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+#ifndef _sys_DeletionManager_h
+#define _sys_DeletionManager_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 <vector>
+#include <algorithm>
+#include <boost/shared_ptr.hpp>
+
+namespace qpid {
+namespace sys {
+
+struct deleter
+{
+ template <typename T>
+ void operator()(T* ptr){ delete ptr;}
+};
+
+/**
+ * DeletionManager keeps track of handles that need to be deleted but may still be
+ * in use by one of the threads concurrently.
+ *
+ * The mode of operation is like this:
+ * - When we want to delete but we might still be using the handle we
+ * * Transfer ownership of the handle to this class
+ * * Mark the handle as (potentially) in use by every thread
+ * - Then subsequently at points where the thread code knows it isn't
+ * using any handles it declares that it is using no handles
+ * - When the last thread declares no use of a handle it automatically
+ * gets deleted by the shared_ptr implementation
+ *
+ * The class only has static members and data and so can only be used once for
+ * any particular handle type
+ */
+template <typename H>
+class DeletionManager
+{
+public:
+ // Mark every thread as using the handle - it will be deleted
+ // below after every thread marks the handle as unused
+ static void markForDeletion(H* handle) {
+ allThreadsStatuses.addHandle(shared_ptr(handle));
+ }
+
+ // Mark this thread is not using any handle -
+ // handles get deleted here when no one else
+ // is using them either
+ static void markAllUnusedInThisThread() {
+ static __thread ThreadStatus* threadStatus = 0;
+
+ // Thread local vars can't be dynamically constructed so we need
+ // to check whether we've made it yet and construct it if not
+ // (no locking necessary for the check as it's thread local!)
+ if (!threadStatus) {
+ threadStatus = new ThreadStatus;
+ allThreadsStatuses.addThreadStatus(threadStatus);
+ }
+
+ ScopedLock<Mutex> l(threadStatus->lock);
+
+ // The actual deletions will happen here when all the shared_ptr
+ // ref counts hit 0 (that is when every thread marks the handle unused)
+ threadStatus->handles.clear();
+ }
+
+private:
+ typedef boost::shared_ptr<H> shared_ptr;
+
+ // In theory we know that we never need more handles than the number of
+ // threads runnning so we could use a fixed size array. However at this point
+ // in the code we don't have easy access to this information.
+ struct ThreadStatus
+ {
+ Mutex lock;
+ std::vector<shared_ptr> handles;
+ };
+
+ class AllThreadsStatuses
+ {
+ Mutex lock;
+ std::vector<ThreadStatus*> statuses;
+
+ struct handleAdder
+ {
+ shared_ptr handle;
+
+ handleAdder(shared_ptr h): handle(h) {}
+
+ void operator()(ThreadStatus* ptr) {
+ ScopedLock<Mutex> l(ptr->lock);
+ ptr->handles.push_back(handle);
+ }
+ };
+
+ public:
+ // Need this to be able to do static initialisation
+ explicit AllThreadsStatuses(int) {}
+
+ ~AllThreadsStatuses() {
+ ScopedLock<Mutex> l(lock);
+ std::for_each(statuses.begin(), statuses.end(), deleter());
+ }
+
+ void addThreadStatus(ThreadStatus* t) {
+ ScopedLock<Mutex> l(lock);
+ statuses.push_back(t);
+ }
+
+ void addHandle(shared_ptr h) {
+ ScopedLock<Mutex> l(lock);
+ std::for_each(statuses.begin(), statuses.end(), handleAdder(h));
+ }
+ };
+
+ static AllThreadsStatuses allThreadsStatuses;
+};
+
+}}
+#endif // _sys_DeletionManager_h