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ZLIB(3)                                                                ZLIB(3)

       zlib - compression/decompression library

       [see zlib.h for full description]

       The  zlib  library  is a general purpose data compression library.  The
       code is thread safe.  It provides in-memory compression and  decompres-
       sion  functions,  including  integrity checks of the uncompressed data.
       This version of  the  library  supports  only  one  compression  method
       (deflation)  but other algorithms will be added later and will have the
       same stream interface.

       Compression can be done in a single  step  if  the  buffers  are  large
       enough  (for  example  if  an input file is mmap'ed), or can be done by
       repeated calls of the compression function.  In the  latter  case,  the
       application  must provide more input and/or consume the output (provid-
       ing more output space) before each call.

       The library also supports reading and writing files  in  gzip(1)  (.gz)
       format with an interface similar to that of stdio.

       The  library  does  not install any signal handler.  The decoder checks
       the consistency of the compressed data, so  the  library  should  never
       crash even in case of corrupted input.

       All  functions  of  the  compression library are documented in the file
       zlib.h.  The distribution  source  includes  examples  of  use  of  the
       library in the files example.c and minigzip.c.

       Changes  to  this  version  are  documented  in the file ChangeLog that
       accompanies the source, and are concerned primarily with bug fixes  and
       portability enhancements.

       A  Java implementation of zlib is available in the Java Development Kit


       A  Perl interface to zlib, written by Paul Marquess (, is
       available at CPAN (Comprehensive Perl Archive Network)  sites,  includ-


       A  Python interface to zlib, written by A.M. Kuchling (,
       is available in Python 1.5 and later versions:


       A zlib binding for tcl(1), written by Andreas Kupries  (a.kupries@west-, is availlable at:


       An experimental package to read and write files in .zip format, written
       on top of zlib by Gilles Vollant (, is available at:

     and also in the  con-
              trib/minizip directory of the main zlib web site.

       The zlib web site can be found at either of these locations:


       The  data  format used by the zlib library is described by RFC (Request
       for Comments) 1950 to 1952 in the files:

     (concerning zlib format)
     (concerning deflate format)
     (concerning gzip format)

       These documents are also available in other formats from:


       Mark Nelson ( wrote an article about zlib for  the  Jan.
       1997  issue  of  Dr. Dobb's Journal; a copy of the article is available


       Before reporting a problem, please check the zlib web  site  to  verify
       that  you have the latest version of zlib; otherwise, obtain the latest
       version and see if the problem still exists.  Please read the zlib  FAQ


       before   asking   for   help.    Send   questions  and/or  comments  to, or (for the  Windows  DLL  version)  to  Gilles  Vollant

       Version 1.2.3 Copyright (C) 1995-2005 Jean-loup Gailly (
       and Mark Adler (

       This software is provided "as-is," without any express or implied  war-
       ranty.   In  no  event  will the authors be held liable for any damages
       arising from the use of this software.  See the distribution  directory
       with  respect  to  requirements  governing redistribution.  The deflate
       format used by zlib was defined by Phil Katz.   The  deflate  and  zlib
       specifications  were  written  by  L. Peter Deutsch.  Thanks to all the
       people who reported problems  and  suggested  various  improvements  in
       zlib; who are too numerous to cite here.

       UNIX manual page by R. P. C. Rodgers, U.S. National Library of Medicine

                                 18 July 2005                          ZLIB(3)


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