337 lines
11 KiB
C#
337 lines
11 KiB
C#
using Dinah.Core;
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using Newtonsoft.Json;
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using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Linq;
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using System.Net;
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using System.Net.Http;
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using System.Threading;
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using System.Threading.Tasks;
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namespace AaxDecrypter
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{
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/// <summary>A resumable, simultaneous file downloader and reader. </summary>
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public class NetworkFileStream : Stream, IUpdatable
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{
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public event EventHandler Updated;
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#region Public Properties
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/// <summary> Location to save the downloaded data. </summary>
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[JsonProperty(Required = Required.Always)]
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public string SaveFilePath { get; }
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/// <summary> Http(s) address of the file to download. </summary>
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[JsonProperty(Required = Required.Always)]
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public Uri Uri { get; private set; }
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/// <summary> Http headers to be sent to the server with the request. </summary>
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[JsonProperty(Required = Required.Always)]
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public Dictionary<string, string> RequestHeaders { get; private set; }
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/// <summary> The position in <see cref="SaveFilePath"/> that has been written and flushed to disk. </summary>
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[JsonProperty(Required = Required.Always)]
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public long WritePosition { get; private set; }
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/// <summary> The total length of the <see cref="Uri"/> file to download. </summary>
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[JsonProperty(Required = Required.Always)]
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public long ContentLength { get; private set; }
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[JsonIgnore]
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public bool IsCancelled => _cancellationSource.IsCancellationRequested;
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private static long _globalSpeedLimit = 0;
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/// <summary>bytes per second</summary>
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public static long GlobalSpeedLimit { get => _globalSpeedLimit; set => _globalSpeedLimit = value <= 0 ? 0 : Math.Max(value, MIN_BYTES_PER_SECOND); }
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#endregion
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#region Private Properties
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private FileStream _writeFile { get; }
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private FileStream _readFile { get; }
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private CancellationTokenSource _cancellationSource { get; } = new();
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private EventWaitHandle _downloadedPiece { get; set; }
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private Task _backgroundDownloadTask { get; set; }
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#endregion
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#region Constants
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//Download buffer size
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private const int DOWNLOAD_BUFF_SZ = 32 * 1024;
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//NetworkFileStream will flush all data in _writeFile to disk after every
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//DATA_FLUSH_SZ bytes are written to the file stream.
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private const int DATA_FLUSH_SZ = 1024 * 1024;
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//Number of times per second the download rate is checkd and throttled
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private const int THROTTLE_FREQUENCY = 8;
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//Minimum throttle rate. The minimum amount of data that can be throttled
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//on each iteration of the download loop is DOWNLOAD_BUFF_SZ.
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private const int MIN_BYTES_PER_SECOND = DOWNLOAD_BUFF_SZ * THROTTLE_FREQUENCY;
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#endregion
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#region Constructor
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/// <summary> A resumable, simultaneous file downloader and reader. </summary>
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/// <param name="saveFilePath">Path to a location on disk to save the downloaded data from <paramref name="uri"/></param>
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/// <param name="uri">Http(s) address of the file to download.</param>
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/// <param name="writePosition">The position in <paramref name="uri"/> to begin downloading.</param>
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/// <param name="requestHeaders">Http headers to be sent to the server with the <see cref="HttpWebRequest"/>.</param>
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public NetworkFileStream(string saveFilePath, Uri uri, long writePosition = 0, Dictionary<string, string> requestHeaders = null)
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{
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ArgumentValidator.EnsureNotNullOrWhiteSpace(saveFilePath, nameof(saveFilePath));
