vtk-m/vtkm/cont/internal/ArrayTransfer.h

//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//
//  Copyright 2014 Sandia Corporation.
//  Copyright 2014 UT-Battelle, LLC.
//  Copyright 2014 Los Alamos National Security.
//
//  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
//  the U.S. Government retains certain rights in this software.
//
//  Under the terms of Contract DE-AC52-06NA25396 with Los Alamos National
//  Laboratory (LANL), the U.S. Government retains certain rights in
//  this software.
//============================================================================
#ifndef vtk_m_cont_internal_ArrayTransfer_h
#define vtk_m_cont_internal_ArrayTransfer_h

#include <vtkm/cont/Storage.h>
#include <vtkm/cont/internal/ArrayManagerExecution.h>

namespace vtkm {
namespace cont {
namespace internal {

/// \brief Class that manages the transfer of data between control and execution.
///
/// This templated class provides a mechanism (used by the ArrayHandle) to
/// transfer data from the control environment to the execution environment and
/// back. The interface for ArrayTransfer is nearly identical to that of
/// ArrayManagerExecution and the default implementation simply delegates all
/// calls to that class.
///
/// The primary motivation for having a separate class is that the
/// ArrayManagerExecution is meant to be specialized for each device adapter
/// whereas the ArrayTransfer is meant to be specialized for each storage type
/// (or specific combination of storage and device adapter). Thus, transfers
/// for most storage tyeps will be delegated through the ArrayManagerExecution,
/// but some storage types, like implicit storage, will be specialized to
/// transfer through a different path.
///
template<typename T, class StorageTag, class DeviceAdapterTag>
class ArrayTransfer
{
private:
  typedef vtkm::cont::internal::Storage<T,StorageTag> StorageType;
  typedef vtkm::cont::internal::ArrayManagerExecution<
      T,StorageTag,DeviceAdapterTag> ArrayManagerType;

public:
  /// The type of value held in the array (vtkm::FloatDefault, vtkm::Vec, etc.)
  ///
  typedef T ValueType;

  /// An array portal that can be used in the control environment.
  ///
  typedef typename StorageType::PortalType PortalControl;
  typedef typename StorageType::PortalConstType PortalConstControl;

  /// An array portal that can be used in the execution environment.
  ///
  typedef typename ArrayManagerType::PortalType PortalExecution;
  typedef typename ArrayManagerType::PortalConstType PortalConstExecution;

  VTKM_CONT_EXPORT
  ArrayTransfer(StorageType *storage) : ArrayManager(storage) {  }

  /// Returns the number of values stored in the array.  Results are undefined
  /// if data has not been loaded or allocated.
  ///
  VTKM_CONT_EXPORT
  vtkm::Id GetNumberOfValues() const
  {
    return this->ArrayManager.GetNumberOfValues();
  }

  /// Prepares the data for use as input in the execution environment. If the
  /// flag \c updateData is true, then data is transferred to the execution
  /// environment. Otherwise, this transfer is (or may be) skipped.
  ///
  /// Returns a constant array portal valid in the execution environment.
  ///
  VTKM_CONT_EXPORT
  PortalConstExecution PrepareForInput(bool updateData)
  {
    return this->ArrayManager.PrepareForInput(updateData);
  }

  /// Prepares the data for use as both input and output in the execution
  /// environment. If the flag \c updateData is true, then data is transferred
  /// to the execution environment. Otherwise, this transfer is (or may be)
  /// skipped.
  ///
  /// Returns a read-write array portal valid in the execution environment.
  ///
  VTKM_CONT_EXPORT
  PortalExecution PrepareForInPlace(bool updateData)
  {
    return this->ArrayManager.PrepareForInPlace(updateData);
  }

  /// Allocates an array in the execution environment of the specified size. If
  /// control and execution share arrays, then this class can allocate data
  /// using the given Storage it can be used directly in the execution
  /// environment.
  ///
  /// Returns a writable array portal valid in the execution environment.
  ///
  VTKM_CONT_EXPORT
  PortalExecution PrepareForOutput(vtkm::Id numberOfValues)
  {
    return this->ArrayManager.PrepareForOutput(numberOfValues);
  }

  /// Allocates data in the given Storage and copies data held in the execution
  /// environment (managed by this class) into the storage object. The
  /// reference to the storage given is the same as that passed to the
  /// constructor. If control and execution share arrays, this can be no
  /// operation. This method should only be called after PrepareForOutput is
  /// called.
  ///
  VTKM_CONT_EXPORT
  void RetrieveOutputData(StorageType *storage) const
  {
    this->ArrayManager.RetrieveOutputData(storage);
  }

  /// Similar to RetrieveOutputData except that instead of writing to the
  /// controlArray itself, it writes to the given control environment
  /// iterator. This allows the user to retrieve data without necessarily
  /// allocating an array in the ArrayContainerControl (assuming that control
  /// and exeuction have seperate memory spaces).
  ///
  template <class IteratorTypeControl>
  VTKM_CONT_EXPORT void CopyInto(IteratorTypeControl dest) const
  {
    this->ArrayManager.CopyInto(dest);
  }

  /// \brief Reduces the size of the array without changing its values.
  ///
  /// This method allows you to resize the array without reallocating it. The
  /// number of entries in the array is changed to \c numberOfValues. The data
  /// in the array (from indices 0 to \c numberOfValues - 1) are the same, but
  /// \c numberOfValues must be equal or less than the preexisting size
  /// (returned from GetNumberOfValues). That is, this method can only be used
  /// to shorten the array, not lengthen.
  ///
  VTKM_CONT_EXPORT
  void Shrink(vtkm::Id numberOfValues)
  {
    this->ArrayManager.Shrink(numberOfValues);
  }

  /// Frees any resources (i.e. memory) allocated for the exeuction
  /// environment, if any.
  ///
  VTKM_CONT_EXPORT
  void ReleaseResources()
  {
    this->ArrayManager.ReleaseResources();
  }

private:
  ArrayManagerType ArrayManager;
};

}
}
} // namespace vtkm::cont::internal

#endif //vtk_m_cont_internal_ArrayTransfer_h