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159 zlib general purpose compression library version 1.1.4
162 <body bgcolor="White" text="Black" vlink="Red" alink="Navy" link="Red">
163 <!-- background="zlibbg.gif" -->
165 <h1> zlib 1.1.4 Manual </h1>
167 <a name="Contents"><h2>Contents</h2>
169 <li> <a href="#Prologue">Prologue</a>
170 <li> <a href="#Introduction">Introduction</a>
171 <li> <a href="#Utility functions">Utility functions</a>
172 <li> <a href="#Basic functions">Basic functions</a>
173 <li> <a href="#Advanced functions">Advanced functions</a>
174 <li> <a href="#Constants">Constants</a>
175 <li> <a href="#struct z_stream_s">struct z_stream_s</a>
176 <li> <a href="#Checksum functions">Checksum functions</a>
177 <li> <a href="#Misc">Misc</a>
180 <a name="Prologue"><h2> Prologue </h2>
181 'zlib' general purpose compression library version 1.1.4, March 11th, 2002
183 Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler
185 This software is provided 'as-is', without any express or implied
186 warranty. In no event will the authors be held liable for any damages
187 arising from the use of this software.
189 Permission is granted to anyone to use this software for any purpose,
190 including commercial applications, and to alter it and redistribute it
191 freely, subject to the following restrictions:
193 <li> The origin of this software must not be misrepresented ; you must not
194 claim that you wrote the original software. If you use this software
195 in a product, an acknowledgment in the product documentation would be
196 appreciated but is not required.
197 <li> Altered source versions must be plainly marked as such, and must not be
198 misrepresented as being the original software.
199 <li> This notice may not be removed or altered from any source distribution.
204 <dd><a href="mailto:jloup@gzip.org">jloup@gzip.org</a>
206 <dd><a href="mailto:madler@alumni.caltech.edu">madler@alumni.caltech.edu</a>
209 The data format used by the zlib library is described by RFCs (Request for
210 Comments) 1950 to 1952 in the files
211 <a href="ftp://ds.internic.net/rfc/rfc1950.txt">
212 ftp://ds.internic.net/rfc/rfc1950.txt </a>
214 <a href="ftp://ds.internic.net/rfc/rfc1951.txt">
216 (<a href="#deflate">deflate</a> format) and
217 <a href="ftp://ds.internic.net/rfc/rfc1952.txt">
221 This manual is converted from zlib.h by
222 <a href="mailto:piaip@csie.ntu.edu.tw"> piaip </a>
224 Visit <a href="http://ftp.cdrom.com/pub/infozip/zlib/">
225 http://ftp.cdrom.com/pub/infozip/zlib/</a>
226 for the official zlib web page.
230 <a name="Introduction"><h2> Introduction </h2>
231 The 'zlib' compression library provides in-memory compression and
232 decompression functions, including integrity checks of the uncompressed
233 data. This version of the library supports only one compression method
234 (deflation) but other algorithms will be added later and will have the same
238 Compression can be done in a single step if the buffers are large
239 enough (for example if an input file is mmap'ed), or can be done by
240 repeated calls of the compression function. In the latter case, the
241 application must provide more input and/or consume the output
242 (providing more output space) before each call.
245 The library also supports reading and writing files in gzip (.gz) format
246 with an interface similar to that of stdio.
249 The library does not install any signal handler. The decoder checks
250 the consistency of the compressed data, so the library should never
251 crash even in case of corrupted input.
255 <a name="Utility functions"><h2> Utility functions </h2>
256 The following utility functions are implemented on top of the
257 <a href="#Basic functions">basic stream-oriented functions</a>.
258 To simplify the interface, some
259 default options are assumed (compression level and memory usage,
260 standard memory allocation functions). The source code of these
261 utility functions can easily be modified if you need special options.
262 <h3> Function list </h3>
264 <li> int <a href="#compress">compress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);
265 <li> int <a href="#compress2">compress2</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen, int level);
266 <li> int <a href="#uncompress">uncompress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);
267 <li> typedef voidp gzFile;
268 <li> gzFile <a href="#gzopen">gzopen</a> (const char *path, const char *mode);
269 <li> gzFile <a href="#gzdopen">gzdopen</a> (int fd, const char *mode);
270 <li> int <a href="#gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy);
271 <li> int <a href="#gzread">gzread</a> (gzFile file, voidp buf, unsigned len);
272 <li> int <a href="#gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len);
273 <li> int VA <a href="#gzprintf">gzprintf</a> (gzFile file, const char *format, ...);
274 <li> int <a href="#gzputs">gzputs</a> (gzFile file, const char *s);
275 <li> char * <a href="#gzgets">gzgets</a> (gzFile file, char *buf, int len);
276 <li> int <a href="#gzputc">gzputc</a> (gzFile file, int c);
277 <li> int <a href="#gzgetc">gzgetc</a> (gzFile file);
278 <li> int <a href="#gzflush">gzflush</a> (gzFile file, int flush);
279 <li> z_off_t <a href="#gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence);
280 <li> z_off_t <a href="#gztell">gztell</a> (gzFile file);
281 <li> int <a href="#gzrewind">gzrewind</a> (gzFile file);
282 <li> int <a href="#gzeof">gzeof</a> (gzFile file);
283 <li> int <a href="#gzclose">gzclose</a> (gzFile file);
284 <li> const char * <a href="#gzerror">gzerror</a> (gzFile file, int *errnum);
286 <h3> Function description </h3>
288 <font color="Blue"><dt> int <a name="compress">compress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);</font>
290 Compresses the source buffer into the destination buffer. sourceLen is
291 the byte length of the source buffer. Upon entry, destLen is the total
292 size of the destination buffer, which must be at least 0.1% larger than
293 sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the
294 compressed buffer.<p>
295 This function can be used to <a href="#compress">compress</a> a whole file at once if the
296 input file is mmap'ed.<p>
297 <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
298 enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output
301 <font color="Blue"><dt> int <a name="compress2">compress2</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen, int level);</font>
303 Compresses the source buffer into the destination buffer. The level
304 parameter has the same meaning as in <a href="#deflateInit">deflateInit</a>. sourceLen is the byte
305 length of the source buffer. Upon entry, destLen is the total size of the
306 destination buffer, which must be at least 0.1% larger than sourceLen plus
307 12 bytes. Upon exit, destLen is the actual size of the compressed buffer.
