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<html>
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<head>
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 <title>
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 zlib general purpose compression library version 1.1.4
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 </title>
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</head>
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<body bgcolor="White" text="Black" vlink="Red" alink="Navy" link="Red">
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<!-- background="zlibbg.gif" -->
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<h1> zlib 1.1.4 Manual </h1>
11
<hr>
12
<a name="Contents"><h2>Contents</h2>
13
<ol type="I">
14
<li> <a href="#Prologue">Prologue</a>
15
<li> <a href="#Introduction">Introduction</a>
16
<li> <a href="#Utility functions">Utility functions</a>
17
<li> <a href="#Basic functions">Basic functions</a>
18
<li> <a href="#Advanced functions">Advanced functions</a>
19
<li> <a href="#Constants">Constants</a>
20
<li> <a href="#struct z_stream_s">struct z_stream_s</a>
21
<li> <a href="#Checksum functions">Checksum functions</a>
22
<li> <a href="#Misc">Misc</a>
23
</ol>
24
<hr>
25
<a name="Prologue"><h2> Prologue </h2>
26
  'zlib' general purpose compression library version 1.1.4, March 11th, 2002
27
  <p>
28
  Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler
29
  <p>
30
  This software is provided 'as-is', without any express or implied
31
  warranty.  In no event will the authors be held liable for any damages
32
  arising from the use of this software.
33
  <p>
34
  Permission is granted to anyone to use this software for any purpose,
35
  including commercial applications, and to alter it and redistribute it
36
  freely, subject to the following restrictions:
37
  <ol>
38
   <li> The origin of this software must not be misrepresented ; you must not
39
     claim that you wrote the original software. If you use this software
40
     in a product, an acknowledgment in the product documentation would be
41
     appreciated but is not required.
42
   <li> Altered source versions must be plainly marked as such, and must not be
43
     misrepresented as being the original software.
44
   <li> This notice may not be removed or altered from any source distribution.
45
  </ol>
46
 
47
  <dl>
48
  <dt>Jean-loup Gailly
49
  <dd><a href="mailto:jloup@gzip.org">jloup@gzip.org</a>
50
  <dt>Mark Adler
51
  <dd><a href="mailto:madler@alumni.caltech.edu">madler@alumni.caltech.edu</a>
52
  </dl>
53
 
54
  The data format used by the zlib library is described by RFCs (Request for
55
  Comments) 1950 to 1952 in the files
56
  <a href="ftp://ds.internic.net/rfc/rfc1950.txt">
57
  ftp://ds.internic.net/rfc/rfc1950.txt </a>
58
  (zlib format),
59
  <a href="ftp://ds.internic.net/rfc/rfc1951.txt">
60
  rfc1951.txt </a>
61
  (<a href="#deflate">deflate</a> format) and
62
  <a href="ftp://ds.internic.net/rfc/rfc1952.txt">
63
  rfc1952.txt </a>
64
  (gzip format).
65
  <p>
66
  This manual is converted from zlib.h by
67
  <a href="mailto:piaip@csie.ntu.edu.tw"> piaip </a>
68
  <p>
69
  Visit <a href="http://ftp.cdrom.com/pub/infozip/zlib/">
70
  http://ftp.cdrom.com/pub/infozip/zlib/</a>
71
  for the official zlib web page.
72
  <p>
73
 
74
<hr>
75
<a name="Introduction"><h2> Introduction </h2>
76
     The 'zlib' compression library provides in-memory compression and
77
  decompression functions, including integrity checks of the uncompressed
78
  data.  This version of the library supports only one compression method
79
  (deflation) but other algorithms will be added later and will have the same
80
  stream interface.
81
  <p>
82
 
83
     Compression can be done in a single step if the buffers are large
84
  enough (for example if an input file is mmap'ed), or can be done by
85
  repeated calls of the compression function.  In the latter case, the
86
  application must provide more input and/or consume the output
87
  (providing more output space) before each call.
88
  <p>
89
 
90
     The library also supports reading and writing files in gzip (.gz) format
91
  with an interface similar to that of stdio.
92
  <p>
93
 
94
     The library does not install any signal handler. The decoder checks
95
  the consistency of the compressed data, so the library should never
96
  crash even in case of corrupted input.
97
  <p>
98
 
99
<hr>
100
<a name="Utility functions"><h2> Utility functions </h2>
101
     The following utility functions are implemented on top of the
102
   <a href="#Basic functions">basic stream-oriented functions</a>.
103
   To simplify the interface, some
104
   default options are assumed (compression level and memory usage,
105
   standard memory allocation functions). The source code of these
106
   utility functions can easily be modified if you need special options.
107
<h3> Function list </h3>
108
<ul>
109
<li> int  <a href="#compress">compress</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen);
110
<li> int  <a href="#compress2">compress2</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen, int level);
111
<li> int  <a href="#uncompress">uncompress</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen);
112
<li> typedef voidp gzFile;
113
<li>  gzFile  <a href="#gzopen">gzopen</a>  (const char *path, const char *mode);
114
<li> gzFile  <a href="#gzdopen">gzdopen</a>  (int fd, const char *mode);
115
<li> int  <a href="#gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy);
116
<li> int     <a href="#gzread">gzread</a>  (gzFile file, voidp buf, unsigned len);
117
<li> int     <a href="#gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len);
118
<li> int VA   <a href="#gzprintf">gzprintf</a> (gzFile file, const char *format, ...);
119
<li> int  <a href="#gzputs">gzputs</a> (gzFile file, const char *s);
120
<li> char *  <a href="#gzgets">gzgets</a> (gzFile file, char *buf, int len);
121
<li> int     <a href="#gzputc">gzputc</a> (gzFile file, int c);
122
<li> int     <a href="#gzgetc">gzgetc</a> (gzFile file);
123
<li> int     <a href="#gzflush">gzflush</a> (gzFile file, int flush);
124
<li> z_off_t     <a href="#gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence);
125
<li> z_off_t     <a href="#gztell">gztell</a> (gzFile file);
126
<li> int     <a href="#gzrewind">gzrewind</a> (gzFile file);
127
<li> int  <a href="#gzeof">gzeof</a> (gzFile file);
128
<li> int     <a href="#gzclose">gzclose</a> (gzFile file);
129
<li> const char *  <a href="#gzerror">gzerror</a> (gzFile file, int *errnum);
130
</ul>
131
<h3> Function description </h3>
132
<dl>
133
<font color="Blue"><dt> int  <a name="compress">compress</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen);</font>
134
<dd>
135
     Compresses the source buffer into the destination buffer.  sourceLen is
136
   the byte length of the source buffer. Upon entry, destLen is the total
137
   size of the destination buffer, which must be at least 0.1% larger than
138
   sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the
139
   compressed buffer.<p>
140
     This function can be used to <a href="#compress">compress</a> a whole file at once if the
141
   input file is mmap'ed.<p>
142
     <a href="#compress">compress</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
143
   enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output
144
   buffer.<p>
145
 
