/// <summary>
/// Finds the next file to download
/// </summary>
protected virtual DownloadRequest GetNextDownloadRequest()
{
DownloadRequest bestRequest = null;
float highestScore = float.MinValue;
lock (m_requests.SyncRoot)
{
for (int i = m_requests.Count - 1; i >= 0; i--)
{
DownloadRequest request = (DownloadRequest)m_requests[i];
if (request.IsDownloading)
continue;
float score = request.CalculateScore();
if (float.IsNegativeInfinity(score))
{
// Request is of no interest anymore, remove it
m_requests.RemoveAt(i);
request.Dispose();
continue;
}
if (score > highestScore)
{
highestScore = score;
bestRequest = request;
}
}
}
return bestRequest;
}
/// <summary>
/// Add a download request to the queue.
/// </summary>
public virtual void Add(DownloadRequest newRequest)
{
if (newRequest == null)
throw new NullReferenceException();
lock (m_requests.SyncRoot)
{
foreach (DownloadRequest request in m_requests)
{
if (request.Key == newRequest.Key)
{
newRequest.Dispose();
return;
}
}
m_requests.Add(newRequest);
if (m_requests.Count > MaxQueueLength)
{
// Remove lowest scoring queued request
DownloadRequest leastImportantRequest = null;
float lowestScore = float.MinValue;
for (int i = m_requests.Count - 1; i >= 0; i--)
{
DownloadRequest request = (DownloadRequest)m_requests[i];
if (request.IsDownloading)
continue;
float score = request.CalculateScore();
if (score == float.MinValue)
{
// Request is of no interest anymore, remove it
m_requests.Remove(request);
request.Dispose();
return;
}
if (score < lowestScore)
{
lowestScore = score;
leastImportantRequest = request;
}
}
if (leastImportantRequest != null)
{
m_requests.Remove(leastImportantRequest);
leastImportantRequest.Dispose();
}
}
}
ServiceDownloadQueue();
}
/// <summary>
/// Callback when download is complete.
/// </summary>
internal void OnComplete(DownloadRequest request)
{
lock (m_requests.SyncRoot)
{
// Remove the finished item from queue
m_requests.Remove(request);
request.Dispose();
}
// Start next download
ServiceDownloadQueue();
}
/// <summary>
/// Removes a request from the download queue.
/// </summary>
public virtual void Remove(DownloadRequest request)
{
lock (m_requests.SyncRoot)
{
for (int i = m_activeDownloads.Count - 1; i >= 0; i--)
if (request == m_activeDownloads[i])
// Already downloading, let it finish
return;
m_requests.Remove(request);
}
request.Dispose();
ServiceDownloadQueue();
}
/// <summary>
/// Remove all requests with a certain owner.
/// </summary>
/// <param name="owner"></param>
public virtual void Clear(object owner)
{
lock (m_requests.SyncRoot)
{
for (int i = m_requests.Count - 1; i >= 0; i--)
{
DownloadRequest request = (DownloadRequest)m_requests[i];
if (request.Owner == owner)
{
m_requests.RemoveAt(i);
request.Dispose();
}
}
}
ServiceDownloadQueue();
}
/// <summary>
/// Starts downloads when there are threads available
/// </summary>
protected virtual void ServiceDownloadQueue()
{
lock (m_requests.SyncRoot)
{
// Remove finished downloads
for (int i = m_activeDownloads.Count - 1; i >= 0; i--)
{
DownloadRequest request = (DownloadRequest)m_activeDownloads[i];
if (!request.IsDownloading)
m_activeDownloads.RemoveAt(i);
}
// Start new downloads
while (m_activeDownloads.Count < MaxConcurrentDownloads)
{
DownloadRequest request = GetNextDownloadRequest();
if (request == null)
break;
m_activeDownloads.Add(request);
request.Start();
}
}
}