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<html> |
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<head> |
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<title> |
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zlib general purpose compression library version 1.1.4 |
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</title> |
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</head> |
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<body bgcolor="White" text="Black" vlink="Red" alink="Navy" link="Red"> |
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<!-- background="zlibbg.gif" --> |
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|
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<h1> zlib 1.1.4 Manual </h1> |
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<hr> |
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<a name="Contents"><h2>Contents</h2> |
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<ol type="I"> |
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<li> <a href="#Prologue">Prologue</a> |
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<li> <a href="#Introduction">Introduction</a> |
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<li> <a href="#Utility functions">Utility functions</a> |
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<li> <a href="#Basic functions">Basic functions</a> |
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<li> <a href="#Advanced functions">Advanced functions</a> |
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<li> <a href="#Constants">Constants</a> |
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<li> <a href="#struct z_stream_s">struct z_stream_s</a> |
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<li> <a href="#Checksum functions">Checksum functions</a> |
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<li> <a href="#Misc">Misc</a> |
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</ol> |
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<hr> |
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<a name="Prologue"><h2> Prologue </h2> |
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'zlib' general purpose compression library version 1.1.4, March 11th, 2002 |
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<p> |
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Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler |
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<p> |
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This software is provided 'as-is', without any express or implied |
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warranty. In no event will the authors be held liable for any damages |
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arising from the use of this software. |
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<p> |
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Permission is granted to anyone to use this software for any purpose, |
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including commercial applications, and to alter it and redistribute it |
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freely, subject to the following restrictions: |
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<ol> |
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<li> The origin of this software must not be misrepresented ; you must not |
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claim that you wrote the original software. If you use this software |
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in a product, an acknowledgment in the product documentation would be |
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appreciated but is not required. |
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<li> Altered source versions must be plainly marked as such, and must not be |
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misrepresented as being the original software. |
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<li> This notice may not be removed or altered from any source distribution. |
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</ol> |
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|
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<dl> |
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<dt>Jean-loup Gailly |
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<dd><a href="mailto:jloup@gzip.org">jloup@gzip.org</a> |
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<dt>Mark Adler |
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<dd><a href="mailto:madler@alumni.caltech.edu">madler@alumni.caltech.edu</a> |
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</dl> |
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|
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The data format used by the zlib library is described by RFCs (Request for |
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Comments) 1950 to 1952 in the files |
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<a href="ftp://ds.internic.net/rfc/rfc1950.txt"> |
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ftp://ds.internic.net/rfc/rfc1950.txt </a> |
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(zlib format), |
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<a href="ftp://ds.internic.net/rfc/rfc1951.txt"> |
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rfc1951.txt </a> |
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(<a href="#deflate">deflate</a> format) and |
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<a href="ftp://ds.internic.net/rfc/rfc1952.txt"> |
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rfc1952.txt </a> |
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(gzip format). |
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<p> |
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This manual is converted from zlib.h by |
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<a href="mailto:piaip@csie.ntu.edu.tw"> piaip </a> |
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<p> |
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Visit <a href="http://ftp.cdrom.com/pub/infozip/zlib/"> |
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http://ftp.cdrom.com/pub/infozip/zlib/</a> |
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for the official zlib web page. |
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<p> |
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|
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<hr> |
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<a name="Introduction"><h2> Introduction </h2> |
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The 'zlib' compression library provides in-memory compression and |
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decompression functions, including integrity checks of the uncompressed |
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data. This version of the library supports only one compression method |
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(deflation) but other algorithms will be added later and will have the same |
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stream interface. |
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<p> |
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|
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Compression can be done in a single step if the buffers are large |
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enough (for example if an input file is mmap'ed), or can be done by |
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repeated calls of the compression function. In the latter case, the |
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application must provide more input and/or consume the output |
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(providing more output space) before each call. |
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<p> |
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|
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The library also supports reading and writing files in gzip (.gz) format |
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with an interface similar to that of stdio. |
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<p> |
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|
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The library does not install any signal handler. The decoder checks |
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the consistency of the compressed data, so the library should never |
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crash even in case of corrupted input. |
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<p> |
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|
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<hr> |
