/// <summary>
/// 开始下载文件
/// </summary>
/// <returns></returns>
public async Task DownloadFile()
{
var(response, contentLength) = await GetContentLength();
lStartPos = 0;
if (System.IO.File.Exists(File.FullName))//另外如果文件已经下载完毕，就不需要再断点续传了，不然请求的range 会不合法会抛出异常。
{
FileStream = System.IO.File.OpenWrite(File.FullName);
lStartPos = FileStream.Length;
FileStream.Seek(lStartPos, System.IO.SeekOrigin.Current); //移动文件流中的当前指针
}
else
{
FileStream = new FileStream(File.FullName, System.IO.FileMode.Create);
lStartPos = 0;
}
FileStream.SetLength(contentLength);
FileWriter = new RandomFileWriter(FileStream);
SegmentManager = new SegmentManager(contentLength);
_progress.Report(new DownloadProgress($"file length = {contentLength}", SegmentManager));
var downloadSegment = SegmentManager.GetNewDownloadSegment();
// 下载第一段
Download(response, downloadSegment);
var supportSegment = await TryDownloadLast(contentLength);
var threadCount = 1;
if (supportSegment)
{
// 多创建几个线程下载
threadCount = 10;
for (var i = 0; i < threadCount; i++)
{
Download(SegmentManager.GetNewDownloadSegment());
}
}
for (var i = 0; i < threadCount; i++)
{
_ = Task.Run(DownloadTask);
}
await FileDownloadTask.Task;
}
public DownloadProgress(string message, SegmentManager segmentManager)
{
Message = message;
SegmentManager = segmentManager;
}
public DownloadProgress(SegmentManager segmentManager)
{
SegmentManager = segmentManager;
}