GetPositionInBaseStream impl for FAT and NTFS

LTRData · Nov 20, 2024 · 1e35f07 · 1e35f07
1 parent 9c103e5
commit 1e35f07
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Showing 8 changed files with 250 additions and 67 deletions.
diff --git a/Library/DiscUtils.Fat/ClusterReader.cs b/Library/DiscUtils.Fat/ClusterReader.cs
@@ -53,12 +53,17 @@ public ClusterReader(Stream stream, int firstDataSector, int sectorsPerCluster,
         _clusterSize = _sectorsPerCluster * _bytesPerSector;
     }
 
+    public Stream BaseStream => _stream;
+
     public int ClusterSize => _clusterSize;
 
     public int BytesPerSector => _bytesPerSector;
 
     public int SectorsPerCluster => _sectorsPerCluster;
 
+    public long GetBaseStreamPositionForCluster(uint cluster)
+        => ((uint)((cluster - 2) * _sectorsPerCluster + _firstDataSector)) * _bytesPerSector;
+
     public void ReadCluster(uint cluster, byte[] buffer, int offset)
     {
         if (offset + ClusterSize > buffer.Length)

diff --git a/Library/DiscUtils.Fat/ClusterStream.cs b/Library/DiscUtils.Fat/ClusterStream.cs
@@ -25,6 +25,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Runtime.InteropServices.ComTypes;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -63,6 +64,23 @@ internal ClusterStream(FatFileSystem fileSystem, FileAccess access, uint firstCl
         _clusterBuffer = new byte[_reader.ClusterSize];
     }
 
+    public override long? GetPositionInBaseStream(Stream baseStream, long virtualPosition)
+    {
+        if (ReferenceEquals(baseStream, this))
+        {
+            return virtualPosition;
+        }
+
+        if (TryGetClusterByPosition(virtualPosition, out var cluster))
+        {
+            var volumePos = _reader.GetBaseStreamPositionForCluster(cluster);
+
+            return _reader.BaseStream.GetPositionInBaseStream(baseStream, volumePos);
+        }
+
+        return null;
+    }
+
     public override bool CanRead => _access is FileAccess.Read or FileAccess.ReadWrite;
 
     public override bool CanSeek => true;

diff --git a/Library/DiscUtils.Fat/FatFileStream.cs b/Library/DiscUtils.Fat/FatFileStream.cs
@@ -48,6 +48,16 @@ public FatFileStream(FatFileSystem fileSystem, Directory dir, long fileId, FileA
         _stream.FirstClusterChanged += FirstClusterAllocatedHandler;
     }
 
+    public override long? GetPositionInBaseStream(Stream baseStream, long virtualPosition)
+    {
+        if (ReferenceEquals(baseStream, this))
+        {
+            return virtualPosition;
+        }
+
+        return _stream?.GetPositionInBaseStream(baseStream, virtualPosition);
+    }
+
     public override bool CanRead => _stream.CanRead;
 
     public override bool CanSeek => _stream.CanSeek;

diff --git a/Library/DiscUtils.Ntfs/File.cs b/Library/DiscUtils.Ntfs/File.cs
@@ -1249,6 +1249,21 @@ public FileStream(File file, NtfsAttribute attr, FileAccess access)
             _wrapped = attr.Open(access);
         }
 
+        public override long? GetPositionInBaseStream(Stream baseStream, long virtualPosition)
+        {
+            if (ReferenceEquals(baseStream, this))
+            {
+                return virtualPosition;
+            }
+
+            if (_wrapped.GetPositionInBaseStream(baseStream, virtualPosition) is { } basePos)
+            {
+                return basePos;
+            }
+
+            return _attr.OffsetToAbsolutePos(virtualPosition);
+        }
+
         public override bool CanRead => _wrapped.CanRead;
 
         public override bool CanSeek => _wrapped.CanSeek;

diff --git a/Library/DiscUtils.Ntfs/NtfsFileStream.cs b/Library/DiscUtils.Ntfs/NtfsFileStream.cs
@@ -88,6 +88,16 @@ public static SparseStream Open(File file, DirectoryEntry entry, AttributeType a
         }
     }
 
+    public override long? GetPositionInBaseStream(Stream baseStream, long virtualPosition)
+    {
+        if (ReferenceEquals(baseStream, this))
+        {
+            return virtualPosition;
+        }
+
+        return _baseStream.GetPositionInBaseStream(baseStream, virtualPosition);
+    }
+
     public override bool CanRead
     {
         get

diff --git a/Library/DiscUtils.Ntfs/NtfsFileSystem.cs b/Library/DiscUtils.Ntfs/NtfsFileSystem.cs
@@ -1357,7 +1357,7 @@ public void SetReparsePoint(string path, ReparsePoint reparsePoint)
             if (stream != null)
             {
                 // If there's an existing reparse point, unhook it.
-                using Stream contentStream = stream.Value.Open(FileAccess.Read);
+                using var contentStream = stream.Value.Open(FileAccess.Read);
                 var rp = contentStream.ReadStruct<ReparsePointRecord>((int)contentStream.Length);
                 _context.ReparsePoints.Remove(rp.Tag, dirEntry.Reference);
             }
@@ -1422,7 +1422,7 @@ public ReparsePoint GetReparsePoint(string path)
             if (stream != null)
             {
 
-                using Stream contentStream = stream.Value.Open(FileAccess.Read);
+                using var contentStream = stream.Value.Open(FileAccess.Read);
                 var rp = contentStream.ReadStruct<ReparsePointRecord>((int)contentStream.Length);
                 return new ReparsePoint((int)rp.Tag, rp.Content);
             }
@@ -2362,7 +2362,7 @@ private void RemoveReparsePoint(File file)
         {
             var rp = new ReparsePointRecord();
 
-            using (Stream contentStream = stream.Value.Open(FileAccess.Read))
+            using (var contentStream = stream.Value.Open(FileAccess.Read))
             {
                 rp.ReadFrom(contentStream, (int)contentStream.Length);
             }