internal compression state.  memLevel=1 uses minimum memory but is
560   slow and reduces compression ratio; memLevel=9 uses maximum memory for
561   optimal speed.  The default value is 8.  See zconf.h for total memory usage
562   as a function of windowBits and memLevel.
563
564     The strategy parameter is used to tune the compression algorithm.  Use the
565   value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
566   filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
567   string match), or Z_RLE to limit match distances to one (run-length
568   encoding).  Filtered data consists mostly of small values with a somewhat
569   random distribution.  In this case, the compression algorithm is tuned to
570   compress them better.  The effect of Z_FILTERED is to force more Huffman
571   coding and less string matching; it is somewhat intermediate between
572   Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY.  Z_RLE is designed to be almost as
573   fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data.  The
574   strategy parameter only affects the compression ratio but not the
575   correctness of the compressed output even if it is not set appropriately.
576   Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler
577   decoder for special applications.
578
579     deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
580   memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid
581   method), or Z_VERSION_ERROR if the zlib library version (zlib_version) is
582   incompatible with the version assumed by the caller (ZLIB_VERSION).  msg is
583   set to null if there is no error message.  deflateInit2 does not perform any
584   compression: this will be done by deflate().
585*/
586
587ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,
588                                             const Bytef *dictionary,
589                                             uInt  dictLength));
590/*
591     Initializes the compression dictionary from the given byte sequence
592   without producing any compressed output.  When using the zlib format, this
593   function must be called immediately after deflateInit, deflateInit2 or
594   deflateReset, and before any call of deflate.  When doing raw deflate, this
595   function must be called either before any call of deflate, or immediately
596   after the completion of a deflate block, i.e. after all input has been
597   consumed and all output has been delivered when using any of the flush
598   options Z_BLOCK, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH, or Z_FULL_FLUSH.  The
599   compressor and decompressor must use exactly the same dictionary (see
600   inflateSetDictionary).
601
602     The dictionary should consist of strings (byte sequences) that are likely
603   to be encountered later in the data to be compressed, with the most commonly
604   used strings preferably put towards the end of the dictionary.  Using a
605   dictionary is most useful when the data to be compressed is short and can be
606   predicted with good accuracy; the data can then be compressed better than
607   with the default empty dictionary.
608
609     Depending on the size of the compression data structures selected by
610   deflateInit or deflateInit2, a part of the dictionary may in effect be
611   discarded, for example if the dictionary is larger than the window size
612   provided in deflateInit or deflateInit2.  Thus the strings most likely to be
613   useful should be put at the end of the dictionary, not at the front.  In
614   addition, the current implementation of deflate will use at most the window
615   size minus 262 bytes of the provided dictionary.
616
617     Upon return of this function, strm->adler is set to the adler32 value
618   of the dictionary; the decompressor may later use this value to determine
619   which dictionary has been used by the compressor.  (The adler32 value
620   applies to the whole dictionary even if only a subset of the dictionary is
621   actually used by the compressor.) If a raw deflate was requested, then the
622   adler32 value is not computed and strm->adler is not set.
623
624     deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
625   parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
626   inconsistent (for example if deflate has already been called for this stream
627   or if not at a block boundary for raw deflate).  deflateSetDictionary does
628   not perform any compression: this will be done by deflate().
629*/
630
631ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,
632                                    z_streamp source));
633/*
634     Sets the destination stream as a complete copy of the source stream.
635
636     This function can be useful when several compression strategies will be
637   tried, for example when there are several ways of pre-processing the input
638   data with a filter.  The streams that will be discarded should then be freed
639   by calling deflateEnd.  Note that deflateCopy duplicates the internal
640   compression state which can be quite large, so this strategy is slow and can
641   consume lots of memory.
642
643     deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
644   enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
645   (such as zalloc being Z_NULL).  msg is left unchanged in both source and
646   destination.
647*/
648
649ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
650/*
651     This function is equivalent to deflateEnd followed by deflateInit,
652   but does not free and reallocate all the internal compression state.  The
653   stream will keep the same compression level and any other attributes that
654   may have been set by deflateInit2.
655
656     deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
657   stream state was inconsistent (such as zalloc or state being Z_NULL).