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ArgumentValidator.EnsureNotNullOrWhiteSpace(uri?.AbsoluteUri, nameof(uri));
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ArgumentValidator.EnsureGreaterThan(writePosition, nameof(writePosition), -1);
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if (!Directory.Exists(Path.GetDirectoryName(saveFilePath)))
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throw new ArgumentException($"Specified {nameof(saveFilePath)} directory \"{Path.GetDirectoryName(saveFilePath)}\" does not exist.");
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SaveFilePath = saveFilePath;
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Uri = uri;
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WritePosition = writePosition;
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RequestHeaders = requestHeaders ?? new();
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_writeFile = new FileStream(SaveFilePath, FileMode.OpenOrCreate, FileAccess.Write, FileShare.ReadWrite)
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{
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Position = WritePosition
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};
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_readFile = new FileStream(SaveFilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
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SetUriForSameFile(uri);
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}
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#endregion
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#region Downloader
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/// <summary> Update the <see cref="JsonFilePersister"/>. </summary>
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private void Update()
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{
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RequestHeaders["Range"] = $"bytes={WritePosition}-";
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try
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{
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Updated?.Invoke(this, EventArgs.Empty);
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}
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catch (Exception ex)
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{
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Serilog.Log.Error(ex, "An error was encountered while saving the download progress to JSON");
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}
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}
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/// <summary> Set a different <see cref="System.Uri"/> to the same file targeted by this instance of <see cref="NetworkFileStream"/> </summary>
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/// <param name="uriToSameFile">New <see cref="System.Uri"/> host must match existing host.</param>
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public void SetUriForSameFile(Uri uriToSameFile)
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{
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ArgumentValidator.EnsureNotNullOrWhiteSpace(uriToSameFile?.AbsoluteUri, nameof(uriToSameFile));
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if (uriToSameFile.Host != Uri.Host)
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throw new ArgumentException($"New uri to the same file must have the same host.\r\n Old Host :{Uri.Host}\r\nNew Host: {uriToSameFile.Host}");
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if (_backgroundDownloadTask is not null)
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throw new InvalidOperationException("Cannot change Uri after download has started.");
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Uri = uriToSameFile;
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RequestHeaders["Range"] = $"bytes={WritePosition}-";
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}
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/// <summary> Begins downloading <see cref="Uri"/> to <see cref="SaveFilePath"/> in a background thread. </summary>
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/// <returns>The downloader <see cref="Task"/></returns>
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private Task BeginDownloading()
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{
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if (ContentLength != 0 && WritePosition == ContentLength)
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return Task.CompletedTask;
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if (ContentLength != 0 && WritePosition > ContentLength)
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throw new WebException($"Specified write position (0x{WritePosition:X10}) is larger than {nameof(ContentLength)} (0x{ContentLength:X10}).");
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var request = new HttpRequestMessage(HttpMethod.Get, Uri);
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foreach (var header in RequestHeaders)
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request.Headers.Add(header.Key, header.Value);
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var response = new HttpClient().Send(request, HttpCompletionOption.ResponseHeadersRead, _cancellationSource.Token);
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if (response.StatusCode != HttpStatusCode.PartialContent)
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throw new WebException($"Server at {Uri.Host} responded with unexpected status code: {response.StatusCode}.");
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//Content length is the length of the range request, and it is only equal
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//to the complete file length if requesting Range: bytes=0-
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if (WritePosition == 0)
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ContentLength = response.Content.Headers.ContentLength.GetValueOrDefault();
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var networkStream = response.Content.ReadAsStream(_cancellationSource.Token);
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_downloadedPiece = new EventWaitHandle(false, EventResetMode.AutoReset);
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//Download the file in the background.
