GP<DjVuImage> DjVuSource::GetPage(int nPage, Observer* observer)
{
ASSERT(nPage >= 0 && nPage < m_nPageCount);
PageData& data = m_pages[nPage];
m_lock.Lock();
GP<DjVuImage> pImage = data.pImage;
if (pImage != NULL)
{
m_lock.Unlock();
return pImage;
}
if (data.hDecodingThread != NULL)
{
// Another thread is already decoding this page. Put
// ourselves in a list of waiting threads
PageRequest request;
m_eventLock.Lock();
if (m_eventCache.empty())
{
request.hEvent = ::CreateEvent(NULL, false, false, NULL);
}
else
{
request.hEvent = m_eventCache.top();
::ResetEvent(request.hEvent);
m_eventCache.pop();
}
m_eventLock.Unlock();
// Temporarily increase priority of the decoding thread if needed
HANDLE hOurThread = ::GetCurrentThread();
int nOurPriority = ::GetThreadPriority(hOurThread);
if (::GetThreadPriority(data.hDecodingThread) < nOurPriority)
::SetThreadPriority(data.hDecodingThread, nOurPriority);
data.requests.push_back(&request);
if (observer != NULL)
data.AddObserver(observer);
m_lock.Unlock();
::WaitForSingleObject(request.hEvent, INFINITE);
pImage = request.pImage;
m_eventLock.Lock();
m_eventCache.push(request.hEvent);
m_eventLock.Unlock();
// Page will be put in cache by the thread which decoded it
return pImage;
}
data.hDecodingThread = ::GetCurrentThread();
data.nOrigThreadPriority = ::GetThreadPriority(data.hDecodingThread);
m_lock.Unlock();
try
{
GP<DjVuFile> file = m_pDjVuDoc->get_djvu_file(nPage);
if (file)
{
pImage = DjVuImage::create(file);
file->resume_decode();
if (pImage && THREADMODEL != NOTHREADS)
pImage->wait_for_complete_decode();
}
}
catch (GException&)
{
}
catch (...)
{
if (pApplication != NULL)
pApplication->ReportFatalError();
}
m_lock.Lock();
if (pImage != NULL)
{
pImage->set_rotate(0);
if (observer != NULL || data.HasObservers())
{
data.pImage = pImage;
if (observer != NULL)
data.AddObserver(observer);
}
data.info.Update(pImage);
if (data.info.bHasText)
m_bHasText = true;
}
// Notify all waiting threads that image is ready
for (size_t i = 0; i < data.requests.size(); ++i)
{
data.requests[i]->pImage = pImage;
::SetEvent(data.requests[i]->hEvent);
}
ASSERT(data.hDecodingThread == ::GetCurrentThread());
::SetThreadPriority(data.hDecodingThread, data.nOrigThreadPriority);
data.hDecodingThread = NULL;
data.requests.clear();
m_lock.Unlock();
return pImage;
}