146
<font color="Blue"><dt> int  <a name="compress2">compress2</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen, int level);</font>
147
<dd>
148
     Compresses the source buffer into the destination buffer. The level
149
   parameter has the same meaning as in <a href="#deflateInit">deflateInit</a>.  sourceLen is the byte
150
   length of the source buffer. Upon entry, destLen is the total size of the
151
   destination buffer, which must be at least 0.1% larger than sourceLen plus
152
   12 bytes. Upon exit, destLen is the actual size of the compressed buffer.
153
   <p>
154
 
155
     <a href="#compress2">compress2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough
156
   memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output buffer,
157
   <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the level parameter is invalid.
158
   <p>
159
 
160
<font color="Blue"><dt> int  <a name="uncompress">uncompress</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen);</font>
161
<dd>
162
     Decompresses the source buffer into the destination buffer.  sourceLen is
163
   the byte length of the source buffer. Upon entry, destLen is the total
164
   size of the destination buffer, which must be large enough to hold the
165
   entire uncompressed data. (The size of the uncompressed data must have
166
   been saved previously by the compressor and transmitted to the decompressor
167
   by some mechanism outside the scope of this compression library.)
168
   Upon exit, destLen is the actual size of the compressed buffer. <p>
169
     This function can be used to decompress a whole file at once if the
170
   input file is mmap'ed.
171
   <p>
172
 
173
     <a href="#uncompress">uncompress</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
174
   enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output
175
   buffer, or <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was corrupted.
176
   <p>
177
 
178
<dt> typedef voidp gzFile;
179
<dd> <p>
180
 
181
<font color="Blue"><dt>  gzFile  <a name="gzopen">gzopen</a>  (const char *path, const char *mode);</font>
182
<dd>
183
     Opens a gzip (.gz) file for reading or writing. The mode parameter
184
   is as in fopen ("rb" or "wb") but can also include a compression level
185
   ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
186
   Huffman only compression as in "wb1h". (See the description
187
   of <a href="#deflateInit2">deflateInit2</a> for more information about the strategy parameter.)
188
   <p>
189
 
190
     <a href="#gzopen">gzopen</a> can be used to read a file which is not in gzip format ; in this
191
   case <a href="#gzread">gzread</a> will directly read from the file without decompression.
192
   <p>
193
 
194
     <a href="#gzopen">gzopen</a> returns NULL if the file could not be opened or if there was
195
   insufficient memory to allocate the (de)compression <a href="#state">state</a> ; errno
196
   can be checked to distinguish the two cases (if errno is zero, the
197
   zlib error is <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a>).
198
   <p>
199
 
200
<font color="Blue"><dt> gzFile  <a name="gzdopen">gzdopen</a>  (int fd, const char *mode);</font>
201
<dd>
202
     <a href="#gzdopen">gzdopen</a>() associates a gzFile with the file descriptor fd.  File
203
   descriptors are obtained from calls like open, dup, creat, pipe or
204
   fileno (in the file has been previously opened with fopen).
205
   The mode parameter is as in <a href="#gzopen">gzopen</a>.
206
   <p>
207
     The next call of <a href="#gzclose">gzclose</a> on the returned gzFile will also close the
208
   file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
209
   descriptor fd. If you want to keep fd open, use <a href="#gzdopen">gzdopen</a>(dup(fd), mode).
210
   <p>
211
     <a href="#gzdopen">gzdopen</a> returns NULL if there was insufficient memory to allocate
212
   the (de)compression <a href="#state">state</a>.
213
   <p>
214
 
215
<font color="Blue"><dt> int  <a name="gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy);</font>
216
<dd>
217
     Dynamically update the compression level or strategy. See the description
218
   of <a href="#deflateInit2">deflateInit2</a> for the meaning of these parameters.
219
   <p>
220
     <a href="#gzsetparams">gzsetparams</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the file was not
221
   opened for writing.
222
   <p>
223
 
224
<font color="Blue"><dt> int     <a name="gzread">gzread</a>  (gzFile file, voidp buf, unsigned len);</font>
225
<dd>
226
     Reads the given number of uncompressed bytes from the compressed file.
227
   If the input file was not in gzip format, <a href="#gzread">gzread</a> copies the given number
228
   of bytes into the buffer.
229
   <p>
230
     <a href="#gzread">gzread</a> returns the number of uncompressed bytes actually read (0 for
231
   end of file, -1 for error).
232
   <p>
233
 
234
<font color="Blue"><dt> int     <a name="gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len);</font>
235
<dd>
236
     Writes the given number of uncompressed bytes into the compressed file.
237
   <a href="#gzwrite">gzwrite</a> returns the number of uncompressed bytes actually written
238
   (0 in case of error).
239
   <p>
240
 
241
<font color="Blue"><dt> int VA   <a name="gzprintf">gzprintf</a> (gzFile file, const char *format, ...);</font>
242
<dd>
243
     Converts, formats, and writes the args to the compressed file under
244
   control of the format string, as in fprintf. <a href="#gzprintf">gzprintf</a> returns the number of
245
   uncompressed bytes actually written (0 in case of error).
246
   <p>
247
 
248
<font color="Blue"><dt> int  <a name="gzputs">gzputs</a> (gzFile file, const char *s);</font>
249
<dd>
250
      Writes the given null-terminated string to the compressed file, excluding
251
   the terminating null character.
252
   <p>
253
      <a href="#gzputs">gzputs</a> returns the number of characters written, or -1 in case of error.
254
      <p>
255
 
256
<font color="Blue"><dt> char *  <a name="gzgets">gzgets</a> (gzFile file, char *buf, int len);</font>
257
<dd>
258
      Reads bytes from the compressed file until len-1 characters are read, or
259
   a newline character is read and transferred to buf, or an end-of-file
260
   condition is encountered.  The string is then terminated with a null
261
   character.
262
   <p>
263
      <a href="#gzgets">gzgets</a> returns buf, or <a href="#Z_NULL">Z_NULL</a> in case of error.
264
      <p>
265
 
266
<font color="Blue"><dt> int     <a name="gzputc">gzputc</a> (gzFile file, int c);</font>
267
<dd>
268
      Writes c, converted to an unsigned char, into the compressed file.
269
   <a href="#gzputc">gzputc</a> returns the value that was written, or -1 in case of error.
270
   <p>
271
 
