我希望能够暂停下载。我可以通过删除现有连接来阻止它们。
我所指的几乎与此处描述的相似：https://superuser.com/questions/170509/whats-the-difference-in-using-pause-stop-in-%C2%B5torrent
我的下载课程：
public class Download
{
public event EventHandler<DownloadStatusChangedEventArgs> DownloadStatusChanged;
public event EventHandler<DownloadProgressChangedEventArgs> DownloadProgressChanged;
public event EventHandler DownloadCompleted;
public bool stop = true; // by default stop is true
public void DownloadFile(string DownloadLink, string Path)
{
stop = false; // always set this bool to false, everytime this method is called
long ExistingLength = 0;
FileStream saveFileStream;
if (File.Exists(Path))
{
FileInfo fileInfo = new FileInfo(Path);
ExistingLength = fileInfo.Length;
}
if (ExistingLength > 0)
saveFileStream = new FileStream(Path, FileMode.Append, FileAccess.Write, FileShare.ReadWrite);
else
saveFileStream = new FileStream(Path, FileMode.Create, FileAccess.Write, FileShare.ReadWrite);
var request = (HttpWebRequest)HttpWebRequest.Create(DownloadLink);
request.Proxy = null;
request.AddRange(ExistingLength);
try
{
using (var response = (HttpWebResponse)request.GetResponse())
{
long FileSize = ExistingLength + response.ContentLength; //response.ContentLength gives me the size that is remaining to be downloaded
bool downloadResumable; // need it for sending empty progress
if ((int)response.StatusCode == 206)
{
Console.WriteLine("Resumable");
var downloadStatusArgs = new DownloadStatusChangedEventArgs();
downloadResumable = true;
downloadStatusArgs.ResumeSupported = downloadResumable;
OnDownloadStatusChanged(downloadStatusArgs);
}
else // sometimes a server that supports partial content will lose its ability to send partial content(weird behavior) and thus the download will lose its resumability
{
Console.WriteLine("Resume Not Supported");
ExistingLength = 0;
var downloadStatusArgs = new DownloadStatusChangedEventArgs();
downloadResumable = false;
downloadStatusArgs.ResumeSupported = downloadResumable;
OnDownloadStatusChanged(downloadStatusArgs);
// restart downloading the file from the beginning because it isn't resumable
// if this isn't done, the method downloads the file from the beginning and starts writing it after the previously half downloaded file, thus increasing the filesize and corrupting the downloaded file
saveFileStream.Dispose(); // dispose object to free it for the next operation
File.WriteAllText(Path, string.Empty); // clear the contents of the half downloaded file that can't be resumed
saveFileStream = saveFileStream = new FileStream(Path, FileMode.Append, FileAccess.Write, FileShare.ReadWrite); // reopen it for writing
}
using (var stream = response.GetResponseStream())
{
byte[] downBuffer = new byte[4096];
int byteSize = 0;
long totalReceived = byteSize + ExistingLength;
var sw = new Stopwatch();
sw.Start();
while ((byteSize = stream.Read(downBuffer, 0, downBuffer.Length)) > 0)
{
saveFileStream.Write(downBuffer, 0, byteSize);
totalReceived += byteSize;
var args = new DownloadProgressChangedEventArgs();
args.BytesReceived = totalReceived;
args.TotalBytesToReceive = FileSize;
float currentSpeed = totalReceived / (float)sw.Elapsed.TotalSeconds;
args.CurrentSpeed = currentSpeed;
if (downloadResumable == true)
{
args.ProgressPercentage = ((float)totalReceived / (float)FileSize) * 100;
long bytesRemainingtoBeReceived = FileSize - totalReceived;
args.TimeLeft = (long)(bytesRemainingtoBeReceived / currentSpeed);
}
else
{
//args.ProgressPercentage = Unknown;
//args.TimeLeft = Unknown;
}
OnDownloadProgressChanged(args);
if (stop == true)
return;
}
sw.Stop();
}
}
var completedArgs = new EventArgs();
OnDownloadCompleted(completedArgs);
saveFileStream.Dispose();
}
catch (WebException e)
{
string filename = System.IO.Path.GetFileName(Path);
Console.WriteLine(e.Message);
saveFileStream.Dispose();
return; //not needed because this is the last line of the method, but let's keep it here
}
}
public void StopDownload()
{
stop = true;
}
protected virtual void OnDownloadStatusChanged(DownloadStatusChangedEventArgs e)
{
EventHandler<DownloadStatusChangedEventArgs> handler = DownloadStatusChanged;
if (handler != null)
{
handler(this, e);
}
}
protected virtual void OnDownloadProgressChanged(DownloadProgressChangedEventArgs e)
{
EventHandler<DownloadProgressChangedEventArgs> handler = DownloadProgressChanged;
if (handler != null)
{
handler(this, e);
}
}
protected virtual void OnDownloadCompleted(EventArgs e)
{
EventHandler handler = DownloadCompleted;
if (handler != null)
{
handler(this, e);
}
}
}
public class DownloadStatusChangedEventArgs : EventArgs
{
public bool ResumeSupported { get; set; }
}
public class DownloadProgressChangedEventArgs : EventArgs
{
public long BytesReceived { get; set; }
public long TotalBytesToReceive { get; set; }
public float ProgressPercentage { get; set; }
public float CurrentSpeed { get; set; } // in bytes
public long TimeLeft { get; set; } // in seconds
}
有人可以帮我吗？
注意：如果您想知道，我已经可以恢复下载了，这不是我想要的。
答案 0 :(得分：2)
在你的代码中（顺便说一句，你应该把它复制到你的问题中），你有一个从流中读取字节的循环。你有一个标志会停止循环。
除了暂停而不是停止之外，你做同样的事情。它可能是另一个标志，但您还需要知道何时恢复，因此您需要一些循环来等待。一个相当简洁的方法是使用锁（互斥锁）。
我不知道C＃所以我不能给你工作代码，但这里有伪代码。使用指向the reference docs的指针，看起来SemaphoreSlim是最适合此目的的最简单的事情。
bool stop = false
bool paused = false
SemaphoreSlim pauseLock = new SemaphoreSlim(1)
method download():
while (stuff to read):
read from stream
write to file
if stop:
break
// This will do nothing if not paused, or will block if paused
pauseLock.Wait()
pauseLock.Release()
method stop():
stop = true
self.unpause() // stop waiting on lock if needed
method pause()
if not paused:
paused = true
// Note this cannot block for more than a moment
// since the download thread doesn't keep the lock held
pauseLock.Wait()
method unpause()
if paused:
paused = false
pauseLock.Release()
当然，这样做可能会导致服务器最终丢弃您的连接（此时您需要恢复，并且您只会在取消暂停后才会注意到这一点。）