From 0657b551964986fc5504a202eaa5e699d1c72f00 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Thu, 14 Sep 2023 13:33:25 +0900
Subject: [PATCH] Avoid `MemoryStream.ToArray` overhead in
 `LegacyByteArrayReader`

---
 osu.Game/Database/ImportTask.cs               |  2 +-
 .../IO/Archives/MemoryStreamArchiveReader.cs  | 30 +++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 osu.Game/IO/Archives/MemoryStreamArchiveReader.cs

diff --git a/osu.Game/Database/ImportTask.cs b/osu.Game/Database/ImportTask.cs
index bf5b377a07..962eab9fa5 100644
--- a/osu.Game/Database/ImportTask.cs
+++ b/osu.Game/Database/ImportTask.cs
@@ -54,7 +54,7 @@ namespace osu.Game.Database
                 if (ZipUtils.IsZipArchive(memoryStream))
                     return new ZipArchiveReader(memoryStream, Path);
 
-                return new LegacyByteArrayReader(memoryStream.ToArray(), Path);
+                return new MemoryStreamArchiveReader(memoryStream, Path);
             }
 
             // This isn't used in any current path. May need to reconsider for performance reasons (ie. if we don't expect the incoming stream to be copied out).
diff --git a/osu.Game/IO/Archives/MemoryStreamArchiveReader.cs b/osu.Game/IO/Archives/MemoryStreamArchiveReader.cs
new file mode 100644
index 0000000000..37ce1e508e
--- /dev/null
+++ b/osu.Game/IO/Archives/MemoryStreamArchiveReader.cs
@@ -0,0 +1,30 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using System.IO;
+
+namespace osu.Game.IO.Archives
+{
+    /// <summary>
+    /// Allows reading a single file from the provided memory stream.
+    /// </summary>
+    public class MemoryStreamArchiveReader : ArchiveReader
+    {
+        private readonly MemoryStream stream;
+
+        public MemoryStreamArchiveReader(MemoryStream stream, string filename)
+            : base(filename)
+        {
+            this.stream = stream;
+        }
+
+        public override Stream GetStream(string name) => new MemoryStream(stream.GetBuffer(), 0, (int)stream.Length);
+
+        public override void Dispose()
+        {
+        }
+
+        public override IEnumerable<string> Filenames => new[] { Name };
+    }
+}