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<a name="Utility functions"><h2> Utility functions </h2> |
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The following utility functions are implemented on top of the |
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<a href="#Basic functions">basic stream-oriented functions</a>. |
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To simplify the interface, some |
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default options are assumed (compression level and memory usage, |
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standard memory allocation functions). The source code of these |
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utility functions can easily be modified if you need special options. |
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<h3> Function list </h3> |
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<ul> |
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<li> int <a href="#compress">compress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen); |
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<li> int <a href="#compress2">compress2</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen, int level); |
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<li> int <a href="#uncompress">uncompress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen); |
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<li> typedef voidp gzFile; |
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<li> gzFile <a href="#gzopen">gzopen</a> (const char *path, const char *mode); |
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<li> gzFile <a href="#gzdopen">gzdopen</a> (int fd, const char *mode); |
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<li> int <a href="#gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy); |
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<li> int <a href="#gzread">gzread</a> (gzFile file, voidp buf, unsigned len); |
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<li> int <a href="#gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len); |
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<li> int VA <a href="#gzprintf">gzprintf</a> (gzFile file, const char *format, ...); |
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<li> int <a href="#gzputs">gzputs</a> (gzFile file, const char *s); |
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<li> char * <a href="#gzgets">gzgets</a> (gzFile file, char *buf, int len); |
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<li> int <a href="#gzputc">gzputc</a> (gzFile file, int c); |
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<li> int <a href="#gzgetc">gzgetc</a> (gzFile file); |
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<li> int <a href="#gzflush">gzflush</a> (gzFile file, int flush); |
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<li> z_off_t <a href="#gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence); |
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<li> z_off_t <a href="#gztell">gztell</a> (gzFile file); |
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<li> int <a href="#gzrewind">gzrewind</a> (gzFile file); |
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<li> int <a href="#gzeof">gzeof</a> (gzFile file); |
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<li> int <a href="#gzclose">gzclose</a> (gzFile file); |
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<li> const char * <a href="#gzerror">gzerror</a> (gzFile file, int *errnum); |
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</ul> |
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<h3> Function description </h3> |
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<dl> |
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<font color="Blue"><dt> int <a name="compress">compress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);</font> |
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<dd> |
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Compresses the source buffer into the destination buffer. sourceLen is |
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the byte length of the source buffer. Upon entry, destLen is the total |
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size of the destination buffer, which must be at least 0.1% larger than |
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sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the |
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compressed buffer.<p> |
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This function can be used to <a href="#compress">compress</a> a whole file at once if the |
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input file is mmap'ed.<p> |
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<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 |
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enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output |
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buffer.<p> |
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|
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<font color="Blue"><dt> int <a name="compress2">compress2</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen, int level);</font> |
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<dd> |
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Compresses the source buffer into the destination buffer. The level |
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parameter has the same meaning as in <a href="#deflateInit">deflateInit</a>. sourceLen is the byte |
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length of the source buffer. Upon entry, destLen is the total size of the |
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destination buffer, which must be at least 0.1% larger than sourceLen plus |
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12 bytes. Upon exit, destLen is the actual size of the compressed buffer. |
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<p> |
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|
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<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 |
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memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output buffer, |
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<a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the level parameter is invalid. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="uncompress">uncompress</a> (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);</font> |
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<dd> |
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Decompresses the source buffer into the destination buffer. sourceLen is |
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the byte length of the source buffer. Upon entry, destLen is the total |
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size of the destination buffer, which must be large enough to hold the |
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entire uncompressed data. (The size of the uncompressed data must have |
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been saved previously by the compressor and transmitted to the decompressor |
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by some mechanism outside the scope of this compression library.) |
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Upon exit, destLen is the actual size of the compressed buffer. <p> |
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This function can be used to decompress a whole file at once if the |
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input file is mmap'ed. |
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<p> |
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|
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<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 |
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enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output |
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buffer, or <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was corrupted. |
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<p> |
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|
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<dt> typedef voidp gzFile; |
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<dd> <p> |
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|
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<font color="Blue"><dt> gzFile <a name="gzopen">gzopen</a> (const char *path, const char *mode);</font> |
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<dd> |
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Opens a gzip (.gz) file for reading or writing. The mode parameter |