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return Task.Run(async () => await DownloadFile(networkStream), _cancellationSource.Token);
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}
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/// <summary> Download <see cref="Uri"/> to <see cref="SaveFilePath"/>.</summary>
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private async Task DownloadFile(Stream networkStream)
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{
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var downloadPosition = WritePosition;
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var nextFlush = downloadPosition + DATA_FLUSH_SZ;
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var buff = new byte[DOWNLOAD_BUFF_SZ];
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try
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{
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DateTime startTime = DateTime.Now;
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long bytesReadSinceThrottle = 0;
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int bytesRead;
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do
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{
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bytesRead = await networkStream.ReadAsync(buff, 0, DOWNLOAD_BUFF_SZ, _cancellationSource.Token);
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await _writeFile.WriteAsync(buff, 0, bytesRead, _cancellationSource.Token);
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downloadPosition += bytesRead;
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if (downloadPosition > nextFlush)
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{
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await _writeFile.FlushAsync(_cancellationSource.Token);
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WritePosition = downloadPosition;
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Update();
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nextFlush = downloadPosition + DATA_FLUSH_SZ;
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_downloadedPiece.Set();
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}
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#region throttle
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bytesReadSinceThrottle += bytesRead;
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if (GlobalSpeedLimit >= MIN_BYTES_PER_SECOND && bytesReadSinceThrottle > GlobalSpeedLimit / THROTTLE_FREQUENCY)
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{
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var delayMS = (int)(startTime.AddSeconds(1d / THROTTLE_FREQUENCY) - DateTime.Now).TotalMilliseconds;
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if (delayMS > 0)
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await Task.Delay(delayMS, _cancellationSource.Token);
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startTime = DateTime.Now;
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bytesReadSinceThrottle = 0;
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}
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#endregion
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} while (downloadPosition < ContentLength && !IsCancelled && bytesRead > 0);
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WritePosition = downloadPosition;
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if (!IsCancelled && WritePosition < ContentLength)
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throw new WebException($"Downloaded size (0x{WritePosition:X10}) is less than {nameof(ContentLength)} (0x{ContentLength:X10}).");
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if (WritePosition > ContentLength)
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throw new WebException($"Downloaded size (0x{WritePosition:X10}) is greater than {nameof(ContentLength)} (0x{ContentLength:X10}).");
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}
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catch (TaskCanceledException)
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{
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Serilog.Log.Information("Download was cancelled");
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}
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finally
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{
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networkStream.Close();
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_writeFile.Close();
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_downloadedPiece.Set();
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Update();
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}
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}
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#endregion
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#region Json Connverters
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public static JsonSerializerSettings GetJsonSerializerSettings()
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=> new JsonSerializerSettings();
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#endregion
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#region Download Stream Reader
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[JsonIgnore]
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public override bool CanRead => true;
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[JsonIgnore]
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public override bool CanSeek => true;
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[JsonIgnore]
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public override bool CanWrite => false;
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[JsonIgnore]
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public override long Length
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{
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get
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{
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_backgroundDownloadTask ??= BeginDownloading();
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return ContentLength;
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}
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}
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[JsonIgnore]
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public override long Position { get => _readFile.Position; set => Seek(value, SeekOrigin.Begin); }
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[JsonIgnore]
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public override bool CanTimeout => false;
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[JsonIgnore]
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public override int ReadTimeout { get => base.ReadTimeout; set => base.ReadTimeout = value; }
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[JsonIgnore]
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public override int WriteTimeout { get => base.WriteTimeout; set => base.WriteTimeout = value; }
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public override void Flush() => throw new InvalidOperationException();
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public override void SetLength(long value) => throw new InvalidOperationException();
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public override void Write(byte[] buffer, int offset, int count) => throw new InvalidOperationException();
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public override int Read(byte[] buffer, int offset, int count)
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{
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_backgroundDownloadTask ??= BeginDownloading();
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var toRead = Math.Min(count, Length - Position);
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WaitToPosition(Position + toRead);
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return IsCancelled ? 0: _readFile.Read(buffer, offset, count);
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}
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public override long Seek(long offset, SeekOrigin origin)
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{
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var newPosition = origin switch
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{
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SeekOrigin.Current => Position + offset,
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SeekOrigin.End => ContentLength + offset,
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_ => offset,
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};
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WaitToPosition(newPosition);
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return _readFile.Position = newPosition;
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}
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/// <summary>Blocks until the file has downloaded to at least <paramref name="requiredPosition"/>, then returns. </summary>
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/// <param name="requiredPosition">The minimum required flished data length in <see cref="SaveFilePath"/>.</param>
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private void WaitToPosition(long requiredPosition)
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{
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while (WritePosition < requiredPosition
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&& _backgroundDownloadTask?.IsCompleted is false
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&& !IsCancelled)
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{
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_downloadedPiece.WaitOne(50);
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}
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}
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public override void Close()
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{
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_cancellationSource.Cancel();
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_backgroundDownloadTask?.Wait();
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_readFile.Close();
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_writeFile.Close();
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Update();
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}
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#endregion
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~NetworkFileStream()
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{
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_downloadedPiece?.Close();
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}
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}
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}
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