310 <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
311 memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output buffer,
312 <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the level parameter is invalid.
315 <font color="Blue"><dt> int <a name="uncompress">uncompress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);</font>
317 Decompresses the source buffer into the destination buffer. sourceLen is
318 the byte length of the source buffer. Upon entry, destLen is the total
319 size of the destination buffer, which must be large enough to hold the
320 entire uncompressed data. (The size of the uncompressed data must have
321 been saved previously by the compressor and transmitted to the decompressor
322 by some mechanism outside the scope of this compression library.)
323 Upon exit, destLen is the actual size of the compressed buffer. <p>
324 This function can be used to decompress a whole file at once if the
325 input file is mmap'ed.
328 <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
329 enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output
330 buffer, or <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was corrupted.
333 <dt> typedef voidp gzFile;
336 <font color="Blue"><dt> gzFile <a name="gzopen">gzopen</a> (const char *path, const char *mode);</font>
338 Opens a gzip (.gz) file for reading or writing. The mode parameter
339 is as in fopen ("rb" or "wb") but can also include a compression level
340 ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
341 Huffman only compression as in "wb1h". (See the description
342 of <a href="#deflateInit2">deflateInit2</a> for more information about the strategy parameter.)
345 <a href="#gzopen">gzopen</a> can be used to read a file which is not in gzip format ; in this
346 case <a href="#gzread">gzread</a> will directly read from the file without decompression.
349 <a href="#gzopen">gzopen</a> returns NULL if the file could not be opened or if there was
350 insufficient memory to allocate the (de)compression <a href="#state">state</a> ; errno
351 can be checked to distinguish the two cases (if errno is zero, the
352 zlib error is <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a>).
355 <font color="Blue"><dt> gzFile <a name="gzdopen">gzdopen</a> (int fd, const char *mode);</font>
357 <a href="#gzdopen">gzdopen</a>() associates a gzFile with the file descriptor fd. File
358 descriptors are obtained from calls like open, dup, creat, pipe or
359 fileno (in the file has been previously opened with fopen).
360 The mode parameter is as in <a href="#gzopen">gzopen</a>.
362 The next call of <a href="#gzclose">gzclose</a> on the returned gzFile will also close the
363 file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
364 descriptor fd. If you want to keep fd open, use <a href="#gzdopen">gzdopen</a>(dup(fd), mode).
366 <a href="#gzdopen">gzdopen</a> returns NULL if there was insufficient memory to allocate
367 the (de)compression <a href="#state">state</a>.
370 <font color="Blue"><dt> int <a name="gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy);</font>
372 Dynamically update the compression level or strategy. See the description
373 of <a href="#deflateInit2">deflateInit2</a> for the meaning of these parameters.
375 <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
379 <font color="Blue"><dt> int <a name="gzread">gzread</a> (gzFile file, voidp buf, unsigned len);</font>
381 Reads the given number of uncompressed bytes from the compressed file.
382 If the input file was not in gzip format, <a href="#gzread">gzread</a> copies the given number
383 of bytes into the buffer.
385 <a href="#gzread">gzread</a> returns the number of uncompressed bytes actually read (0 for
386 end of file, -1 for error).
389 <font color="Blue"><dt> int <a name="gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len);</font>
391 Writes the given number of uncompressed bytes into the compressed file.
392 <a href="#gzwrite">gzwrite</a> returns the number of uncompressed bytes actually written
393 (0 in case of error).
396 <font color="Blue"><dt> int VA <a name="gzprintf">gzprintf</a> (gzFile file, const char *format, ...);</font>
398 Converts, formats, and writes the args to the compressed file under
399 control of the format string, as in fprintf. <a href="#gzprintf">gzprintf</a> returns the number of
400 uncompressed bytes actually written (0 in case of error).
403 <font color="Blue"><dt> int <a name="gzputs">gzputs</a> (gzFile file, const char *s);</font>
405 Writes the given null-terminated string to the compressed file, excluding
406 the terminating null character.
408 <a href="#gzputs">gzputs</a> returns the number of characters written, or -1 in case of error.
411 <font color="Blue"><dt> char * <a name="gzgets">gzgets</a> (gzFile file, char *buf, int len);</font>
413 Reads bytes from the compressed file until len-1 characters are read, or
414 a newline character is read and transferred to buf, or an end-of-file
415 condition is encountered. The string is then terminated with a null
418 <a href="#gzgets">gzgets</a> returns buf, or <a href="#Z_NULL">Z_NULL</a> in case of error.