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is as in fopen ("rb" or "wb") but can also include a compression level |
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("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for |
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Huffman only compression as in "wb1h". (See the description |
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of <a href="#deflateInit2">deflateInit2</a> for more information about the strategy parameter.) |
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<p> |
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|
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<a href="#gzopen">gzopen</a> can be used to read a file which is not in gzip format ; in this |
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case <a href="#gzread">gzread</a> will directly read from the file without decompression. |
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<p> |
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|
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<a href="#gzopen">gzopen</a> returns NULL if the file could not be opened or if there was |
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insufficient memory to allocate the (de)compression <a href="#state">state</a> ; errno |
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can be checked to distinguish the two cases (if errno is zero, the |
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zlib error is <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a>). |
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<p> |
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|
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<font color="Blue"><dt> gzFile <a name="gzdopen">gzdopen</a> (int fd, const char *mode);</font> |
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<dd> |
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<a href="#gzdopen">gzdopen</a>() associates a gzFile with the file descriptor fd. File |
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descriptors are obtained from calls like open, dup, creat, pipe or |
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fileno (in the file has been previously opened with fopen). |
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The mode parameter is as in <a href="#gzopen">gzopen</a>. |
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<p> |
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The next call of <a href="#gzclose">gzclose</a> on the returned gzFile will also close the |
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file descriptor fd, just like fclose(fdopen(fd), mode) closes the file |
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descriptor fd. If you want to keep fd open, use <a href="#gzdopen">gzdopen</a>(dup(fd), mode). |
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<p> |
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<a href="#gzdopen">gzdopen</a> returns NULL if there was insufficient memory to allocate |
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the (de)compression <a href="#state">state</a>. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy);</font> |
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<dd> |
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Dynamically update the compression level or strategy. See the description |
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of <a href="#deflateInit2">deflateInit2</a> for the meaning of these parameters. |
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<p> |
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<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 |
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opened for writing. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzread">gzread</a> (gzFile file, voidp buf, unsigned len);</font> |
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<dd> |
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Reads the given number of uncompressed bytes from the compressed file. |
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If the input file was not in gzip format, <a href="#gzread">gzread</a> copies the given number |
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of bytes into the buffer. |
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<p> |
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<a href="#gzread">gzread</a> returns the number of uncompressed bytes actually read (0 for |
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end of file, -1 for error). |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len);</font> |
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<dd> |
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Writes the given number of uncompressed bytes into the compressed file. |
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<a href="#gzwrite">gzwrite</a> returns the number of uncompressed bytes actually written |
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(0 in case of error). |
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<p> |
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|
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<font color="Blue"><dt> int VA <a name="gzprintf">gzprintf</a> (gzFile file, const char *format, ...);</font> |
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<dd> |
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Converts, formats, and writes the args to the compressed file under |
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control of the format string, as in fprintf. <a href="#gzprintf">gzprintf</a> returns the number of |
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uncompressed bytes actually written (0 in case of error). |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzputs">gzputs</a> (gzFile file, const char *s);</font> |
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<dd> |
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Writes the given null-terminated string to the compressed file, excluding |
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the terminating null character. |
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<p> |
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<a href="#gzputs">gzputs</a> returns the number of characters written, or -1 in case of error. |
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<p> |
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|
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<font color="Blue"><dt> char * <a name="gzgets">gzgets</a> (gzFile file, char *buf, int len);</font> |
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<dd> |
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Reads bytes from the compressed file until len-1 characters are read, or |
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a newline character is read and transferred to buf, or an end-of-file |
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condition is encountered. The string is then terminated with a null |
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character. |
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<p> |
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<a href="#gzgets">gzgets</a> returns buf, or <a href="#Z_NULL">Z_NULL</a> in case of error. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzputc">gzputc</a> (gzFile file, int c);</font> |
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<dd> |
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Writes c, converted to an unsigned char, into the compressed file. |
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<a href="#gzputc">gzputc</a> returns the value that was written, or -1 in case of error. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzgetc">gzgetc</a> (gzFile file);</font> |
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<dd> |
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Reads one byte from the compressed file. <a href="#gzgetc">gzgetc</a> returns this byte |
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or -1 in case of end of file or error. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzflush">gzflush</a> (gzFile file, int flush);</font> |
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<dd> |
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Flushes all pending output into the compressed file. The parameter |
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flush is as in the <a href="#deflate">deflate</a>() function. The return value is the zlib |
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error number (see function <a href="#gzerror">gzerror</a> below). <a href="#gzflush">gzflush</a> returns <a href="#Z_OK">Z_OK</a> if |
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the flush parameter is <a href="#Z_FINISH">Z_FINISH</a> and all output could be flushed. |