272
<font color="Blue"><dt> int     <a name="gzgetc">gzgetc</a> (gzFile file);</font>
273
<dd>
274
      Reads one byte from the compressed file. <a href="#gzgetc">gzgetc</a> returns this byte
275
   or -1 in case of end of file or error.
276
   <p>
277
 
278
<font color="Blue"><dt> int     <a name="gzflush">gzflush</a> (gzFile file, int flush);</font>
279
<dd>
280
     Flushes all pending output into the compressed file. The parameter
281
   flush is as in the <a href="#deflate">deflate</a>() function. The return value is the zlib
282
   error number (see function <a href="#gzerror">gzerror</a> below). <a href="#gzflush">gzflush</a> returns <a href="#Z_OK">Z_OK</a> if
283
   the flush parameter is <a href="#Z_FINISH">Z_FINISH</a> and all output could be flushed.
284
   <p>
285
     <a href="#gzflush">gzflush</a> should be called only when strictly necessary because it can
286
   degrade compression.
287
   <p>
288
 
289
<font color="Blue"><dt> z_off_t     <a name="gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence);</font>
290
<dd>
291
      Sets the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the
292
   given compressed file. The offset represents a number of bytes in the
293
   uncompressed data stream. The whence parameter is defined as in lseek(2);
294
   the value SEEK_END is not supported.
295
   <p>
296
     If the file is opened for reading, this function is emulated but can be
297
   extremely slow. If the file is opened for writing, only forward seeks are
298
   supported ; <a href="#gzseek">gzseek</a> then compresses a sequence of zeroes up to the new
299
   starting position.
300
   <p>
301
      <a href="#gzseek">gzseek</a> returns the resulting offset location as measured in bytes from
302
   the beginning of the uncompressed stream, or -1 in case of error, in
303
   particular if the file is opened for writing and the new starting position
304
   would be before the current position.
305
   <p>
306
 
307
<font color="Blue"><dt> int     <a name="gzrewind">gzrewind</a> (gzFile file);</font>
308
<dd>
309
     Rewinds the given file. This function is supported only for reading.
310
     <p>
311
   <a href="#gzrewind">gzrewind</a>(file) is equivalent to (int)<a href="#gzseek">gzseek</a>(file, 0L, SEEK_SET)
312
   <p>
313
 
314
<font color="Blue"><dt> z_off_t     <a name="gztell">gztell</a> (gzFile file);</font>
315
<dd>
316
     Returns the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the
317
   given compressed file. This position represents a number of bytes in the
318
   uncompressed data stream.
319
   <p>
320
 
321
   <a href="#gztell">gztell</a>(file) is equivalent to <a href="#gzseek">gzseek</a>(file, 0L, SEEK_CUR)
322
   <p>
323
 
324
<font color="Blue"><dt> int  <a name="gzeof">gzeof</a> (gzFile file);</font>
325
<dd>
326
     Returns 1 when EOF has previously been detected reading the given
327
   input stream, otherwise zero.
328
   <p>
329
 
330
<font color="Blue"><dt> int     <a name="gzclose">gzclose</a> (gzFile file);</font>
331
<dd>
332
     Flushes all pending output if necessary, closes the compressed file
333
   and deallocates all the (de)compression <a href="#state">state</a>. The return value is the zlib
334
   error number (see function <a href="#gzerror">gzerror</a> below).
335
   <p>
336
 
337
<font color="Blue"><dt> const char *  <a name="gzerror">gzerror</a> (gzFile file, int *errnum);</font>
338
<dd>
339
     Returns the error message for the last error which occurred on the
340
   given compressed file. errnum is set to zlib error number. If an
341
   error occurred in the file system and not in the compression library,
342
   errnum is set to <a href="#Z_ERRNO">Z_ERRNO</a> and the application may consult errno
343
   to get the exact error code.
344
   <p>
345
</dl>
346
<hr>
347
<a name="Basic functions"><h2> Basic functions </h2>
348
<h3> Function list </h3>
349
<ul>
350
<li>  const char *  <a href="#zlibVersion">zlibVersion</a> (void);
351
<li>  int  <a href="#deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level);
352
<li>  int  <a href="#deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);
353
<li>  int  <a href="#deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);
354
<li>  int  <a href="#inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm);
355
<li>  int  <a href="#inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);
356
<li>  int  <a href="#inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);
357
</ul>
358
 
359
<h3> Function description </h3>
360
<dl>
361
<font color="Blue"><dt>  const char *  <a name="zlibVersion">zlibVersion</a> (void);</font>
362
<dd> The application can compare <a href="#zlibVersion">zlibVersion</a> and ZLIB_VERSION for consistency.
363
   If the first character differs, the library code actually used is
364
   not compatible with the zlib.h header file used by the application.
365
   This check is automatically made by <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a>.
366
   <p>
367
 
368
<font color="Blue"><dt> int  <a name="deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level);</font>
369
<dd>
370
     Initializes the internal stream <a href="#state">state</a> for compression. The fields
371
   <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by the caller.
372
   If <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> are set to <a href="#Z_NULL">Z_NULL</a>, <a href="#deflateInit">deflateInit</a> updates them to
373
   use default allocation functions.
374
   <p>
375
 
376
     The compression level must be <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a>, or between 0 and 9:
377
   1 gives best speed, 9 gives best compression, 0 gives no compression at
378
   all (the input data is simply copied a block at a time).
379
   <p>
380
 
381
   <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a> requests a default compromise between speed and
382
   compression (currently equivalent to level 6).
383
   <p>
384
 
385
     <a href="#deflateInit">deflateInit</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
386
   enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if level is not a valid compression level,
387
   <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version (<a href="#zlib_version">zlib_version</a>) is incompatible
388
   with the version assumed by the caller (ZLIB_VERSION).
389
   <a href="#msg">msg</a> is set to null if there is no error message.  <a href="#deflateInit">deflateInit</a> does not
390
   perform any compression: this will be done by <a href="#deflate">deflate</a>().
391
   <p>
392
 
393
<font color="Blue"><dt>  int  <a name="deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font>
394
<dd>
395
    <a href="#deflate">deflate</a> compresses as much data as possible, and stops when the input
396
  buffer becomes empty or the output buffer becomes full. It may introduce some
397
  output latency (reading input without producing any output) except when
398
  forced to flush.<p>
399
 
400
    The detailed semantics are as follows. <a href="#deflate">deflate</a> performs one or both of the
401
  following actions:
402
 
403
  <ul>
404
  <li> Compress more input starting at <a href="#next_in">next_in</a> and update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a>
405
    accordingly. If not all input can be processed (because there is not
406
    enough room in the output buffer), <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> are updated and
407
    processing will resume at this point for the next call of <a href="#deflate">deflate</a>().
408
 
