优化0速度重试逻辑 降低资源占用

src/N_m3u8DL-RE/Downloader/SimpleDownloader.cs

@@ -11,6 +11,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace N_m3u8DL_RE.Downloader
@@ -55,16 +56,38 @@ namespace N_m3u8DL_RE.Downloader
 
         private async Task<DownloadResult?> DownClipAsync(string url, string path, SpeedContainer speedContainer, long? fromPosition, long? toPosition, Dictionary<string, string>? headers = null, int retryCount = 3)
         {
+            CancellationTokenSource? cancellationTokenSource = null;
         retry:
             try
             {
+                cancellationTokenSource = new();
                 var des = Path.ChangeExtension(path, null);
+
                 //已下载过跳过
                 if (File.Exists(des))
                 {
                     return new DownloadResult() { ActualContentLength = 0, ActualFilePath = des };
                 }
-                var result = await DownloadUtil.DownloadToFileAsync(url, path, speedContainer, headers, fromPosition, toPosition);
+
+                //另起线程进行监控
+                using var watcher = Task.Factory.StartNew(async () =>
+                {
+                    while (true)
+                    {
+                        if (cancellationTokenSource == null || cancellationTokenSource.IsCancellationRequested) break;
+                        if (speedContainer.ShouldStop)
+                        {
+                            cancellationTokenSource.Cancel();
+                            Logger.DebugMarkUp("Cancel...");
+                            break;
+                        }
+                        await Task.Delay(500);
+                    }
+                });
+
+                //调用下载
+                var result = await DownloadUtil.DownloadToFileAsync(url, path, speedContainer, cancellationTokenSource, headers, fromPosition, toPosition);
+                
                 //下载完成后改名
                 if (result.Success || !DownloaderConfig.CheckContentLength)
                 {
@@ -86,6 +109,15 @@ namespace N_m3u8DL_RE.Downloader
                 //throw new Exception("download failed", ex);
                 return null;
             }
+            finally
+            {
+                if (cancellationTokenSource != null)
+                {
+                    //调用后销毁
+                    cancellationTokenSource.Dispose();
+                    cancellationTokenSource = null;
+                }
+            }
         }
     }
 }

src/N_m3u8DL-RE/Util/DownloadUtil.cs

@@ -36,7 +36,7 @@ namespace N_m3u8DL_RE.Util
             };
         }
 
-        public static async Task<DownloadResult> DownloadToFileAsync(string url, string path, SpeedContainer speedContainer, Dictionary<string, string>? headers = null, long? fromPosition = null, long? toPosition = null)
+        public static async Task<DownloadResult> DownloadToFileAsync(string url, string path, SpeedContainer speedContainer, CancellationTokenSource cancellationTokenSource, Dictionary<string, string>? headers = null, long? fromPosition = null, long? toPosition = null)
         {
             Logger.Debug(ResString.fetch + url);
             if (url.StartsWith("file:"))
@@ -55,21 +55,6 @@ namespace N_m3u8DL_RE.Util
                 }
             }
             Logger.Debug(request.Headers.ToString());
-            CancellationTokenSource cancellationTokenSource = new(); //取消下载
-            using var watcher = Task.Factory.StartNew(async () =>
-            {
-                while (true)
-                {
-                    if (speedContainer == null) break;
-                    if (speedContainer.ShouldStop)
-                    {
-                        cancellationTokenSource.Cancel();
-                        Logger.DebugMarkUp("Cancel...");
-                        break;
-                    }
-                    await Task.Delay(500);
-                }
-            });
             try
             {
                 using var response = await AppHttpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, cancellationTokenSource.Token);
@@ -90,7 +75,7 @@ namespace N_m3u8DL_RE.Util
                         {
                             redirectedUrl = respHeaders.Location.AbsoluteUri;
                         }
-                        return await DownloadToFileAsync(redirectedUrl, path, speedContainer, headers, fromPosition, toPosition);
+                        return await DownloadToFileAsync(redirectedUrl, path, speedContainer, cancellationTokenSource, headers, fromPosition, toPosition);
                     }
                 }
                 response.EnsureSuccessStatusCode();
@@ -104,7 +89,7 @@ namespace N_m3u8DL_RE.Util
                 while ((size = await responseStream.ReadAsync(buffer, cancellationTokenSource.Token)) > 0)
                 {
                     speedContainer.Add(size);
-                    await stream.WriteAsync(buffer, 0, size, cancellationTokenSource.Token);
+                    await stream.WriteAsync(buffer, 0, size);
                 }
 
                 return new DownloadResult()