421 <font color="Blue"><dt> int <a name="gzputc">gzputc</a> (gzFile file, int c);</font>
423 Writes c, converted to an unsigned char, into the compressed file.
424 <a href="#gzputc">gzputc</a> returns the value that was written, or -1 in case of error.
427 <font color="Blue"><dt> int <a name="gzgetc">gzgetc</a> (gzFile file);</font>
429 Reads one byte from the compressed file. <a href="#gzgetc">gzgetc</a> returns this byte
430 or -1 in case of end of file or error.
433 <font color="Blue"><dt> int <a name="gzflush">gzflush</a> (gzFile file, int flush);</font>
435 Flushes all pending output into the compressed file. The parameter
436 flush is as in the <a href="#deflate">deflate</a>() function. The return value is the zlib
437 error number (see function <a href="#gzerror">gzerror</a> below). <a href="#gzflush">gzflush</a> returns <a href="#Z_OK">Z_OK</a> if
438 the flush parameter is <a href="#Z_FINISH">Z_FINISH</a> and all output could be flushed.
440 <a href="#gzflush">gzflush</a> should be called only when strictly necessary because it can
444 <font color="Blue"><dt> z_off_t <a name="gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence);</font>
446 Sets the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the
447 given compressed file. The offset represents a number of bytes in the
448 uncompressed data stream. The whence parameter is defined as in lseek(2);
449 the value SEEK_END is not supported.
451 If the file is opened for reading, this function is emulated but can be
452 extremely slow. If the file is opened for writing, only forward seeks are
453 supported ; <a href="#gzseek">gzseek</a> then compresses a sequence of zeroes up to the new
456 <a href="#gzseek">gzseek</a> returns the resulting offset location as measured in bytes from
457 the beginning of the uncompressed stream, or -1 in case of error, in
458 particular if the file is opened for writing and the new starting position
459 would be before the current position.
462 <font color="Blue"><dt> int <a name="gzrewind">gzrewind</a> (gzFile file);</font>
464 Rewinds the given file. This function is supported only for reading.
466 <a href="#gzrewind">gzrewind</a>(file) is equivalent to (int)<a href="#gzseek">gzseek</a>(file, 0L, SEEK_SET)
469 <font color="Blue"><dt> z_off_t <a name="gztell">gztell</a> (gzFile file);</font>
471 Returns the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the
472 given compressed file. This position represents a number of bytes in the
473 uncompressed data stream.
476 <a href="#gztell">gztell</a>(file) is equivalent to <a href="#gzseek">gzseek</a>(file, 0L, SEEK_CUR)
479 <font color="Blue"><dt> int <a name="gzeof">gzeof</a> (gzFile file);</font>
481 Returns 1 when EOF has previously been detected reading the given
482 input stream, otherwise zero.
485 <font color="Blue"><dt> int <a name="gzclose">gzclose</a> (gzFile file);</font>
487 Flushes all pending output if necessary, closes the compressed file
488 and deallocates all the (de)compression <a href="#state">state</a>. The return value is the zlib
489 error number (see function <a href="#gzerror">gzerror</a> below).
492 <font color="Blue"><dt> const char * <a name="gzerror">gzerror</a> (gzFile file, int *errnum);</font>
494 Returns the error message for the last error which occurred on the
495 given compressed file. errnum is set to zlib error number. If an
496 error occurred in the file system and not in the compression library,
497 errnum is set to <a href="#Z_ERRNO">Z_ERRNO</a> and the application may consult errno
498 to get the exact error code.
502 <a name="Basic functions"><h2> Basic functions </h2>
503 <h3> Function list </h3>
505 <li> const char * <a href="#zlibVersion">zlibVersion</a> (void);
506 <li> int <a href="#deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level);
507 <li> int <a href="#deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);
508 <li> int <a href="#deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);
509 <li> int <a href="#inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm);
510 <li> int <a href="#inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);
511 <li> int <a href="#inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);
514 <h3> Function description </h3>
516 <font color="Blue"><dt> const char * <a name="zlibVersion">zlibVersion</a> (void);</font>
517 <dd> The application can compare <a href="#zlibVersion">zlibVersion</a> and ZLIB_VERSION for consistency.
518 If the first character differs, the library code actually used is
519 not compatible with the zlib.h header file used by the application.
520 This check is automatically made by <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a>.
523 <font color="Blue"><dt> int <a name="deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level);</font>
525 Initializes the internal stream <a href="#state">state</a> for compression. The fields
526 <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by the caller.
527 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
528 use default allocation functions.
531 The compression level must be <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a>, or between 0 and 9:
532 1 gives best speed, 9 gives best compression, 0 gives no compression at
533 all (the input data is simply copied a block at a time).
536 <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a> requests a default compromise between speed and
537 compression (currently equivalent to level 6).
540 <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
541 enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if level is not a valid compression level,
542 <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version (<a href="#zlib_version">zlib_version</a>) is incompatible
543 with the version assumed by the caller (ZLIB_VERSION).
544 <a href="#msg">msg</a> is set to null if there is no error message. <a href="#deflateInit">deflateInit</a> does not
545 perform any compression: this will be done by <a href="#deflate">deflate</a>().
