Public API Reference

cstool/framedataholder.h

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/*
    Copyright (C) 2004 by Jorrit Tyberghein
              (C) 2004 by Frank Richter

    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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#ifndef __CS_CSTOOL_FRAMEDATAHOLDER_H__
#define __CS_CSTOOL_FRAMEDATAHOLDER_H__

#include "csutil/array.h"

template <class T>
class csFrameDataHolder
{
  struct FrameData
  {
    uint lastFrame;
    T data;
  };
  csArray<FrameData> data;
  size_t lastData;
  uint nextShrink;
  uint lastFrame;
  uint clearReq;

  void NewFrame()
  {
    if (clearReq != (uint)~0)
    {
      data.DeleteAll();
      clearReq = (uint)~0;
    }
    // Try to shrink the cache to a size that reflects what's needed
    if (lastFrame > nextShrink)
    {
      /* lastData is reset every frame, so it gives a good indicator
       * on how much has been used the last frame */
      data.Truncate (lastData+1);
      data.ShrinkBestFit ();
      nextShrink = (uint)~0;
    }
    else if (lastData+1 < data.GetSize())
    {
      // Last frame we used less cache than available.
      // "Schedule" a shrink in the future.
      nextShrink = lastFrame + 5;
    }
    lastData = 0;
  }
public:
  csFrameDataHolder () : lastData(0), nextShrink((uint)~0),
        lastFrame((uint)~0), clearReq((uint)~0)
  { }
  ~csFrameDataHolder () { }

  T& GetUnusedData (bool& created, uint frameNumber)
  {
    if (lastFrame != frameNumber)
    {
      NewFrame();
      lastFrame = frameNumber;
    }
    created = false;
    if ((data.GetSize() == 0) || (data[lastData].lastFrame == frameNumber))
    {
      size_t startPoint = lastData;
      //check the list
      if (data.GetSize() > 0)
      {
        do
        {
          if (data[lastData].lastFrame != frameNumber)
            break;
          lastData++;
          if (lastData >= data.GetSize()) lastData = 0;
        }
        while (lastData != startPoint);
      }
      if (lastData == startPoint)
      {
        data.SetSize ((lastData = data.GetSize ()) + 1);
        created = true;
      }
    }
  
    FrameData& frameData = data[lastData];
    frameData.lastFrame = frameNumber;
    return frameData.data;
  }
  
  void Clear (bool instaClear = false)
  {
    if (instaClear)
      data.DeleteAll();
    else
      // Don't clear just yet, rather, clear when we enter the next frame.
      clearReq = lastFrame;
  }
};

#endif // __CS_CSTOOL_FRAMEDATAHOLDER_H__

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