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

dep/include/zthread/BiasedReadWriteLock.h

@@ -0,0 +1,319 @@
+/*
+ * 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 __ZTBIASEDREADWRITELOCK_H__
+#define __ZTBIASEDREADWRITELOCK_H__
+
+#include "zthread/ReadWriteLock.h"
+#include "zthread/Condition.h"
+#include "zthread/Guard.h"
+#include "zthread/FastMutex.h"
+
+namespace ZThread {
+
+  /**
+   * @class BiasedReadWriteLock
+   *
+   * @author Eric Crahen <http://www.code-foo.com>
+   * @date <2003-07-16T10:22:34-0400>
+   * @version 2.2.7
+   *  
+   * A BiasedReadWriteLock has a bias toward writers. It will prefer read-write access over 
+   * read-only access when many threads are contending for access to either Lockable this
+   * ReadWriteLock provides.
+   *
+   * @see ReadWriteLock 
+   */
+  class BiasedReadWriteLock : public ReadWriteLock {
+
+    FastMutex _lock;
+    Condition _condRead;
+    Condition _condWrite;
+  
+    volatile int _activeWriters;
+    volatile int _activeReaders; 
+
+    volatile int _waitingReaders;
+    volatile int _waitingWriters;
+
+    //! @class ReadLock
+    class ReadLock : public Lockable {
+
+      BiasedReadWriteLock& _rwlock;
+
+    public:
+
+      ReadLock(BiasedReadWriteLock& rwlock) : _rwlock(rwlock) {}
+
+      virtual ~ReadLock() {}
+
+      virtual void acquire() {
+        _rwlock.beforeRead();
+      }
+
+      virtual bool tryAcquire(unsigned long timeout) {            
+        return _rwlock.beforeReadAttempt(timeout);
+      }
+
+      virtual void release() {
+        _rwlock.afterRead();
+      }
+
+    };
+
+    //! @class WriteLock
+    class WriteLock : public Lockable {
+
+      BiasedReadWriteLock& _rwlock;
+
+    public:
+
+      WriteLock(BiasedReadWriteLock& rwlock) : _rwlock(rwlock) {}
+
+      virtual ~WriteLock() {}
+
+
+      virtual void acquire() {
+        _rwlock.beforeWrite();
+      }
+
+      virtual bool tryAcquire(unsigned long timeout) {            
+        return _rwlock.beforeWriteAttempt(timeout);
+      }
+
+      virtual void release() {
+        _rwlock.afterWrite();
+      }
+
+    };
+
+    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.
+     */
+    BiasedReadWriteLock() : _condRead(_lock), _condWrite(_lock), _rlock(*this), _wlock(*this) {
+
+      _activeWriters = 0;
+      _activeReaders = 0;
+ 
+      _waitingReaders = 0;
+      _waitingWriters = 0;
+
+    }
+
+    //! Destroy this ReadWriteLock
+    virtual ~BiasedReadWriteLock() {}
+
+    /**
+     * @see ReadWriteLock::getReadLock()
+     */
+    virtual Lockable& getReadLock() { return _rlock; }
+
+    /**
+     * @see ReadWriteLock::getWriteLock()
+     */
+    virtual Lockable& getWriteLock() { return _wlock; }
+
+  
+  protected:
+
+    void beforeRead() {
+    
+      Guard<FastMutex> guard(_lock); 
+    
+      ++_waitingReaders;  
+    
+      while(!allowReader()) {
+      
+        try {
+        
+          // wait
+          _condRead.wait();
+        
+        } catch(...) {
+        
+          --_waitingReaders;        
+          throw;
+
+        }
+      
+      }
+    
+      --_waitingReaders;
+      ++_activeReaders;
+    
+    }
+
+    bool beforeReadAttempt(unsigned long timeout) {
+      
+      Guard<FastMutex> guard(_lock); 
+      bool result = false;
+
+      ++_waitingReaders;  
+
+      while(!allowReader()) {
+        
+        try {
+          
+          result = _condRead.wait(timeout);
+          
+        } catch(...) {
+          
+          --_waitingReaders;          
+          throw;
+
+        }
+
+      }
+      
+      --_waitingReaders;
+      ++_activeReaders;
+
+      return result;
+    }   
+  
+
+    void afterRead() {
+
+      bool wakeReader = false;
+      bool wakeWriter = false;
+
+      {
+
+        Guard<FastMutex> guard(_lock);
+      
+        --_activeReaders;
+
+        wakeReader = (_waitingReaders > 0);
+        wakeWriter = (_waitingWriters > 0);
+
+      }
+
+      if(wakeWriter)
+        _condWrite.signal();
+    
+      else if(wakeReader)
+        _condRead.signal();
+
+    }
+
+    void beforeWrite() {
+    
+      Guard<FastMutex> guard(_lock);
+  
+      ++_waitingWriters;
+
+      while(!allowWriter()) {
+        
+        try {
+
+          _condWrite.wait();
+          
+        } catch(...) {
+
+          --_waitingWriters;
+          throw;
+
+        }
+        
+      }
+      
+      --_waitingWriters;
+      ++_activeWriters;    
+
+    }
+
+    bool beforeWriteAttempt(unsigned long timeout) {
+  
+      Guard<FastMutex> guard(_lock);
+      bool result = false;
+
+      ++_waitingWriters;
+
+      while(!allowWriter()) {
+        
+        try {
+
+          result = _condWrite.wait(timeout);
+          
+        } catch(...) {
+
+          --_waitingWriters;
+          throw;
+        }
+        
+      }
+      
+      --_waitingWriters;
+      ++_activeWriters;
+      
+      return result;
+
+    }
+
+    void afterWrite() {
+
+      bool wakeReader = false;
+      bool wakeWriter = false;
+
+      {
+
+        Guard<FastMutex> guard(_lock);
+      
+        --_activeWriters;
+      
+        wakeReader = (_waitingReaders > 0);
+        wakeWriter = (_waitingWriters > 0);
+
+      }
+
+      if(wakeWriter)
+        _condWrite.signal();
+    
+      else if(wakeReader)
+        _condRead.signal();
+   
+    }
+
+    bool allowReader() {
+      return (_activeWriters == 0);   
+    }
+
+    bool allowWriter() {
+      return (_activeWriters == 0 && _activeReaders == 0);
+    }
+
+  };
+
+}; // __ZTBIASEDREADWRITELOCK_H__
+
+#endif