548 <font color="Blue"><dt> int <a name="deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font>
550 <a href="#deflate">deflate</a> compresses as much data as possible, and stops when the input
551 buffer becomes empty or the output buffer becomes full. It may introduce some
552 output latency (reading input without producing any output) except when
555 The detailed semantics are as follows. <a href="#deflate">deflate</a> performs one or both of the
559 <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>
560 accordingly. If not all input can be processed (because there is not
561 enough room in the output buffer), <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> are updated and
562 processing will resume at this point for the next call of <a href="#deflate">deflate</a>().
565 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>
566 accordingly. This action is forced if the parameter flush is non zero.
567 Forcing flush frequently degrades the compression ratio, so this parameter
568 should be set only when necessary (in interactive applications).
569 Some output may be provided even if flush is not set.
572 Before the call of <a href="#deflate">deflate</a>(), the application should ensure that at least
573 one of the actions is possible, by providing more input and/or consuming
574 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>
575 should never be zero before the call. The application can consume the
576 compressed output when it wants, for example when the output buffer is full
577 (<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>
578 and with zero <a href="#avail_out">avail_out</a>, it must be called again after making room in the
579 output buffer because there might be more output pending.
582 If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, all pending output is
583 flushed to the output buffer and the output is aligned on a byte boundary, so
584 that the decompressor can get all input data available so far. (In particular
585 <a href="#avail_in">avail_in</a> is zero after the call if enough output space has been provided
586 before the call.) Flushing may degrade compression for some compression
587 algorithms and so it should be used only when necessary.
590 If flush is set to <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>, all output is flushed as with
591 <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, and the compression <a href="#state">state</a> is reset so that decompression can
592 restart from this point if previous compressed data has been damaged or if
593 random access is desired. Using <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a> too often can seriously degrade
597 If <a href="#deflate">deflate</a> returns with <a href="#avail_out">avail_out</a> == 0, this function must be called again
598 with the same value of the flush parameter and more output space (updated
599 <a href="#avail_out">avail_out</a>), until the flush is complete (<a href="#deflate">deflate</a> returns with non-zero
600 <a href="#avail_out">avail_out</a>).
603 If the parameter flush is set to <a href="#Z_FINISH">Z_FINISH</a>, pending input is processed,
604 pending output is flushed and <a href="#deflate">deflate</a> returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> if there
605 was enough output space ; if <a href="#deflate">deflate</a> returns with <a href="#Z_OK">Z_OK</a>, this function must be
606 called again with <a href="#Z_FINISH">Z_FINISH</a> and more output space (updated <a href="#avail_out">avail_out</a>) but no
607 more input data, until it returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> or an error. After
608 <a href="#deflate">deflate</a> has returned <a href="#Z_STREAM_END">Z_STREAM_END</a>, the only possible operations on the
609 stream are <a href="#deflateReset">deflateReset</a> or <a href="#deflateEnd">deflateEnd</a>.
612 <a href="#Z_FINISH">Z_FINISH</a> can be used immediately after <a href="#deflateInit">deflateInit</a> if all the compression
613 is to be done in a single step. In this case, <a href="#avail_out">avail_out</a> must be at least
614 0.1% larger than <a href="#avail_in">avail_in</a> plus 12 bytes. If <a href="#deflate">deflate</a> does not return
615 <a href="#Z_STREAM_END">Z_STREAM_END</a>, then it must be called again as described above.
618 <a href="#deflate">deflate</a>() sets strm-> <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all input read
619 so far (that is, <a href="#total_in">total_in</a> bytes).
622 <a href="#deflate">deflate</a>() may update <a href="#data_type">data_type</a> if it can make a good guess about
623 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
624 binary. This field is only for information purposes and does not affect
625 the compression algorithm in any manner.
628 <a href="#deflate">deflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input
629 processed or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if all input has been
630 consumed and all output has been produced (only when flush is set to
631 <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
632 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
633 (for example <a href="#avail_in">avail_in</a> or <a href="#avail_out">avail_out</a> was zero).
636 <font color="Blue"><dt> int <a name="deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
638 All dynamically allocated data structures for this stream are freed.
639 This function discards any unprocessed input and does not flush any
643 <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
644 stream <a href="#state">state</a> was inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the stream was freed
645 prematurely (some input or output was discarded). In the error case,
646 <a href="#msg">msg</a> may be set but then points to a static string (which must not be
650 <font color="Blue"><dt> int <a name="inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
652 Initializes the internal stream <a href="#state">state</a> for decompression. The fields
653 <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
654 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
655 value depends on the compression method), <a href="#inflateInit">inflateInit</a> determines the
656 compression method from the zlib header and allocates all data structures
657 accordingly ; otherwise the allocation will be deferred to the first call of
658 <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
659 use default allocation functions.
662 <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
663 memory, <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version is incompatible with the
664 version assumed by the caller. <a href="#msg">msg</a> is set to null if there is no error
665 message. <a href="#inflateInit">inflateInit</a> does not perform any decompression apart from reading
666 the zlib header if present: this will be done by <a href="#inflate">inflate</a>(). (So <a href="#next_in">next_in</a> and
667 <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.)
670 <font color="Blue"><dt> int <a name="inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font>
672 <a href="#inflate">inflate</a> decompresses as much data as possible, and stops when the input
673 buffer becomes empty or the output buffer becomes full. It may some
674 introduce some output latency (reading input without producing any output)
675 except when forced to flush.
