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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, assuming that the standard library functions  used
       are  thread  safe, such as memory allocation routines.  It provides in-
       memory compression and  decompression  functions,  including  integrity
       checks  of the uncompressed data.  This version of the library supports
       only one compression method (deflation) but  other  algorithms  may  be
       added later with the same stream interface.

       Compression  can  be  done  in  a  single step if the buffers are large
       enough or can be done by repeated calls of  the  compression  function.
       In the latter case, the application must provide more input and/or con-
       sume the output (providing 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 the 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, as well as other exam-
       ples in the examples/ directory.

       Changes to this version are  documented  in  the  file  ChangeLog  that
       accompanies the source.

       zlib is available in Java using the package:


       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:


       zlib is built into tcl:


       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
              contrib/minizip  directory of the main zlib source distribution.


       The zlib web site can be found at:


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

      (for  the  zlib  header and
              trailer format)
     (for the deflate  compressed
              data format)
      (for  the  gzip  header and
              trailer format)

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



       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 1.2.4 Copyright (C) 1995-2010 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

                                 14 March 2010                         zlib(3)

zlib 1.2.4 - Generated Mon Mar 15 08:02:17 CDT 2010
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