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<p> |
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<a href="#gzflush">gzflush</a> should be called only when strictly necessary because it can |
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degrade compression. |
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<p> |
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|
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<font color="Blue"><dt> z_off_t <a name="gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence);</font> |
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<dd> |
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Sets the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the |
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given compressed file. The offset represents a number of bytes in the |
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uncompressed data stream. The whence parameter is defined as in lseek(2); |
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the value SEEK_END is not supported. |
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<p> |
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If the file is opened for reading, this function is emulated but can be |
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extremely slow. If the file is opened for writing, only forward seeks are |
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supported ; <a href="#gzseek">gzseek</a> then compresses a sequence of zeroes up to the new |
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starting position. |
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<p> |
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<a href="#gzseek">gzseek</a> returns the resulting offset location as measured in bytes from |
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the beginning of the uncompressed stream, or -1 in case of error, in |
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particular if the file is opened for writing and the new starting position |
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would be before the current position. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzrewind">gzrewind</a> (gzFile file);</font> |
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<dd> |
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Rewinds the given file. This function is supported only for reading. |
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<p> |
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<a href="#gzrewind">gzrewind</a>(file) is equivalent to (int)<a href="#gzseek">gzseek</a>(file, 0L, SEEK_SET) |
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<p> |
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|
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<font color="Blue"><dt> z_off_t <a name="gztell">gztell</a> (gzFile file);</font> |
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<dd> |
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Returns the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the |
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given compressed file. This position represents a number of bytes in the |
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uncompressed data stream. |
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<p> |
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|
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<a href="#gztell">gztell</a>(file) is equivalent to <a href="#gzseek">gzseek</a>(file, 0L, SEEK_CUR) |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzeof">gzeof</a> (gzFile file);</font> |
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<dd> |
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Returns 1 when EOF has previously been detected reading the given |
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input stream, otherwise zero. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="gzclose">gzclose</a> (gzFile file);</font> |
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<dd> |
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Flushes all pending output if necessary, closes the compressed file |
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and deallocates all the (de)compression <a href="#state">state</a>. The return value is the zlib |
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error number (see function <a href="#gzerror">gzerror</a> below). |
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<p> |
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|
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<font color="Blue"><dt> const char * <a name="gzerror">gzerror</a> (gzFile file, int *errnum);</font> |
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<dd> |
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Returns the error message for the last error which occurred on the |
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given compressed file. errnum is set to zlib error number. If an |
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error occurred in the file system and not in the compression library, |
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errnum is set to <a href="#Z_ERRNO">Z_ERRNO</a> and the application may consult errno |
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to get the exact error code. |
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<p> |
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</dl> |
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<hr> |
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<a name="Basic functions"><h2> Basic functions </h2> |
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<h3> Function list </h3> |
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<ul> |
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<li> const char * <a href="#zlibVersion">zlibVersion</a> (void); |
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<li> int <a href="#deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level); |
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<li> int <a href="#deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush); |
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<li> int <a href="#deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm); |
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<li> int <a href="#inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm); |
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<li> int <a href="#inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush); |
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<li> int <a href="#inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm); |
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</ul> |
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|
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<h3> Function description </h3> |
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<dl> |
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<font color="Blue"><dt> const char * <a name="zlibVersion">zlibVersion</a> (void);</font> |
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<dd> The application can compare <a href="#zlibVersion">zlibVersion</a> and ZLIB_VERSION for consistency. |
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If the first character differs, the library code actually used is |
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not compatible with the zlib.h header file used by the application. |
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This check is automatically made by <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a>. |
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<p> |
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|
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<font color="Blue"><dt> int <a name="deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level);</font> |
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<dd> |
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Initializes the internal stream <a href="#state">state</a> for compression. The fields |
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<a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by the caller. |
||||
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 |
||||
use default allocation functions. |
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<p> |
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|
||||
The compression level must be <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a>, or between 0 and 9: |
||||
1 gives best speed, 9 gives best compression, 0 gives no compression at |
||||
all (the input data is simply copied a block at a time). |
||||
<p> |
||||
|
||||
<a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a> requests a default compromise between speed and |