409
  <li>
410
    Provide more output starting at <a href="#next_out">next_out</a> and update <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a>
411
    accordingly. This action is forced if the parameter flush is non zero.
412
    Forcing flush frequently degrades the compression ratio, so this parameter
413
    should be set only when necessary (in interactive applications).
414
    Some output may be provided even if flush is not set.
415
  </ul> <p>
416
 
417
  Before the call of <a href="#deflate">deflate</a>(), the application should ensure that at least
418
  one of the actions is possible, by providing more input and/or consuming
419
  more output, and updating <a href="#avail_in">avail_in</a> or <a href="#avail_out">avail_out</a> accordingly ; <a href="#avail_out">avail_out</a>
420
  should never be zero before the call. The application can consume the
421
  compressed output when it wants, for example when the output buffer is full
422
  (<a href="#avail_out">avail_out</a> == 0), or after each call of <a href="#deflate">deflate</a>(). If <a href="#deflate">deflate</a> returns <a href="#Z_OK">Z_OK</a>
423
  and with zero <a href="#avail_out">avail_out</a>, it must be called again after making room in the
424
  output buffer because there might be more output pending.
425
  <p>
426
 
427
    If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, all pending output is
428
  flushed to the output buffer and the output is aligned on a byte boundary, so
429
  that the decompressor can get all input data available so far. (In particular
430
  <a href="#avail_in">avail_in</a> is zero after the call if enough output space has been provided
431
  before the call.)  Flushing may degrade compression for some compression
432
  algorithms and so it should be used only when necessary.
433
  <p>
434
 
435
    If flush is set to <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>, all output is flushed as with
436
  <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, and the compression <a href="#state">state</a> is reset so that decompression can
437
  restart from this point if previous compressed data has been damaged or if
438
  random access is desired. Using <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a> too often can seriously degrade
439
  the compression.
440
  <p>
441
 
442
    If <a href="#deflate">deflate</a> returns with <a href="#avail_out">avail_out</a> == 0, this function must be called again
443
  with the same value of the flush parameter and more output space (updated
444
  <a href="#avail_out">avail_out</a>), until the flush is complete (<a href="#deflate">deflate</a> returns with non-zero
445
  <a href="#avail_out">avail_out</a>).
446
  <p>
447
 
448
    If the parameter flush is set to <a href="#Z_FINISH">Z_FINISH</a>, pending input is processed,
449
  pending output is flushed and <a href="#deflate">deflate</a> returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> if there
450
  was enough output space ; if <a href="#deflate">deflate</a> returns with <a href="#Z_OK">Z_OK</a>, this function must be
451
  called again with <a href="#Z_FINISH">Z_FINISH</a> and more output space (updated <a href="#avail_out">avail_out</a>) but no
452
  more input data, until it returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> or an error. After
453
  <a href="#deflate">deflate</a> has returned <a href="#Z_STREAM_END">Z_STREAM_END</a>, the only possible operations on the
454
  stream are <a href="#deflateReset">deflateReset</a> or <a href="#deflateEnd">deflateEnd</a>.
455
  <p>
456
 
457
    <a href="#Z_FINISH">Z_FINISH</a> can be used immediately after <a href="#deflateInit">deflateInit</a> if all the compression
458
  is to be done in a single step. In this case, <a href="#avail_out">avail_out</a> must be at least
459
  0.1% larger than <a href="#avail_in">avail_in</a> plus 12 bytes.  If <a href="#deflate">deflate</a> does not return
460
  <a href="#Z_STREAM_END">Z_STREAM_END</a>, then it must be called again as described above.
461
  <p>
462
 
463
    <a href="#deflate">deflate</a>() sets strm-&gt <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all input read
464
  so far (that is, <a href="#total_in">total_in</a> bytes).
465
  <p>
466
 
467
    <a href="#deflate">deflate</a>() may update <a href="#data_type">data_type</a> if it can make a good guess about
468
  the input data type (<a href="#Z_ASCII">Z_ASCII</a> or <a href="#Z_BINARY">Z_BINARY</a>). In doubt, the data is considered
469
  binary. This field is only for information purposes and does not affect
470
  the compression algorithm in any manner.
471
  <p>
472
 
473
    <a href="#deflate">deflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input
474
  processed or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if all input has been
475
  consumed and all output has been produced (only when flush is set to
476
  <a href="#Z_FINISH">Z_FINISH</a>), <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream <a href="#state">state</a> was inconsistent (for example
477
  if <a href="#next_in">next_in</a> or <a href="#next_out">next_out</a> was NULL), <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if no progress is possible
478
  (for example <a href="#avail_in">avail_in</a> or <a href="#avail_out">avail_out</a> was zero).
479
  <p>
480
 
481
<font color="Blue"><dt>  int  <a name="deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
482
<dd>
483
     All dynamically allocated data structures for this stream are freed.
484
   This function discards any unprocessed input and does not flush any
485
   pending output.
486
   <p>
487
 
488
     <a href="#deflateEnd">deflateEnd</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the
489
   stream <a href="#state">state</a> was inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the stream was freed
490
   prematurely (some input or output was discarded). In the error case,
491
   <a href="#msg">msg</a> may be set but then points to a static string (which must not be
492
   deallocated).
493
   <p>
494
 
495
<font color="Blue"><dt>  int  <a name="inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
496
<dd>
497
        Initializes the internal stream <a href="#state">state</a> for decompression. The fields
498
   <a href="#next_in">next_in</a>, <a href="#avail_in">avail_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by
499
   the caller. If <a href="#next_in">next_in</a> is not <a href="#Z_NULL">Z_NULL</a> and <a href="#avail_in">avail_in</a> is large enough (the exact
500
   value depends on the compression method), <a href="#inflateInit">inflateInit</a> determines the
501
   compression method from the zlib header and allocates all data structures
502
   accordingly ; otherwise the allocation will be deferred to the first call of
503
   <a href="#inflate">inflate</a>.  If <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> are set to <a href="#Z_NULL">Z_NULL</a>, <a href="#inflateInit">inflateInit</a> updates them to
504
   use default allocation functions.
505
   <p>
506
 
507
     <a href="#inflateInit">inflateInit</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough
508
   memory, <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version is incompatible with the
509
   version assumed by the caller.  <a href="#msg">msg</a> is set to null if there is no error
510
   message. <a href="#inflateInit">inflateInit</a> does not perform any decompression apart from reading
511
   the zlib header if present: this will be done by <a href="#inflate">inflate</a>().  (So <a href="#next_in">next_in</a> and
512
   <a href="#avail_in">avail_in</a> may be modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.)
513
   <p>
514
 
