/// <summary>
/// 暂停下载
/// </summary>
public void Pause()
{
lock (this._syncRoot)
{
if (this._cts == null)
{
return;
}
this._cts.Cancel();
this._cts = null;
this._writer.UnregisterSegment(this._id);
this._status = SegmentThreadStatuses.Paused;
}
this.OnPaused(new ThreadExitedArgs(this._workID));
}
/// <summary>
/// 开始下载
/// </summary>
public void Start()
{
var cts = new CancellationTokenSource();
lock (this._syncRoot)
{
if (this._cts != null)
{
cts.Dispose();
throw new Exception("The thread is running.");
}
this._cts = cts;
this._status = SegmentThreadStatuses.Running;
}
Task.Run(() => { return(this.DownloadProc(cts)); }, cts.Token);
}
/// <summary>
/// 下载线程
/// </summary>
/// <param name="cts">检测是否取消</param>
/// <returns></returns>
private async Task DownloadProc(CancellationTokenSource cts)
{
var ct = cts.Token;
try
{
while (true)// 循环下载文件片段
{
RegisteredSegment segment;
lock (this._syncRoot)
{
ct.ThrowIfCancellationRequested(); // 检测是否取消下载
segment = this._writer.RegisterSegment(this._id); // 获取需要下载的片段
}
if (segment == null)
{
break; // 注册的片段为null，证明下载已经完成或就快完成，这个线程已经获取不到任务了
}
await this.DownloadSegment(segment, ct); // 下载片段
lock (this._syncRoot)
{
ct.ThrowIfCancellationRequested();
this._writer.UnregisterSegment(this._id);// 取消注册下载片段
}
}// while
// 设置线程状态为空闲
lock (this._syncRoot)
{
ct.ThrowIfCancellationRequested();
this._status = SegmentThreadStatuses.Idle;
}
}
catch (OperationCanceledException)
{
// 线程状态在Stop方法中被设置为了Cancelled，这里就不用设置了
return;// 表示取消
}
catch (Exception)
{
// 设置线程状态为失败
lock (this._syncRoot)
{
if (!ct.IsCancellationRequested)
{
this._status = SegmentThreadStatuses.Failed;
}
}
return;// 出现未知异常，停止下载
}
finally
{
bool isRaiseCompleted = false;
bool isRaiseFailed = false;
// 取消注册片段
lock (this._syncRoot)
{
if (!ct.IsCancellationRequested)
{
this._cts = null;
this._writer.UnregisterSegment(this._id);
isRaiseCompleted = this._status == SegmentThreadStatuses.Idle;
isRaiseFailed = this._status == SegmentThreadStatuses.Failed;
}
}
cts.Dispose();// 释放取消资源
if (isRaiseCompleted)
{
this.OnCompleted(new ThreadExitedArgs(this._workID));
}
if (isRaiseFailed)
{
this.OnFailed(new ThreadExitedArgs(this._workID));
}
}// finally
}
