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+#ifndef QPID_PLUGIN_H
+#define QPID_PLUGIN_H
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+
+#include <boost/noncopyable.hpp>
+#include <boost/function.hpp>
+#include <vector>
+#include "qpid/CommonImportExport.h"
+
+/**@file Generic plug-in framework. */
+
+namespace qpid {
+struct Options;
+
+/**
+ * Plug-in base class.
+ */
+class Plugin : private boost::noncopyable {
+ public:
+ typedef std::vector<Plugin*> Plugins;
+ /** Default value returned by initOrder() */
+ static const int DEFAULT_INIT_ORDER=1000;
+
+ /**
+ * Base interface for targets that can receive plug-ins.
+ * Also allows plug-ins to attach a a function to be called
+ * when the target is 'finalized'.
+ */
+ class Target : private boost::noncopyable
+ {
+ public:
+ /** Calls finalize() if not already called. */
+ QPID_COMMON_EXTERN virtual ~Target();
+
+ /** Run all the finalizers */
+ QPID_COMMON_EXTERN void finalize();
+
+ /** Add a function to run when finalize() is called */
+ QPID_COMMON_EXTERN void addFinalizer(const boost::function<void()>&);
+
+ private:
+ std::vector<boost::function<void()> > finalizers;
+ };
+
+ /**
+ * Constructor registers the plug-in to appear in getPlugins().
+ *
+ * A concrete Plugin is instantiated as a global or static
+ * member variable in a library so it is registered during
+ * initialization when the library is loaded.
+ */
+ QPID_COMMON_EXTERN Plugin();
+
+ QPID_COMMON_EXTERN virtual ~Plugin();
+
+ /**
+ * Configuration options for the plugin.
+ * Then will be updated during option parsing by the host program.
+ *
+ * @return An options group or 0 for no options. Default returns 0.
+ * Plugin retains ownership of return value.
+ */
+ QPID_COMMON_EXTERN virtual Options* getOptions();
+
+ /**
+ * Initialize Plugin functionality on a Target, called before
+ * initializing the target.
+ *
+ * Plugins should ignore targets they don't recognize.
+ *
+ * Called before the target itself is initialized.
+ */
+ virtual void earlyInitialize(Target&) = 0;
+
+ /**
+ * Initialize Plugin functionality on a Target. Called after
+ * initializing the target.
+ *
+ * Plugins should ignore targets they don't recognize.
+ *
+ * Called after the target is fully initialized.
+ */
+ virtual void initialize(Target&) = 0;
+
+ /**
+ * Initialization order. If a plugin does not override this, it
+ * returns DEFAULT_INIT_ORDER. Plugins that need to be initialized
+ * earlier/later than normal can override initOrder to return
+ * a lower/higher value than DEFAULT_INIT_ORDER.
+ */
+ QPID_COMMON_EXTERN virtual int initOrder() const;
+
+ /** List of registered Plugin objects.
+ * Caller must not delete plugin pointers.
+ */
+ QPID_COMMON_EXTERN static const Plugins& getPlugins();
+
+ /** Call earlyInitialize() on all registered plugins */
+ QPID_COMMON_EXTERN static void earlyInitAll(Target&);
+
+ /** Call initialize() on all registered plugins */
+ QPID_COMMON_EXTERN static void initializeAll(Target&);
+
+ /** For each registered plugin, add plugin.getOptions() to opts. */
+ QPID_COMMON_EXTERN static void addOptions(Options& opts);
+};
+
+} // namespace qpid
+
+#endif /*!QPID_PLUGIN_H*/