||||
compression (currently equivalent to level 6). |
||||
<p> |
||||
|
||||
<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 |
||||
enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if level is not a valid compression level, |
||||
<a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version (<a href="#zlib_version">zlib_version</a>) is incompatible |
||||
with the version assumed by the caller (ZLIB_VERSION). |
||||
<a href="#msg">msg</a> is set to null if there is no error message. <a href="#deflateInit">deflateInit</a> does not |
||||
perform any compression: this will be done by <a href="#deflate">deflate</a>(). |
||||
<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font> |
||||
<dd> |
||||
<a href="#deflate">deflate</a> compresses as much data as possible, and stops when the input |
||||
buffer becomes empty or the output buffer becomes full. It may introduce some |
||||
output latency (reading input without producing any output) except when |
||||
forced to flush.<p> |
||||
|
||||
The detailed semantics are as follows. <a href="#deflate">deflate</a> performs one or both of the |
||||
following actions: |
||||
|
||||
<ul> |
||||
<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> |
||||
accordingly. If not all input can be processed (because there is not |
||||
enough room in the output buffer), <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> are updated and |
||||
processing will resume at this point for the next call of <a href="#deflate">deflate</a>(). |
||||
|
||||
<li> |
||||
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> |
||||
accordingly. This action is forced if the parameter flush is non zero. |
||||
Forcing flush frequently degrades the compression ratio, so this parameter |
||||
should be set only when necessary (in interactive applications). |
||||
Some output may be provided even if flush is not set. |
||||
</ul> <p> |
||||
|
||||
Before the call of <a href="#deflate">deflate</a>(), the application should ensure that at least |
||||
one of the actions is possible, by providing more input and/or consuming |
||||
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> |
||||
should never be zero before the call. The application can consume the |
||||
compressed output when it wants, for example when the output buffer is full |
||||
(<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> |
||||
and with zero <a href="#avail_out">avail_out</a>, it must be called again after making room in the |
||||
output buffer because there might be more output pending. |
||||
<p> |
||||
|
||||
If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, all pending output is |
||||
flushed to the output buffer and the output is aligned on a byte boundary, so |
||||
that the decompressor can get all input data available so far. (In particular |
||||
<a href="#avail_in">avail_in</a> is zero after the call if enough output space has been provided |
||||
before the call.) Flushing may degrade compression for some compression |
||||
algorithms and so it should be used only when necessary. |
||||
<p> |
||||
|
||||
If flush is set to <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>, all output is flushed as with |
||||
<a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, and the compression <a href="#state">state</a> is reset so that decompression can |
||||
restart from this point if previous compressed data has been damaged or if |
||||
random access is desired. Using <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a> too often can seriously degrade |
||||
the compression. |
||||
<p> |
||||
|
||||
If <a href="#deflate">deflate</a> returns with <a href="#avail_out">avail_out</a> == 0, this function must be called again |
||||
with the same value of the flush parameter and more output space (updated |
||||
<a href="#avail_out">avail_out</a>), until the flush is complete (<a href="#deflate">deflate</a> returns with non-zero |
||||
<a href="#avail_out">avail_out</a>). |
||||
<p> |
||||
|
||||
If the parameter flush is set to <a href="#Z_FINISH">Z_FINISH</a>, pending input is processed, |
||||
pending output is flushed and <a href="#deflate">deflate</a> returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> if there |
||||
was enough output space ; if <a href="#deflate">deflate</a> returns with <a href="#Z_OK">Z_OK</a>, this function must be |
||||
called again with <a href="#Z_FINISH">Z_FINISH</a> and more output space (updated <a href="#avail_out">avail_out</a>) but no |
||||
more input data, until it returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> or an error. After |
||||
<a href="#deflate">deflate</a> has returned <a href="#Z_STREAM_END">Z_STREAM_END</a>, the only possible operations on the |
||||
stream are <a href="#deflateReset">deflateReset</a> or <a href="#deflateEnd">deflateEnd</a>. |
||||
<p> |
||||
|
||||
<a href="#Z_FINISH">Z_FINISH</a> can be used immediately after <a href="#deflateInit">deflateInit</a> if all the compression |
||||
is to be done in a single step. In this case, <a href="#avail_out">avail_out</a> must be at least |
||||
0.1% larger than <a href="#avail_in">avail_in</a> plus 12 bytes. If <a href="#deflate">deflate</a> does not return |
||||
<a href="#Z_STREAM_END">Z_STREAM_END</a>, then it must be called again as described above. |
||||
<p> |
||||
|
||||
<a href="#deflate">deflate</a>() sets strm-> <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all input read |
||||
so far (that is, <a href="#total_in">total_in</a> bytes). |
||||
<p> |
||||
|
||||
<a href="#deflate">deflate</a>() may update <a href="#data_type">data_type</a> if it can make a good guess about |
||||
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 |
||||
binary. This field is only for information purposes and does not affect |
||||
the compression algorithm in any manner. |
||||
<p> |
||||
|
||||
<a href="#deflate">deflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input |
||||
processed or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if all input has been |
||||
consumed and all output has been produced (only when flush is set to |
||||
<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 |
||||
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 |
||||
(for example <a href="#avail_in">avail_in</a> or <a href="#avail_out">avail_out</a> was zero). |
||||
<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
||||
<dd> |
||||
All dynamically allocated data structures for this stream are freed. |
||||
This function discards any unprocessed input and does not flush any |
||||
pending output. |
||||
<p> |
||||
|
||||
<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 |
||||
stream <a href="#state">state</a> was inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the stream was freed |
||||
prematurely (some input or output was discarded). In the error case, |
||||
<a href="#msg">msg</a> may be set but then points to a static string (which must not be |
||||
deallocated). |
||||
<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
||||
<dd> |
||||
Initializes the internal stream <a href="#state">state</a> for decompression. The 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 before by |
||||
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 |
||||
value depends on the compression method), <a href="#inflateInit">inflateInit</a> determines the |
||||
compression method from the zlib header and allocates all data structures |
||||
accordingly ; otherwise the allocation will be deferred to the first call of |
||||
<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 |
||||
use default allocation functions. |
||||
<p> |
||||
|
||||
<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 |
||||
memory, <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version is incompatible with the |
||||
version assumed by the caller. <a href="#msg">msg</a> is set to null if there is no error |
||||
message. <a href="#inflateInit">inflateInit</a> does not perform any decompression apart from reading |
||||
the zlib header if 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 modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.) |
||||
<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font> |
||||
<dd> |
||||
<a href="#inflate">inflate</a> decompresses as much data as possible, and stops when the input |
||||
buffer becomes empty or the output buffer becomes full. It may some |
||||
introduce some output latency (reading input without producing any output) |
||||
except when forced to flush. |
||||
<p> |
||||
|
||||
The detailed semantics are as follows. <a href="#inflate">inflate</a> performs one or both of the |
||||
following actions: |
||||
|
||||
<ul> |
||||
<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> |
||||
accordingly. If not all input can be processed (because there is not |
||||
enough room in the output buffer), <a href="#next_in">next_in</a> is updated and processing |
