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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-> <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-> <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-> <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-> <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->avail_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 | ||
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