Fix byte order incorrectly reversing

Author: ArchLeaders

src/MessageStudio/Formats/BinaryText/ImmutableMsbt.cs

@@ -38,11 +38,11 @@ public ImmutableMsbtEntry this[ReadOnlySpan<byte> label] {
     public ImmutableMsbt(ref RevrsReader reader)
     {
         ref MsbtHeader header = ref reader.Read<MsbtHeader, MsbtHeader.Reverser>();
-        if (header.ByteOrderMark is Endianness.Little) {
+        if (header.ByteOrderMark != reader.Endianness) {
             // Reverse the buffer back to LE
             // since it's initially read in BE
-            reader.Reverse<MsbtHeader, MsbtHeader.DataReverser>(0);
-            reader.Endianness = Endianness.Little;
+            reader.Endianness = header.ByteOrderMark;
+            reader.Reverse<MsbtHeader, MsbtHeader.Reverser>(0);
         }
 
         if (header.Magic != Msbt.MSBT_MAGIC) {
@@ -71,6 +71,7 @@ public ImmutableMsbt(ref RevrsReader reader)
         }
 
         Header = header;
+        Header.ByteOrderMark = reader.Endianness;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]

src/MessageStudio/Formats/BinaryText/Structures/MsbtHeader.cs

@@ -6,13 +6,13 @@
 namespace MessageStudio.Formats.BinaryText.Structures;
 
 [StructLayout(LayoutKind.Explicit, Size = 32)]
-public readonly struct MsbtHeader
+public struct MsbtHeader
 {
     [FieldOffset(0x00)]
     public readonly ulong Magic;
 
     [FieldOffset(0x08)]
-    public readonly Endianness ByteOrderMark;
+    public Endianness ByteOrderMark;
 
     [FieldOffset(0x0C)]
     public readonly TextEncoding Encoding;
@@ -47,18 +47,4 @@ public static void Reverse(in Span<byte> buffer)
             buffer[0x12..0x16].Reverse();
         }
     }
-
-    /// <summary>
-    /// Reverser for only the data,
-    /// the BoM is not reversed
-    /// </summary>
-    public class DataReverser : IStructReverser
-    {
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void Reverse(in Span<byte> buffer)
-        {
-            buffer[0x0E..0x10].Reverse();
-            buffer[0x12..0x16].Reverse();
-        }
-    }
 }