/// <summary>
/// Instantiates a new instance of the DownloadTask.DownloadProgress class.
/// </summary>
/// <param name="percent">Percent completed.</param>
/// <param name="bytes">Number of bytes downloaded so far.</param>
/// <param name="totalBytes">Total number of bytes to be downloaded, i.e. the file size.</param>
/// <param name="speed">Download speed.</param>
/// <param name="eta">Estimated time of arrival (completion).</param>
public DownloadProgress(double percent, FileSize bytes, FileSize totalBytes, DownloadSpeed speed, TimeSpan eta, TimeSpan elapsed)
{
_percentComplete = percent;
_bytesDownloaded = bytes;
_totalBytes = totalBytes;
_speed = speed;
_eta = eta;
_elapsed = elapsed;
}
/// <summary>
/// Starts downloading the file.
/// </summary>
/// <param name="saveLocation">Path to where the file will be saved.</param>
/// <param name="onProgressChanged">Interface to track download progress.</param>
/// <returns>A System.Threading.Task that represents the download operation.</returns>
/// <exception cref="System.NotSupportedException">
/// Invalid URI scheme.
/// </exception>
/// <exception cref="System.Security.SecurityException">
/// Permission is not granted to connect to remote server.
/// </exception>
/// <exception cref="System.UriFormatException">The download URL is invalid.</exception>
/// <exception cref="System.Net.WebException">An error occurred while processing the request.</exception>
/// <exception cref="System.ArgumentException">
/// path is an empty string (""), contains only white space, or contains one
/// or more invalid characters.
/// </exception>
/// <exception cref="System.IO.IOException">
/// An I/O error, such as specifying FileMode.CreateNew when the file specified
/// by path already exists, occurred. -or-The stream has been closed.
/// </exception>
/// <exception cref="System.Security.SecurityException">
/// The caller does not have the required permission.
/// </exception>
/// <exception cref="System.IO.DirectoryNotFoundException">
/// The specified path is invalid, such as being on an unmapped drive.
/// </exception>
/// <exception cref="System.UnauthorizedAccessException">
/// The access requested is not permitted by the operating system for the specified
/// path, such as when access is Write or ReadWrite and the file or directory
/// is set for read-only access.
/// </exception>
/// <exception cref="System.IO.PathTooLongException">
/// The specified path, file name, or both exceed the system-defined maximum
/// length. For example, on Windows-based platforms, paths must be less than
/// 248 characters, and file names must be less than 260 characters.
/// </exception>
public Task DownloadAsync(string saveLocation, IProgress <DownloadProgress> onProgressChanged = null)
{
if (!IsInitialized)
{
throw new InvalidOperationException("The object has not been initialized. You must call DownloadTask.Initialize() first.");
}
if (isDisposed)
{
throw new ObjectDisposedException("DownloadTask", "Cannot start because this instance has been disposed.");
}
if (Status == DownloadTaskStatus.Failed || Status == DownloadTaskStatus.Canceled)
{
downloadWatch.Reset();
}
Status = DownloadTaskStatus.Starting;
downloadWatch.Start();
elapsedTimer.Start();
FullPath = saveLocation; // filename after download
FileName = Path.GetFileName(FullPath);
_saveToIncomlete = FullPath + IncompleteDlExt; // save here temporarily (until download completes)
progressReporter = onProgressChanged; // save so that it can be used for resumption
cancelSource = new CancellationTokenSource(); // disposed after paused, canceled, completed. a new one is use when resuming
return(Task.Factory.StartNew(() => {
HttpWebResponse response = null;
FileStream fStream = null;
try {
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(_url);
