lumiera_/src/proc/engine/buffer-provider.cpp

/*
  BufferProvider  -  Abstraction for Buffer management during playback/render

  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.

* *****************************************************/


#include "proc/engine/buffer-provider.hpp"
#include "proc/engine/buffer-metadata.hpp"
#include "lib/util.hpp"

using util::isSameObject;

namespace engine {
  
  
  namespace { // impl. details and definitions
    
    const uint DEFAULT_DESCRIPTOR = 0;
    
  }
  
  LUMIERA_ERROR_DEFINE (BUFFER_MANAGEMENT, "Problem providing working buffers");
  

  
  BufferProvider::BufferProvider (Literal implementationID)
    : meta_(new BufferMetadata (implementationID))
    { }
  
  BufferProvider::~BufferProvider() { }
  
  
  /** @internal verify the given descriptor.
   *  @return true if it corresponds to a buffer
   *          currently locked and usable by client code
   */
  bool
  BufferProvider::verifyValidity (BufferDescriptor const&)
  {
    UNIMPLEMENTED ("BufferProvider basic and default implementation");
  }
  
  
  BufferDescriptor
  BufferProvider::getDescriptorFor (size_t storageSize)
  {
    return BufferDescriptor (*this, meta_->key (storageSize));
  }
  
  
  BufferDescriptor
  BufferProvider::getDescriptorFor(size_t storageSize, TypeHandler specialTreatment)
  {
    return BufferDescriptor (*this, meta_->key (storageSize, specialTreatment));
  }
  
  
  BuffHandle
  BufferProvider::buildHandle (HashVal typeID, void* storage, LocalKey const& implID)
  {
    metadata::Key& typeKey = meta_->get (typeID);
    metadata::Entry& entry = meta_->markLocked(typeKey, newBlock, implID);
    
    return BuffHandle (BufferDescriptor(*this, entry), newBlock);
  }
  
  
  /** BufferProvider API: declare in advance the need for working buffers.
   *  This optional call allows client code to ensure the availability of the
   *  necessary working space, prior to starting the actual operations. The
   *  client may reasonably assume to get the actual number of buffers, as
   *  indicated by the return value. A provider may be able to handle
   *  various kinds of buffers (e.g. of differing size), which are
   *  distinguished by the \em type embodied into the BufferDescriptor.
   * @return maximum number of simultaneously usable buffers of this type,
   *         to be retrieved later through calls to #lockBuffer.
   * @throw error::State when no buffer of this kind can be provided
   * @note the returned count may differ from the requested count.
   */
  uint
  BufferProvider::announce (uint count, BufferDescriptor const& type)
  {
    uint actually_possible = prepareBuffers (count, type);
    if (!actually_possible)
      throw error::State ("unable to fulfil request for buffers"
                         ,LUMIERA_ERROR_BUFFER_MANAGEMENT);
    return actually_possible;
  }
  
  
  /** BufferProvider API: retrieve a single buffer for exclusive use.
   *  This call actually claims a buffer of this type and marks it for
   *  use by client code. The returned handle allows for convenient access,
   *  but provides no automatic tracking or memory management. The client is
   *  explicitly responsible to invoke #releaseBuffer (which can be done directly
   *  on the BuffHandle).
   * @return a copyable handle, representing this buffer and this usage transaction.
   * @throw error::State when unable to provide this buffer
   * @note this function may be used right away, without prior announcing, but then
   *       the client should be prepared for exceptions. The #announce operation allows
   *       to establish a reliably available baseline.
   */
  BuffHandle
  BufferProvider::lockBuffer (BufferDescriptor const& type)
  {
    REQUIRE (was_created_by_this_provider (type));
    
    return provideLockedBuffer (type);
  }     // is expected to call buildHandle() --> state transition
  
  
  /** BufferProvider API: state transition to \em emitted state.
   *  Client code may signal a state transition through this optional operation.
   *  The actual meaning of an "emitted" buffer is implementation defined; similarly,
   *  some back-ends may actually do something when emitting a buffer (e.g. commit data
   *  to cache), while others just set a flag or do nothing at all. This state transition
   *  may be invoked at most once per locked buffer.
   * @throw error::Fatal in case of invalid state transition sequence. Only a locked buffer
   *        may be emitted, and at most once.
   * @warning by convention, emitting a buffer implies that the contained data is ready and
   *        might be used by other parts of the application.
   *        An emitted buffer should not be modified anymore. 
   */
  void
  BufferProvider::emitBuffer (BuffHandle const&)
  {
    
  }
  
  
  /** BufferProvider API: declare done and detach.
   *  Client code is required to release \em each previously locked buffer eventually.
   * @warning invalidates the BuffHandle, clients mustn't access the buffer anymore.
   *          Right after releasing, an access through the handle will throw;
   *          yet the buffer might be re-used and the handle become valid
   *          later on accidentally. 
   * @note EX_FREE
   */
  void
  BufferProvider::releaseBuffer (BuffHandle const&)
  {
    
  }
  
  
  bool
  BufferProvider::was_created_by_this_provider (BufferDescriptor const& descr)  const
  {
    return isSameObject (this, descr.provider_);
  }
    
  
  
  
  
  /* === BufferDescriptor and BuffHandle === */
  
  bool
  BufferDescriptor::verifyValidity()  const
  {
    return provider_->verifyValidity(*this);
  }
  
  
  void
  BuffHandle::emit()
  {
    UNIMPLEMENTED ("forward buffer emit call to buffer provider");
  }
  
  
  void
  BuffHandle::release()
  {
    UNIMPLEMENTED ("forward buffer release call to buffer provider");
  }
  


} // namespace engine