def fill(self, byte):
"""
fill: byte -> None
Adds the given raw byte to this APIFrame. If this APIFrame is marked
as escaped and this byte is an escape byte, the next byte in a call
to fill() will be unescaped.
"""
if self._unescape_next_byte:
byte = intToByte(byteToInt(byte) ^ 0x20)
self._unescape_next_byte = False
elif self.escaped and byte == APIFrame.ESCAPE_BYTE:
self._unescape_next_byte = True
return
self.raw_data += intToByte(byteToInt(byte))
def escape(data):
"""
escape: byte string -> byte string
When a 'special' byte is encountered in the given data string,
it is preceded by an escape byte and XORed with 0x20.
"""
escaped_data = b""
for byte in data:
if intToByte(byteToInt(byte)) in APIFrame.ESCAPE_BYTES:
escaped_data += APIFrame.ESCAPE_BYTE
escaped_data += intToByte(0x20 ^ byteToInt(byte))
else:
escaped_data += intToByte(byteToInt(byte))
return escaped_data
def checksum(self):
"""
checksum: None -> single checksum byte
checksum adds all bytes of the binary, unescaped data in the
frame, saves the last byte of the result, and subtracts it from
0xFF. The final result is the checksum
"""
total = 0
# Add together all bytes
for byte in self.data:
total += byteToInt(byte)
# Only keep the last byte
total = total & 0xFF
return intToByte(0xFF - total)