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extern/stdcxx/4.2.1/examples/manual/mutex.cpp

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+/**************************************************************************
+ *
+ * mutex.cpp - Example program for mutex.
+ *
+ * This program illustraes how to mutexes are used to synchronize access
+ * to resources in a multi-threaded program.
+ * 
+ * NOTE: this program exposes implementation details of the Rogue Wave(R)
+ *       C++ Standard library which are subject to change without notice
+ *       from one version of the library to another. Portable code should
+ *       avoid relying on any implementation details.
+ *
+ * $Id: mutex.cpp 550991 2007-06-26 23:58:07Z sebor $
+ *
+ ***************************************************************************
+ *
+ * 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.
+ *
+ * Copyright 1994-2006 Rogue Wave Software.
+ * 
+ **************************************************************************/
+
+#include <iostream>      // for cout
+#include <rw/_mutex.h>   // for __rw::__rw_mutex
+
+#include <examples.h>
+
+
+#ifdef _RWSTD_REENTRANT
+
+// An integer shared amongst multiple threads.
+int shared;
+
+// A mutex used to synchronize updates to shared.
+__rw::__rw_mutex shared_mutex;
+
+// Increment shared by one.  Uses a mutex directly.
+void increment_shared ()
+{
+    shared_mutex._C_acquire();  // Lock the mutex.
+    ++shared;
+    shared_mutex._C_release();  // Unlock the mutex.
+}
+
+
+// Decrement shared by one.  Uses a mutex guard.
+void decrement_shared ()
+{
+    _RWSTD_MT_GUARD (shared_mutex);  // Acquire the lock on shared_mutex.
+    --shared;
+    // The lock on shared is released when destructor is called on guard.
+}
+
+
+int exchange_shared ()
+{
+    int new_value = shared;
+
+    new_value *= new_value;
+
+    // atomically assign new_value to shared and return shared's old value
+    int old_value = _RWSTD_ATOMIC_SWAP (shared, new_value, shared_mutex);
+
+    return old_value;
+}
+
+#endif   // _RWSTD_REENTRANT
+
+
+int main()
+{
+#ifdef _RWSTD_REENTRANT
+
+    increment_shared();
+    decrement_shared();
+
+    std::cout << "Multi Threading enabled" << std::endl;
+
+#else   // if !defined (_RWSTD_REENTRANT)
+
+    std::cout << "Multi Threading not enabled" << std::endl;
+
+#endif   // _RWSTD_REENTRANT
+
+    return 0;
+}