From 28f4808dbbceaf4388d50a911ddeca117387cdef Mon Sep 17 00:00:00 2001
From: Deterous <138427222+Deterous@users.noreply.github.com>
Date: Mon, 30 Mar 2026 10:54:16 +0900
Subject: [PATCH] Read/write with variable initial offset (#74)

---
 SabreTools.Serialization.Readers/XDVDFS.cs | 15 +++++++++------
 SabreTools.Wrappers/XDVDFS.Extraction.cs   | 11 +++++++----
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/SabreTools.Serialization.Readers/XDVDFS.cs b/SabreTools.Serialization.Readers/XDVDFS.cs
index 2e7990c2..cea61242 100644
--- a/SabreTools.Serialization.Readers/XDVDFS.cs
+++ b/SabreTools.Serialization.Readers/XDVDFS.cs
@@ -22,6 +22,9 @@ namespace SabreTools.Serialization.Readers
 
             try
             {
+                // Cache the current offset
+                long initialOffset = data.Position;
+
                 // Create a new Volume to fill
                 var volume = new Volume();
 
@@ -39,7 +42,7 @@ namespace SabreTools.Serialization.Readers
                 volume.LayoutDescriptor = ParseLayoutDescriptor(data);
 
                 // Parse the descriptors from the root directory descriptor
-                var dd = ParseDirectoryDescriptors(data, vd.RootOffset, vd.RootSize);
+                var dd = ParseDirectoryDescriptors(data, initialOffset, vd.RootOffset, vd.RootSize);
                 if (dd is null)
                     return null;
 
@@ -129,7 +132,7 @@ namespace SabreTools.Serialization.Readers
         /// <param name="offset">Sector number descriptor is located at</param>
         /// <param name="size">Number of bytes descriptor contains</param>
         /// <returns>Filled Dictionary of int to DirectoryDescriptors on success, null on error</returns>
-        public static Dictionary<uint, DirectoryDescriptor>? ParseDirectoryDescriptors(Stream data, uint offset, uint size)
+        public static Dictionary<uint, DirectoryDescriptor>? ParseDirectoryDescriptors(Stream data, long initialOffset, uint offset, uint size)
         {
             // Ensure descriptor size is valid
             if (size < 14)
@@ -141,7 +144,7 @@ namespace SabreTools.Serialization.Readers
 
             var obj = new Dictionary<uint, DirectoryDescriptor>();
 
-            var dd = ParseDirectoryDescriptor(data, offset, size);
+            var dd = ParseDirectoryDescriptor(data, initialOffset, offset, size);
             if (dd is null)
                 return null;
 
@@ -157,7 +160,7 @@ namespace SabreTools.Serialization.Readers
                         continue;
 
                     // Get all descriptors from child
-                    var descriptors = ParseDirectoryDescriptors(data, dr.ExtentOffset, dr.ExtentSize);
+                    var descriptors = ParseDirectoryDescriptors(data, initialOffset, dr.ExtentOffset, dr.ExtentSize);
                     if (descriptors is null)
                         continue;
 
@@ -180,7 +183,7 @@ namespace SabreTools.Serialization.Readers
         /// <param name="offset">Sector number descriptor is located at</param>
         /// <param name="size">Number of bytes descriptor contains</param>
         /// <returns>Filled DirectoryDescriptor on success, null on error</returns>
-        public static DirectoryDescriptor? ParseDirectoryDescriptor(Stream data, uint offset, uint size)
+        public static DirectoryDescriptor? ParseDirectoryDescriptor(Stream data, long initialOffset, uint offset, uint size)
         {
             // Ensure descriptor size is valid
             if (size < Constants.MinimumRecordLength)
@@ -193,7 +196,7 @@ namespace SabreTools.Serialization.Readers
             var obj = new DirectoryDescriptor();
             var records = new List<DirectoryRecord>();
 
-            data.SeekIfPossible(((long)offset) * Constants.SectorSize, SeekOrigin.Begin);
+            data.SeekIfPossible(initialOffset + ((long)offset) * Constants.SectorSize, SeekOrigin.Begin);
             long curPosition;
             while (size > data.Position - (((long)offset) * Constants.SectorSize))
             {
diff --git a/SabreTools.Wrappers/XDVDFS.Extraction.cs b/SabreTools.Wrappers/XDVDFS.Extraction.cs
index 29ba3fb1..0deec455 100644
--- a/SabreTools.Wrappers/XDVDFS.Extraction.cs
+++ b/SabreTools.Wrappers/XDVDFS.Extraction.cs
@@ -25,14 +25,17 @@ namespace SabreTools.Wrappers
             // Clear the extraction state
             extractedFiles.Clear();
 
+            // Cache the current offset
+            long initialOffset = _dataSource.Position;
+
             // Extract files from all directories from root directory
-            return ExtractDescriptor(outputDirectory, includeDebug, VolumeDescriptor.RootOffset);
+            return ExtractDescriptor(outputDirectory, includeDebug, initialOffset, VolumeDescriptor.RootOffset);
         }
 
         /// <summary>
         /// Extracts all directory records recursively from directory descriptor
         /// </summary>
-        public bool ExtractDescriptor(string outputDirectory, bool includeDebug, uint sectorNumber)
+        public bool ExtractDescriptor(string outputDirectory, bool includeDebug, long initialOffset, uint sectorNumber)
         {
             // If no descriptor exists at that sector, we cannot extract from it
             if (!DirectoryDescriptors.ContainsKey(sectorNumber))
@@ -58,7 +61,7 @@ namespace SabreTools.Wrappers
                     if (!string.IsNullOrEmpty(outputPath) && !Directory.Exists(outputPath))
                         Directory.CreateDirectory(outputPath);
 
-                    allExtracted |= ExtractDescriptor(outputPath, includeDebug, dr.ExtentOffset);
+                    allExtracted |= ExtractDescriptor(outputPath, includeDebug, initialOffset, dr.ExtentOffset);
                 }
                 else
                 {
@@ -88,7 +91,7 @@ namespace SabreTools.Wrappers
                     lock (_dataSourceLock)
                     {
                         long fileOffset = ((long)dr.ExtentOffset) * Constants.SectorSize;
-                        _dataSource.SeekIfPossible(fileOffset, SeekOrigin.Begin);
+                        _dataSource.SeekIfPossible(initialOffset + fileOffset, SeekOrigin.Begin);
 
                         // Get the length, and make sure it won't EOF
                         uint length = dr.ExtentSize;