Reduce memory copy when buffering is not required (#572)

aioesphomeapi/_frame_helper/base.pxd

@@ -2,6 +2,8 @@
 import cython
 
 
+cdef bint TYPE_CHECKING
+
 cdef class APIFrameHelper:
 
     cdef object _loop
@@ -10,7 +12,7 @@ cdef class APIFrameHelper:
     cdef object _transport
     cdef public object _writer
     cdef public object _ready_future
-    cdef bytearray _buffer
+    cdef bytes _buffer
     cdef cython.uint _buffer_len
     cdef cython.uint _pos
     cdef object _client_info
@@ -18,4 +20,9 @@ cdef class APIFrameHelper:
     cdef object _debug_enabled
 
     @cython.locals(original_pos=cython.uint, new_pos=cython.uint)
-    cdef _read_exactly(self, int length)
+    cdef bytes _read_exactly(self, int length)
+
+    cdef _add_to_buffer(self, bytes data)
+
+    @cython.locals(end_of_frame_pos=cython.uint)
+    cdef _remove_from_buffer(self)

aioesphomeapi/_frame_helper/base.py

@@ -4,7 +4,7 @@ import asyncio
 import logging
 from abc import abstractmethod
 from functools import partial
-from typing import Callable, cast
+from typing import TYPE_CHECKING, Callable, cast
 
 from ..core import HandshakeAPIError, SocketClosedAPIError
 
@@ -55,7 +55,7 @@ class APIFrameHelper:
         self._transport: asyncio.Transport | None = None
         self._writer: None | (Callable[[bytes | bytearray | memoryview], None]) = None
         self._ready_future = self._loop.create_future()
-        self._buffer = bytearray()
+        self._buffer: bytes | None = None
         self._buffer_len = 0
         self._pos = 0
         self._client_info = client_info
@@ -66,13 +66,48 @@ class APIFrameHelper:
         if not self._ready_future.done():
             self._ready_future.set_exception(exc)
 
-    def _read_exactly(self, length: _int) -> bytearray | None:
+    def _add_to_buffer(self, data: bytes) -> None:
+        """Add data to the buffer."""
+        if self._buffer_len == 0:
+            # This is the best case scenario, we don't have to copy the data
+            # and can just use the buffer directly. This is the most common
+            # case as well.
+            self._buffer = data
+        else:
+            if TYPE_CHECKING:
+                assert self._buffer is not None, "Buffer should be set"
+            # This is the worst case scenario, we have to copy the data
+            # and can't just use the buffer directly. This is also very
+            # uncommon since we usually read the entire frame at once.
+            self._buffer += data
+        self._buffer_len += len(data)
+
+    def _remove_from_buffer(self) -> None:
+        """Remove data from the buffer."""
+        end_of_frame_pos = self._pos
+        self._buffer_len -= end_of_frame_pos
+        if self._buffer_len == 0:
+            # This is the best case scenario, we can just set the buffer to None
+            # and don't have to copy the data. This is the most common case as well.
+            self._buffer = None
+            return
+        if TYPE_CHECKING:
+            assert self._buffer is not None, "Buffer should be set"
+        # This is the worst case scenario, we have to copy the data
+        # and can't just use the buffer directly. This should only happen
+        # when we read multiple frames at once because the event loop
+        # is blocked and we cannot pull the data out of the buffer fast enough.
+        self._buffer = self._buffer[end_of_frame_pos:]
+
+    def _read_exactly(self, length: _int) -> bytes | None:
         """Read exactly length bytes from the buffer or None if all the bytes are not yet available."""
         original_pos = self._pos
         new_pos = original_pos + length
         if self._buffer_len < new_pos:
             return None
         self._pos = new_pos
+        if TYPE_CHECKING:
+            assert self._buffer is not None, "Buffer should be set"
         return self._buffer[original_pos:new_pos]
 
     async def perform_handshake(self, timeout: float) -> None:

aioesphomeapi/_frame_helper/noise.pxd

@@ -3,7 +3,7 @@ import cython
 from .base cimport APIFrameHelper
 
 
-cdef object TYPE_CHECKING
+cdef bint TYPE_CHECKING
 
 cdef class APINoiseFrameHelper(APIFrameHelper):
 
@@ -18,10 +18,15 @@ cdef class APINoiseFrameHelper(APIFrameHelper):
     cdef bint _is_ready
 
     @cython.locals(
-        header=bytearray,
+        header=bytes,
         preamble=cython.uint, 
         msg_size_high=cython.uint, 
         msg_size_low=cython.uint,
-        end_of_frame_pos=cython.uint,
     )    
-    cpdef data_received(self, bytes data)
+    cpdef data_received(self, bytes data)
+
+    @cython.locals(
+        type_high=cython.uint,
+        type_low=cython.uint
+    )
+    cpdef _handle_frame(self, bytes data)

aioesphomeapi/_frame_helper/noise.py

@@ -139,8 +139,7 @@ class APINoiseFrameHelper(APIFrameHelper):
         await super().perform_handshake(timeout)
 
     def data_received(self, data: bytes) -> None:
-        self._buffer += data
-        self._buffer_len += len(data)
+        self._add_to_buffer(data)
         while self._buffer:
             self._pos = 0
             header = self._read_exactly(3)
@@ -170,9 +169,7 @@ class APINoiseFrameHelper(APIFrameHelper):
             except Exception as err:  # pylint: disable=broad-except
                 self._handle_error_and_close(err)
             finally:
-                end_of_frame_pos = self._pos
-                del self._buffer[:end_of_frame_pos]
-                self._buffer_len -= end_of_frame_pos
+                self._remove_from_buffer()
 
     def _send_hello_handshake(self) -> None:
         """Send a ClientHello to the server."""
@@ -198,7 +195,7 @@ class APINoiseFrameHelper(APIFrameHelper):
                 f"{self._log_name}: Error while writing data: {err}"
             ) from err
 
