1 files changed, 162 insertions, 0 deletions
diff --git a/Jellyfin.Api/Helpers/ProgressiveFileStream.cs b/Jellyfin.Api/Helpers/ProgressiveFileStream.cs
new file mode 100644
index 000000000..b3566b6f8
--- /dev/null
+++ b/Jellyfin.Api/Helpers/ProgressiveFileStream.cs
@@ -0,0 +1,162 @@
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+using Jellyfin.Api.Models.PlaybackDtos;
+using MediaBrowser.Model.IO;
+
+namespace Jellyfin.Api.Helpers
+{
+    /// <summary>
+    /// A progressive file stream for transferring transcoded files as they are written to.
+    /// </summary>
+    public class ProgressiveFileStream : Stream
+    {
+        private readonly FileStream _fileStream;
+        private readonly TranscodingJobDto? _job;
+        private readonly TranscodingJobHelper _transcodingJobHelper;
+        private readonly bool _allowAsyncFileRead;
+        private int _bytesWritten;
+        private bool _disposed;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ProgressiveFileStream"/> class.
+        /// </summary>
+        /// <param name="filePath">The path to the transcoded file.</param>
+        /// <param name="job">The transcoding job information.</param>
+        /// <param name="transcodingJobHelper">The transcoding job helper.</param>
+        public ProgressiveFileStream(string filePath, TranscodingJobDto? job, TranscodingJobHelper transcodingJobHelper)
+        {
+            _job = job;
+            _transcodingJobHelper = transcodingJobHelper;
+            _bytesWritten = 0;
+
+            var fileOptions = FileOptions.SequentialScan;
+            _allowAsyncFileRead = false;
+
+            // use non-async filestream along with read due to https://github.com/dotnet/corefx/issues/6039
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                fileOptions |= FileOptions.Asynchronous;
+                _allowAsyncFileRead = true;
+            }
+
+            _fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite, IODefaults.FileStreamBufferSize, fileOptions);
+        }
+
+        /// <inheritdoc />
+        public override bool CanRead => _fileStream.CanRead;
+
+        /// <inheritdoc />
+        public override bool CanSeek => false;
+
+        /// <inheritdoc />
+        public override bool CanWrite => false;
+
+        /// <inheritdoc />
+        public override long Length => throw new NotSupportedException();
+
+        /// <inheritdoc />
+        public override long Position
+        {
+            get => throw new NotSupportedException();
+            set => throw new NotSupportedException();
+        }
+
+        /// <inheritdoc />
+        public override void Flush()
+        {
+            _fileStream.Flush();
+        }
+
+        /// <inheritdoc />
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            return _fileStream.Read(buffer, offset, count);
+        }
+
+        /// <inheritdoc />
+        public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            int totalBytesRead = 0;
+            int remainingBytesToRead = count;
+
+            while (remainingBytesToRead > 0)
+            {
+                cancellationToken.ThrowIfCancellationRequested();
+                int bytesRead;
+                if (_allowAsyncFileRead)
+                {
+                    bytesRead = await _fileStream.ReadAsync(buffer, offset, remainingBytesToRead, cancellationToken).ConfigureAwait(false);
+                }
+                else
+                {
+                    bytesRead = _fileStream.Read(buffer, offset, remainingBytesToRead);
+                }
+
+                remainingBytesToRead -= bytesRead;
+                if (bytesRead > 0)
+                {
+                    _bytesWritten += bytesRead;
+                    totalBytesRead += bytesRead;
+
+                    if (_job != null)
+                    {
+                        _job.BytesDownloaded = Math.Max(_job.BytesDownloaded ?? _bytesWritten, _bytesWritten);
+                    }
+                }
+                else
+                {
+                    if (_job == null || _job.HasExited)
+                    {
+                        break;
+                    }
+
+                    await Task.Delay(100, cancellationToken).ConfigureAwait(false);
+                }
+            }
+
+            return totalBytesRead;
+        }
+
+        /// <inheritdoc />
+        public override long Seek(long offset, SeekOrigin origin)
+            => throw new NotSupportedException();
+
+        /// <inheritdoc />
+        public override void SetLength(long value)
+            => throw new NotSupportedException();
+
+        /// <inheritdoc />
+        public override void Write(byte[] buffer, int offset, int count)
+            => throw new NotSupportedException();
+
+        /// <inheritdoc />
+        protected override void Dispose(bool disposing)
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            try
+            {
+                if (disposing)
+                {
+                    _fileStream.Dispose();
+
+                    if (_job != null)
+                    {
+                        _transcodingJobHelper.OnTranscodeEndRequest(_job);
+                    }
+                }
+            }
+            finally
+            {
+                _disposed = true;
+                base.Dispose(disposing);
+            }
+        }
+    }
+}