io_scene_fbx/encode_bin.py

@@ -3,11 +3,13 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 try:
-    from . import data_types
+    from . import data_types, fbx_utils
 except:
     import data_types
+    import fbx_utils
 
 from struct import pack
+from contextlib import contextmanager
 import array
 import numpy as np
 import zlib
@@ -51,6 +53,57 @@ class FBXElem:
         self._end_offset = -1
         self._props_length = -1
 
+    @classmethod
+    @contextmanager
+    def enable_multithreading_cm(cls):
+        """Temporarily enable multithreaded array compression.
+
+        The context manager handles starting up and shutting down the threads.
+
+        Only exits once all the threads are done (either all tasks were completed or an error occurred and the threads
+        were stopped prematurely).
+
+        Writing to a file is temporarily disabled as a safeguard."""
+        # __enter__()
+        orig_func = cls._add_compressed_array_helper
+        orig_write = cls._write
+
+        def insert_compressed_array(props, insert_at, data, length):
+            # zlib.compress releases the GIL, so can be multithreaded.
+            data = zlib.compress(data, 1)
+            comp_len = len(data)
+
+            encoding = 1
+            data = pack('<3I', length, encoding, comp_len) + data
+            props[insert_at] = data
+
+        with fbx_utils.MultiThreadedTaskConsumer.new_cpu_bound_cm(insert_compressed_array) as wrapped_func:
+            try:
+                def _add_compressed_array_helper_multi(self, data, length):
+                    # Append a dummy value that will be replaced with the compressed array data later.
+                    self.props.append(...)
+                    # The index to insert the compressed array into.
+                    insert_at = len(self.props) - 1
+                    # Schedule the array to be compressed on a separate thread and then inserted into the hierarchy at
+                    # `insert_at`.
+                    wrapped_func(self.props, insert_at, data, length)
+
+                # As an extra safeguard, temporarily replace the `_write` function to raise an error if called.
+                def temp_write(*_args, **_kwargs):
+                    raise RuntimeError("Writing is not allowed until multithreaded array compression has been disabled")
+
+                cls._add_compressed_array_helper = _add_compressed_array_helper_multi
+                cls._write = temp_write
+
+                # Return control back to the caller of __enter__().
+                yield
+            finally:
+                # __exit__()
+                # Restore the original functions.
+                cls._add_compressed_array_helper = orig_func
+                cls._write = orig_write
+            # Exiting the MultiThreadedTaskConsumer context manager will wait for all scheduled tasks to complete.
+
     def add_bool(self, data):
         assert(isinstance(data, bool))
         data = pack('?', data)
@@ -130,21 +183,26 @@ class FBXElem:
         self.props_type.append(data_types.STRING)
         self.props.append(data)
 
+    def _add_compressed_array_helper(self, data, length):
+        """Note: This function may be swapped out by enable_multithreading_cm with an equivalent that supports
+        multithreading."""
+        data = zlib.compress(data, 1)
+        comp_len = len(data)
+
+        encoding = 1
+        data = pack('<3I', length, encoding, comp_len) + data
+        self.props.append(data)
+
     def _add_array_helper(self, data, prop_type, length):
+        self.props_type.append(prop_type)
         # mimic behavior of fbxconverter (also common sense)
         # we could make this configurable.
         encoding = 0 if len(data) <= 128 else 1
         if encoding == 0:
-            pass
+            data = pack('<3I', length, encoding, len(data)) + data
-        elif encoding == 1:
-            data = zlib.compress(data, 1)
-
-        comp_len = len(data)
-
-        data = pack('<3I', length, encoding, comp_len) + data
-
-        self.props_type.append(prop_type)
             self.props.append(data)
+        elif encoding == 1:
+            self._add_compressed_array_helper(data, length)
 
     def _add_parray_helper(self, data, array_type, prop_type):
         assert (isinstance(data, array.array))

io_scene_fbx/export_fbx_bin.py

@@ -3509,6 +3509,10 @@ def save_single(operator, scene, depsgraph, filepath="",
     # Generate some data about exported scene...
     scene_data = fbx_data_from_scene(scene, depsgraph, settings)
 
+    # Enable multithreaded array compression in FBXElem and wait until all threads are done before exiting the context
+    # manager.
+    with encode_bin.FBXElem.enable_multithreading_cm():
+        # Writing elements into an FBX hierarchy can now begin.
         root = elem_empty(None, b"")  # Root element has no id, as it is not saved per se!
 
         # Mostly FBXHeaderExtension and GlobalSettings.
@@ -3533,7 +3537,7 @@ def save_single(operator, scene, depsgraph, filepath="",
         # Cleanup!
         fbx_scene_data_cleanup(scene_data)
 
-    # And we are down, we can write the whole thing!
+    # And we are done, all multithreaded tasks are complete, and we can write the whole thing to file!
     encode_bin.write(filepath, root, FBX_VERSION)
 
     # Clear cached ObjectWrappers!