Set BKHD padding upon serialization to properly align DATA chunk

Author: henbagle

ME3Tweaks.Wwiser.Tests/FormatTests/BankHeaderPaddingTests.cs

@@ -0,0 +1,39 @@
+namespace ME3Tweaks.Wwiser.Tests.FormatTests;
+
+public class BankHeaderPaddingTests
+{
+    [TestCase(8)]
+    [TestCase(24)]
+    [TestCase(0x158)]
+    public void DataProperlyAligned_PaddingIsZero(long dataOffset)
+    {
+        var padding = new BankHeaderPadding();
+        padding.SetPadding(dataOffset);
+        
+        Assert.That(padding.Padding.Length, Is.EqualTo(0));
+    }
+    
+    [TestCase(0, 8)]
+    [TestCase(4, 4)]
+    [TestCase(33, 7)]
+    public void DataNotAligned_PaddingAlignsProperly(long dataOffset, long expectedPadding)
+    {
+        var padding = new BankHeaderPadding();
+        padding.SetPadding(dataOffset);
+        
+        Assert.That(padding.Padding.Length, Is.LessThanOrEqualTo(8));
+        Assert.That(padding.Padding.Length, Is.EqualTo(expectedPadding));
+    }
+    
+    [TestCase(15, 9)]
+    [TestCase(12, 12)]
+    [TestCase(0x15E, 10)]
+    public void DataNotAligned_PaddingProperlyOffsetBy8(long dataOffset, long expectedPadding)
+    {
+        var padding = new BankHeaderPadding();
+        padding.SetPadding(dataOffset);
+        
+        Assert.That(padding.Padding.Length, Is.GreaterThan(8));
+        Assert.That(padding.Padding.Length, Is.EqualTo(expectedPadding));
+    }
+}

ME3Tweaks.Wwiser/Model/BankHeaderChunk.cs

@@ -118,6 +118,21 @@ public void Deserialize(Stream stream, Endianness endianness, BinarySerializatio
             <= 141 => chunkSize - 0x14,
             _ => chunkSize - 0x14 - 0x04 - 0x10
         };
+        
+        /// <summary>
+        /// Sets the necessary padding for the DATA chunk. DATA must start at a multiple of 16 bytes + 8. IE 8, 24, 40, etc
+        /// </summary>
+        /// <param name="dataChunkOffset">Initial offset of the DATA chunk</param>
+        public void SetPadding(long dataChunkOffset)
+        {
+            var initAlignment = dataChunkOffset % 16;
+            Padding = initAlignment switch
+            {
+                < 8 => new byte[8 - initAlignment],
+                > 8 => new byte[8 + (16 - initAlignment)],
+                _ => Array.Empty<byte>()
+            };
+        }
     }
 
     [Flags]

ME3Tweaks.Wwiser/WwiseBankParser.cs

@@ -153,6 +153,8 @@ public async Task SerializeToAsync(Stream stream)
         {
             throw new InvalidOperationException("Cannot serialize a null WwiseBank");
         }
+        
+        SetBankHeaderPadding();
         await _serializer.SerializeAsync(stream,WwiseBank.ToModel(), CreateSerializationContext());
     }
 
@@ -162,9 +164,24 @@ public void SerializeTo(Stream stream)
         {
             throw new InvalidOperationException("Cannot serialize a null WwiseBank");
         }
+
+        SetBankHeaderPadding();
         _serializer.Serialize(stream,WwiseBank.ToModel(), CreateSerializationContext());
     }
 
+    private void SetBankHeaderPadding()
+    {
+        if (WwiseBank?.DATA is not null)
+        {
+            var context = CreateSerializationContext();
+            var bkhdSize= _serializer.SizeOf(WwiseBank.BKHD, context);
+            var didxSize = _serializer.SizeOf(WwiseBank.DIDX, context);
+            var dataOffset = bkhdSize + didxSize;
+
+            WwiseBank.BKHD.Padding.SetPadding(dataOffset);
+        }
+    }
+
     private BankSerializationContext CreateSerializationContext()
     {
         return new BankSerializationContext(Version: Version, UseModulator: false, UseFeedback: UseFeedback);