Reuse plain frame bodies during serialization

CHANGELOG.rst

@@ -19,7 +19,7 @@ dev
 
 **Bugfixes**
 
--
+- Avoided copying unmodified DATA and HEADERS bodies during serialization.
 
 6.1.0 (2025-01-22)
 ------------------

src/hyperframe/frame.py

@@ -304,6 +304,10 @@ def serialize_body(self) -> bytes:
         padding = b"\0" * self.pad_length
         if isinstance(self.data, memoryview):
             self.data = self.data.tobytes()
+
+        if type(self.data) is bytes and type(padding_data) is bytes and not padding_data and not padding:
+            return self.data
+
         return b"".join([padding_data, self.data, padding])
 
     def parse_body(self, data: memoryview) -> None:
@@ -748,6 +752,16 @@ def serialize_body(self) -> bytes:
         else:
             priority_data = b""
 
+        if (
+            type(self.data) is bytes
+            and type(padding_data) is bytes
+            and not padding_data
+            and type(priority_data) is bytes
+            and not priority_data
+            and not padding
+        ):
+            return self.data
+
         return b"".join([padding_data, priority_data, self.data, padding])
 
     def parse_body(self, data: memoryview) -> None:

tests/test_frames.py

@@ -142,6 +142,12 @@ def test_data_frame_serializes_properly(self, data):
         s = f.serialize()
         assert s == self.payload
 
+    def test_plain_data_frame_reuses_bytes_body(self):
+        data = b'testdata'
+        f = DataFrame(1, data)
+
+        assert f.serialize_body() is data
+
     def test_data_frame_with_padding_serializes_properly(self):
         f = DataFrame(1)
         f.flags = set(['END_STREAM', 'PADDED'])
@@ -791,6 +797,12 @@ def test_headers_frame_serializes_properly(self):
             b'hello world'
         )
 
+    def test_plain_headers_frame_reuses_bytes_body(self):
+        data = b'hello world'
+        f = HeadersFrame(1, data)
+
+        assert f.serialize_body() is data
+
     def test_headers_frame_parses_properly(self):
         s = (
             b'\x00\x00\x0B\x01\x05\x00\x00\x00\x01' +