515
<font color="Blue"><dt>  int  <a name="inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font>
516
<dd>
517
    <a href="#inflate">inflate</a> decompresses as much data as possible, and stops when the input
518
  buffer becomes empty or the output buffer becomes full. It may some
519
  introduce some output latency (reading input without producing any output)
520
  except when forced to flush.
521
  <p>
522
 
523
  The detailed semantics are as follows. <a href="#inflate">inflate</a> performs one or both of the
524
  following actions:
525
 
526
  <ul>
527
  <li> Decompress more input starting at <a href="#next_in">next_in</a> and update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a>
528
    accordingly. If not all input can be processed (because there is not
529
    enough room in the output buffer), <a href="#next_in">next_in</a> is updated and processing
530
    will resume at this point for the next call of <a href="#inflate">inflate</a>().
531
 
532
  <li> Provide more output starting at <a href="#next_out">next_out</a> and update <a href="#next_out">next_out</a> and
533
    <a href="#avail_out">avail_out</a> accordingly.  <a href="#inflate">inflate</a>() provides as much output as possible,
534
    until there is no more input data or no more space in the output buffer
535
    (see below about the flush parameter).
536
  </ul> <p>
537
 
538
  Before the call of <a href="#inflate">inflate</a>(), the application should ensure that at least
539
  one of the actions is possible, by providing more input and/or consuming
540
  more output, and updating the next_* and avail_* values accordingly.
541
  The application can consume the uncompressed output when it wants, for
542
  example when the output buffer is full (<a href="#avail_out">avail_out</a> == 0), or after each
543
  call of <a href="#inflate">inflate</a>(). If <a href="#inflate">inflate</a> returns <a href="#Z_OK">Z_OK</a> and with zero <a href="#avail_out">avail_out</a>, it
544
  must be called again after making room in the output buffer because there
545
  might be more output pending.
546
  <p>
547
 
548
    If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, <a href="#inflate">inflate</a> flushes as much
549
  output as possible to the output buffer. The flushing behavior of <a href="#inflate">inflate</a> is
550
  not specified for values of the flush parameter other than <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>
551
  and <a href="#Z_FINISH">Z_FINISH</a>, but the current implementation actually flushes as much output
552
  as possible anyway.
553
  <p>
554
 
555
    <a href="#inflate">inflate</a>() should normally be called until it returns <a href="#Z_STREAM_END">Z_STREAM_END</a> or an
556
  error. However if all decompression is to be performed in a single step
557
  (a single call of <a href="#inflate">inflate</a>), the parameter flush should be set to
558
  <a href="#Z_FINISH">Z_FINISH</a>. In this case all pending input is processed and all pending
559
  output is flushed ; <a href="#avail_out">avail_out</a> must be large enough to hold all the
560
  uncompressed data. (The size of the uncompressed data may have been saved
561
  by the compressor for this purpose.) The next operation on this stream must
562
  be <a href="#inflateEnd">inflateEnd</a> to deallocate the decompression <a href="#state">state</a>. The use of <a href="#Z_FINISH">Z_FINISH</a>
563
  is never required, but can be used to inform <a href="#inflate">inflate</a> that a faster routine
564
  may be used for the single <a href="#inflate">inflate</a>() call.
565
  <p>
566
 
567
     If a preset dictionary is needed at this point (see <a href="#inflateSetDictionary">inflateSetDictionary</a>
568
  below), <a href="#inflate">inflate</a> sets strm-<a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of the
569
  dictionary chosen by the compressor and returns <a href="#Z_NEED_DICT">Z_NEED_DICT</a> ; otherwise
570
  it sets strm-&gt <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all output produced
571
  so far (that is, <a href="#total_out">total_out</a> bytes) and returns <a href="#Z_OK">Z_OK</a>, <a href="#Z_STREAM_END">Z_STREAM_END</a> or
572
  an error code as described below. At the end of the stream, <a href="#inflate">inflate</a>()
573
  checks that its computed <a href="#adler32">adler32</a> checksum is equal to that saved by the
574
  compressor and returns <a href="#Z_STREAM_END">Z_STREAM_END</a> only if the checksum is correct.
575
  <p>
576
 
577
    <a href="#inflate">inflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input processed
578
  or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if the end of the compressed data has
579
  been reached and all uncompressed output has been produced, <a href="#Z_NEED_DICT">Z_NEED_DICT</a> if a
580
  preset dictionary is needed at this point, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was
581
  corrupted (input stream not conforming to the zlib format or incorrect
582
  <a href="#adler32">adler32</a> checksum), <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent
583
  (for example if <a href="#next_in">next_in</a> or <a href="#next_out">next_out</a> was NULL), <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
584
  enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if no progress is possible or if there was not
585
  enough room in the output buffer when <a href="#Z_FINISH">Z_FINISH</a> is used. In the <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a>
586
  case, the application may then call <a href="#inflateSync">inflateSync</a> to look for a good
587
  compression block.
588
  <p>
589
 
590
<font color="Blue"><dt>  int  <a name="inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
591
<dd>
592
     All dynamically allocated data structures for this stream are freed.
593
   This function discards any unprocessed input and does not flush any
594
   pending output.
595
   <p>
596
 
597
     <a href="#inflateEnd">inflateEnd</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream <a href="#state">state</a>
598
   was inconsistent. In the error case, <a href="#msg">msg</a> may be set but then points to a
599
   static string (which must not be deallocated).
600
</dl>
601
<hr>
602
<a name="Advanced functions"><h2> Advanced functions </h2>
603
    The following functions are needed only in some special applications.
604
<h3> Function list </h3>
605
<ul>
606
<li>  int  <a href="#deflateInit2">deflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm,
607
<li> int  <a href="#deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt  dictLength);
608
<li> int  <a href="#deflateCopy">deflateCopy</a> (<a href="#z_streamp">z_streamp</a> dest, <a href="#z_streamp">z_streamp</a> source);
609
<li> int  <a href="#deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);
610
<li> int  <a href="#deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy);
611
<li> int  <a href="#inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int  windowBits);
612
<li>  int  <a href="#inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt  dictLength);
613
<li> int  <a href="#inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm);
614
<li> int  <a href="#inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);
615
 
616
</ul>
617
<h3> Function description </h3>
618
<dl>
619
<font color="Blue"><dt>  int  <a name="deflateInit2">deflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int  level, int  method, int  windowBits, int  memLevel, int  strategy);</font>
620
 
621
<dd> This is another version of <a href="#deflateInit">deflateInit</a> with more compression options. The
622
   fields <a href="#next_in">next_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by
623
   the caller.<p>
624
 