||||
will resume at this point for the next call of <a href="#inflate">inflate</a>(). |
||||
|
||||
<li> 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> accordingly. <a href="#inflate">inflate</a>() provides as much output as possible, |
||||
until there is no more input data or no more space in the output buffer |
||||
(see below about the flush parameter). |
||||
</ul> <p> |
||||
|
||||
Before the call of <a href="#inflate">inflate</a>(), the application should ensure that at least |
||||
one of the actions is possible, by providing more input and/or consuming |
||||
more output, and updating the next_* and avail_* values accordingly. |
||||
The application can consume the uncompressed output when it wants, for |
||||
example when the output buffer is full (<a href="#avail_out">avail_out</a> == 0), or after each |
||||
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 |
||||
must be called again after making room in the output buffer because there |
||||
might be more output pending. |
||||
<p> |
||||
|
||||
If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, <a href="#inflate">inflate</a> flushes as much |
||||
output as possible to the output buffer. The flushing behavior of <a href="#inflate">inflate</a> is |
||||
not specified for values of the flush parameter other than <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> |
||||
and <a href="#Z_FINISH">Z_FINISH</a>, but the current implementation actually flushes as much output |
||||
as possible anyway. |
||||
<p> |
||||
|
||||
<a href="#inflate">inflate</a>() should normally be called until it returns <a href="#Z_STREAM_END">Z_STREAM_END</a> or an |
||||
error. However if all decompression is to be performed in a single step |
||||
(a single call of <a href="#inflate">inflate</a>), the parameter flush should be set to |
||||
<a href="#Z_FINISH">Z_FINISH</a>. In this case all pending input is processed and all pending |
||||
output is flushed ; <a href="#avail_out">avail_out</a> must be large enough to hold all the |
||||
uncompressed data. (The size of the uncompressed data may have been saved |
||||
by the compressor for this purpose.) The next operation on this stream must |
||||
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> |
||||
is never required, but can be used to inform <a href="#inflate">inflate</a> that a faster routine |
||||
may be used for the single <a href="#inflate">inflate</a>() call. |
||||
<p> |
||||
|
||||
If a preset dictionary is needed at this point (see <a href="#inflateSetDictionary">inflateSetDictionary</a> |
||||
below), <a href="#inflate">inflate</a> sets strm-<a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of the |
||||
dictionary chosen by the compressor and returns <a href="#Z_NEED_DICT">Z_NEED_DICT</a> ; otherwise |
||||
it sets strm-> <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all output produced |
||||
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 |
||||
an error code as described below. At the end of the stream, <a href="#inflate">inflate</a>() |
||||
checks that its computed <a href="#adler32">adler32</a> checksum is equal to that saved by the |
||||
compressor and returns <a href="#Z_STREAM_END">Z_STREAM_END</a> only if the checksum is correct. |
||||
<p> |
||||
|
||||
<a href="#inflate">inflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input processed |
||||
or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if the end of the compressed data has |
||||
been reached and all uncompressed output has been produced, <a href="#Z_NEED_DICT">Z_NEED_DICT</a> if a |
||||
preset dictionary is needed at this point, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was |
||||
corrupted (input stream not conforming to the zlib format or incorrect |
||||
<a href="#adler32">adler32</a> checksum), <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent |
||||
(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 |
||||
enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if no progress is possible or if there was not |
||||
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> |
||||
case, the application may then call <a href="#inflateSync">inflateSync</a> to look for a good |
||||
compression block. |
||||
<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
||||
<dd> |
||||
All dynamically allocated data structures for this stream are freed. |
||||
This function discards any unprocessed input and does not flush any |
||||
pending output. |
||||
<p> |
||||
|
||||
<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> |
||||
was inconsistent. In the error case, <a href="#msg">msg</a> may be set but then points to a |
||||
static string (which must not be deallocated). |
||||
</dl> |
||||
<hr> |
||||
<a name="Advanced functions"><h2> Advanced functions </h2> |
||||
The following functions are needed only in some special applications. |
||||
<h3> Function list </h3> |
||||
<ul> |
||||
<li> int <a href="#deflateInit2">deflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, |
||||
<li> int <a href="#deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength); |
||||
<li> int <a href="#deflateCopy">deflateCopy</a> (<a href="#z_streamp">z_streamp</a> dest, <a href="#z_streamp">z_streamp</a> source); |
||||
<li> int <a href="#deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm); |
||||
<li> int <a href="#deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy); |
||||
<li> int <a href="#inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int windowBits); |
||||
<li> int <a href="#inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength); |
||||
<li> int <a href="#inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm); |
||||
<li> int <a href="#inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm); |
||||
|
||||
</ul> |
||||
<h3> Function description </h3> |
||||
<dl> |
||||
<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> |
||||
|
||||
<dd> This is another version of <a href="#deflateInit">deflateInit</a> with more compression options. The |
||||
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 |
||||
the caller.<p> |
||||
|
||||
The method parameter is the compression method. It must be <a href="#Z_DEFLATED">Z_DEFLATED</a> in |
||||
this version of the library.<p> |
||||
|
||||
The windowBits parameter is the base two logarithm of the window size |
||||
(the size of the history buffer). It should be in the range 8..15 for this |
||||
version of the library. Larger values of this parameter result in better |
||||
compression at the expense of memory usage. The default value is 15 if |
||||
<a href="#deflateInit">deflateInit</a> is used instead.<p> |
||||
|
||||
The memLevel parameter specifies how much memory should be allocated |
||||
for the internal compression <a href="#state">state</a>. memLevel=1 uses minimum memory but |
||||
is slow and reduces compression ratio ; memLevel=9 uses maximum memory |
||||
for optimal speed. The default value is 8. See zconf.h for total memory |
||||
usage as a function of windowBits and memLevel.<p> |
||||
|
||||
The strategy parameter is used to tune the compression algorithm. Use the |
||||
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 |
||||
filter (or predictor), or <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a> to force Huffman encoding only (no |
||||
string match). Filtered data consists mostly of small values with a |
||||
somewhat random distribution. In this case, the compression algorithm is |
||||
tuned to <a href="#compress">compress</a> them better. The effect of <a href="#Z_FILTERED">Z_FILTERED</a> is to force more |
||||
Huffman coding and less string matching ; it is somewhat intermediate |
||||
between Z_DEFAULT and <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a>. The strategy parameter only affects |
||||
the compression ratio but not the correctness of the compressed output even |
||||
if it is not set appropriately.<p> |
||||
|
||||
<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 |
||||
memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as an invalid |
||||
method). <a href="#msg">msg</a> is set to null if there is no error message. <a href="#deflateInit2">deflateInit2</a> does |
||||
not perform any compression: this will be done by <a href="#deflate">deflate</a>().<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength);</font> |
||||
<dd> |
||||
Initializes the compression dictionary from the given byte sequence |
||||
without producing any compressed output. This function must be called |
||||
immediately after <a href="#deflateInit">deflateInit</a>, <a href="#deflateInit2">deflateInit2</a> or <a href="#deflateReset">deflateReset</a>, before any |
||||
call of <a href="#deflate">deflate</a>. The compressor and decompressor must use exactly the same |
||||
dictionary (see <a href="#inflateSetDictionary">inflateSetDictionary</a>).<p> |
||||
|
||||
The dictionary should consist of strings (byte sequences) that are likely |
