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package autodie::Scope::GuardStack;
use strict;
use warnings;
use autodie::Scope::Guard;
# ABSTRACT: Hook stack for managing scopes via %^H
our $VERSION = '2.32'; # VERSION
my $H_KEY_STEM = __PACKAGE__ . '/guard';
my $COUNTER = 0;
# This code schedules the cleanup of subroutines at the end of
# scope. It's directly inspired by chocolateboy's excellent
# Scope::Guard module.
sub new {
my ($class) = @_;
return bless([], $class);
}
sub push_hook {
my ($self, $hook) = @_;
my $h_key = $H_KEY_STEM . ($COUNTER++);
my $size = @{$self};
$^H{$h_key} = autodie::Scope::Guard->new(sub {
# Pop the stack until we reach the right size
# - this may seem weird, but it is to avoid relying
# on "destruction order" of keys in %^H.
#
# Example:
# {
# use autodie; # hook 1
# no autodie; # hook 2
# use autodie; # hook 3
# }
#
# Here we want call hook 3, then hook 2 and finally hook 1.
# Any other order could have undesired consequences.
#
# Suppose hook 2 is destroyed first, it will pop hook 3 and
# then hook 2. hook 3 will then be destroyed, but do nothing
# since its "frame" was already popped and finally hook 1
# will be popped and take its own frame with it.
#
# We need to check that $self still exists since things can get weird
# during global destruction.
$self->_pop_hook while $self && @{$self} > $size;
});
push(@{$self}, [$hook, $h_key]);
return;
}
sub _pop_hook {
my ($self) = @_;
my ($hook, $key) = @{ pop(@{$self}) };
my $ref = delete($^H{$key});
$hook->();
return;
}
sub DESTROY {
my ($self) = @_;
# To be honest, I suspect @{$self} will always be empty here due
# to the subs in %^H having references to the stack (which would
# keep the stack alive until those have been destroyed). Anyhow,
# it never hurt to be careful.
$self->_pop_hook while @{$self};
return;
}
1;
__END__
=head1 NAME
autodie::Scope::GuardStack - Hook stack for managing scopes via %^H
=head1 SYNOPSIS
use autodie::Scope::GuardStack;
my $stack = autodie::Scope::GuardStack->new
$^H{'my-key'} = $stack;
$stack->push_hook(sub {});
=head1 DESCRIPTION
This class is a stack of hooks to be called in the right order as
scopes go away. The stack is only useful when inserted into C<%^H>
and will pop hooks as their "scope" is popped. This is useful for
uninstalling or reinstalling subs in a namespace as a pragma goes
out of scope.
Due to how C<%^H> works, this class is only useful during the
compilation phase of a perl module and relies on the internals of how
perl handles references in C<%^H>. This module is not a part of
autodie's public API.
=head2 Methods
=head3 new
my $stack = autodie::Scope::GuardStack->new;
Creates a new C<autodie::Scope::GuardStack>. The stack is initially
empty and must be inserted into C<%^H> by the creator.
=head3 push_hook
$stack->push_hook(sub {});
Add a sub to the stack. The sub will be called once the current
compile-time "scope" is left. Multiple hooks can be added per scope
=head1 AUTHOR
Copyright 2013, Niels Thykier E<lt>niels@thykier.netE<gt>
=head1 LICENSE
This module is free software. You may distribute it under the
same terms as Perl itself.
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