Imported MaNGOS revision 6767 from http://mangos.svn.sourceforge.net/svnroot/mangos/trunk/

dep/include/zthread/FairReadWriteLock.h

@@ -0,0 +1,183 @@
+/*
+ * Copyright (c) 2005, Eric Crahen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is furnished
+ * to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#ifndef __ZTFAIRREADWRITELOCK_H__
+#define __ZTFAIRREADWRITELOCK_H__
+
+#include "zthread/ReadWriteLock.h"
+#include "zthread/Condition.h"
+#include "zthread/Guard.h"
+#include "zthread/Mutex.h"
+
+namespace ZThread {
+
+  /**
+   * @class FairReadWriteLock
+   *
+   * @author Eric Crahen <http://www.code-foo.com>
+   * @date <2003-07-16T10:26:25-0400>
+   * @version 2.2.7
+   *  
+   * A FairReadWriteLock maintains a balance between the order read-only access 
+   * and read-write access is allowed. Threads contending for the pair of Lockable
+   * objects this ReadWriteLock provides will gain access to the locks in FIFO order.
+   *
+   * @see ReadWriteLock 
+   */
+  class FairReadWriteLock : public ReadWriteLock {
+
+    Mutex _lock;
+    Condition _cond;
+  
+    volatile int _readers;
+
+    //! @class ReadLock
+    class ReadLock : public Lockable {
+
+      FairReadWriteLock& _rwlock;
+
+    public:
+
+      ReadLock(FairReadWriteLock& rwlock) : _rwlock(rwlock) {}
+
+      virtual ~ReadLock() {}
+
+      virtual void acquire() {
+
+        Guard<Mutex> g(_rwlock._lock);
+        ++_rwlock._readers; 
+
+      }
+
+      virtual bool tryAcquire(unsigned long timeout) {
+      
+        if(!_rwlock._lock.tryAcquire(timeout))
+          return false;
+
+        ++_rwlock._readers; 
+        _rwlock._lock.release();
+
+        return true;
+      }
+
+      virtual void release() {
+
+        Guard<Mutex> g(_rwlock._lock);
+        --_rwlock._readers; 
+
+        if(_rwlock._readers == 0)
+          _rwlock._cond.signal();
+
+      }
+
+    };
+
+    //! @class WriteLock
+    class WriteLock : public Lockable {
+
+      FairReadWriteLock& _rwlock;
+
+    public:
+
+      WriteLock(FairReadWriteLock& rwlock) : _rwlock(rwlock) {}
+
+      virtual ~WriteLock() {}
+
+      virtual void acquire() {
+
+        _rwlock._lock.acquire();
+
+        try {
+
+          while(_rwlock._readers > 0)
+            _rwlock._cond.wait();
+
+        } catch(...) {
+
+          _rwlock._lock.release();
+          throw;
+
+        }
+
+      }
+
+      virtual bool tryAcquire(unsigned long timeout) {
+      
+        if(!_rwlock._lock.tryAcquire(timeout))
+          return false;
+
+        try {
+
+          while(_rwlock._readers > 0)
+            _rwlock._cond.wait(timeout);
+
+        } catch(...) {
+
+          _rwlock._lock.release();
+          throw;
+
+        }
+
+        return true;
+
+      }
+
+      virtual void release() {
+        _rwlock._lock.release();
+      }
+
+    };
+
+    friend class ReadLock;
+    friend class WriteLock;
+
+    ReadLock _rlock;
+    WriteLock _wlock;
+
+  public:
+  
+    /**
+     * Create a BiasedReadWriteLock
+     *
+     * @exception Initialization_Exception thrown if resources could not be 
+     *            allocated for this object.
+     */
+    FairReadWriteLock() : _cond(_lock), _readers(0), _rlock(*this), _wlock(*this) {}
+
+    //! Destroy this ReadWriteLock
+    virtual ~FairReadWriteLock() {}
+
+    /**
+     * @see ReadWriteLock::getReadLock()
+     */
+    virtual Lockable& getReadLock() { return _rlock; }
+
+    /**
+     * @see ReadWriteLock::getWriteLock()
+     */
+    virtual Lockable& getWriteLock() { return _wlock; }
+  
+  };
+
+}; // __ZTFAIRREADWRITELOCK_H__
+
+#endif