625
     The method parameter is the compression method. It must be <a href="#Z_DEFLATED">Z_DEFLATED</a> in
626
   this version of the library.<p>
627
 
628
     The windowBits parameter is the base two logarithm of the window size
629
   (the size of the history buffer).  It should be in the range 8..15 for this
630
   version of the library. Larger values of this parameter result in better
631
   compression at the expense of memory usage. The default value is 15 if
632
   <a href="#deflateInit">deflateInit</a> is used instead.<p>
633
 
634
     The memLevel parameter specifies how much memory should be allocated
635
   for the internal compression <a href="#state">state</a>. memLevel=1 uses minimum memory but
636
   is slow and reduces compression ratio ; memLevel=9 uses maximum memory
637
   for optimal speed. The default value is 8. See zconf.h for total memory
638
   usage as a function of windowBits and memLevel.<p>
639
 
640
     The strategy parameter is used to tune the compression algorithm. Use the
641
   value <a href="#Z_DEFAULT_STRATEGY">Z_DEFAULT_STRATEGY</a> for normal data, <a href="#Z_FILTERED">Z_FILTERED</a> for data produced by a
642
   filter (or predictor), or <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a> to force Huffman encoding only (no
643
   string match).  Filtered data consists mostly of small values with a
644
   somewhat random distribution. In this case, the compression algorithm is
645
   tuned to <a href="#compress">compress</a> them better. The effect of <a href="#Z_FILTERED">Z_FILTERED</a> is to force more
646
   Huffman coding and less string matching ; it is somewhat intermediate
647
   between Z_DEFAULT and <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a>. The strategy parameter only affects
648
   the compression ratio but not the correctness of the compressed output even
649
   if it is not set appropriately.<p>
650
 
651
      <a href="#deflateInit2">deflateInit2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough
652
   memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as an invalid
653
   method). <a href="#msg">msg</a> is set to null if there is no error message.  <a href="#deflateInit2">deflateInit2</a> does
654
   not perform any compression: this will be done by <a href="#deflate">deflate</a>().<p>
655
 
656
<font color="Blue"><dt> int  <a name="deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt  dictLength);</font>
657
<dd>
658
     Initializes the compression dictionary from the given byte sequence
659
   without producing any compressed output. This function must be called
660
   immediately after <a href="#deflateInit">deflateInit</a>, <a href="#deflateInit2">deflateInit2</a> or <a href="#deflateReset">deflateReset</a>, before any
661
   call of <a href="#deflate">deflate</a>. The compressor and decompressor must use exactly the same
662
   dictionary (see <a href="#inflateSetDictionary">inflateSetDictionary</a>).<p>
663
 
664
     The dictionary should consist of strings (byte sequences) that are likely
665
   to be encountered later in the data to be compressed, with the most commonly
666
   used strings preferably put towards the end of the dictionary. Using a
667
   dictionary is most useful when the data to be compressed is short and can be
668
   predicted with good accuracy ; the data can then be compressed better than
669
   with the default empty dictionary.<p>
670
 
671
     Depending on the size of the compression data structures selected by
672
   <a href="#deflateInit">deflateInit</a> or <a href="#deflateInit2">deflateInit2</a>, a part of the dictionary may in effect be
673
   discarded, for example if the dictionary is larger than the window size in
674
   <a href="#deflate">deflate</a> or deflate2. Thus the strings most likely to be useful should be
675
   put at the end of the dictionary, not at the front.<p>
676
 
677
     Upon return of this function, strm-&gt <a href="#adler">adler</a> is set to the Adler32 value
678
   of the dictionary ; the decompressor may later use this value to determine
679
   which dictionary has been used by the compressor. (The Adler32 value
680
   applies to the whole dictionary even if only a subset of the dictionary is
681
   actually used by the compressor.)<p>
682
 
683
     <a href="#deflateSetDictionary">deflateSetDictionary</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a
684
   parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is
685
   inconsistent (for example if <a href="#deflate">deflate</a> has already been called for this stream
686
   or if the compression method is bsort). <a href="#deflateSetDictionary">deflateSetDictionary</a> does not
687
   perform any compression: this will be done by <a href="#deflate">deflate</a>().<p>
688
 
689
<font color="Blue"><dt> int  <a name="deflateCopy">deflateCopy</a> (<a href="#z_streamp">z_streamp</a> dest, <a href="#z_streamp">z_streamp</a> source);</font>
690
<dd>
691
     Sets the destination stream as a complete copy of the source stream.<p>
692
 
693
     This function can be useful when several compression strategies will be
694
   tried, for example when there are several ways of pre-processing the input
695
   data with a filter. The streams that will be discarded should then be freed
696
   by calling <a href="#deflateEnd">deflateEnd</a>.  Note that <a href="#deflateCopy">deflateCopy</a> duplicates the internal
697
   compression <a href="#state">state</a> which can be quite large, so this strategy is slow and
698
   can consume lots of memory.<p>
699
 
700
     <a href="#deflateCopy">deflateCopy</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
701
   enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source stream <a href="#state">state</a> was inconsistent
702
   (such as <a href="#zalloc">zalloc</a> being NULL). <a href="#msg">msg</a> is left unchanged in both source and
703
   destination.<p>
704
 
705
<font color="Blue"><dt> int  <a name="deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
706
<dd>     This function is equivalent to <a href="#deflateEnd">deflateEnd</a> followed by <a href="#deflateInit">deflateInit</a>,
707
   but does not free and reallocate all the internal compression <a href="#state">state</a>.
708
   The stream will keep the same compression level and any other attributes
709
   that may have been set by <a href="#deflateInit2">deflateInit2</a>.<p>
710
 
711
      <a href="#deflateReset">deflateReset</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source
712
   stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL).<p>
713
 
714
<font color="Blue"><dt> int  <a name="deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy);</font>
715
<dd>
716
     Dynamically update the compression level and compression strategy.  The
717
   interpretation of level and strategy is as in <a href="#deflateInit2">deflateInit2</a>.  This can be
718
   used to switch between compression and straight copy of the input data, or
719
   to switch to a different kind of input data requiring a different
720
   strategy. If the compression level is changed, the input available so far
721
   is compressed with the old level (and may be flushed); the new level will
722
   take effect only at the next call of <a href="#deflate">deflate</a>().<p>
723
 
724
     Before the call of <a href="#deflateParams">deflateParams</a>, the stream <a href="#state">state</a> must be set as for
725
   a call of <a href="#deflate">deflate</a>(), since the currently available input may have to
726
   be compressed and flushed. In particular, strm-&gt <a href="#avail_out">avail_out</a> must be
727
   non-zero.<p>
728
 