request.UseDefaultCredentials = true;
request.Proxy = WebRequest.GetSystemWebProxy();
byte[] buffer = new byte[BufferSize];
FileMode mode;
long bytesDownloaded = 0;
if (File.Exists(_saveToIncomlete) && ResumeSupported) // dl has been started before; try to resume
{
FileInfo fInfo = new FileInfo(_saveToIncomlete);
if (fInfo.Length < this.Size.Value) // incomplete file must be smaller than total download size
// add range header to resume where left off
{
request.AddRange(fInfo.Length);
bytesDownloaded = fInfo.Length;
mode = FileMode.Append;
}
else // otherwise, it's another file with the same name or it got currupted
{
File.Delete(_saveToIncomlete);
mode = FileMode.Create;
}
}
else // resume not supported; start from beginning
{
mode = FileMode.Create;
}
// begin download
fStream = new FileStream(_saveToIncomlete, mode, FileAccess.Write);
response = (HttpWebResponse)request.GetResponse();
using (Stream dlStream = response.GetResponseStream()) { // download stream
// for measuring speed
const int reportInterval = 200; // ms
int tmpBytes = 0;
Stopwatch watch = new Stopwatch();
Func <DownloadProgress> ProgressSnapshot = () => {
double percent;
TimeSpan eta;
FileSize totalSize;
FileSize curSize = new FileSize(bytesDownloaded);
DownloadSpeed speed;
if (Status == DownloadTaskStatus.Completed)
{
speed = new DownloadSpeed(Size.Value, Elapsed);
}
else
{
speed = new DownloadSpeed(tmpBytes, watch.Elapsed); // current speed
}
if (Size.Value > 0) // got file size from server
{
totalSize = new FileSize(this.Size.Value);
percent = (double)bytesDownloaded / Size.Value * 100;
eta = TimeSpan.FromSeconds((this.Size.Value - bytesDownloaded) / (bytesDownloaded / Elapsed.TotalSeconds)); // eta from average speed
}
else // size is not known (happens with webpages)
{
totalSize = new FileSize(bytesDownloaded); // use number of bytes downloaded so far as size
percent = -1;
eta = TimeSpan.FromSeconds(-1);
}
return new DownloadProgress(percent, curSize, totalSize, speed, eta, Elapsed);
};
while (true)
{
Status = DownloadTaskStatus.Downloading;
watch.Start();
int bytesRead = dlStream.Read(buffer, 0, buffer.Length);
watch.Stop();
if (watch.ElapsedMilliseconds >= reportInterval)
{
lock (Progress) {
Progress.Update(ProgressSnapshot());
}
if (onProgressChanged != null)
{
onProgressChanged.Report(Progress);
}
tmpBytes = 0;
watch.Reset();
}
bytesDownloaded += bytesRead; // total downloaded so far
tmpBytes += bytesRead; // total since last progress report
if (bytesRead < 1) // dl completed or failed
{
if (fStream.Length < Size.Value) // downloaded less than required
{
Status = DownloadTaskStatus.Failed;
}
else
{
Status = DownloadTaskStatus.Completed;
}
lock (Progress) {
Progress.Update(ProgressSnapshot());
}
if (onProgressChanged != null)
{
onProgressChanged.Report(Progress);
}
break;
}
// write block to file
fStream.Write(buffer, 0, bytesRead);
fStream.Flush();
try { // check for cancellation (pause or cancel)
cancelSource.Token.ThrowIfCancellationRequested();
}
catch (OperationCanceledException) {
if (Status == DownloadTaskStatus.Pausing)
{
Status = DownloadTaskStatus.Paused;
}
else
{
Status = DownloadTaskStatus.Canceled;
}
throw;
}
}
}
}
catch (Exception ex) {
if (!(ex is OperationCanceledException)) // something went wrong
{
Status = DownloadTaskStatus.Failed;
throw;
}
}
finally {
downloadWatch.Stop();
elapsedTimer.Stop();
if (response != null)
{
response.Dispose();
}
if (fStream != null)
{
fStream.Dispose();
}
if (cancelSource != null)
{
cancelSource.Dispose();
cancelSource = null;
}
if (Status == DownloadTaskStatus.Completed)
{
File.Move(_saveToIncomlete, _saveTo); // rename temporary file
}
else if (Status == DownloadTaskStatus.Canceled)
{
if (DeleteWhenCanceled)
{
File.Delete(_saveToIncomlete);
}
}
}
}, TaskCreationOptions.LongRunning));
}