/*
  BUFFHANDLE.hpp  -  Buffer handling support for the render engine

  Copyright (C)         Lumiera.org
    2008,               Hermann Vosseler <Ichthyostega@web.de>

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of
  the License, or (at your option) any later version.

  This program 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 General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

/** @file buffhandle.hpp
 ** Various bits needed to support the buffer management within the render nodes.
 ** When pulling data from predecessor nodes and calculating new data, each render node
 ** needs several input and output buffers. These may be allocated and provided by several
 ** different "buffer providers" (for example the frame cache). Typically, the real buffers
 ** will be passed as parameters to the actual job instance when scheduled, drawing on the
 ** results of prerequisite jobs. Yet the actual job implementation remains agnostic with
 ** respect to the way actual buffers are provided; the invocation just pushes BuffHandle
 ** objects around. The actual render function gets an array of C-pointers to the actual
 ** buffers, and for accessing those buffers, the node needs to keep a table of buffer
 ** pointers, and for releasing the buffers later on, we utilise the buffer handles.
 ** The usage pattern of those buffer pointer tables is stack-like, thus the actual
 ** implementation utilises a single large buffer pointer array per pull() call
 ** sequence and dynamically claims small chunks for each node.
 ** 
 ** @see nodewiring-def.hpp
 ** @see nodeoperation.hpp
 ** @see bufftable.hpp       storage for the buffer table
 ** @see engine::RenderInvocation
 */

#ifndef ENGINE_BUFFHANDLE_H
#define ENGINE_BUFFHANDLE_H


#include "lib/error.hpp"
#include "lib/streamtype.hpp"
#include "lib/bool-checkable.hpp"


namespace engine {
  
  
  
  /**
   * Handle for a buffer for processing data, abstracting away the actual implementation.
   * The real buffer pointer can be retrieved by dereferencing this smart-handle class.
   * 
   * @todo as of 6/2011 it isn't clear how buffer handles are actually created
   *       and how the lifecycle (and memory) management works
   */
  struct BuffHandle
    : lib::BoolCheckable<BuffHandle>
    {
      typedef lumiera::StreamType::ImplFacade::DataBuffer Buff;
      typedef Buff* PBuff;
      
      PBuff 
      operator->()  const 
        { 
          return pBuffer_; 
        }
      Buff&
      operator* ()  const
        {
          ENSURE (pBuffer_);
          return *pBuffer_;
        }
      
      bool
      isValid()  const
        {
          return pBuffer_;
        }
      
      
      //////////////////////TODO: the whole logic how to create a BuffHandle needs to be solved in a more clever way. --> TICKET #249
      BuffHandle()
        : pBuffer_(0),
          sourceID_(0)
        { }
      
      /** 
       * @deprecated placeholder implementation
       * @todo rework the Lifecycle handling of buffers  //////////TICKET #249
       */
      BuffHandle(PBuff existingBuffer)
        : pBuffer_(existingBuffer)
        , sourceID_(0)
        { }
      
    private:
      PBuff pBuffer_; 
      long sourceID_;   ////TICKET #249 this is a placeholder for a "type-like information", to be used for lifecycle management and sanity checks....
    };
  
  
  /**
   * Buffer Type information.
   * Given a BufferDescriptor, it is possible to allocate a buffer
   * of suitable size and type by using BufferProvider::lockBuffer().
   */
  struct BufferDescriptor
    {
      long typeToken_; 
    };
  
  
  class ProcNode;
  typedef ProcNode* PNode;
  
  
  struct ChannelDescriptor  ///////TODO collapse this with BufferDescriptor?
    {
      BufferDescriptor bufferType;
    };
  
  struct InChanDescriptor : ChannelDescriptor
    {
      PNode dataSrc;    ///< the ProcNode to pull this input from
      uint srcChannel; ///<  output channel to use on the predecessor node
    };
  
  
  
} // namespace engine
#endif