729
     <a href="#deflateParams">deflateParams</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source
730
   stream <a href="#state">state</a> was inconsistent or if a parameter was invalid, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a>
731
   if strm-&gtavail_out was zero.<p>
732
 
733
<font color="Blue"><dt> int  <a name="inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int  windowBits);</font>
734
 
735
<dd>     This is another version of <a href="#inflateInit">inflateInit</a> with an extra parameter. The
736
   fields <a href="#next_in">next_in</a>, <a href="#avail_in">avail_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized
737
   before by the caller.<p>
738
 
739
     The windowBits parameter is the base two logarithm of the maximum window
740
   size (the size of the history buffer).  It should be in the range 8..15 for
741
   this version of the library. The default value is 15 if <a href="#inflateInit">inflateInit</a> is used
742
   instead. If a compressed stream with a larger window size is given as
743
   input, <a href="#inflate">inflate</a>() will return with the error code <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> instead of
744
   trying to allocate a larger window.<p>
745
 
746
      <a href="#inflateInit2">inflateInit2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough
747
   memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as a negative
748
   memLevel). <a href="#msg">msg</a> is set to null if there is no error message.  <a href="#inflateInit2">inflateInit2</a>
749
   does not perform any decompression apart from reading the zlib header if
750
   present: this will be done by <a href="#inflate">inflate</a>(). (So <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> may be
751
   modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.)<p>
752
 
753
<font color="Blue"><dt>  int  <a name="inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt  dictLength);</font>
754
<dd>
755
     Initializes the decompression dictionary from the given uncompressed byte
756
   sequence. This function must be called immediately after a call of <a href="#inflate">inflate</a>
757
   if this call returned <a href="#Z_NEED_DICT">Z_NEED_DICT</a>. The dictionary chosen by the compressor
758
   can be determined from the Adler32 value returned by this call of
759
   <a href="#inflate">inflate</a>. The compressor and decompressor must use exactly the same
760
   dictionary (see <a href="#deflateSetDictionary">deflateSetDictionary</a>).<p>
761
 
762
     <a href="#inflateSetDictionary">inflateSetDictionary</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a
763
   parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is
764
   inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the given dictionary doesn't match the
765
   expected one (incorrect Adler32 value). <a href="#inflateSetDictionary">inflateSetDictionary</a> does not
766
   perform any decompression: this will be done by subsequent calls of
767
   <a href="#inflate">inflate</a>().<p>
768
 
769
<font color="Blue"><dt> int  <a name="inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
770
 
771
<dd>    Skips invalid compressed data until a full flush point (see above the
772
  description of <a href="#deflate">deflate</a> with <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>) can be found, or until all
773
  available input is skipped. No output is provided.<p>
774
 
775
    <a href="#inflateSync">inflateSync</a> returns <a href="#Z_OK">Z_OK</a> if a full flush point has been found, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a>
776
  if no more input was provided, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if no flush point has been found,
777
  or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent. In the success
778
  case, the application may save the current current value of <a href="#total_in">total_in</a> which
779
  indicates where valid compressed data was found. In the error case, the
780
  application may repeatedly call <a href="#inflateSync">inflateSync</a>, providing more input each time,
781
  until success or end of the input data.<p>
782
 
783
<font color="Blue"><dt> int  <a name="inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
784
<dd>
785
     This function is equivalent to <a href="#inflateEnd">inflateEnd</a> followed by <a href="#inflateInit">inflateInit</a>,
786
   but does not free and reallocate all the internal decompression <a href="#state">state</a>.
787
   The stream will keep attributes that may have been set by <a href="#inflateInit2">inflateInit2</a>.
788
   <p>
789
 
790
      <a href="#inflateReset">inflateReset</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source
791
   stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL).
792
   <p>
793
</dl>
794
 
795
<hr>
796
<a name="Checksum functions"><h2> Checksum functions </h2>
797
     These functions are not related to compression but are exported
798
   anyway because they might be useful in applications using the
799
   compression library.
800
<h3> Function list </h3>
801
<ul>
802
<li> uLong  <a href="#adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len);
803
<li> uLong  <a href="#crc32">crc32</a>   (uLong crc, const Bytef *buf, uInt len);
804
</ul>
805
<h3> Function description </h3>
806
<dl>
807
<font color="Blue"><dt> uLong  <a name="adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len);</font>
808
<dd>
809
     Update a running Adler-32 checksum with the bytes buf[0..len-1] and
810
   return the updated checksum. If buf is NULL, this function returns
811
   the required initial value for the checksum.
812
   <p>
813
   An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
814
   much faster. Usage example:
815
   <pre>
816
 
817
     uLong <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0);
818
 
819
     while (read_buffer(buffer, length) != EOF) {
820
       <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(<a href="#adler">adler</a>, buffer, length);
821
     }
822
     if (<a href="#adler">adler</a> != original_adler) error();
823
   </pre>
824
 
825
<font color="Blue"><dt> uLong  <a name="crc32">crc32</a>   (uLong crc, const Bytef *buf, uInt len);</font>
826
<dd>
827
     Update a running crc with the bytes buf[0..len-1] and return the updated
828
   crc. If buf is NULL, this function returns the required initial value
829
   for the crc. Pre- and post-conditioning (one's complement) is performed
830
   within this function so it shouldn't be done by the application.
831
   Usage example:
832
   <pre>
833
 
834
     uLong crc = <a href="#crc32">crc32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0);
835
 
836
     while (read_buffer(buffer, length) != EOF) {
837
       crc = <a href="#crc32">crc32</a>(crc, buffer, length);
838
     }
839
     if (crc != original_crc) error();
840
   </pre>
841
</dl>
842
<hr>
843
<a name="struct z_stream_s"><h2> struct z_stream_s </h2>
844
<font color="Blue">
845
<a name="z_stream_s">
846
<pre>
847
typedef struct z_stream_s {
848
    Bytef    *<a name="next_in">next_in</a>;  /* next input byte */
849
    uInt     <a name="avail_in">avail_in</a>;  /* number of bytes available at <a href="#next_in">next_in</a> */
850
    uLong    <a name="total_in">total_in</a>;  /* total nb of input bytes read so far */
851
 
852
    Bytef    *<a name="next_out">next_out</a>; /* next output byte should be put there */
853
    uInt     <a name="avail_out">avail_out</a>; /* remaining free space at <a href="#next_out">next_out</a> */
854
    uLong    <a name="total_out">total_out</a>; /* total nb of bytes output so far */
855
 
856
    char     *<a name="msg">msg</a>;      /* last error message, NULL if no error */
857
    struct internal_state FAR *<a name="state">state</a>; /* not visible by applications */
858
 