678 The detailed semantics are as follows. <a href="#inflate">inflate</a> performs one or both of the
682 <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>
683 accordingly. If not all input can be processed (because there is not
684 enough room in the output buffer), <a href="#next_in">next_in</a> is updated and processing
685 will resume at this point for the next call of <a href="#inflate">inflate</a>().
687 <li> Provide more output starting at <a href="#next_out">next_out</a> and update <a href="#next_out">next_out</a> and
688 <a href="#avail_out">avail_out</a> accordingly. <a href="#inflate">inflate</a>() provides as much output as possible,
689 until there is no more input data or no more space in the output buffer
690 (see below about the flush parameter).
693 Before the call of <a href="#inflate">inflate</a>(), the application should ensure that at least
694 one of the actions is possible, by providing more input and/or consuming
695 more output, and updating the next_* and avail_* values accordingly.
696 The application can consume the uncompressed output when it wants, for
697 example when the output buffer is full (<a href="#avail_out">avail_out</a> == 0), or after each
698 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
699 must be called again after making room in the output buffer because there
700 might be more output pending.
703 If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, <a href="#inflate">inflate</a> flushes as much
704 output as possible to the output buffer. The flushing behavior of <a href="#inflate">inflate</a> is
705 not specified for values of the flush parameter other than <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>
706 and <a href="#Z_FINISH">Z_FINISH</a>, but the current implementation actually flushes as much output
710 <a href="#inflate">inflate</a>() should normally be called until it returns <a href="#Z_STREAM_END">Z_STREAM_END</a> or an
711 error. However if all decompression is to be performed in a single step
712 (a single call of <a href="#inflate">inflate</a>), the parameter flush should be set to
713 <a href="#Z_FINISH">Z_FINISH</a>. In this case all pending input is processed and all pending
714 output is flushed ; <a href="#avail_out">avail_out</a> must be large enough to hold all the
715 uncompressed data. (The size of the uncompressed data may have been saved
716 by the compressor for this purpose.) The next operation on this stream must
717 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>
718 is never required, but can be used to inform <a href="#inflate">inflate</a> that a faster routine
719 may be used for the single <a href="#inflate">inflate</a>() call.
722 If a preset dictionary is needed at this point (see <a href="#inflateSetDictionary">inflateSetDictionary</a>
723 below), <a href="#inflate">inflate</a> sets strm-<a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of the
724 dictionary chosen by the compressor and returns <a href="#Z_NEED_DICT">Z_NEED_DICT</a> ; otherwise
725 it sets strm-> <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all output produced
726 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
727 an error code as described below. At the end of the stream, <a href="#inflate">inflate</a>()
728 checks that its computed <a href="#adler32">adler32</a> checksum is equal to that saved by the
729 compressor and returns <a href="#Z_STREAM_END">Z_STREAM_END</a> only if the checksum is correct.
732 <a href="#inflate">inflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input processed
733 or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if the end of the compressed data has
734 been reached and all uncompressed output has been produced, <a href="#Z_NEED_DICT">Z_NEED_DICT</a> if a
735 preset dictionary is needed at this point, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was
736 corrupted (input stream not conforming to the zlib format or incorrect
737 <a href="#adler32">adler32</a> checksum), <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent
738 (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
739 enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if no progress is possible or if there was not
740 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>
741 case, the application may then call <a href="#inflateSync">inflateSync</a> to look for a good
745 <font color="Blue"><dt> int <a name="inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
747 All dynamically allocated data structures for this stream are freed.
748 This function discards any unprocessed input and does not flush any
752 <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>
753 was inconsistent. In the error case, <a href="#msg">msg</a> may be set but then points to a
754 static string (which must not be deallocated).