658*/
659
660ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
661                                      int level,
662                                      int strategy));
663/*
664     Dynamically update the compression level and compression strategy.  The
665   interpretation of level and strategy is as in deflateInit2.  This can be
666   used to switch between compression and straight copy of the input data, or
667   to switch to a different kind of input data requiring a different strategy.
668   If the compression level is changed, the input available so far is
669   compressed with the old level (and may be flushed); the new level will take
670   effect only at the next call of deflate().
671
672     Before the call of deflateParams, the stream state must be set as for
673   a call of deflate(), since the currently available input may have to be
674   compressed and flushed.  In particular, strm->avail_out must be non-zero.
675
676     deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
677   stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR if
678   strm->avail_out was zero.
679*/
680
681ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm,
682                                    int good_length,
683                                    int max_lazy,
684                                    int nice_length,
685                                    int max_chain));
686/*
687     Fine tune deflate's internal compression parameters.  This should only be
688   used by someone who understands the algorithm used by zlib's deflate for
689   searching for the best matching string, and even then only by the most
690   fanatic optimizer trying to squeeze out the last compressed bit for their
691   specific input data.  Read the deflate.c source code for the meaning of the
692   max_lazy, good_length, nice_length, and max_chain parameters.
693
694     deflateTune() can be called after deflateInit() or deflateInit2(), and
695   returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.
696 */
697
698ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,
699                                       uLong sourceLen));
700/*
701     deflateBound() returns an upper bound on the compressed size after
702   deflation of sourceLen bytes.  It must be called after deflateInit() or
703   deflateInit2(), and after deflateSetHeader(), if used.  This would be used
704   to allocate an output buffer for deflation in a single pass, and so would be
705   called before deflate().  If that first deflate() call is provided the
706   sourceLen input bytes, an output buffer allocated to the size returned by
707   deflateBound(), and the flush value Z_FINISH, then deflate() is guaranteed
708   to return Z_STREAM_END.  Note that it is possible for the compressed size to
709   be larger than the value returned by deflateBound() if flush options other
710   than Z_FINISH or Z_NO_FLUSH are used.
711*/
712
713ZEXTERN int ZEXPORT deflatePending OF((z_streamp strm,
714                                       unsigned *pending,
715                                       int *bits));
716/*
717     deflatePending() returns the number of bytes and bits of output that have
718   been generated, but not yet provided in the available output.  The bytes not
719   provided would be due to the available output space having being consumed.
720   The number of bits of output not provided are between 0 and 7, where they
721   await more bits to join them in order to fill out a full byte.  If pending
722   or bits are Z_NULL, then those values are not set.
723
724     deflatePending returns Z_OK if success, or Z_STREAM_ERROR if the source
725   stream state was inconsistent.
726 */
727
728ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,
729                                     int bits,
730                                     int value));
731/*
732     deflatePrime() inserts bits in the deflate output stream.  The intent
733   is that this function is used to start off the deflate output with the bits
734   leftover from a previous deflate stream when appending to it.  As such, this
735   function can only be used for raw deflate, and must be used before the first
736   deflate() call after a deflateInit2() or deflateReset().  bits must be less
737   than or equal to 16, and that many of the least significant bits of value
738   will be inserted in the output.
739
740     deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough
741   room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the
742   source stream state was inconsistent.
743*/
744
745ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm,
746                                         gz_headerp head));
747/*
748     deflateSetHeader() provides gzip header information for when a gzip
749   stream is requested by deflateInit2().  deflateSetHeader() may be called
750   after deflateInit2() or deflateReset() and before the first call of
751   deflate().  The text, time, os, extra field, name, and comment information
752   in the provided gz_header structure are written to the gzip header (xflag is
753   ignored -- the extra flags are set according to the compression level).  The
754   caller must assure that, if not Z_NULL, name and comment are terminated with
755   a zero byte, and that if extra is not Z_NULL, that extra_len bytes are
756   available there.  If hcrc is true, a gzip header crc is included.  Note that
757   the current versions of the command-line version of gzip (up through version
758   1.3.x) do not support header crc's, and will report that it is a "multi-part
759   gzip file" and give up.
760
761     If deflateSetHeader is not used, the default gzip header has text false,
762   the time set to zero, and os set to 255, with no extra, name, or comment
763   fields.  The gzip header is returned to the default state by deflateReset().
