protected async Task <Chunk> DownloadChunk(Uri address, Chunk chunk, CancellationToken token)
{
try
{
if (token.IsCancellationRequested)
{
return(chunk);
}
var request = GetRequest("GET", address);
if (chunk.Start + chunk.Position >= chunk.End && chunk.Data?.LongLength == chunk.Length)
{
return(chunk); // downloaded completely before
}
if (chunk.Position >= chunk.Length && chunk.Data == null)
{
chunk.Position = 0; // downloaded again and reset chunk position
}
request.AddRange(chunk.Start + chunk.Position, chunk.End);
using var httpWebResponse = request.GetResponse() as HttpWebResponse;
if (httpWebResponse == null)
{
return(chunk);
}
var stream = httpWebResponse.GetResponseStream();
var destinationStream = new ThrottledStream(stream,
Package.Options.ParallelDownload
? Package.Options.MaximumBytesPerSecond / Package.Options.ChunkCount
: Package.Options.MaximumBytesPerSecond);
using (stream)
{
if (stream == null)
{
return(chunk);
}
if (Package.Options.OnTheFlyDownload)
{
await ReadStreamOnTheFly(destinationStream, chunk, token);
}
else
{
await ReadStreamOnTheFile(destinationStream, chunk, token);
}
}
return(chunk);
}
catch (TaskCanceledException) // when stream reader timeout occured
{
// re-request
if (token.IsCancellationRequested == false)
{
await DownloadChunk(address, chunk, token);
}
}
catch (WebException) when(token.IsCancellationRequested == false &&
chunk.FailoverCount++ <= Package.Options.MaxTryAgainOnFailover) // when the host forcibly closed the connection.
{
await Task.Delay(Package.Options.Timeout, token);
chunk.Checkpoint();
// re-request
await DownloadChunk(address, chunk, token);
}
catch (Exception e) when(token.IsCancellationRequested == false &&
chunk.FailoverCount++ <= Package.Options.MaxTryAgainOnFailover &&
(e.HasSource("System.Net.Http") ||
e.HasSource("System.Net.Sockets") ||
e.HasSource("System.Net.Security") ||
e.InnerException is SocketException))
{
// wait and decrease speed to low pressure on host
Package.Options.Timeout += chunk.CanContinue() ? 0 : 500;
chunk.Checkpoint();
await Task.Delay(Package.Options.Timeout, token);
// re-request
await DownloadChunk(address, chunk, token);
}
catch (Exception e) // Maybe no internet!
{
OnDownloadFileCompleted(new AsyncCompletedEventArgs(e, false, Package));
Debugger.Break();
}
return(chunk);
}
public ChunkDownloader(Chunk chunk, DownloadConfiguration config)
{
Chunk = chunk;
Configuration = config;
}