757 <a name="Advanced functions"><h2> Advanced functions </h2>
758 The following functions are needed only in some special applications.
759 <h3> Function list </h3>
761 <li> int <a href="#deflateInit2">deflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm,
762 <li> int <a href="#deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength);
763 <li> int <a href="#deflateCopy">deflateCopy</a> (<a href="#z_streamp">z_streamp</a> dest, <a href="#z_streamp">z_streamp</a> source);
764 <li> int <a href="#deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);
765 <li> int <a href="#deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy);
766 <li> int <a href="#inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int windowBits);
767 <li> int <a href="#inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength);
768 <li> int <a href="#inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm);
769 <li> int <a href="#inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);
772 <h3> Function description </h3>
774 <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>
776 <dd> This is another version of <a href="#deflateInit">deflateInit</a> with more compression options. The
777 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
780 The method parameter is the compression method. It must be <a href="#Z_DEFLATED">Z_DEFLATED</a> in
781 this version of the library.<p>
783 The windowBits parameter is the base two logarithm of the window size
784 (the size of the history buffer). It should be in the range 8..15 for this
785 version of the library. Larger values of this parameter result in better
786 compression at the expense of memory usage. The default value is 15 if
787 <a href="#deflateInit">deflateInit</a> is used instead.<p>
789 The memLevel parameter specifies how much memory should be allocated
790 for the internal compression <a href="#state">state</a>. memLevel=1 uses minimum memory but
791 is slow and reduces compression ratio ; memLevel=9 uses maximum memory
792 for optimal speed. The default value is 8. See zconf.h for total memory
793 usage as a function of windowBits and memLevel.<p>
795 The strategy parameter is used to tune the compression algorithm. Use the
796 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
797 filter (or predictor), or <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a> to force Huffman encoding only (no
798 string match). Filtered data consists mostly of small values with a
799 somewhat random distribution. In this case, the compression algorithm is
800 tuned to <a href="#compress">compress</a> them better. The effect of <a href="#Z_FILTERED">Z_FILTERED</a> is to force more
801 Huffman coding and less string matching ; it is somewhat intermediate
802 between Z_DEFAULT and <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a>. The strategy parameter only affects
803 the compression ratio but not the correctness of the compressed output even
804 if it is not set appropriately.<p>
806 <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
807 memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as an invalid
808 method). <a href="#msg">msg</a> is set to null if there is no error message. <a href="#deflateInit2">deflateInit2</a> does
809 not perform any compression: this will be done by <a href="#deflate">deflate</a>().<p>
811 <font color="Blue"><dt> int <a name="deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength);</font>
813 Initializes the compression dictionary from the given byte sequence
814 without producing any compressed output. This function must be called
815 immediately after <a href="#deflateInit">deflateInit</a>, <a href="#deflateInit2">deflateInit2</a> or <a href="#deflateReset">deflateReset</a>, before any
816 call of <a href="#deflate">deflate</a>. The compressor and decompressor must use exactly the same
817 dictionary (see <a href="#inflateSetDictionary">inflateSetDictionary</a>).<p>
819 The dictionary should consist of strings (byte sequences) that are likely
820 to be encountered later in the data to be compressed, with the most commonly
821 used strings preferably put towards the end of the dictionary. Using a
822 dictionary is most useful when the data to be compressed is short and can be
823 predicted with good accuracy ; the data can then be compressed better than
824 with the default empty dictionary.<p>
826 Depending on the size of the compression data structures selected by
827 <a href="#deflateInit">deflateInit</a> or <a href="#deflateInit2">deflateInit2</a>, a part of the dictionary may in effect be
828 discarded, for example if the dictionary is larger than the window size in
829 <a href="#deflate">deflate</a> or deflate2. Thus the strings most likely to be useful should be
830 put at the end of the dictionary, not at the front.<p>
832 Upon return of this function, strm-> <a href="#adler">adler</a> is set to the Adler32 value
833 of the dictionary ; the decompressor may later use this value to determine
834 which dictionary has been used by the compressor. (The Adler32 value
835 applies to the whole dictionary even if only a subset of the dictionary is
836 actually used by the compressor.)<p>
838 <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
839 parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is
840 inconsistent (for example if <a href="#deflate">deflate</a> has already been called for this stream
841 or if the compression method is bsort). <a href="#deflateSetDictionary">deflateSetDictionary</a> does not
842 perform any compression: this will be done by <a href="#deflate">deflate</a>().<p>
844 <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>
846 Sets the destination stream as a complete copy of the source stream.<p>
848 This function can be useful when several compression strategies will be
849 tried, for example when there are several ways of pre-processing the input
850 data with a filter. The streams that will be discarded should then be freed
851 by calling <a href="#deflateEnd">deflateEnd</a>. Note that <a href="#deflateCopy">deflateCopy</a> duplicates the internal
852 compression <a href="#state">state</a> which can be quite large, so this strategy is slow and
853 can consume lots of memory.<p>
855 <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
856 enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source stream <a href="#state">state</a> was inconsistent
857 (such as <a href="#zalloc">zalloc</a> being NULL). <a href="#msg">msg</a> is left unchanged in both source and
860 <font color="Blue"><dt> int <a name="deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
861 <dd> This function is equivalent to <a href="#deflateEnd">deflateEnd</a> followed by <a href="#deflateInit">deflateInit</a>,
862 but does not free and reallocate all the internal compression <a href="#state">state</a>.
