Add length: property to gfx/vtx (#334)

* Add length: property to gfx/vtx & improve yaml merging

* 1 bird

src/splat/segtypes/n64/gfx.py

@@ -4,7 +4,7 @@
 """
 
 import re
-from typing import Optional
+from typing import Dict, List, Optional, Union
 
 from pathlib import Path
 
@@ -275,3 +275,9 @@ def should_scan(self) -> bool:
 
     def should_split(self) -> bool:
         return self.extract and options.opts.is_mode_active("gfx")
+
+    @staticmethod
+    def estimate_size(yaml: Union[Dict, List]) -> Optional[int]:
+        if isinstance(yaml, dict) and "length" in yaml:
+            return yaml["length"] * 0x10
+        return None

src/splat/segtypes/n64/vtx.py

@@ -7,7 +7,7 @@
 
 import struct
 from pathlib import Path
-from typing import Optional
+from typing import Dict, List, Optional, Union
 
 from ...util import options, log
 
@@ -100,3 +100,9 @@ def should_scan(self) -> bool:
 
     def should_split(self) -> bool:
         return self.extract and options.opts.is_mode_active("vtx")
+
+    @staticmethod
+    def estimate_size(yaml: Union[Dict, List]) -> Optional[int]:
+        if isinstance(yaml, dict) and "length" in yaml:
+            return yaml["length"] * 0x10
+        return None