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<html>
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<head>
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 <title>
4 
 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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10 
<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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