764
765     deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
766   stream state was inconsistent.
767*/
768
769/*
770ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
771                                     int  windowBits));
772
773     This is another version of inflateInit with an extra parameter.  The
774   fields next_in, avail_in, zalloc, zfree and opaque must be initialized
775   before by the caller.
776
777     The windowBits parameter is the base two logarithm of the maximum window
778   size (the size of the history buffer).  It should be in the range 8..15 for
779   this version of the library.  The default value is 15 if inflateInit is used
780   instead.  windowBits must be greater than or equal to the windowBits value
781   provided to deflateInit2() while compressing, or it must be equal to 15 if
782   deflateInit2() was not used.  If a compressed stream with a larger window
783   size is given as input, inflate() will return with the error code
784   Z_DATA_ERROR instead of trying to allocate a larger window.
785
786     windowBits can also be zero to request that inflate use the window size in
787   the zlib header of the compressed stream.
788
789     windowBits can also be -8..-15 for raw inflate.  In this case, -windowBits
790   determines the window size.  inflate() will then process raw deflate data,
791   not looking for a zlib or gzip header, not generating a check value, and not
792   looking for any check values for comparison at the end of the stream.  This
793   is for use with other formats that use the deflate compressed data format
794   such as zip.  Those formats provide their own check values.  If a custom
795   format is developed using the raw deflate format for compressed data, it is
796   recommended that a check value such as an adler32 or a crc32 be applied to
797   the uncompressed data as is done in the zlib, gzip, and zip formats.  For
798   most applications, the zlib format should be used as is.  Note that comments
799   above on the use in deflateInit2() applies to the magnitude of windowBits.
800
801     windowBits can also be greater than 15 for optional gzip decoding.  Add
802   32 to windowBits to enable zlib and gzip decoding with automatic header
803   detection, or add 16 to decode only the gzip format (the zlib format will
804   return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is a
805   crc32 instead of an adler32.
806
807     inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
808   memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
809   version assumed by the caller, or Z_STREAM_ERROR if the parameters are
810   invalid, such as a null pointer to the structure.  msg is set to null if
811   there is no error message.  inflateInit2 does not perform any decompression
812   apart from possibly reading the zlib header if present: actual decompression
813   will be done by inflate().  (So next_in and avail_in may be modified, but
814   next_out and avail_out are unused and unchanged.) The current implementation
815   of inflateInit2() does not process any header information -- that is
816   deferred until inflate() is called.
817*/
818
819ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,
820                                             const Bytef *dictionary,
821                                             uInt  dictLength));
822/*
823     Initializes the decompression dictionary from the given uncompressed byte
824   sequence.  This function must be called immediately after a call of inflate,
825   if that call returned Z_NEED_DICT.  The dictionary chosen by the compressor
826   can be determined from the adler32 value returned by that call of inflate.
827   The compressor and decompressor must use exactly the same dictionary (see
828   deflateSetDictionary).  For raw inflate, this function can be called at any
829   time to set the dictionary.  If the provided dictionary is smaller than the
830   window and there is already data in the window, then the provided dictionary
831   will amend what's there.  The application must insure that the dictionary
832   that was used for compression is provided.
833
834     inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
835   parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
836   inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
837   expected one (incorrect adler32 value).  inflateSetDictionary does not
838   perform any decompression: this will be done by subsequent calls of
839   inflate().
840*/
841
842ZEXTERN int ZEXPORT inflateGetDictionary OF((z_streamp strm,
843                                             Bytef *dictionary,
844                                             uInt  *dictLength));
845/*
846     Returns the sliding dictionary being maintained by inflate.  dictLength is
847   set to the number of bytes in the dictionary, and that many bytes are copied
848   to dictionary.  dictionary must have enough space, where 32768 bytes is
849   always enough.  If inflateGetDictionary() is called with dictionary equal to
850   Z_NULL, then only the dictionary length is returned, and nothing is copied.
851   Similary, if dictLength is Z_NULL, then it is not set.
852
853     inflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the
854   stream state is inconsistent.
855*/
856
857ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
858/*
859     Skips invalid compressed data until a possible full flush point (see above
860   for the description of deflate with Z_FULL_FLUSH) can be found, or until all
861   available input is skipped.  No output is provided.
