From 4f6b63abf59c2478968506e0e779d0992323534f Mon Sep 17 00:00:00 2001
From: Oliver Tappe
Date: Mon, 24 Mar 2008 10:41:16 +0000
Subject: * Switched from explicit cleanup functions to "resource acquisition
 by definition",   implemented by the new ScopedResource class. This change
 improves robustness   with respect to signals and unexpected errors and makes
 the code cleaner.

git-svn-id: http://svn.openslx.org/svn/openslx/openslx/trunk@1678 95ad53e4-c205-0410-b2fa-d234c58c8868
---
 lib/OpenSLX/ScopedResource.pm | 91 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 lib/OpenSLX/ScopedResource.pm

(limited to 'lib/OpenSLX/ScopedResource.pm')

diff --git a/lib/OpenSLX/ScopedResource.pm b/lib/OpenSLX/ScopedResource.pm
new file mode 100644
index 00000000..c905b50a
--- /dev/null
+++ b/lib/OpenSLX/ScopedResource.pm
@@ -0,0 +1,91 @@
+# Copyright (c) 2008 - OpenSLX GmbH
+#
+# This program is free software distributed under the GPL version 2.
+# See http://openslx.org/COPYING
+#
+# If you have any feedback please consult http://openslx.org/feedback and
+# send your suggestions, praise, or complaints to feedback@openslx.org
+#
+# General information about OpenSLX can be found at http://openslx.org/
+# -----------------------------------------------------------------------------
+# ScopedResource.pm
+#    - a helper class that releases resources if the object leaves scope
+# -----------------------------------------------------------------------------
+package OpenSLX::ScopedResource;
+
+use strict;
+use warnings;
+
+our $VERSION = 1.01;        # API-version . implementation-version
+
+# make sure that we catch any signals in order to properly released scoped
+# resources
+use sigtrap qw( die normal-signals error-signals );
+
+use OpenSLX::Basics;
+
+sub new
+{
+    my $class = shift;
+    my $params = shift;
+    
+    checkParams($params, {
+        name    => '!',
+        acquire => '!',
+        release => '!',
+    });
+
+    my $self = {
+        name    => $params->{name},
+        owner   => 0,
+        acquire => $params->{acquire},
+        release => $params->{release},
+    };
+    
+    bless $self, $class;
+    
+    $self->acquire();
+    
+    return $self;
+}
+
+sub acquire
+{
+    my $self = shift;
+
+    # acquire the resource and set ourselves as owner
+    if ($self->{acquire}->()) {
+        vlog(1, "process $$ acquired resource $self->{name}");
+        $self->{owner} = $$;
+    }
+}
+
+sub release
+{
+    my $self = shift;
+
+    # only release the resource if invoked by the owning process
+    vlog(3, "process $$ tries to release resource $self->{name}");
+    return if $self->{owner} != $$;
+    
+    # release the resource and unset owner
+    if ($self->{release}->()) {
+        vlog(1, "process $$ released resource $self->{name}");
+        $self->{owner} = 0;
+    }
+}
+
+sub DESTROY
+{
+    my $self = shift;
+    
+    $self->release();
+    
+    # remove references to functions, in order to release any closures
+    $self->{acquire} = undef;
+    $self->{release} = undef;
+    
+    return;
+}
+
+1;
-- 
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