XS(3pm)
NAME
Readonly::XS - Companion module for Readonly.pm, to speed up read-only
scalar variables.
VERSION
This document describes version 1.04 of Readonly::XS, December 6, 2005.
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) 2003-2005 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.
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