859
    alloc_func <a name="zalloc">zalloc</a>;  /* used to allocate the internal <a href="#state">state</a> */
860
    free_func  <a name="zfree">zfree</a>;   /* used to free the internal <a href="#state">state</a> */
861
    voidpf     <a name="opaque">opaque</a>;  /* private data object passed to <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> */
862
 
863
    int     <a name="data_type">data_type</a>;  /* best guess about the data type: ascii or binary */
864
    uLong   <a name="adler">adler</a>;      /* <a href="#adler32">adler32</a> value of the uncompressed data */
865
    uLong   <a name="reserved">reserved</a>;   /* <a href="#reserved">reserved</a> for future use */
866
} <a href="#z_stream_s">z_stream</a> ;
867
 
868
typedef <a href="#z_stream_s">z_stream</a> FAR * <a name="z_streamp">z_streamp</a>;  ÿ
869
</pre>
870
</font>
871
   The application must update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> when <a href="#avail_in">avail_in</a> has
872
   dropped to zero. It must update <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> when <a href="#avail_out">avail_out</a>
873
   has dropped to zero. The application must initialize <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and
874
   <a href="#opaque">opaque</a> before calling the init function. All other fields are set by the
875
   compression library and must not be updated by the application. <p>
876
 
877
   The <a href="#opaque">opaque</a> value provided by the application will be passed as the first
878
   parameter for calls of <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a>. This can be useful for custom
879
   memory management. The compression library attaches no meaning to the
880
   <a href="#opaque">opaque</a> value. <p>
881
 
882
   <a href="#zalloc">zalloc</a> must return <a href="#Z_NULL">Z_NULL</a> if there is not enough memory for the object.
883
   If zlib is used in a multi-threaded application, <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be
884
   thread safe. <p>
885
 
886
   On 16-bit systems, the functions <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be able to allocate
887
   exactly 65536 bytes, but will not be required to allocate more than this
888
   if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
889
   pointers returned by <a href="#zalloc">zalloc</a> for objects of exactly 65536 bytes *must*
890
   have their offset normalized to zero. The default allocation function
891
   provided by this library ensures this (see zutil.c). To reduce memory
892
   requirements and avoid any allocation of 64K objects, at the expense of
893
   compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
894
   <p>
895
 
896
   The fields <a href="#total_in">total_in</a> and <a href="#total_out">total_out</a> can be used for statistics or
897
   progress reports. After compression, <a href="#total_in">total_in</a> holds the total size of
898
   the uncompressed data and may be saved for use in the decompressor
899
   (particularly if the decompressor wants to decompress everything in
900
   a single step). <p>
901
 
902
<hr>
903
<a name="Constants"><h2> Constants </h2>
904
<font color="Blue">
905
<pre>
906
#define <a name="Z_NO_FLUSH">Z_NO_FLUSH</a>      0
907
#define <a name="Z_PARTIAL_FLUSH">Z_PARTIAL_FLUSH</a> 1
908
        /* will be removed, use <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> instead */
909
#define <a name="Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>    2
910
#define <a name="Z_FULL_FLUSH">Z_FULL_FLUSH</a>    3
911
#define <a name="Z_FINISH">Z_FINISH</a>        4
912
/* Allowed flush values ; see <a href="#deflate">deflate</a>() below for details */
913
 
914
#define <a name="Z_OK">Z_OK</a>            0
915
#define <a name="Z_STREAM_END">Z_STREAM_END</a>    1
916
#define <a name="Z_NEED_DICT">Z_NEED_DICT</a>     2
917
#define <a name="Z_ERRNO">Z_ERRNO</a>        (-1)
918
#define <a name="Z_STREAM_ERROR">Z_STREAM_ERROR</a> (-2)
919
#define <a name="Z_DATA_ERROR">Z_DATA_ERROR</a>   (-3)
920
#define <a name="Z_MEM_ERROR">Z_MEM_ERROR</a>    (-4)
921
#define <a name="Z_BUF_ERROR">Z_BUF_ERROR</a>    (-5)
922
#define <a name="Z_VERSION_ERROR">Z_VERSION_ERROR</a> (-6)
923
/* Return codes for the compression/decompression functions. Negative
924
 * values are errors, positive values are used for special but normal events.
925
 */
926
 
927
#define <a name="Z_NO_COMPRESSION">Z_NO_COMPRESSION</a>         0
928
#define <a name="Z_BEST_SPEED">Z_BEST_SPEED</a>             1
929
#define <a name="Z_BEST_COMPRESSION">Z_BEST_COMPRESSION</a>       9
930
#define <a name="Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a>  (-1)
931
/* compression levels */
932
 
933
#define <a name="Z_FILTERED">Z_FILTERED</a>            1
934
#define <a name="Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a>        2
935
#define <a name="Z_DEFAULT_STRATEGY">Z_DEFAULT_STRATEGY</a>    0
936
/* compression strategy ; see <a href="#deflateInit2">deflateInit2</a>() below for details */
937
 
938
#define <a name="Z_BINARY">Z_BINARY</a>   0
939
#define <a name="Z_ASCII">Z_ASCII</a>    1
940
#define <a name="Z_UNKNOWN">Z_UNKNOWN</a>  2
941
/* Possible values of the <a href="#data_type">data_type</a> field */
942
 
943
#define <a name="Z_DEFLATED">Z_DEFLATED</a>   8
944
/* The <a href="#deflate">deflate</a> compression method (the only one supported in this version) */
945
 
946
#define <a name="Z_NULL">Z_NULL</a>  0  /* for initializing <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a>, <a href="#opaque">opaque</a> */
947
 
948
#define <a name="zlib_version">zlib_version</a> <a href="#zlibVersion">zlibVersion</a>()
949
/* for compatibility with versions less than 1.0.2 */
950
</pre>
951
</font>
952
 
953
<hr>
954
<a name="Misc"><h2> Misc </h2>
955
 <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a> are macros to allow checking the zlib version
956
 and the compiler's view of <a href="#z_stream_s">z_stream</a>.
957
 <p>
958
 Other functions:
959
 <dl>
960
 <font color="Blue"><dt> const char   *  <a name="zError">zError</a>           (int err);</font>
961
 <font color="Blue"><dt> int             <a name="inflateSyncPoint">inflateSyncPoint</a> (<a href="#z_streamp">z_streamp</a> z);</font>
962
 <font color="Blue"><dt> const uLongf *  <a name="get_crc_table">get_crc_table</a>    (void);</font>
963
 </dl>
964
 <hr>
965
 <font size="-1">
966
 Last update: Wed Oct 13 20:42:34 1999<br>
967
 piapi@csie.ntu.edu.tw
968
 </font>
969
 
970
</body>
971
</html>

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