package autodie::Scope::GuardStack; use strict; use warnings; use autodie::Scope::Guard; # ABSTRACT: Hook stack for managing scopes via %^H our $VERSION = '2.26'; # 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. 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 Eniels@thykier.netE =head1 LICENSE This module is free software. You may distribute it under the same terms as Perl itself.