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/root/src/subsynth/syn/Util/FlyWeightPool.h

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/****************** <SYN heading BEGIN do not edit this line> *****************
 *
 * subsynth - modular audio synthesizer
 * subsynth is (C) Copyright 2001-2002 by Kevin Meinert
 *
 * Original Author: Kevin Meinert
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * -----------------------------------------------------------------
 * File:          $RCSfile: FlyWeightPool.h,v $
 * Date modified: $Date: 2002/04/08 16:13:29 $
 * Version:       $Revision: 1.13 $
 * -----------------------------------------------------------------
 *
 ****************** <SYN heading END do not edit this line> ******************/
#ifndef FLYWEIGHT_POOL
#define FLYWEIGHT_POOL

#include <list>
#include <assert.h>
#ifdef HAVE_VPR
#include <vpr/Sync/Mutex.h>
#endif

namespace syn
{
   
   template <class type>
   class FlyWeightPool
   {
   public:
      FlyWeightPool() : mAutoGrow( false ), mNumCheckedOut( 0 ), mSize( 0 ) 
      {
         this->acquire();
            mPool.resize( mSize );
         this->release();
      }
      ~FlyWeightPool()
      {
         assert( this != NULL && "this would be bad indeed" );
         this->acquire();
            assert( mNumCheckedOut == 0 && "not everyone has checked their items back into the pool" );
            assert( mPool.size() == mSize && "not everyone has checked their items back into the pool" );
            while (mPool.size() > 0)
            {
               delete mPool.front();
               mPool.pop_front();
            }
         this->release();
      }
      
      void setAutoGrow( bool grow ) { mAutoGrow = grow; }
      bool autoGrow() const { return mAutoGrow; }

#ifdef HAVE_VPR
      void acquire() const { mMutex.acquire(); }
      bool tryAcquire() const { return mMutex.tryAcquire(); }
      void release() const { mMutex.release(); }
#else
      void acquire() const {  }
      bool tryAcquire() const { return false; }
      void release() const {  }
#endif 

      void resize( unsigned int s )
      {
         this->acquire();
         {
            this->resize_nonthreadsafe( s );
         }      
         this->release();
      }
   
      unsigned int size() const { return mSize; }
   
      int available() const { return mPool.size(); }
   
      bool empty() const { return mPool.size() == 0; }
      
      void take( type* &t )
      {
         this->acquire();
            if (mAutoGrow && this->empty())
            {
               this->resize_nonthreadsafe( (this->size() + 1) * 2 );
            }         
            assert( this->empty() == false && "need to check empty() before take()ing" );
            t = mPool.front();
            mPool.pop_front();
            ++mNumCheckedOut;
         this->release();
      }
   
      void putback( type* t )
      {
         this->acquire();
         {
            if (mPool.size() < mSize)
               mPool.push_front( t );
   
            // resize was called, and this is our lazy way of 
            // deleting the extra flyweight...
            else
               delete t;
            
            --mNumCheckedOut;
         }
         this->release();
      }   
   
   private:
      void resize_nonthreadsafe( unsigned int s )
      {
         // compute deltas to grow or shrink
         int size_to_grow = (int)s - (int)mSize;
         int size_to_shrink = -size_to_grow;
         int x;
         
         // if user wants us to grow, add items to the pool
         for (x = 0; x < size_to_grow; ++x)
         {
            mPool.push_front( new type );
         }
         
         // if user wants us to shrink, remove items from the pool
         for (x = 0; x < size_to_shrink && mPool.size() > 0; ++x)
         {
            delete mPool.back();
            mPool.pop_back();
         }
         
         // resize is done, record the new size...
         mSize = s;
      }
   
#ifdef HAVE_VPR
      mutable vpr::Mutex mMutex;
#endif
      bool mAutoGrow;
      int mNumCheckedOut;
      unsigned int mSize;
      std::list<type*> mPool;

      
   };
   
}
#endif

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