1 files changed, 96 insertions, 0 deletions
diff --git a/src/Jellyfin.Extensions/StreamExtensions.cs b/src/Jellyfin.Extensions/StreamExtensions.cs
index 0cfac384e3..fa019b0059 100644
--- a/src/Jellyfin.Extensions/StreamExtensions.cs
+++ b/src/Jellyfin.Extensions/StreamExtensions.cs
@@ -1,9 +1,12 @@
+using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text;
 using System.Threading;
+using System.Threading.Tasks;
 
 namespace Jellyfin.Extensions
 {
@@ -12,6 +15,8 @@ namespace Jellyfin.Extensions
     /// </summary>
     public static class StreamExtensions
     {
+        private const int StreamComparisonBufferSize = 65536;
+
         /// <summary>
         /// Reads all lines in the <see cref="Stream" />.
         /// </summary>
@@ -60,5 +65,96 @@ namespace Jellyfin.Extensions
                 yield return line;
             }
         }
+
+        /// <summary>
+        /// Determines whether a stream is identical to a file on disk.
+        /// </summary>
+        /// <param name="stream">The stream to compare.</param>
+        /// <param name="path">The file path to compare against.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+        /// <returns>True if the stream and file are identical; otherwise false.</returns>
+        public static async Task<bool> IsFileIdenticalAsync(this Stream stream, string path, CancellationToken cancellationToken)
+        {
+            ArgumentNullException.ThrowIfNull(stream);
+            ArgumentException.ThrowIfNullOrEmpty(path);
+
+            if (!stream.CanSeek)
+            {
+                return false;
+            }
+
+            var originalPosition = stream.Position;
+            try
+            {
+                stream.Position = 0;
+
+                var existingFileStream = new FileStream(
+                    path,
+                    FileMode.Open,
+                    FileAccess.Read,
+                    FileShare.Read,
+                    bufferSize: StreamComparisonBufferSize,
+                    FileOptions.Asynchronous | FileOptions.SequentialScan);
+                await using (existingFileStream.ConfigureAwait(false))
+                {
+                    return await stream.IsStreamIdenticalAsync(existingFileStream, cancellationToken).ConfigureAwait(false);
+                }
+            }
+            finally
+            {
+                stream.Position = originalPosition;
+            }
+        }
+
+        /// <summary>
+        /// Determines whether two streams are identical.
+        /// </summary>
+        /// <param name="a">The first stream to compare.</param>
+        /// <param name="b">The second stream to compare.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+        /// <returns>True if the streams are identical; otherwise false.</returns>
+        public static async Task<bool> IsStreamIdenticalAsync(this Stream a, Stream b, CancellationToken cancellationToken)
+        {
+            ArgumentNullException.ThrowIfNull(a);
+            ArgumentNullException.ThrowIfNull(b);
+
+            if (b.Length != a.Length)
+            {
+                return false;
+            }
+
+            var bufferA = ArrayPool<byte>.Shared.Rent(StreamComparisonBufferSize);
+            var bufferB = ArrayPool<byte>.Shared.Rent(StreamComparisonBufferSize);
+            try
+            {
+                while (true)
+                {
+                    cancellationToken.ThrowIfCancellationRequested();
+
+                    var bytesReadA = await a.ReadAsync(bufferA.AsMemory(), cancellationToken).ConfigureAwait(false);
+                    var bytesReadB = await b.ReadAsync(bufferB.AsMemory(), cancellationToken).ConfigureAwait(false);
+
+                    if (bytesReadA != bytesReadB)
+                    {
+                        return false;
+                    }
+
+                    if (bytesReadA == 0)
+                    {
+                        return true;
+                    }
+
+                    if (!bufferA.AsSpan(0, bytesReadA).SequenceEqual(bufferB.AsSpan(0, bytesReadB)))
+                    {
+                        return false;
+                    }
+                }
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(bufferA);
+                ArrayPool<byte>.Shared.Return(bufferB);
+            }
+        }
     }
 }