863 The stream will keep the same compression level and any other attributes
864 that may have been set by <a href="#deflateInit2">deflateInit2</a>.<p>
866 <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
867 stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL).<p>
869 <font color="Blue"><dt> int <a name="deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy);</font>
871 Dynamically update the compression level and compression strategy. The
872 interpretation of level and strategy is as in <a href="#deflateInit2">deflateInit2</a>. This can be
873 used to switch between compression and straight copy of the input data, or
874 to switch to a different kind of input data requiring a different
875 strategy. If the compression level is changed, the input available so far
876 is compressed with the old level (and may be flushed); the new level will
877 take effect only at the next call of <a href="#deflate">deflate</a>().<p>
879 Before the call of <a href="#deflateParams">deflateParams</a>, the stream <a href="#state">state</a> must be set as for
880 a call of <a href="#deflate">deflate</a>(), since the currently available input may have to
881 be compressed and flushed. In particular, strm-> <a href="#avail_out">avail_out</a> must be
884 <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
885 stream <a href="#state">state</a> was inconsistent or if a parameter was invalid, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a>
886 if strm->avail_out was zero.<p>
888 <font color="Blue"><dt> int <a name="inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int windowBits);</font>
890 <dd> This is another version of <a href="#inflateInit">inflateInit</a> with an extra parameter. The
891 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
892 before by the caller.<p>
894 The windowBits parameter is the base two logarithm of the maximum window
895 size (the size of the history buffer). It should be in the range 8..15 for
896 this version of the library. The default value is 15 if <a href="#inflateInit">inflateInit</a> is used
897 instead. If a compressed stream with a larger window size is given as
898 input, <a href="#inflate">inflate</a>() will return with the error code <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> instead of
899 trying to allocate a larger window.<p>
901 <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
902 memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as a negative
903 memLevel). <a href="#msg">msg</a> is set to null if there is no error message. <a href="#inflateInit2">inflateInit2</a>
904 does not perform any decompression apart from reading the zlib header if
905 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
906 modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.)<p>
908 <font color="Blue"><dt> int <a name="inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength);</font>
910 Initializes the decompression dictionary from the given uncompressed byte
911 sequence. This function must be called immediately after a call of <a href="#inflate">inflate</a>
912 if this call returned <a href="#Z_NEED_DICT">Z_NEED_DICT</a>. The dictionary chosen by the compressor
913 can be determined from the Adler32 value returned by this call of
914 <a href="#inflate">inflate</a>. The compressor and decompressor must use exactly the same
915 dictionary (see <a href="#deflateSetDictionary">deflateSetDictionary</a>).<p>
917 <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
918 parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is
919 inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the given dictionary doesn't match the
920 expected one (incorrect Adler32 value). <a href="#inflateSetDictionary">inflateSetDictionary</a> does not
921 perform any decompression: this will be done by subsequent calls of
922 <a href="#inflate">inflate</a>().<p>
924 <font color="Blue"><dt> int <a name="inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
926 <dd> Skips invalid compressed data until a full flush point (see above the
927 description of <a href="#deflate">deflate</a> with <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>) can be found, or until all
928 available input is skipped. No output is provided.<p>
930 <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>
931 if no more input was provided, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if no flush point has been found,
932 or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent. In the success
933 case, the application may save the current current value of <a href="#total_in">total_in</a> which
934 indicates where valid compressed data was found. In the error case, the
935 application may repeatedly call <a href="#inflateSync">inflateSync</a>, providing more input each time,
936 until success or end of the input data.<p>
938 <font color="Blue"><dt> int <a name="inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
940 This function is equivalent to <a href="#inflateEnd">inflateEnd</a> followed by <a href="#inflateInit">inflateInit</a>,
941 but does not free and reallocate all the internal decompression <a href="#state">state</a>.
942 The stream will keep attributes that may have been set by <a href="#inflateInit2">inflateInit2</a>.
945 <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
946 stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL).
951 <a name="Checksum functions"><h2> Checksum functions </h2>
952 These functions are not related to compression but are exported
953 anyway because they might be useful in applications using the
955 <h3> Function list </h3>
957 <li> uLong <a href="#adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len);
958 <li> uLong <a href="#crc32">crc32</a> (uLong crc, const Bytef *buf, uInt len);
960 <h3> Function description </h3>
962 <font color="Blue"><dt> uLong <a name="adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len);</font>
964 Update a running Adler-32 checksum with the bytes buf[0..len-1] and
965 return the updated checksum. If buf is NULL, this function returns
966 the required initial value for the checksum.
968 An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
969 much faster. Usage example:
972 uLong <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0);
974 while (read_buffer(buffer, length) != EOF) {
975 <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(<a href="#adler">adler</a>, buffer, length);
977 if (<a href="#adler">adler</a> != original_adler) error();
980 <font color="Blue"><dt> uLong <a name="crc32">crc32</a> (uLong crc, const Bytef *buf, uInt len);</font>
982 Update a running crc with the bytes buf[0..len-1] and return the updated
983 crc. If buf is NULL, this function returns the required initial value
984 for the crc. Pre- and post-conditioning (one's complement) is performed
985 within this function so it shouldn't be done by the application.
989 uLong crc = <a href="#crc32">crc32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0);
991 while (read_buffer(buffer, length) != EOF) {
992 crc = <a href="#crc32">crc32</a>(crc, buffer, length);
994 if (crc != original_crc) error();
998 <a name="struct z_stream_s"><h2> struct z_stream_s </h2>
1000 <a name="z_stream_s">
1002 typedef struct z_stream_s {
1003 Bytef *<a name="next_in">next_in</a>; /* next input byte */
1004 uInt <a name="avail_in">avail_in</a>; /* number of bytes available at <a href="#next_in">next_in</a> */
1005 uLong <a name="total_in">total_in</a>; /* total nb of input bytes read so far */
1007 Bytef *<a name="next_out">next_out</a>; /* next output byte should be put there */
1008 uInt <a name="avail_out">avail_out</a>; /* remaining free space at <a href="#next_out">next_out</a> */
1009 uLong <a name="total_out">total_out</a>; /* total nb of bytes output so far */
1011 char *<a name="msg">msg</a>; /* last error message, NULL if no error */
1012 struct internal_state FAR *<a name="state">state</a>; /* not visible by applications */
1014 alloc_func <a name="zalloc">zalloc</a>; /* used to allocate the internal <a href="#state">state</a> */
1015 free_func <a name="zfree">zfree</a>; /* used to free the internal <a href="#state">state</a> */
1016 voidpf <a name="opaque">opaque</a>; /* private data object passed to <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> */
1018 int <a name="data_type">data_type</a>; /* best guess about the data type: ascii or binary */
1019 uLong <a name="adler">adler</a>; /* <a href="#adler32">adler32</a> value of the uncompressed data */
1020 uLong <a name="reserved">reserved</a>; /* <a href="#reserved">reserved</a> for future use */
1021 } <a href="#z_stream_s">z_stream</a> ;
1023 typedef <a href="#z_stream_s">z_stream</a> FAR * <a name="z_streamp">z_streamp</a>; ΓΏ
1026 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
1027 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>
1028 has dropped to zero. The application must initialize <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and
1029 <a href="#opaque">opaque</a> before calling the init function. All other fields are set by the
1030 compression library and must not be updated by the application. <p>
1032 The <a href="#opaque">opaque</a> value provided by the application will be passed as the first
1033 parameter for calls of <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a>. This can be useful for custom
1034 memory management. The compression library attaches no meaning to the
1035 <a href="#opaque">opaque</a> value. <p>
1037 <a href="#zalloc">zalloc</a> must return <a href="#Z_NULL">Z_NULL</a> if there is not enough memory for the object.