-    def _handle_hello(self, server_hello: bytearray) -> None:
+    def _handle_hello(self, server_hello: bytes) -> None:
         """Perform the handshake with the server."""
         if not server_hello:
             self._handle_error_and_close(
@@ -269,7 +266,7 @@ class APINoiseFrameHelper(APIFrameHelper):
         proto.start_handshake()
         self._proto = proto
 
-    def _handle_handshake(self, msg: bytearray) -> None:
+    def _handle_handshake(self, msg: bytes) -> None:
         _LOGGER.debug("Starting handshake...")
         if msg[0] != 0:
             explanation = msg[1:].decode()
@@ -333,12 +330,12 @@ class APINoiseFrameHelper(APIFrameHelper):
                 f"{self._log_name}: Error while writing data: {err}"
             ) from err
 
-    def _handle_frame(self, frame: bytearray) -> None:
+    def _handle_frame(self, frame: bytes) -> None:
         """Handle an incoming frame."""
         if TYPE_CHECKING:
             assert self._decrypt is not None, "Handshake should be complete"
         try:
-            msg = self._decrypt(bytes(frame))
+            msg = self._decrypt(frame)
         except InvalidTag as ex:
             self._handle_error_and_close(
                 ProtocolAPIError(f"{self._log_name}: Bad encryption frame: {ex!r}")
@@ -348,11 +345,11 @@ class APINoiseFrameHelper(APIFrameHelper):
         # 2 bytes: message type
         # 2 bytes: message length
         # N bytes: message data
-        self._on_pkt((msg[0] << 8) | msg[1], msg[4:])
+        type_high = msg[0]
+        type_low = msg[1]
+        self._on_pkt((type_high << 8) | type_low, msg[4:])
 
-    def _handle_closed(  # pylint: disable=unused-argument
-        self, frame: bytearray
-    ) -> None:
+    def _handle_closed(self, frame: bytes) -> None:  # pylint: disable=unused-argument
         """Handle a closed frame."""
         self._handle_error(ProtocolAPIError(f"{self._log_name}: Connection closed"))
 

aioesphomeapi/_frame_helper/plain_text.pxd

@@ -3,7 +3,7 @@ import cython
 from .base cimport APIFrameHelper
 
 
-cdef object TYPE_CHECKING
+cdef bint TYPE_CHECKING
 cdef object WRITE_EXCEPTIONS
 cdef object bytes_to_varuint, varuint_to_bytes
 
@@ -12,12 +12,12 @@ cdef class APIPlaintextFrameHelper(APIFrameHelper):
     @cython.locals(
         msg_type=bytes,
         length=bytes,
-        init_bytes=bytearray, 
-        add_length=bytearray,
+        init_bytes=bytes,
+        add_length=bytes,
         end_of_frame_pos=cython.uint,
         length_int=cython.uint,
         preamble=cython.uint, 
         length_high=cython.uint, 
         maybe_msg_type=cython.uint
     )
-    cpdef data_received(self, bytes data)
+    cpdef data_received(self, bytes data)

aioesphomeapi/_frame_helper/plain_text.py

@@ -39,8 +39,7 @@ class APIPlaintextFrameHelper(APIFrameHelper):
             ) from err
 
     def data_received(self, data: bytes) -> None:  # pylint: disable=too-many-branches
-        self._buffer += data
-        self._buffer_len += len(data)
+        self._add_to_buffer(data)
         while self._buffer:
             # Read preamble, which should always 0x00
             # Also try to get the length and msg type
@@ -80,10 +79,10 @@ class APIPlaintextFrameHelper(APIFrameHelper):
                     msg_type_int = maybe_msg_type
                 else:
                     # Message type is longer than 1 byte
-                    msg_type = bytes(init_bytes[2:3])
+                    msg_type = init_bytes[2:3]
             else:
                 # Length is longer than 1 byte
-                length = bytes(init_bytes[1:3])
+                length = init_bytes[1:3]
                 # If the message is long, we need to read the rest of the length
                 while length[-1] & 0x80 == 0x80:
                     add_length = self._read_exactly(1)
@@ -112,18 +111,16 @@ class APIPlaintextFrameHelper(APIFrameHelper):
             if length_int == 0:
                 packet_data = b""
             else:
-                packet_data_bytearray = self._read_exactly(length_int)
+                maybe_packet_data = self._read_exactly(length_int)
                 # The packet data is not yet available, wait for more data
                 # to arrive before continuing, since callback_packet has not
                 # been called yet the buffer will not be cleared and the next
                 # call to data_received will continue processing the packet
                 # at the start of the frame.
-                if packet_data_bytearray is None:
+                if maybe_packet_data is None:
                     return
-                packet_data = bytes(packet_data_bytearray)
+                packet_data = maybe_packet_data
 
-            end_of_frame_pos = self._pos
-            del self._buffer[:end_of_frame_pos]
-            self._buffer_len -= end_of_frame_pos
+            self._remove_from_buffer()
             self._on_pkt(msg_type_int, packet_data)
             # If we have more data, continue processing