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1<html>
2<head>
3 <title>
4 zlib general purpose compression library version 1.1.4
5 </title>
6</head>
7<body bgcolor="White" text="Black" vlink="Red" alink="Navy" link="Red">
8<!-- background="zlibbg.gif" -->
9
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>
847typedef 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
868typedef <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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