Add Support for Geometry Node Cache (#92890)

Add support for geometry node simulation cache files.

This also adds support for dealing with dynamic arrays in Blender's
DNA, because `modifier.bakes` is a pointer to such an array.

Co-authored-by: Sybren A. Stüvel <sybren@blender.org>
Reviewed-on: https://projects.blender.org/blender/blender-asset-tracer/pulls/92890

blender_asset_tracer/blendfile/__init__.py

@@ -633,8 +633,8 @@ class BlendFileBlock:
         self.bfile.fileobj.seek(self.file_offset, os.SEEK_SET)
         return self.bfile.fileobj.read(self.size)
 
-    def as_string(self) -> str:
-        """Interpret the bytes of this datablock as null-terminated utf8 string."""
+    def as_bytes_string(self) -> bytes:
+        """Interpret the bytes of this datablock as null-terminated string of raw bytes."""
         the_bytes = self.raw_data()
         try:
             first_null = the_bytes.index(0)
@@ -642,6 +642,11 @@ class BlendFileBlock:
             pass
         else:
             the_bytes = the_bytes[:first_null]
+        return the_bytes
+
+    def as_string(self) -> str:
+        """Interpret the bytes of this datablock as null-terminated utf8 string."""
+        the_bytes = self.as_bytes_string()
         return the_bytes.decode()
 
     def get_recursive_iter(
@@ -820,6 +825,10 @@ class BlendFileBlock:
     def __setitem__(self, item: bytes, value) -> None:
         self.set(item, value)
 
+    def has_field(self, name: bytes) -> bool:
+        dna_struct = self.bfile.structs[self.sdna_index]
+        return dna_struct.has_field(name)
+
     def keys(self) -> typing.Iterator[bytes]:
         """Generator, yields all field names of this block."""
         return (f.name.name_only for f in self.dna_type.fields)

blender_asset_tracer/blendfile/iterators.py

@@ -20,6 +20,7 @@
 # (c) 2014, Blender Foundation - Campbell Barton
 # (c) 2018, Blender Foundation - Sybren A. Stüvel
 import typing
+import copy
 
 from blender_asset_tracer import cdefs
 from . import BlendFileBlock
@@ -70,3 +71,24 @@ def modifiers(object_block: BlendFileBlock) -> typing.Iterator[BlendFileBlock]:
     # 'ob->modifiers[...]'
     mods = object_block.get_pointer((b"modifiers", b"first"))
     yield from listbase(mods, next_path=(b"modifier", b"next"))
+
+
+def dynamic_array(block: BlendFileBlock) -> typing.Iterator[BlendFileBlock]:
+    """
+    Generator that yields each element of a dynamic array as a separate block.
+
+    Dynamic arrays are multiple contiguous elements accessed via a single
+    pointer. BAT interprets these as a single data block, making it hard to
+    access individual elements. This function divides the array into individual
+    blocks by creating modified copies of the original block.
+    """
+
+    element_size = block.dna_type.size
+
+    sub_block = copy.copy(block)
+    sub_block.size = element_size
+
+    for i in range(block.count):
+        # When sub_block's data is read, it'll be read from this offset in the blend file.
+        sub_block.file_offset = block.file_offset + i * element_size
+        yield sub_block