From 83a2e6fb8de033f7eecf31c8ed698512e2b8ea3c Mon Sep 17 00:00:00 2001
From: Adam Hathcock <adam@hathcock.uk>
Date: Fri, 2 Oct 2026 13:51:35 +0100
Subject: [PATCH] use arraypool

---
 src/SharpCompress/Common/Rar/RarVolume.cs     | 49 +++++++++++++++----
 .../Rar/RarArchiveAsyncTests.cs               | 21 ++++++++
 .../SharpCompress.Test/Rar/RarArchiveTests.cs | 11 +++++
 3 files changed, 72 insertions(+), 9 deletions(-)

diff --git a/src/SharpCompress/Common/Rar/RarVolume.cs b/src/SharpCompress/Common/Rar/RarVolume.cs
index 1b7de043..7c1d0221 100644
--- a/src/SharpCompress/Common/Rar/RarVolume.cs
+++ b/src/SharpCompress/Common/Rar/RarVolume.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -66,9 +67,25 @@ public abstract class RarVolume : Volume
                         var fh = (FileHeader)header;
                         if (fh.FileName == "CMT")
                         {
-                            var buffer = new byte[fh.CompressedSize];
-                            fh.PackedStream.NotNull().ReadFully(buffer);
-                            Comment = Encoding.UTF8.GetString(buffer, 0, buffer.Length - 1);
+                            var commentSize = checked((int)fh.CompressedSize);
+                            var buffer = ArrayPool<byte>.Shared.Rent(commentSize);
+                            try
+                            {
+                                // Pooled buffers can be larger than the comment payload.
+                                if (
+                                    !fh
+                                        .PackedStream.NotNull()
+                                        .ReadFully(buffer.AsSpan(0, commentSize))
+                                )
+                                {
+                                    throw new EndOfStreamException();
+                                }
+                                Comment = Encoding.UTF8.GetString(buffer, 0, commentSize - 1);
+                            }
+                            finally
+                            {
+                                ArrayPool<byte>.Shared.Return(buffer);
+                            }
                         }
                     }
                     break;
@@ -115,12 +132,26 @@ public abstract class RarVolume : Volume
                         var fh = (FileHeader)header;
                         if (fh.FileName == "CMT")
                         {
-                            var buffer = new byte[fh.CompressedSize];
-                            await fh
-                                .PackedStream.NotNull()
-                                .ReadFullyAsync(buffer, cancellationToken)
-                                .ConfigureAwait(false);
-                            Comment = Encoding.UTF8.GetString(buffer, 0, buffer.Length - 1);
+                            var commentSize = checked((int)fh.CompressedSize);
+                            var buffer = ArrayPool<byte>.Shared.Rent(commentSize);
+                            try
+                            {
+                                // Pooled buffers can be larger than the comment payload.
+                                if (
+                                    !await fh
+                                        .PackedStream.NotNull()
+                                        .ReadFullyAsync(buffer, 0, commentSize, cancellationToken)
+                                        .ConfigureAwait(false)
+                                )
+                                {
+                                    throw new EndOfStreamException();
+                                }
+                                Comment = Encoding.UTF8.GetString(buffer, 0, commentSize - 1);
+                            }
+                            finally
+                            {
+                                ArrayPool<byte>.Shared.Return(buffer);
+                            }
                         }
                     }
                     break;
diff --git a/tests/SharpCompress.Test/Rar/RarArchiveAsyncTests.cs b/tests/SharpCompress.Test/Rar/RarArchiveAsyncTests.cs
index b3cd79bd..afe0027a 100644
--- a/tests/SharpCompress.Test/Rar/RarArchiveAsyncTests.cs
+++ b/tests/SharpCompress.Test/Rar/RarArchiveAsyncTests.cs
@@ -1,9 +1,11 @@
 using System.IO;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using SharpCompress.Archives;
 using SharpCompress.Archives.Rar;
 using SharpCompress.Common;
+using SharpCompress.Common.Rar;
 using SharpCompress.Compressors.LZMA.Utilities;
 using SharpCompress.Readers;
 using SharpCompress.Test.Mocks;
@@ -13,6 +15,25 @@ namespace SharpCompress.Test.Rar;
 
 public class RarArchiveAsyncTests : ArchiveTests
 {
+    [Fact]
+    public async ValueTask Rar5_Comment_Archive_Async()
+    {
+        await using var archive = await RarArchive.OpenAsyncArchive(
+            Path.Combine(TEST_ARCHIVES_PATH, "Rar5.comment.rar"),
+            cancellationToken: CancellationToken.None
+        );
+        var entryCount = 0;
+        await foreach (var entry in archive.EntriesAsync.WithCancellation(CancellationToken.None))
+        {
+            entryCount++;
+        }
+        Assert.True(entryCount > 0);
+        await foreach (var volume in archive.VolumesAsync.WithCancellation(CancellationToken.None))
+        {
+            Assert.Equal("This is another comment\n", ((RarVolume)volume).Comment);
+        }
+    }
+
     [Theory]
     [InlineData("Rar15.rar")]
     [InlineData("Rar2.rar")]
diff --git a/tests/SharpCompress.Test/Rar/RarArchiveTests.cs b/tests/SharpCompress.Test/Rar/RarArchiveTests.cs
index 65f5a0d2..968d567a 100644
--- a/tests/SharpCompress.Test/Rar/RarArchiveTests.cs
+++ b/tests/SharpCompress.Test/Rar/RarArchiveTests.cs
@@ -4,6 +4,7 @@ using System.Linq;
 using SharpCompress.Archives;
 using SharpCompress.Archives.Rar;
 using SharpCompress.Common;
+using SharpCompress.Common.Rar;
 using SharpCompress.Compressors.LZMA.Utilities;
 using SharpCompress.Readers;
 using SharpCompress.Test.Mocks;
@@ -13,6 +14,16 @@ namespace SharpCompress.Test.Rar;
 
 public class RarArchiveTests : ArchiveTests
 {
+    [Fact]
+    public void Rar5_Comment_Archive()
+    {
+        using var archive = RarArchive.OpenArchive(
+            Path.Combine(TEST_ARCHIVES_PATH, "Rar5.comment.rar")
+        );
+        Assert.NotEmpty(archive.Entries);
+        Assert.Equal("This is another comment\n", ((RarVolume)archive.Volumes.First()).Comment);
+    }
+
     [Theory]
     [InlineData("Rar15.rar")]
     [InlineData("Rar2.rar")]