||||
to be encountered later in the data to be compressed, with the most commonly |
||||
used strings preferably put towards the end of the dictionary. Using a |
||||
dictionary is most useful when the data to be compressed is short and can be |
||||
predicted with good accuracy ; the data can then be compressed better than |
||||
with the default empty dictionary.<p> |
||||
|
||||
Depending on the size of the compression data structures selected by |
||||
<a href="#deflateInit">deflateInit</a> or <a href="#deflateInit2">deflateInit2</a>, a part of the dictionary may in effect be |
||||
discarded, for example if the dictionary is larger than the window size in |
||||
<a href="#deflate">deflate</a> or deflate2. Thus the strings most likely to be useful should be |
||||
put at the end of the dictionary, not at the front.<p> |
||||
|
||||
Upon return of this function, strm-> <a href="#adler">adler</a> is set to the Adler32 value |
||||
of the dictionary ; the decompressor may later use this value to determine |
||||
which dictionary has been used by the compressor. (The Adler32 value |
||||
applies to the whole dictionary even if only a subset of the dictionary is |
||||
actually used by the compressor.)<p> |
||||
|
||||
<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 |
||||
parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is |
||||
inconsistent (for example if <a href="#deflate">deflate</a> has already been called for this stream |
||||
or if the compression method is bsort). <a href="#deflateSetDictionary">deflateSetDictionary</a> does not |
||||
perform any compression: this will be done by <a href="#deflate">deflate</a>().<p> |
||||
|
||||
<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> |
||||
<dd> |
||||
Sets the destination stream as a complete copy of the source stream.<p> |
||||
|
||||
This function can be useful when several compression strategies will be |
||||
tried, for example when there are several ways of pre-processing the input |
||||
data with a filter. The streams that will be discarded should then be freed |
||||
by calling <a href="#deflateEnd">deflateEnd</a>. Note that <a href="#deflateCopy">deflateCopy</a> duplicates the internal |
||||
compression <a href="#state">state</a> which can be quite large, so this strategy is slow and |
||||
can consume lots of memory.<p> |
||||
|
||||
<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 |
||||
enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source stream <a href="#state">state</a> was inconsistent |
||||
(such as <a href="#zalloc">zalloc</a> being NULL). <a href="#msg">msg</a> is left unchanged in both source and |
||||
destination.<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
||||
<dd> This function is equivalent to <a href="#deflateEnd">deflateEnd</a> followed by <a href="#deflateInit">deflateInit</a>, |
||||
but does not free and reallocate all the internal compression <a href="#state">state</a>. |
||||
The stream will keep the same compression level and any other attributes |
||||
that may have been set by <a href="#deflateInit2">deflateInit2</a>.<p> |
||||
|
||||
<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 |
||||
stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL).<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy);</font> |
||||
<dd> |
||||
Dynamically update the compression level and compression strategy. The |
||||
interpretation of level and strategy is as in <a href="#deflateInit2">deflateInit2</a>. This can be |
||||
used to switch between compression and straight copy of the input data, or |
||||
to switch to a different kind of input data requiring a different |
||||
strategy. If the compression level is changed, the input available so far |
||||
is compressed with the old level (and may be flushed); the new level will |
||||
take effect only at the next call of <a href="#deflate">deflate</a>().<p> |
||||
|
||||
Before the call of <a href="#deflateParams">deflateParams</a>, the stream <a href="#state">state</a> must be set as for |
||||
a call of <a href="#deflate">deflate</a>(), since the currently available input may have to |
||||
be compressed and flushed. In particular, strm-> <a href="#avail_out">avail_out</a> must be |
||||
non-zero.<p> |
||||
|
||||
<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 |
||||
stream <a href="#state">state</a> was inconsistent or if a parameter was invalid, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> |
||||
if strm->avail_out was zero.<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int windowBits);</font> |
||||
|
||||
<dd> This is another version of <a href="#inflateInit">inflateInit</a> with an extra parameter. The |
||||
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 |
||||
before by the caller.<p> |
||||
|
||||
The windowBits parameter is the base two logarithm of the maximum window |
||||
size (the size of the history buffer). It should be in the range 8..15 for |
||||
this version of the library. The default value is 15 if <a href="#inflateInit">inflateInit</a> is used |
||||
instead. If a compressed stream with a larger window size is given as |
||||
input, <a href="#inflate">inflate</a>() will return with the error code <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> instead of |
||||
trying to allocate a larger window.<p> |
||||
|
||||
<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 |
||||
memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as a negative |
||||
memLevel). <a href="#msg">msg</a> is set to null if there is no error message. <a href="#inflateInit2">inflateInit2</a> |
||||
does not perform any decompression apart from reading the zlib header if |
||||
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 |
||||
modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.)<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt dictLength);</font> |
||||
<dd> |
||||
Initializes the decompression dictionary from the given uncompressed byte |
||||
sequence. This function must be called immediately after a call of <a href="#inflate">inflate</a> |
||||
if this call returned <a href="#Z_NEED_DICT">Z_NEED_DICT</a>. The dictionary chosen by the compressor |
||||
can be determined from the Adler32 value returned by this call of |
||||
<a href="#inflate">inflate</a>. The compressor and decompressor must use exactly the same |
||||
dictionary (see <a href="#deflateSetDictionary">deflateSetDictionary</a>).<p> |
||||
|
||||
<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 |
||||
parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is |
||||
inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the given dictionary doesn't match the |
||||
expected one (incorrect Adler32 value). <a href="#inflateSetDictionary">inflateSetDictionary</a> does not |
||||
perform any decompression: this will be done by subsequent calls of |
||||
<a href="#inflate">inflate</a>().<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
||||
|
||||
<dd> Skips invalid compressed data until a full flush point (see above the |
||||
description of <a href="#deflate">deflate</a> with <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>) can be found, or until all |
||||
available input is skipped. No output is provided.<p> |
||||
|
||||
<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> |
||||
if no more input was provided, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if no flush point has been found, |
||||
or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent. In the success |
||||
case, the application may save the current current value of <a href="#total_in">total_in</a> which |
||||
indicates where valid compressed data was found. In the error case, the |
||||
application may repeatedly call <a href="#inflateSync">inflateSync</a>, providing more input each time, |
||||
until success or end of the input data.<p> |
||||
|
||||
<font color="Blue"><dt> int <a name="inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font> |
||||
<dd> |
||||
This function is equivalent to <a href="#inflateEnd">inflateEnd</a> followed by <a href="#inflateInit">inflateInit</a>, |
||||
but does not free and reallocate all the internal decompression <a href="#state">state</a>. |
||||
The stream will keep attributes that may have been set by <a href="#inflateInit2">inflateInit2</a>. |
||||
<p> |
||||
|
||||
<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 |
||||
stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL). |
||||
<p> |
||||
</dl> |
||||
|
||||
<hr> |
||||
<a name="Checksum functions"><h2> Checksum functions </h2> |
||||
These functions are not related to compression but are exported |
||||
anyway because they might be useful in applications using the |
||||
compression library. |
||||
<h3> Function list </h3> |
||||
<ul> |
||||
<li> uLong <a href="#adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len); |
||||
