Package::Stash(3pm) User Contributed Perl Documentation Package::Stash(3pm)
NAME
Package::Stash - Routines for manipulating stashes
VERSION
version 0.40
SYNOPSIS
my $stash = Package::Stash->new('Foo');
$stash->add_symbol('%foo', {bar => 1});
# $Foo::foo{bar} == 1
$stash->has_symbol('$foo') # false
my $namespace = $stash->namespace;
*{ $namespace->{foo} }{HASH} # {bar => 1}
DESCRIPTION
Manipulating stashes (Perl's symbol tables) is occasionally necessary,
but incredibly messy, and easy to get wrong. This module hides all of
that behind a simple API.
NOTE: Most methods in this class require a variable specification that
includes a sigil. If this sigil is absent, it is assumed to represent
the IO slot.
Due to limitations in the typeglob API available to perl code, and to
typeglob manipulation in perl being quite slow, this module provides
two implementations - one in pure perl, and one using XS. The XS
implementation is to be preferred for most usages; the pure perl one is
provided for cases where XS modules are not a possibility. The current
implementation in use can be set by setting
$ENV{PACKAGE_STASH_IMPLEMENTATION} or $Package::Stash::IMPLEMENTATION
before loading Package::Stash (with the environment variable taking
precedence), otherwise, it will use the XS implementation if possible,
falling back to the pure perl one.
METHODS
new $package_name
Creates a new "Package::Stash" object, for the package given as the
only argument.
name
Returns the name of the package that this object represents.
namespace
Returns the raw stash itself.
add_symbol $variable $value %opts
Adds a new package symbol, for the symbol given as $variable, and
optionally gives it an initial value of $value. $variable should be the
name of variable including the sigil, so
Package::Stash->new('Foo')->add_symbol('%foo')
will create %Foo::foo.
Valid options (all optional) are "filename", "first_line_num", and
"last_line_num".
$opts{filename}, $opts{first_line_num}, and $opts{last_line_num} can be
used to indicate where the symbol should be regarded as having been
defined. Currently these values are only used if the symbol is a
subroutine ('"&"' sigil) and only if "$^P & 0x10" is true, in which
case the special %DB::sub hash is updated to record the values of
"filename", "first_line_num", and "last_line_num" for the subroutine.
If these are not passed, their values are inferred (as much as
possible) from "caller" information.
remove_glob $name
Removes all package variables with the given name, regardless of sigil.
has_symbol $variable
Returns whether or not the given package variable (including sigil)
exists.
get_symbol $variable
Returns the value of the given package variable (including sigil).
get_or_add_symbol $variable
Like "get_symbol", except that it will return an empty hashref or
arrayref if the variable doesn't exist.
remove_symbol $variable
Removes the package variable described by $variable (which includes the
sigil); other variables with the same name but different sigils will be
untouched.
list_all_symbols $type_filter
Returns a list of package variable names in the package, without
sigils. If a "type_filter" is passed, it is used to select package
variables of a given type, where valid types are the slots of a
typeglob ('SCALAR', 'CODE', 'HASH', etc). Note that if the package
contained any "BEGIN" blocks, perl will leave an empty typeglob in the
"BEGIN" slot, so this will show up if no filter is used (and similarly
for "INIT", "END", etc).
get_all_symbols $type_filter
Returns a hashref, keyed by the variable names in the package. If
$type_filter is passed, the hash will contain every variable of that
type in the package as values, otherwise, it will contain the typeglobs
corresponding to the variable names (basically, a clone of the stash).
This is especially useful for debuggers and profilers, which use
%DB::sub to determine where the source code for a subroutine can be
found. See
<http://perldoc.perl.org/perldebguts.html#Debugger-Internals> for more
information about %DB::sub.
WORKING WITH VARIABLES
It is important to note, that when working with scalar variables, the
default behavior is to copy values.
my $stash = Package::Stash->new('Some::Namespace');
my $variable = 1;
# $Some::Namespace::name is a copy of $variable
$stash->add_symbol('$name', $variable);
$variable++
# $Some::Namespace::name == 1 , $variable == 2
This will likely confuse people who expect it to work the same as
typeglob assignment, which simply creates new references to existing
variables.
my $variable = 1;
{
no strict 'refs';
# assign $Package::Stash::name = $variable
*{'Package::Stash::name'} = \$variable;
}
$variable++ # affects both names
If this behaviour is desired when working with Package::Stash, simply
pass Package::Stash a scalar ref:
my $stash = Package::Stash->new('Some::Namespace');
my $variable = 1;
# $Some::Namespace::name is now $variable
$stash->add_symbol('$name', \$variable);
$variable++
# $Some::Namespace::name == 2 , $variable == 2
This will be what you want as well if you're ever working with Readonly
variables:
use Readonly;
Readonly my $value, 'hello';
$stash->add_symbol('$name', \$value); # reference
print $Some::Namespace::name; # hello
# Tries to modify the read-only 'hello' and dies.
$Some::Namespace::name .= " world";
$stash->add_symbol('$name', $value); # copy
print $Some::Namespace::name; # hello
# No problem, modifying a copy, not the original
$Some::Namespace::name .= " world";
BUGS / CAVEATS
• Prior to perl 5.10, scalar slots are only considered to exist if
they are defined
This is due to a shortcoming within perl itself. See "Making
References" in perlref point 7 for more information.
• GLOB and FORMAT variables are not (yet) accessible through this
module.
• Also, see the BUGS section for the specific backends
(Package::Stash::XS and Package::Stash::PP)
SEE ALSO
• Class::MOP::Package
This module is a factoring out of code that used to live here
HISTORY
Based on code from Class::MOP::Package, by Stevan Little and the Moose
Cabal.
SUPPORT
Bugs may be submitted through the RT bug tracker
<https://rt.cpan.org/Public/Dist/Display.html?Name=Package-Stash> (or
bug-Package-Stash@rt.cpan.org <mailto:bug-Package-Stash@rt.cpan.org>).
AUTHORS
• Stevan Little <stevan.little@iinteractive.com>
• Jesse Luehrs <doy@tozt.net>
CONTRIBUTORS
• Karen Etheridge <ether@cpan.org>
• Carlos Lima <carlos@multi>
• Christian Walde <walde.christian@googlemail.com>
• Dave Rolsky <autarch@urth.org>
• Justin Hunter <justin.d.hunter@gmail.com>
• Kent Fredric <kentfredric@gmail.com>
• Niko Tyni <ntyni@debian.org>
• Renee <reb@perl-services.de>
• Tim Bunce <Tim.Bunce@pobox.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2022 by Jesse Luehrs.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
perl v5.34.0 2022-02-25 Package::Stash(3pm)
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