XS(3)							User Contributed Perl Documentation						     XS(3)

NAME

       Readonly::XS - Companion module for Readonly.pm, to speed up read-only scalar variables.

VERSION

       This document describes version 1.05 of Readonly::XS, February 24, 2009.

SYNOPSIS

	 Install this module, but do not use it.

DESCRIPTION

       The Readonly module (q.v.) is an effective way to create non-modifiable variables.  However, it's relatively slow.

       The reason it's slow is that is implements the read-only-ness of variables via tied objects.  This mechanism is inherently slow.  Perl
       simply has to do a lot of work under the hood to make tied variables work.

       This module corrects the speed problem, at least with respect to scalar variables.  When Readonly::XS is installed, Readonly uses it to
       access the internals of scalar variables.  Instead of creating a scalar variable object and tying it, Readonly simply flips the SvREADONLY
       bit in the scalar's FLAGS structure.

       Readonly arrays and hashes are not sped up by this, since the SvREADONLY flag only works for scalars.  Arrays and hashes always use the tie
       interface.

       Why implement this as a separate module?  Because not everyone can use XS.  Not everyone has a C compiler.  Also, installations with a
       statically-linked perl may not want to recompile their perl binary just for this module.  Rather than render Readonly.pm useless for
	these people, the XS portion was put into a separate module.

       Programs that you write do not need to know whether Readonly::XS is installed or not.  They should just "use Readonly" and let Readonly
       worry about whether or not it can use XS.  If the Readonly::XS is present, Readonly will be faster.  If not, it won't.  Either way, it will
       still work, and your code will not have to change.

       Your program can check whether Readonly.pm is using XS or not by examining the $Readonly::XSokay variable.  It will be true if the XS
       module was found and is being used.  Please do not change this variable.

   EXPORTS
       None.

SEE ALSO

       Readonly.pm

AUTHOR 
/ COPYRIGHT
       Eric Roode, roode@cpan.org

       Copyright (c) 2003-2009 by Eric J. Roode. All Rights Reserved.  This module is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

       To avoid my spam filter, please include "Perl", "module", or this module's name in the message's subject line, and/or GPG-sign your
       message.

perl v5.16.3							    2009-02-24								     XS(3)