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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

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 (or [email protected]).

AUTHORS

CONTRIBUTORS

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.