public async Task Crawl()
{
List <Task> downloadTask = new List <Task>();
pendingUrls.Enqueue(InitialUrl);
while (pendingUrls.Count > 0)
{
if (!pendingUrls.TryDequeue(out var current))
{
continue;
}
;
if (CompletedUrls.Count + DownloadingUrls.Count > MaxCount)
{
break;
}
//限制并发
if (MaxParallel > 0 && DownloadingUrls.Count >= MaxParallel)
{
await Task.Delay(100);
continue;
}
//下载开始事件
var downEvent = new BeforeDownloadEventArgs()
{
Url = current,
Cancelled = false
};
BeforeDownload?.Invoke(this, downEvent);
if (!downEvent.Cancelled)
{
lock (urlLock)
{
DownloadingUrls.Add(current);
}
var down = DownLoad(current, nameIndex++.ToString())
.ContinueWith(taks =>
{
if (taks.IsFaulted)
{
FailedUrls.Add(current);
lock (urlLock)
{
DownloadingUrls.Remove(current);
}
return;
}
CompletedUrls.Add(current);
lock (urlLock)
{
DownloadingUrls.Remove(current);
}
var ev = new DownloadedEventArgs()
{
Html = taks.Result,
OverrideUrlParse = false,
Url = current
};
Downloaded?.Invoke(this, ev);
//覆盖默认的url解析
if (ev.OverrideUrlParse && ev.NextUrls != null)
{
foreach (var u in ev.NextUrls)
{
AddPending(u);
}
}
else
{
Parse(taks.Result, current);//解析,并加入新的链接
}
});
downloadTask.Add(down);
Downloading?.Invoke(this, new DownloadingEventArgs()
{
Url = current
});
}
if (pendingUrls.Count <= 0)
{
await Task.WhenAny(downloadTask);
downloadTask.RemoveAll(t => t.IsCompleted);
}
}
await Task.WhenAll(downloadTask);
this.CrawlerCompleted?.Invoke(this, new CrawlerCompletedEventArgs()
{
FailedCount = FailedUrls.Count,
SuccessCount = CompletedUrls.Count
});
}
