From eb1def3f3a221a8fda80c5c09667f3d9c2c1bf22 Mon Sep 17 00:00:00 2001
From: LTRData <ol@ltr-data.se>
Date: Wed, 20 Nov 2024 20:40:57 +0100
Subject: [PATCH] Fixed PathToExtents to FatFileSystem

---
 Library/DiscUtils.Fat/ClusterStream.cs        |  5 +++++
 Library/DiscUtils.Fat/FatFileStream.cs        |  3 ++-
 Library/DiscUtils.Fat/FatFileSystem.cs        |  8 +++++++-
 Tests/LibraryTests/Fat/FatFileSystemTest.cs   |  8 +++++++-
 Tests/LibraryTests/Ntfs/NtfsFileSystemTest.cs | 16 ++++++++++++++--
 5 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/Library/DiscUtils.Fat/ClusterStream.cs b/Library/DiscUtils.Fat/ClusterStream.cs
index 0113e090..a50c94e1 100644
--- a/Library/DiscUtils.Fat/ClusterStream.cs
+++ b/Library/DiscUtils.Fat/ClusterStream.cs
@@ -638,5 +638,10 @@ public IEnumerable<Range<long, long>> EnumerateAllocatedClusters()
             firstCluster = null;
             lastCluster = null;
         }
+
+        if (firstCluster.HasValue && lastCluster.HasValue)
+        {
+            yield return new(firstCluster.Value, lastCluster.Value - firstCluster.Value + 1);
+        }
     }
 }
\ No newline at end of file
diff --git a/Library/DiscUtils.Fat/FatFileStream.cs b/Library/DiscUtils.Fat/FatFileStream.cs
index 870f26d0..42719e74 100644
--- a/Library/DiscUtils.Fat/FatFileStream.cs
+++ b/Library/DiscUtils.Fat/FatFileStream.cs
@@ -177,5 +177,6 @@ private void FirstClusterAllocatedHandler(uint cluster)
         _dir.UpdateEntry(_dirId, dirEntry);
     }
 
-    public IEnumerable<Range<long, long>> EnumerateAllocatedClusters() => _stream.EnumerateAllocatedClusters();
+    public IEnumerable<Range<long, long>> EnumerateAllocatedClusters()
+        => _stream.EnumerateAllocatedClusters();
 }
\ No newline at end of file
diff --git a/Library/DiscUtils.Fat/FatFileSystem.cs b/Library/DiscUtils.Fat/FatFileSystem.cs
index 455c4909..9db82127 100644
--- a/Library/DiscUtils.Fat/FatFileSystem.cs
+++ b/Library/DiscUtils.Fat/FatFileSystem.cs
@@ -410,7 +410,13 @@ public override SparseStream OpenFile(string path, FileMode mode, FileAccess acc
     }
 
     public IEnumerable<StreamExtent> PathToExtents(string path)
-        => PathToClusters(path).Select(range => new StreamExtent(range.Offset * ClusterSize, range.Count * ClusterSize));
+    {
+        var stream = (FatFileStream)OpenFile(path, FileMode.Open, FileAccess.Read);
+        
+        return stream
+            .EnumerateAllocatedClusters()
+            .Select(range => new StreamExtent(ClusterReader.GetBaseStreamPositionForCluster((uint)range.Offset), ClusterSize * range.Count));
+    }
 
     public IEnumerable<Range<long, long>> PathToClusters(string path)
     {
diff --git a/Tests/LibraryTests/Fat/FatFileSystemTest.cs b/Tests/LibraryTests/Fat/FatFileSystemTest.cs
index 0a5d02b2..af6753c9 100644
--- a/Tests/LibraryTests/Fat/FatFileSystemTest.cs
+++ b/Tests/LibraryTests/Fat/FatFileSystemTest.cs
@@ -477,6 +477,12 @@ public void TestFindPosition()
             file.Write(pattern);
         }
 
+        var firstExt = fs
+            .PathToExtents("Test.txt")
+            .FirstOrDefault();
+
+        Assert.NotEqual(0, firstExt.Start);
+
         long? locationOnDisk;
 
         Span<byte> buffer = stackalloc byte[pattern.Length];
@@ -492,7 +498,7 @@ public void TestFindPosition()
         }
 
         Assert.NotNull(locationOnDisk);
-        Assert.NotEqual(0, locationOnDisk.Value);
+        Assert.Equal(firstExt.Start, locationOnDisk.Value);
 
         diskStream.Position = locationOnDisk.Value;
         buffer.Clear();
diff --git a/Tests/LibraryTests/Ntfs/NtfsFileSystemTest.cs b/Tests/LibraryTests/Ntfs/NtfsFileSystemTest.cs
index 76c329ad..e14ebee6 100644
--- a/Tests/LibraryTests/Ntfs/NtfsFileSystemTest.cs
+++ b/Tests/LibraryTests/Ntfs/NtfsFileSystemTest.cs
@@ -877,6 +877,12 @@ public void TestFindPositionSmallFile()
             file.Write(pattern);
         }
 
+        var firstExt = fs
+            .PathToExtents("Test.txt")
+            .FirstOrDefault();
+
+        Assert.NotEqual(0, firstExt.Start);
+
         long? locationOnDisk;
 
         Span<byte> buffer = stackalloc byte[pattern.Length];
@@ -892,7 +898,7 @@ public void TestFindPositionSmallFile()
         }
 
         Assert.NotNull(locationOnDisk);
-        Assert.NotEqual(0, locationOnDisk.Value);
+        Assert.Equal(firstExt.Start, locationOnDisk.Value);
 
         diskStream.Position = locationOnDisk.Value;
         buffer.Clear();
@@ -920,6 +926,12 @@ public void TestFindPositionBigFile()
             file.Write(pattern);
         }
 
+        var firstExt = fs
+            .PathToExtents("Test.txt")
+            .FirstOrDefault();
+
+        Assert.NotEqual(0, firstExt.Start);
+
         long? locationOnDisk;
 
         var buffer = new byte[pattern.Length];
@@ -935,7 +947,7 @@ public void TestFindPositionBigFile()
         }
 
         Assert.NotNull(locationOnDisk);
-        Assert.NotEqual(0, locationOnDisk.Value);
+        Assert.Equal(firstExt.Start, locationOnDisk.Value);
 
         diskStream.Position = locationOnDisk.Value;
         buffer.AsSpan().Clear();