private void EnsureDownloader()
{
if (_byteRangeDownloader == null)
{
_byteRangeDownloader = new ByteRangeDownloader(_uri,
_tempFileStream,
_readEventHandles[(int)ReadEvent.ByteRangeReadEvent].SafeWaitHandle,
_tempFileMutex);
// Local assert to allow Proxy get/set under partial trust
new WebPermission(PermissionState.Unrestricted).Assert(); // Blessed
try
{
_byteRangeDownloader.Proxy = _originalRequest.Proxy;
}
finally
{
WebPermission.RevertAssert();
}
_byteRangeDownloader.Credentials = _originalRequest.Credentials;
_byteRangeDownloader.CachePolicy = _originalRequest.CachePolicy;
_byteRangesAvailable = new ArrayList(); // byte ranges that are downloaded
}
}
void IByteRangeDownloaderService.InitializeByteRangeDownloader(
String url,
String tempFile,
SafeWaitHandle eventHandle)
{
if (url == null)
{
throw new ArgumentNullException("url");
}
if(tempFile == null)
{
throw new ArgumentNullException("tempFile");
}
if(eventHandle == null)
{
throw new ArgumentNullException("eventHandle");
}
if (eventHandle.IsInvalid || eventHandle.IsClosed)
{
throw new ArgumentException(SR.Get(SRID.InvalidEventHandle), "eventHandle");
}
Uri requestedUri = new Uri(url, UriKind.Absolute);
if(tempFile.Length <= 0)
{
throw new ArgumentException(SR.Get(SRID.InvalidTempFileName), "tempFile");
}
ByteRangeDownloader loader = new ByteRangeDownloader(requestedUri, tempFile, eventHandle);
// We defined _downloader as Object for performance reasons. If we define it as ByteRangeDownloader the whole
// class will be loaded although it might not be used at all. By declaring it as Object we can prevent it
// from being loaded. This technique is used in other areas.
_downloader = (Object) loader;
}
