Fix some misc issues with deserializing pre-Bytecode 13 games

UndertaleModLib/Models/UndertaleGameObject.cs

@@ -180,15 +180,7 @@ public void Serialize(UndertaleWriter writer)
         writer.Write(Solid);
         writer.Write(Depth);
         writer.Write(Persistent);
-        // This apparently has a different notation than everything else...
-        if (_parentId.Resource == null)
-        {
-            writer.Write(-100);
-        }
-        else
-        {
-            writer.WriteUndertaleObject(_parentId);
-        }
+        writer.WriteUndertaleObject(_parentId);
         writer.WriteUndertaleObject(_textureMaskId);
         writer.Write(UsesPhysics);
         writer.Write(IsSensor);
@@ -221,18 +213,7 @@ public void Unserialize(UndertaleReader reader)
         Solid = reader.ReadBoolean();
         Depth = reader.ReadInt32();
         Persistent = reader.ReadBoolean();
-        _parentId = new UndertaleResourceById<UndertaleGameObject, UndertaleChunkOBJT>();
-        int parent = reader.ReadInt32();
-        if (parent == -100)
-        {
-            _parentId.UnserializeById(reader, -1);
-        }
-        else
-        {
-            if (parent < 0 && parent != -1) // Technically can be -100 (undefined), -2 (other), or -1 (self). Other makes no sense here though
-                throw new Exception("Invalid value for parent - should be -100 or object id, got " + parent);
-            _parentId.UnserializeById(reader, parent);
-        }
+        _parentId = reader.ReadUndertaleObject<UndertaleResourceById<UndertaleGameObject, UndertaleChunkOBJT>>();
         _textureMaskId = reader.ReadUndertaleObject<UndertaleResourceById<UndertaleSprite, UndertaleChunkSPRT>>();
         UsesPhysics = reader.ReadBoolean();
         IsSensor = reader.ReadBoolean();
@@ -270,7 +251,7 @@ public static uint UnserializeChildObjectCount(UndertaleReader reader)
         int physicsShapeVertexCount = reader.ReadInt32();
         reader.Position += 12 + (uint)physicsShapeVertexCount * UndertalePhysicsVertex.ChildObjectsSize;
 
-        count += 2 + 1 + UndertalePointerList<UndertalePointerList<Event>>.UnserializeChildObjectCount(reader);
+        count += 3 + 1 + UndertalePointerList<UndertalePointerList<Event>>.UnserializeChildObjectCount(reader);
 
         return count;
     }

UndertaleModLib/Models/UndertaleGeneralInfo.cs

@@ -496,9 +496,20 @@ public void Unserialize(UndertaleReader reader)
         LicenseMD5 = reader.ReadBytes(16);
         Timestamp = reader.ReadUInt64();
         DisplayName = reader.ReadUndertaleString();
-        ActiveTargets = reader.ReadUInt64();
-        FunctionClassifications = (FunctionClassification)reader.ReadUInt64();
-        SteamAppID = reader.ReadInt32();
+        if (BytecodeVersion >= 14)
+        {
+            ActiveTargets = reader.ReadUInt64();
+            FunctionClassifications = (FunctionClassification)reader.ReadUInt64();
+        }
+        else if (BytecodeVersion >= 12)
+        {
+            FunctionClassifications = (FunctionClassification)reader.ReadUInt64();
+            ActiveTargets = reader.ReadUInt64(); // FIXME: What actually is this?
+        }
+        else
+            FunctionClassifications = (FunctionClassification)reader.ReadUInt64();
+        if (BytecodeVersion >= 13)
+            SteamAppID = reader.ReadInt32();
         if (BytecodeVersion >= 14)
             DebuggerPort = reader.ReadUInt32();
         RoomOrder = reader.ReadUndertaleObject<UndertaleSimpleResourcesList<UndertaleRoom, UndertaleChunkROOM>>();
@@ -550,9 +561,14 @@ public static uint UnserializeChildObjectCount(UndertaleReader reader)
     {
         reader.Position++; // "IsDebuggerDisabled"
         byte bytecodeVer = reader.ReadByte();
-        bool readDebugPort = bytecodeVer >= 14;
 
-        reader.Position += (uint)(122 + (readDebugPort ? 4 : 0));
+        reader.Position += 110;
+        if (bytecodeVer >= 12)
+            reader.Position += 8; // "ActiveTargets"
+        if (bytecodeVer >= 13)
+            reader.Position += 4; // "SteamAppID"
+        if (bytecodeVer >= 14)
+            reader.Position += 4; // "DebuggerPort"
 
