1 files changed, 91 insertions, 0 deletions
diff --git a/qpid/cpp/src/qpid/sys/Stoppable.h b/qpid/cpp/src/qpid/sys/Stoppable.h
new file mode 100644
index 0000000000..af21af46ba
--- /dev/null
+++ b/qpid/cpp/src/qpid/sys/Stoppable.h
@@ -0,0 +1,91 @@
+#ifndef QPID_SYS_STOPPABLE_H
+#define QPID_SYS_STOPPABLE_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.
+ *
+ */
+namespace qpid {
+namespace sys {
+
+/**
+ * An activity that may be executed by multiple threads, and can be stopped.
+ * Stopping prevents new threads from entering and waits till exiting busy threads leave.
+ */
+class Stoppable {
+  public:
+    Stoppable() : busy(0), stopped(false) {}
+    ~Stoppable() { stop(); }
+
+    /** Mark the scope of a busy thread like this:
+     * <pre>
+     * {
+     *   Stoppable::Scope working(stoppable);
+     *   if (working) { do stuff }
+     * }
+     * </pre>
+     */
+    class Scope {
+        Stoppable& state;
+        bool entered;
+      public:
+        Scope(Stoppable& s) : state(s) { entered = s.enter(); }
+        ~Scope() { if (entered) state.exit(); }
+        operator bool() const { return entered; }
+    };
+
+  friend class Scope;
+
+    /** Mark  stopped, wait for all threads to leave their busy scope. */
+    void stop() {
+        sys::Monitor::ScopedLock l(lock);
+        stopped = true;
+        while (busy > 0) lock.wait();
+    }
+
+    /** Set the state to started.
+     *@pre state is stopped and no theads are busy.
+     */
+    void start() {
+        sys::Monitor::ScopedLock l(lock);
+        assert(stopped && busy == 0); // FIXME aconway 2011-05-06: error handling.
+        stopped = false;
+    }
+
+  private:
+    uint busy;
+    bool stopped;
+    sys::Monitor lock;
+
+    bool enter() {
+        sys::Monitor::ScopedLock l(lock);
+        if (!stopped) ++busy;
+        return !stopped;
+    }
+
+    void exit() {
+        sys::Monitor::ScopedLock l(lock);
+        assert(busy > 0);
+        if (--busy == 0) lock.notifyAll();
+    }
+};
+
+}} // namespace qpid::sys
+
+#endif  /*!QPID_SYS_STOPPABLE_H*/