Renamed module tracer → trace

This is consistent with the other module names.

blender_asset_tracer/trace/modifier_walkers.py

@@ -0,0 +1,64 @@
+"""Modifier handling code used in blocks2assets.py
+
+The _modifier_xxx() functions all yield result.BlockUsage objects for external
+files used by the modifiers.
+"""
+import typing
+
+from blender_asset_tracer import blendfile, bpathlib, cdefs
+from . import result
+
+
+def _modifier_filepath(modifier: blendfile.BlendFileBlock, block_name: bytes) \
+        -> typing.Iterator[result.BlockUsage]:
+    """Just yield the 'filepath' field."""
+    path, field = modifier.get(b'filepath', return_field=True)
+    yield result.BlockUsage(modifier, path, path_full_field=field, block_name=block_name)
+
+
+def _modifier_ocean(modifier: blendfile.BlendFileBlock, block_name: bytes) \
+        -> typing.Iterator[result.BlockUsage]:
+    if not modifier[b'cached']:
+        return
+
+    path, field = modifier.get(b'cachepath', return_field=True)
+    # The path indicates the directory containing the cached files.
+    yield result.BlockUsage(modifier, path, is_sequence=True, path_full_field=field,
+                            block_name=block_name)
+
+
+def _modifier_particle_system(modifier: blendfile.BlendFileBlock, block_name: bytes) \
+        -> typing.Iterator[result.BlockUsage]:
+    psys = modifier.get_pointer(b'psys')
+    if psys is None:
+        return
+
+    pointcache = psys.get_pointer(b'pointcache')
+    if pointcache is None:
+        return
+
+    flag = pointcache[b'flag']
+
+    if flag & cdefs.PTCACHE_DISK_CACHE:
+        # See ptcache_path() in pointcache.c
+        name, field = pointcache.get(b'name', return_field=True)
+        path = b'//%b%b/%b_*%b' % (
+            cdefs.PTCACHE_PATH,
+            modifier.bfile.filepath.stem.encode(),
+            name,
+            cdefs.PTCACHE_EXT)
+        bpath = bpathlib.BlendPath(path)
+        yield result.BlockUsage(pointcache, bpath, path_full_field=field,
+                                is_sequence=True, block_name=block_name)
+
+    if flag & cdefs.PTCACHE_EXTERNAL:
+        path, field = pointcache.get(b'path', return_field=True)
+        yield result.BlockUsage(pointcache, path, path_full_field=field,
+                                is_sequence=True, block_name=block_name)
+
+
+modifier_handlers = {
+    cdefs.eModifierType_ParticleSystem: _modifier_particle_system,
+    cdefs.eModifierType_Ocean: _modifier_ocean,
+    cdefs.eModifierType_MeshCache: _modifier_filepath,
+}