From 279f86d91039152461f8196dbcc3e2bf4a182e57 Mon Sep 17 00:00:00 2001
From: Alex Barney <thealexbarney@gmail.com>
Date: Fri, 13 Oct 2023 23:54:13 -0700
Subject: [PATCH] Fix a bug in ConvertToFsCommonPath

---
 src/LibHac/Fs/Fsa/MountUtility.cs             |  2 +-
 .../Fs/FsaTests/MountUtilityTests.cs          | 44 ++++++++++++++++++-
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/src/LibHac/Fs/Fsa/MountUtility.cs b/src/LibHac/Fs/Fsa/MountUtility.cs
index b7a144ea..0749c2a2 100644
--- a/src/LibHac/Fs/Fsa/MountUtility.cs
+++ b/src/LibHac/Fs/Fsa/MountUtility.cs
@@ -292,7 +292,7 @@ public static class MountUtility
         if (mountNameLength + commonPathLength > commonPathBuffer.Length)
             return ResultFs.TooLongPath.Log();
 
-        StringUtils.Copy(commonPathBuffer.Slice(commonPathLength), subPath);
+        StringUtils.Copy(commonPathBuffer.Slice(mountNameLength), subPath);
         return Result.Success;
     }
 }
\ No newline at end of file
diff --git a/tests/LibHac.Tests/Fs/FsaTests/MountUtilityTests.cs b/tests/LibHac.Tests/Fs/FsaTests/MountUtilityTests.cs
index 371e3236..301b0eaa 100644
--- a/tests/LibHac.Tests/Fs/FsaTests/MountUtilityTests.cs
+++ b/tests/LibHac.Tests/Fs/FsaTests/MountUtilityTests.cs
@@ -1,8 +1,11 @@
-using LibHac.Common;
+using System;
+using LibHac.Common;
 using LibHac.Fs;
 using LibHac.Fs.Fsa;
 using LibHac.Fs.Shim;
 using LibHac.Tests.Fs.FileSystemClientTests;
+using LibHac.Tools.Fs;
+using LibHac.Util;
 using Xunit;
 
 namespace LibHac.Tests.Fs.FsaTests;
@@ -32,4 +35,43 @@ public class MountUtilityTests
         Assert.Success(fs.MountSdCard(mountName.ToU8Span()));
         Assert.Result(ResultFs.InvalidMountName, fs.GetEntryType(out _, path.ToU8Span()));
     }
+
+    private class TestCommonMountNameGenerator : ICommonMountNameGenerator
+    {
+        public void Dispose() { }
+
+        public Result GenerateCommonMountName(Span<byte> nameBuffer)
+        {
+            ReadOnlySpan<byte> mountName = "@Test"u8;
+            
+            // Add 2 for the mount name separator and null terminator
+            int requiredNameBufferSize = StringUtils.GetLength(mountName, PathTool.MountNameLengthMax) + 2;
+
+            Assert.True(nameBuffer.Length >= requiredNameBufferSize);
+
+            var sb = new U8StringBuilder(nameBuffer);
+            sb.Append(mountName).Append(StringTraits.DriveSeparator);
+
+            Assert.Equal(sb.Length, requiredNameBufferSize - 1);
+
+            return Result.Success;
+        }
+    }
+
+    [Fact]
+    public void ConvertToFsCommonPath_MountedWithCommonPath_ReturnsCommonPath()
+    {
+        FileSystemClient fs = FileSystemServerFactory.CreateClient(true);
+
+        using var fileSystem = new UniqueRef<IFileSystem>(new InMemoryFileSystem());
+        using var mountNameGenerator = new UniqueRef<ICommonMountNameGenerator>(new TestCommonMountNameGenerator());
+        Assert.Success(fs.Register("mount"u8, ref fileSystem.Ref, ref mountNameGenerator.Ref));
+        
+        byte[] outputPath = new byte[100];
+        Assert.Success(fs.ConvertToFsCommonPath(new U8SpanMutable(outputPath), "mount:/entry1/entry2"u8));
+
+        string expected = "@Test:/entry1/entry2";
+        string actual = StringUtils.Utf8ZToString(outputPath);
+        Assert.Equal(expected, actual);
+    }
 }
\ No newline at end of file