         // "RoomOrder"
         return 1 + UndertaleSimpleResourcesList<UndertaleRoom, UndertaleChunkROOM>.UnserializeChildObjectCount(reader);

UndertaleModLib/UndertaleChunks.cs

@@ -674,6 +674,16 @@ internal override void UnserializeChunk(UndertaleReader reader)
     public class UndertaleChunkFONT : UndertaleListChunk<UndertaleFont>
     {
         public override string Name => "FONT";
+
+        /// <summary>
+        /// Padding bytes at the end of the chunk.
+        /// </summary>
+        /// <remarks>
+        /// Appeared at some point after bytecode version 6, according to the existing copy of GMS 1.0.98.
+        /// Before bytecode version 12 (observed in bytecode 11), this contained unknown data of varying length.
+        /// Afterwards, this contains UTF-16 codepoints representing ASCII's 0x00-0xFF, and is consistently
+        /// 512 bytes long.
+        /// </remarks>
         public byte[] Padding;
 
         private static bool checkedFor2022_2;
@@ -795,14 +805,22 @@ internal override void SerializeChunk(UndertaleWriter writer)
         {
             base.SerializeChunk(writer);
 
-            if (Padding == null)
+            if (writer.undertaleData.GeneralInfo.BytecodeVersion > 6)
             {
-                for (ushort i = 0; i < 0x80; i++)
-                    writer.Write(i);
-                for (ushort i = 0; i < 0x80; i++)
-                    writer.Write((ushort)0x3f);
-            } else
-                writer.Write(Padding);
+                if (Padding == null)
+                {
+                    // TODO: Before bytecode 12 the size of Padding is variable.
+                    // (though we don't properly support them in other places yet)
+                    for (ushort i = 0; i < 0x80; i++)
+                        writer.Write(i);
+                    for (ushort i = 0; i < 0x80; i++)
+                        writer.Write((ushort)0x3f);
+                }
+                else
+                {
+                    writer.Write(Padding);
+                }
+            }
         }
 
         internal override void UnserializeChunk(UndertaleReader reader)
@@ -815,7 +833,19 @@ internal override void UnserializeChunk(UndertaleReader reader)
 
             base.UnserializeChunk(reader);
 
-            Padding = reader.ReadBytes(512);
+            if (reader.undertaleData.GeneralInfo.BytecodeVersion > 6)
+            {
+                if (reader.undertaleData.GeneralInfo.BytecodeVersion >= 12)
+                {
+                    Padding = reader.ReadBytes(512);
+                }
+                else
+                {
+                    // FIXME: how did GMAC the calculate the size of padding?
+                    int remainingBytes = (int)(Length - (reader.Position - 8));
+                    Padding = reader.ReadBytes(remainingBytes);
+                }
+            }
         }
 
         internal override uint UnserializeObjectCount(UndertaleReader reader)

UndertaleModLib/UndertaleIO.cs

@@ -76,7 +76,7 @@ public int SerializeById(UndertaleWriter writer)
                     if (CachedId < 0)
                         throw new IOException("Unregistered object");
                 }
-                else
+                else if (CachedId != -100)
                 {
                     if (typeof(ChunkT) == typeof(UndertaleChunkAGRP))
                         CachedId = 0;
@@ -89,7 +89,8 @@ public int SerializeById(UndertaleWriter writer)
 
         public void UnserializeById(UndertaleReader reader, int id)
         {
-            if (id < -1)
+            // In rare cases -100 (undefined in GML) is used instead of -1
+            if (id < -1 && id != -100)
                 throw new IOException("Invalid value for resource ID (" + typeof(ChunkT).Name + "): " + id);
             CachedId = id;
             reader.RequestResourceUpdate(this);
@@ -650,7 +651,7 @@ public void ToHere()
 
         public void Align(int alignment, byte paddingbyte = 0x00)
         {
-            while ((AbsPosition & (alignment - 1)) != paddingbyte)
+            while ((AbsPosition & (alignment - 1)) != 0)
             {
                 DebugUtil.Assert(ReadByte() == paddingbyte, "Invalid alignment padding");
             }
@@ -860,7 +861,7 @@ public void ThrowIfUnwrittenObjects()
 
         public void Align(int alignment, byte paddingbyte = 0x00)
         {
-            while ((Position & (alignment - 1)) != paddingbyte)
+            while ((Position & (alignment - 1)) != 0)
             {
                 Write(paddingbyte);
             }