Speed up querystring callback dispatch (#316)

Author: Kludex

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+* Speed up querystring callback dispatch [#316](https://github.com/Kludex/python-multipart/pull/316).
+
 ## 0.0.32 (2026-06-04)
 
 * Speed up partial-boundary scanning for CR/LF-dense part data [#300](https://github.com/Kludex/python-multipart/pull/300).

python_multipart/multipart.py

@@ -78,6 +78,14 @@ class FormParserConfig(FileConfig):
 _missing = object()
 
 
+def _noop_event() -> None:
+    pass
+
+
+def _noop_data(_data: bytes, _start: int, _end: int) -> None:
+    pass
+
+
 class QuerystringState(IntEnum):
     """Querystring parser states.
 
@@ -836,6 +844,19 @@ def _internal_write(self, data: bytes, length: int) -> int:
         state = self.state
         strict_parsing = self.strict_parsing
         found_sep = self._found_sep
+        callbacks = cast("QuerystringCallbacks", self.callbacks)
+        on_field_start = callbacks.get("on_field_start")
+        on_field_name = callbacks.get("on_field_name")
+        on_field_data = callbacks.get("on_field_data")
+        on_field_end = callbacks.get("on_field_end")
+        if on_field_start is None:
+            on_field_start = _noop_event
+        if on_field_name is None:
+            on_field_name = _noop_data
+        if on_field_data is None:
+            on_field_data = _noop_data
+        if on_field_end is None:
+            on_field_end = _noop_event
 
         i = 0
         while i < length:
@@ -865,7 +886,7 @@ def _internal_write(self, data: bytes, length: int) -> int:
                     # Emit a field-start event, and go to that state.  Also,
                     # reset the "found_sep" flag, for the next time we get to
                     # this state.
-                    self.callback("field_start")
+                    on_field_start()
                     i -= 1
                     state = QuerystringState.FIELD_NAME
                     found_sep = False
@@ -885,7 +906,8 @@ def _internal_write(self, data: bytes, length: int) -> int:
 
                 if equals_pos != -1:
                     # Emit this name.
-                    self.callback("field_name", data, i, equals_pos)
+                    if i != equals_pos:
+                        on_field_name(data, i, equals_pos)
 
                     # Jump i to this position.  Note that it will then have 1
                     # added to it below, which means the next iteration of this
@@ -900,15 +922,17 @@ def _internal_write(self, data: bytes, length: int) -> int:
                         # end - there's no data callback at all (not even with
                         # a blank value).
                         if sep_pos != -1:
-                            self.callback("field_name", data, i, sep_pos)
-                            self.callback("field_end")
+                            if i != sep_pos:
+                                on_field_name(data, i, sep_pos)
+                            on_field_end()
 
                             i = sep_pos - 1
                             state = QuerystringState.BEFORE_FIELD
                         else:
                             # Otherwise, no separator in this block, so the
                             # rest of this chunk must be a name.
-                            self.callback("field_name", data, i, length)
+                            if i != length:
+                                on_field_name(data, i, length)
                             i = length
 
                     else:
@@ -924,7 +948,8 @@ def _internal_write(self, data: bytes, length: int) -> int:
 
                         # No separator in the rest of this chunk, so it's just
                         # a field name.
-                        self.callback("field_name", data, i, length)
+                        if i != length:
+                            on_field_name(data, i, length)
                         i = length
 
             elif state == QuerystringState.FIELD_DATA:
@@ -934,8 +959,9 @@ def _internal_write(self, data: bytes, length: int) -> int:
                 # If we found it, callback this bit as data and then go back
                 # to expecting to find a field.
                 if sep_pos != -1:
-                    self.callback("field_data", data, i, sep_pos)
-                    self.callback("field_end")
+                    if i != sep_pos:
+                        on_field_data(data, i, sep_pos)
+                    on_field_end()
 
                     # Note that we go to the separator, which brings us to the
                     # "before field" state.  This allows us to properly emit
@@ -946,7 +972,8 @@ def _internal_write(self, data: bytes, length: int) -> int:
 
                 # Otherwise, emit the rest as data and finish.
                 else:
-                    self.callback("field_data", data, i, length)
+                    if i != length:
+                        on_field_data(data, i, length)
                     i = length
 
             else:  # pragma: no cover (error case)
@@ -965,10 +992,17 @@ def finalize(self) -> None:
         if we're still in the middle of a field, an on_field_end callback, and
         then the on_end callback.
         """
+        callbacks = cast("QuerystringCallbacks", self.callbacks)
         # If we're currently in the middle of a field, we finish it.
         if self.state in (QuerystringState.FIELD_DATA, QuerystringState.FIELD_NAME):
-            self.callback("field_end")
-        self.callback("end")
+            on_field_end = callbacks.get("on_field_end")
+            if on_field_end is None:
+                on_field_end = _noop_event
+            on_field_end()
+        on_end = callbacks.get("on_end")
+        if on_end is None:
+            on_end = _noop_event
+        on_end()
 
     def __repr__(self) -> str:
         return "{}(strict_parsing={!r}, max_size={!r})".format(

tests/test_multipart.py

@@ -365,6 +365,10 @@ def on_foo() -> None:
             nonlocal called
             called += 1
 
+        def on_data(data: bytes, start: int, end: int) -> None:
+            nonlocal called
+            called += 1
+
         self.b.set_callback("foo", on_foo)  # type: ignore[arg-type]
         self.b.callback("foo")  # type: ignore[arg-type]
         self.assertEqual(called, 1)
@@ -373,6 +377,12 @@ def on_foo() -> None:
         self.b.callback("foo")  # type: ignore[arg-type]
         self.assertEqual(called, 1)
 
+        self.b.set_callback("data", on_data)
+        self.b.callback("data", b"", 0, 0)
+        self.assertEqual(called, 1)
+        self.b.callback("data", b"x", 0, 1)
+        self.assertEqual(called, 2)
+
 
 class TestQuerystringParser(unittest.TestCase):
     def assert_fields(self, *args: tuple[bytes, bytes], **kwargs: Any) -> None:
@@ -413,6 +423,25 @@ def test_simple_querystring(self) -> None:
 
         self.assert_fields((b"foo", b"bar"))
 
+    def test_no_callbacks(self) -> None:
+        parser = QuerystringParser()
+
+        self.assertEqual(parser.write(b"foo=bar"), 7)
+        parser.finalize()
+
+    def test_none_callbacks(self) -> None:
+        callbacks: Any = {
+            "on_field_start": None,
+            "on_field_name": None,
+            "on_field_data": None,
+            "on_field_end": None,
+            "on_end": None,
+        }
+        parser = QuerystringParser(callbacks)
+
+        self.assertEqual(parser.write(b"foo=bar"), 7)
+        parser.finalize()
+
     def test_querystring_blank_beginning(self) -> None:
         self.p.write(b"&foo=bar")