ZLIB(3)                C LIBRARY FUNCTIONS                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 stan-
     dard 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 consume 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

     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

     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  test/example.c  and
     test/minigzip.c,  as well as other examples in the examples/

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

     zlib is built in to many languages  and  operating  systems,
     including  but not limited to Java, Python, .NET, PHP, Perl,
     Ruby, Swift, and Go.

     An experimental package to read and write files in the  .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.

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     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; other-
     wise, obtain the latest version and see if the problem still
     exists.  Please read the zlib FAQ at:

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


     Version 1.2.11

     Copyright (C) 1995-2017 Jean-loup Gailly and Mark Adler

     This software is provided 'as-is', without  any  express  or
     implied  warranty.   In  no  event  will the authors be held
     liable  for  any  damages  arising  from  the  use  of  this

     Permission is granted to anyone to use this software for any
     purpose,  including commercial applications, and to alter it
     and redistribute it freely, subject to  the  following  res-

        The origin of this software must not  be  misrepresented;
        you  must not claim that you wrote the original software.
        If you use this software in a product, an  acknowledgment

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ZLIB(3)                C LIBRARY FUNCTIONS                ZLIB(3)

        in  the product documentation would be appreciated but is
        not required.

        Altered source versions must be plainly marked  as  such,
        and  must  not  be  misrepresented  as being the original

        This notice may not be removed or altered from any source

     Jean-loup Gailly        Mark Adler

     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 (

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