Function parse_frame

aiohttp/websocket.py:217–278

Return the next frame from the socket.

(buf, continuation=False)

def parse_frame(buf, continuation=False):
    """Return the next frame from the socket."""
    # read header
    data = yield from buf.read(2)
    first_byte, second_byte = data

    fin = (first_byte >> 7) & 1
    rsv1 = (first_byte >> 6) & 1
    rsv2 = (first_byte >> 5) & 1
    rsv3 = (first_byte >> 4) & 1
    opcode = first_byte & 0xf

    # frame-fin = %x0 ; more frames of this message follow
    #           / %x1 ; final frame of this message
    # frame-rsv1 = %x0 ; 1 bit, MUST be 0 unless negotiated otherwise
    # frame-rsv2 = %x0 ; 1 bit, MUST be 0 unless negotiated otherwise
    # frame-rsv3 = %x0 ; 1 bit, MUST be 0 unless negotiated otherwise
    if rsv1 or rsv2 or rsv3:
        raise WebSocketError(
            CLOSE_PROTOCOL_ERROR,
            'Received frame with non-zero reserved bits')

    if opcode > 0x7 and fin == 0:
        raise WebSocketError(
            CLOSE_PROTOCOL_ERROR,
            'Received fragmented control frame')

    if fin == 0 and opcode == OPCODE_CONTINUATION and not continuation:
        raise WebSocketError(
            CLOSE_PROTOCOL_ERROR,
            'Received new fragment frame with non-zero '
            'opcode {!r}'.format(opcode))

    has_mask = (second_byte >> 7) & 1
    length = (second_byte) & 0x7f

    # Control frames MUST have a payload length of 125 bytes or less
    if opcode > 0x7 and length > 125:
        raise WebSocketError(
            CLOSE_PROTOCOL_ERROR,
            "Control frame payload cannot be larger than 125 bytes")

    # read payload
    if length == 126:
        data = yield from buf.read(2)
        length = UNPACK_LEN2(data)[0]
    elif length > 126:
        data = yield from buf.read(8)
        length = UNPACK_LEN3(data)[0]

    if has_mask:
        mask = yield from buf.read(4)

    if length:
        payload = yield from buf.read(length)
    else:
        payload = bytearray()