862
863     inflateSync searches for a 00 00 FF FF pattern in the compressed data.
864   All full flush points have this pattern, but not all occurrences of this
865   pattern are full flush points.
866
867     inflateSync returns Z_OK if a possible full flush point has been found,
868   Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point
869   has been found, or Z_STREAM_ERROR if the stream structure was inconsistent.
870   In the success case, the application may save the current current value of
871   total_in which indicates where valid compressed data was found.  In the
872   error case, the application may repeatedly call inflateSync, providing more
873   input each time, until success or end of the input data.
874*/
875
876ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,
877                                    z_streamp source));
878/*
879     Sets the destination stream as a complete copy of the source stream.
880
881     This function can be useful when randomly accessing a large stream.  The
882   first pass through the stream can periodically record the inflate state,
883   allowing restarting inflate at those points when randomly accessing the
884   stream.
885
886     inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
887   enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
888   (such as zalloc being Z_NULL).  msg is left unchanged in both source and
889   destination.
890*/
891
892ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
893/*
894     This function is equivalent to inflateEnd followed by inflateInit,
895   but does not free and reallocate all the internal decompression state.  The
896   stream will keep attributes that may have been set by inflateInit2.
897
898     inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
899   stream state was inconsistent (such as zalloc or state being Z_NULL).
900*/
901
902ZEXTERN int ZEXPORT inflateReset2 OF((z_streamp strm,
903                                      int windowBits));
904/*
905     This function is the same as inflateReset, but it also permits changing
906   the wrap and window size requests.  The windowBits parameter is interpreted
907   the same as it is for inflateInit2.
908
909     inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source
910   stream state was inconsistent (such as zalloc or state being Z_NULL), or if
911   the windowBits parameter is invalid.
912*/
913
914ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm,
915                                     int bits,
916                                     int value));
917/*
918     This function inserts bits in the inflate input stream.  The intent is
919   that this function is used to start inflating at a bit position in the
920   middle of a byte.  The provided bits will be used before any bytes are used
921   from next_in.  This function should only be used with raw inflate, and
922   should be used before the first inflate() call after inflateInit2() or
923   inflateReset().  bits must be less than or equal to 16, and that many of the
924   least significant bits of value will be inserted in the input.
925
926     If bits is negative, then the input stream bit buffer is emptied.  Then
927   inflatePrime() can be called again to put bits in the buffer.  This is used
928   to clear out bits leftover after feeding inflate a block description prior
929   to feeding inflate codes.
930
931     inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
932   stream state was inconsistent.
933*/
934
935ZEXTERN long ZEXPORT inflateMark OF((z_streamp strm));
936/*
937     This function returns two values, one in the lower 16 bits of the return
938   value, and the other in the remaining upper bits, obtained by shifting the
939   return value down 16 bits.  If the upper value is -1 and the lower value is
940   zero, then inflate() is currently decoding information outside of a block.
941   If the upper value is -1 and the lower value is non-zero, then inflate is in
942   the middle of a stored block, with the lower value equaling the number of
943   bytes from the input remaining to copy.  If the upper value is not -1, then
944   it is the number of bits back from the current bit position in the input of
945   the code (literal or length/distance pair) currently being processed.  In
946   that case the lower value is the number of bytes already emitted for that
947   code.
948
949     A code is being processed if inflate is waiting for more input to complete
950   decoding of the code, or if it has completed decoding but is waiting for
951   more output space to write the literal or match data.
952
953     inflateMark() is used to mark locations in the input data for random
954   access, which may be at bit positions, and to note those cases where the
955   output of a code may span boundaries of random access blocks.  The current
956   location in the input stream can be determined from avail_in and data_type
957   as noted in the description for the Z_BLOCK flush parameter for inflate.
958
959     inflateMark returns the value noted above or -1 << 16 if the provided
960   source stream state was inconsistent.
961*/
962
963ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm,
964                                         gz_headerp head));
965/*
966     inflateGetHeader() requests that gzip header information be stored in the
967   provided gz_header structure.  inflateGetHeader() may be called after
968   inflateInit2() or inflateReset(), and before the first call of inflate().
969   As inflate() processes the gzip stream, head->done is zero until …

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