1038 If zlib is used in a multi-threaded application, <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be
1041 On 16-bit systems, the functions <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be able to allocate
1042 exactly 65536 bytes, but will not be required to allocate more than this
1043 if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
1044 pointers returned by <a href="#zalloc">zalloc</a> for objects of exactly 65536 bytes *must*
1045 have their offset normalized to zero. The default allocation function
1046 provided by this library ensures this (see zutil.c). To reduce memory
1047 requirements and avoid any allocation of 64K objects, at the expense of
1048 compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
1051 The fields <a href="#total_in">total_in</a> and <a href="#total_out">total_out</a> can be used for statistics or
1052 progress reports. After compression, <a href="#total_in">total_in</a> holds the total size of
1053 the uncompressed data and may be saved for use in the decompressor
1054 (particularly if the decompressor wants to decompress everything in
1058 <a name="Constants"><h2> Constants </h2>
1061 #define <a name="Z_NO_FLUSH">Z_NO_FLUSH</a> 0
1062 #define <a name="Z_PARTIAL_FLUSH">Z_PARTIAL_FLUSH</a> 1
1063 /* will be removed, use <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> instead */
1064 #define <a name="Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> 2
1065 #define <a name="Z_FULL_FLUSH">Z_FULL_FLUSH</a> 3
1066 #define <a name="Z_FINISH">Z_FINISH</a> 4
1067 /* Allowed flush values ; see <a href="#deflate">deflate</a>() below for details */
1069 #define <a name="Z_OK">Z_OK</a> 0
1070 #define <a name="Z_STREAM_END">Z_STREAM_END</a> 1
1071 #define <a name="Z_NEED_DICT">Z_NEED_DICT</a> 2
1072 #define <a name="Z_ERRNO">Z_ERRNO</a> (-1)
1073 #define <a name="Z_STREAM_ERROR">Z_STREAM_ERROR</a> (-2)
1074 #define <a name="Z_DATA_ERROR">Z_DATA_ERROR</a> (-3)
1075 #define <a name="Z_MEM_ERROR">Z_MEM_ERROR</a> (-4)
1076 #define <a name="Z_BUF_ERROR">Z_BUF_ERROR</a> (-5)
1077 #define <a name="Z_VERSION_ERROR">Z_VERSION_ERROR</a> (-6)
1078 /* Return codes for the compression/decompression functions. Negative
1079 * values are errors, positive values are used for special but normal events.
1082 #define <a name="Z_NO_COMPRESSION">Z_NO_COMPRESSION</a> 0
1083 #define <a name="Z_BEST_SPEED">Z_BEST_SPEED</a> 1
1084 #define <a name="Z_BEST_COMPRESSION">Z_BEST_COMPRESSION</a> 9
1085 #define <a name="Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a> (-1)
1086 /* compression levels */
1088 #define <a name="Z_FILTERED">Z_FILTERED</a> 1
1089 #define <a name="Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a> 2
1090 #define <a name="Z_DEFAULT_STRATEGY">Z_DEFAULT_STRATEGY</a> 0
1091 /* compression strategy ; see <a href="#deflateInit2">deflateInit2</a>() below for details */
1093 #define <a name="Z_BINARY">Z_BINARY</a> 0
1094 #define <a name="Z_ASCII">Z_ASCII</a> 1
1095 #define <a name="Z_UNKNOWN">Z_UNKNOWN</a> 2
1096 /* Possible values of the <a href="#data_type">data_type</a> field */
1098 #define <a name="Z_DEFLATED">Z_DEFLATED</a> 8
1099 /* The <a href="#deflate">deflate</a> compression method (the only one supported in this version) */
1101 #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> */
1103 #define <a name="zlib_version">zlib_version</a> <a href="#zlibVersion">zlibVersion</a>()
1104 /* for compatibility with versions less than 1.0.2 */
1109 <a name="Misc"><h2> Misc </h2>
1110 <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a> are macros to allow checking the zlib version
1111 and the compiler's view of <a href="#z_stream_s">z_stream</a>.
1115 <font color="Blue"><dt> const char * <a name="zError">zError</a> (int err);</font>
1116 <font color="Blue"><dt> int <a name="inflateSyncPoint">inflateSyncPoint</a> (<a href="#z_streamp">z_streamp</a> z);</font>
1117 <font color="Blue"><dt> const uLongf * <a name="get_crc_table">get_crc_table</a> (void);</font>
1121 Last update: Wed Oct 13 20:42:34 1999<br>
1122 piapi@csie.ntu.edu.tw
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