* src/qpid/sys/Serializer.h: Serialize calls to a function,

	by queueing and dispatching in a separate thread if necessary.

	* src/qpid/sys/*/Mutex.h: trylock to return a bool.


git-svn-id: https://svn.apache.org/repos/asf/incubator/qpid/trunk/qpid@556679 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 125 insertions, 0 deletions

diff --git a/cpp/src/qpid/sys/Serializer.cpp b/cpp/src/qpid/sys/Serializer.cpp
new file mode 100644
index 0000000000..db2b3cab6d
--- /dev/null
+++ b/cpp/src/qpid/sys/Serializer.cpp
@@ -0,0 +1,125 @@
+/*
+ *
+ * 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 "qpid/sys/Serializer.h"
+#include "qpid/log/Statement.h"
+
+#include <boost/bind.hpp>
+
+#include <assert.h>
+
+namespace qpid {
+namespace sys {
+
+Serializer::Serializer(bool allowImmediate, Task notifyDispatchFn)
+    : state(IDLE), immediate(allowImmediate), notifyDispatch(notifyDispatchFn)
+{
+    if (notifyDispatch.empty())
+        notifyDispatch = boost::bind(&Serializer::notifyWorker, this);
+}
+
+Serializer::~Serializer() {
+    {
+        Mutex::ScopedLock l(lock);
+        state = SHUTDOWN;
+        lock.notify();
+    }
+    if (worker.id() != 0)
+        worker.join();
+}
+
+void Serializer::dispatch(Task& task) {
+    Mutex::ScopedUnlock u(lock);
+    // Preconditions: lock is held, state is EXECUTING or DISPATCHING
+    assert(state != IDLE);
+    assert(state != SHUTDOWN);
+    assert(state == EXECUTING || state == DISPATCHING);
+    try {
+        task();
+    } catch (const std::exception& e) {
+        QPID_LOG(error, "Unexpected exception in Serializer::dispatch"
+                 << e.what());
+        assert(0);              // Should not happen.
+    } catch (...) {
+        QPID_LOG(error, "Unexpected exception in Serializer::dispatch.");
+        assert(0);              // Should not happen.
+    }
+}
+
+void Serializer::execute(Task task) {
+    bool needNotify = false;
+    {
+        Mutex::ScopedLock l(lock);
+        assert(state != SHUTDOWN);
+        if (immediate && state == IDLE) {
+            state = EXECUTING;
+            dispatch(task);
+            if (state != SHUTDOWN) {
+                assert(state == EXECUTING);
+                state = IDLE;
+            }
+        }
+        else 
+            queue.push_back(task);
+
+        if (!queue.empty() && state == IDLE) {
+            state = DISPATCHING;
+            needNotify = true;
+        }
+    }
+    if (needNotify)
+        notifyDispatch();       // Not my function, call outside lock.
+}
+
+void Serializer::dispatch() {
+    Mutex::ScopedLock l(lock);
+    // TODO aconway 2007-07-16: This loop could be unbounded
+    // if other threads add work while we're in dispatch(Task&).
+    // If we need to bound it we could dispatch just the elements
+    // that were enqueued when dispatch() was first called - save
+    // begin() iterator and pop only up to that.
+    while (!queue.empty() && state != SHUTDOWN) {
+        assert(state == DISPATCHING);
+        dispatch(queue.front());
+        queue.pop_front();
+    }
+    if (state != SHUTDOWN) {
+        assert(state == DISPATCHING);
+        state = IDLE;
+    }
+}
+
+void Serializer::notifyWorker() {
+    if (!worker.id())
+        worker = Thread(*this);
+    else
+        lock.notify();
+}
+
+void Serializer::run() {
+    Mutex::ScopedLock l(lock);
+    while (state != SHUTDOWN) {
+        dispatch();
+        lock.wait();
+    }
+}
+
+}} // namespace qpid::sys