Simplified slcan serial reading

Author: Aaron Fulton

can/interfaces/slcan.py

@@ -219,15 +219,10 @@ def _read(self, timeout: float | None) -> str | None:
                 # Due to accessing `serialPortOrig.in_waiting` too often will reduce the performance.
                 # We read the `serialPortOrig.in_waiting` only once here.
                 size = self.serialPortOrig.in_waiting or 1
-                if in_waiting > 0:
-                    self._buffer.extend(self.serialPortOrig.read(in_waiting))
-                else:
-                    byte = self.serialPortOrig.read(1)
-                    if byte:
-                        self._buffer.extend(byte)
+                self._buffer.extend(self.serialPortOrig.read(size))
 
                 for i, byte in enumerate(self._buffer):
-                    if self._buffer[i] in (self._OK[0], self._ERROR[0]):
+                    if byte in (self._OK[0], self._ERROR[0]):
                         string = self._buffer[: i + 1].decode()
                         del self._buffer[: i + 1]
                         return string