From 4c429e921228259f47795f8ad913ad3eff8fac71 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sybren=20A=2E=20St=C3=BCvel?= <sybren@blender.org>
Date: Fri, 11 Jul 2025 15:19:53 +0200
Subject: [PATCH] Read blendfile sub-version

Add support for reading the blend file's sub-version.
---
 blender_asset_tracer/blendfile/__init__.py | 22 ++++++++++++++++++++++
 tests/test_blendfile_loading.py            | 12 ++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/blender_asset_tracer/blendfile/__init__.py b/blender_asset_tracer/blendfile/__init__.py
index 041db61..e09ce3f 100644
--- a/blender_asset_tracer/blendfile/__init__.py
+++ b/blender_asset_tracer/blendfile/__init__.py
@@ -122,6 +122,7 @@ class BlendFile:
         self.filepath = path
         self.raw_filepath = path
         self._is_modified = False
+        self.file_subversion = 0
         self.fileobj = self._open_file(path, mode)
 
         self.blocks = []  # type: BFBList
@@ -169,6 +170,8 @@ class BlendFile:
 
             if block.code == b"DNA1":
                 self.decode_structs(block)
+            elif block.code == b"GLOB":
+                self.decode_glob(block)
             else:
                 self.fileobj.seek(block.size, os.SEEK_CUR)
 
@@ -356,6 +359,25 @@ class BlendFile:
                 dna_struct.append_field(field)
                 dna_offset += dna_size
 
+    def decode_glob(self, block: "BlendFileBlock") -> None:
+        """Partially decode the GLOB block to get the file sub-version."""
+        # Before this, the subversion didn't exist in 'FileGlobal'.
+        if self.header.version <= 242:
+            self.file_subversion = 0
+            return
+
+        # GLOB can appear in the file before DNA1, and so we cannot use DNA to
+        # parse the fields.
+
+        # The subversion is always the `short` at offset 4.
+        # block_data = io.BytesIO(block.raw_data())
+        endian = self.header.endian
+        self.fileobj.seek(4, os.SEEK_CUR)  # Skip the next 4 bytes.
+        self.file_subversion = endian.read_short(self.fileobj)
+
+        # Skip to the next block.
+        self.fileobj.seek(block.file_offset + block.size, os.SEEK_SET)
+
     def abspath(self, relpath: bpathlib.BlendPath) -> bpathlib.BlendPath:
         """Construct an absolute path from a blendfile-relative path."""
 
diff --git a/tests/test_blendfile_loading.py b/tests/test_blendfile_loading.py
index 505b101..4dea438 100644
--- a/tests/test_blendfile_loading.py
+++ b/tests/test_blendfile_loading.py
@@ -477,3 +477,15 @@ class BlendFileCacheTest(AbstractBlendFileTest):
         self.assertIs(bf, blendfile._cached_bfiles[other])
 
         self.assertEqual(str(bf.raw_filepath), bf.fileobj.name)
+
+
+class BlendFileSubVersionTest(AbstractBlendFileTest):
+    def test_file_subversion(self) -> None:
+        self.bf = blendfile.BlendFile(self.blendfiles / "multiple_materials.blend")
+        self.assertEqual(self.bf.file_subversion, 3)
+
+        self.bf = blendfile.BlendFile(
+            self.blendfiles
+            / "compositor_nodes/compositor_nodes_blender500_library.blend"
+        )
+        self.assertEqual(self.bf.file_subversion, 36)