<li> uLong <a href="#crc32">crc32</a> (uLong crc, const Bytef *buf, uInt len); |
||||
</ul> |
||||
<h3> Function description </h3> |
||||
<dl> |
||||
<font color="Blue"><dt> uLong <a name="adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len);</font> |
||||
<dd> |
||||
Update a running Adler-32 checksum with the bytes buf[0..len-1] and |
||||
return the updated checksum. If buf is NULL, this function returns |
||||
the required initial value for the checksum. |
||||
<p> |
||||
An Adler-32 checksum is almost as reliable as a CRC32 but can be computed |
||||
much faster. Usage example: |
||||
<pre> |
||||
|
||||
uLong <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0); |
||||
|
||||
while (read_buffer(buffer, length) != EOF) { |
||||
<a href="#adler">adler</a> = <a href="#adler32">adler32</a>(<a href="#adler">adler</a>, buffer, length); |
||||
} |
||||
if (<a href="#adler">adler</a> != original_adler) error(); |
||||
</pre> |
||||
|
||||
<font color="Blue"><dt> uLong <a name="crc32">crc32</a> (uLong crc, const Bytef *buf, uInt len);</font> |
||||
<dd> |
||||
Update a running crc with the bytes buf[0..len-1] and return the updated |
||||
crc. If buf is NULL, this function returns the required initial value |
||||
for the crc. Pre- and post-conditioning (one's complement) is performed |
||||
within this function so it shouldn't be done by the application. |
||||
Usage example: |
||||
<pre> |
||||
|
||||
uLong crc = <a href="#crc32">crc32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0); |
||||
|
||||
while (read_buffer(buffer, length) != EOF) { |
||||
crc = <a href="#crc32">crc32</a>(crc, buffer, length); |
||||
} |
||||
if (crc != original_crc) error(); |
||||
</pre> |
||||
</dl> |
||||
<hr> |
||||
<a name="struct z_stream_s"><h2> struct z_stream_s </h2> |
||||
<font color="Blue"> |
||||
<a name="z_stream_s"> |
||||
<pre> |
||||
typedef struct z_stream_s { |
||||
Bytef *<a name="next_in">next_in</a>; /* next input byte */ |
||||
uInt <a name="avail_in">avail_in</a>; /* number of bytes available at <a href="#next_in">next_in</a> */ |
||||
uLong <a name="total_in">total_in</a>; /* total nb of input bytes read so far */ |
||||
|
||||
Bytef *<a name="next_out">next_out</a>; /* next output byte should be put there */ |
||||
uInt <a name="avail_out">avail_out</a>; /* remaining free space at <a href="#next_out">next_out</a> */ |
||||
uLong <a name="total_out">total_out</a>; /* total nb of bytes output so far */ |
||||
|
||||
char *<a name="msg">msg</a>; /* last error message, NULL if no error */ |
||||
struct internal_state FAR *<a name="state">state</a>; /* not visible by applications */ |
||||
|
||||
alloc_func <a name="zalloc">zalloc</a>; /* used to allocate the internal <a href="#state">state</a> */ |
||||
free_func <a name="zfree">zfree</a>; /* used to free the internal <a href="#state">state</a> */ |
||||
voidpf <a name="opaque">opaque</a>; /* private data object passed to <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> */ |
||||
|
||||
int <a name="data_type">data_type</a>; /* best guess about the data type: ascii or binary */ |
||||
uLong <a name="adler">adler</a>; /* <a href="#adler32">adler32</a> value of the uncompressed data */ |
||||
uLong <a name="reserved">reserved</a>; /* <a href="#reserved">reserved</a> for future use */ |
||||
} <a href="#z_stream_s">z_stream</a> ; |
||||
|
||||
typedef <a href="#z_stream_s">z_stream</a> FAR * <a name="z_streamp">z_streamp</a>; ÿ |
||||
</pre> |
||||
</font> |
||||
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 |
||||
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> |
||||
has dropped to zero. The application must initialize <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and |
||||
<a href="#opaque">opaque</a> before calling the init function. All other fields are set by the |
||||
compression library and must not be updated by the application. <p> |
||||
|
||||
The <a href="#opaque">opaque</a> value provided by the application will be passed as the first |
||||
parameter for calls of <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a>. This can be useful for custom |
||||
memory management. The compression library attaches no meaning to the |
||||
<a href="#opaque">opaque</a> value. <p> |
||||
|
||||
<a href="#zalloc">zalloc</a> must return <a href="#Z_NULL">Z_NULL</a> if there is not enough memory for the object. |
||||
If zlib is used in a multi-threaded application, <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be |
||||
thread safe. <p> |
||||
|
||||
On 16-bit systems, the functions <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be able to allocate |
||||
exactly 65536 bytes, but will not be required to allocate more than this |
||||
if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS, |
||||
pointers returned by <a href="#zalloc">zalloc</a> for objects of exactly 65536 bytes *must* |
||||
have their offset normalized to zero. The default allocation function |
||||
provided by this library ensures this (see zutil.c). To reduce memory |
||||
requirements and avoid any allocation of 64K objects, at the expense of |
||||
compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h). |
||||
<p> |
||||
|
||||
The fields <a href="#total_in">total_in</a> and <a href="#total_out">total_out</a> can be used for statistics or |
||||
progress reports. After compression, <a href="#total_in">total_in</a> holds the total size of |
||||
the uncompressed data and may be saved for use in the decompressor |
||||
(particularly if the decompressor wants to decompress everything in |
||||
a single step). <p> |
||||
|
||||
<hr> |
||||
<a name="Constants"><h2> Constants </h2> |
||||
<font color="Blue"> |
||||
<pre> |
||||
#define <a name="Z_NO_FLUSH">Z_NO_FLUSH</a> 0 |
||||
#define <a name="Z_PARTIAL_FLUSH">Z_PARTIAL_FLUSH</a> 1 |
||||
/* will be removed, use <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> instead */ |
||||
#define <a name="Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> 2 |
||||
#define <a name="Z_FULL_FLUSH">Z_FULL_FLUSH</a> 3 |
||||
#define <a name="Z_FINISH">Z_FINISH</a> 4 |
||||
/* Allowed flush values ; see <a href="#deflate">deflate</a>() below for details */ |
||||
|
||||
#define <a name="Z_OK">Z_OK</a> 0 |
||||
#define <a name="Z_STREAM_END">Z_STREAM_END</a> 1 |
||||
#define <a name="Z_NEED_DICT">Z_NEED_DICT</a> 2 |
||||
#define <a name="Z_ERRNO">Z_ERRNO</a> (-1) |
||||
#define <a name="Z_STREAM_ERROR">Z_STREAM_ERROR</a> (-2) |
||||
#define <a name="Z_DATA_ERROR">Z_DATA_ERROR</a> (-3) |
||||
#define <a name="Z_MEM_ERROR">Z_MEM_ERROR</a> (-4) |
||||
#define <a name="Z_BUF_ERROR">Z_BUF_ERROR</a> (-5) |
||||
#define <a name="Z_VERSION_ERROR">Z_VERSION_ERROR</a> (-6) |
||||
/* Return codes for the compression/decompression functions. Negative |
||||
* values are errors, positive values are used for special but normal events. |
||||
*/ |
||||
|
||||
#define <a name="Z_NO_COMPRESSION">Z_NO_COMPRESSION</a> 0 |
||||
#define <a name="Z_BEST_SPEED">Z_BEST_SPEED</a> 1 |
||||
#define <a name="Z_BEST_COMPRESSION">Z_BEST_COMPRESSION</a> 9 |
||||
#define <a name="Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a> (-1) |
||||
/* compression levels */ |
||||
|
||||
#define <a name="Z_FILTERED">Z_FILTERED</a> 1 |
||||
#define <a name="Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a> 2 |
||||
#define <a name="Z_DEFAULT_STRATEGY">Z_DEFAULT_STRATEGY</a> 0 |
||||
/* compression strategy ; see <a href="#deflateInit2">deflateInit2</a>() below for details */ |
||||
|
||||
#define <a name="Z_BINARY">Z_BINARY</a> 0 |
||||
#define <a name="Z_ASCII">Z_ASCII</a> 1 |
||||
#define <a name="Z_UNKNOWN">Z_UNKNOWN</a> 2 |
||||
/* Possible values of the <a href="#data_type">data_type</a> field */ |
||||
|
||||
#define <a name="Z_DEFLATED">Z_DEFLATED</a> 8 |
||||
/* The <a href="#deflate">deflate</a> compression method (the only one supported in this version) */ |
||||
|
||||
#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> */ |
||||
|
||||
#define <a name="zlib_version">zlib_version</a> <a href="#zlibVersion">zlibVersion</a>() |
||||
/* for compatibility with versions less than 1.0.2 */ |
||||
</pre> |
||||
</font> |
||||
|
||||
<hr> |
||||
<a name="Misc"><h2> Misc </h2> |
||||
<a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a> are macros to allow checking the zlib version |
||||
and the compiler's view of <a href="#z_stream_s">z_stream</a>. |
||||
<p> |
||||
Other functions: |
||||
<dl> |
||||
<font color="Blue"><dt> const char * <a name="zError">zError</a> (int err);</font> |
||||
<font color="Blue"><dt> int <a name="inflateSyncPoint">inflateSyncPoint</a> (<a href="#z_streamp">z_streamp</a> z);</font> |
||||
<font color="Blue"><dt> const uLongf * <a name="get_crc_table">get_crc_table</a> (void);</font> |
||||
</dl> |
||||
<hr> |
||||
<font size="-1"> |
||||
Last update: Wed Oct 13 20:42:34 1999<br> |
||||
piapi@csie.ntu.edu.tw |
||||
</font> |
||||
|
||||
</body> |
||||
</html> |
||||
Loading…
Reference in new issue