mitkImageWriteAccessor.cpp

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/*===================================================================

The Medical Imaging Interaction Toolkit (MITK)

Copyright (c) German Cancer Research Center,
Division of Medical and Biological Informatics.
All rights reserved.

This software is distributed WITHOUT ANY WARRANTY; without
even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE.

See LICENSE.txt or http://www.mitk.org for details.

===================================================================*/

#include "mitkImageWriteAccessor.h"

mitk::ImageWriteAccessor::ImageWriteAccessor(ImagePointer image, const mitk::ImageDataItem *iDI, int OptionFlags)
  : ImageAccessorBase(image.GetPointer(), iDI, OptionFlags), m_Image(image)

{
  OrganizeWriteAccess();
}

mitk::ImageWriteAccessor::~ImageWriteAccessor()
{
  // In case of non-coherent memory, copied area needs to be written back
  // TODO

  m_Image->m_ReadWriteLock.Lock();

  // delete self from list of ImageReadAccessors in Image
  auto it = std::find(m_Image->m_Writers.begin(), m_Image->m_Writers.end(), this);
  m_Image->m_Writers.erase(it);

  // delete lock, if there are no waiting ImageAccessors
  if (m_WaitLock->m_WaiterCount <= 0)
  {
    m_WaitLock->m_Mutex.Unlock();
    delete m_WaitLock;
  }
  else
  {
    m_WaitLock->m_Mutex.Unlock();
  }

  m_Image->m_ReadWriteLock.Unlock();
}

const mitk::Image *mitk::ImageWriteAccessor::GetImage() const
{
  return m_Image.GetPointer();
}

void mitk::ImageWriteAccessor::OrganizeWriteAccess()
{
  m_Image->m_ReadWriteLock.Lock();

  bool readOverlap = false;
  bool writeOverlap = false;

  ImageAccessorWaitLock *overlapLock = nullptr;

  // Check, if there is any Read-Access going on
  if (m_Image->m_Readers.size() > 0)
  {
    // Check for every ReadAccessor, if the Region of this ImageAccessors overlaps
    // make sure this iterator is not used, when m_ReadWriteLock is Unlocked!
    auto it = m_Image->m_Readers.begin();

    for (; it != m_Image->m_Readers.end(); ++it)
    {
      ImageAccessorBase *r = *it;

      if ((r->m_Options & IgnoreLock) == 0 && Overlap(r))
      {
        // An Overlap was detected.

        PreventRecursiveMutexLock(r);

        readOverlap = true;
        overlapLock = r->m_WaitLock;
        break;
      } // if
    }   // for
  }     // if

  // Check, if there is any Write-Access going on
  if (m_Image->m_Writers.size() > 0)
  {
    // Check for every WriteAccessor, if the Region of this ImageAccessors overlaps
    // make sure this iterator is not used, when m_ReadWriteLock is Unlocked!
    auto it = m_Image->m_Writers.begin();

    for (; it != m_Image->m_Writers.end(); ++it)
    {
      ImageAccessorBase *w = *it;

      if (Overlap(w))
      {
        // An Overlap was detected.

        PreventRecursiveMutexLock(w);

        // save overlapping Waitlock
        writeOverlap = true;
        overlapLock = w->m_WaitLock;
        break;

      } // if
    }   // for
  }     // if

  if (readOverlap || writeOverlap)
  {
    // Throw an exception or wait for the WriteAccessor w until it is released and start again with the request
    // afterwards.
    if (!(m_Options & ExceptionIfLocked))
    {
      // WAIT
      overlapLock->m_WaiterCount += 1;
      m_Image->m_ReadWriteLock.Unlock();
      ImageAccessorBase::WaitForReleaseOf(overlapLock);

      // after waiting for the ImageAccessor, start this method again
      OrganizeWriteAccess();
      return;
    }
    else
    {
      // THROW EXCEPTION
      m_Image->m_ReadWriteLock.Unlock();
      mitkThrowException(mitk::MemoryIsLockedException)
        << "The image part being ordered by the ImageAccessor is already in use and locked";
      // MITK_ERROR("Speicherbereich belegt");
      return;
    }
  }

  // Now, we know, that there is no conflict with a Read- or Write-Access
  // Lock the Mutex in ImageAccessorBase, to make sure that every other ImageAccessor has to wait
  m_WaitLock->m_Mutex.Lock();

  // insert self into Writers list in Image
  m_Image->m_Writers.push_back(this);

  // printf("WriteAccess %d %d\n",(int) m_Image->m_Readers.size(),(int) m_Image->m_Writers.size());
  // fflush(0);
  m_Image->m_ReadWriteLock.Unlock();
}