SSM_PiMonitorElewarr/pimonitor/PMPacket.py

"""
Created on 13-04-2013

@author: citan
"""

import array


class PMPacket(object):
    # 0x80
    # destination byte
    # source byte
    # data size byte
    # ...
    # checksum byte sum of every byte in packet (incl. header)

    _header_byte = 0x80
    _valid_bytes = [0xFF, 0xA8, 0xE8]

    def __init__(self, dst, src, data):
        self._dst = dst
        self._src = src
        self._data = data

    @classmethod
    def from_array(cls, data):
        validate = PMPacket.is_valid(data)
        if not validate[0]:
            raise Exception('packet', validate[1])

        dst = data[1]
        src = data[2]
        data = data[4:-1]
        return cls(dst, src, data)

    @classmethod
    def is_valid(cls, data):
        # TODO: check E8
        valid = True
        msg = ""

        valid = valid and (len(data) > 5)
        msg += "invalid length (too short), " if (not valid) else ""

        valid = valid and (data[0] == PMPacket._header_byte)
        msg += "invalid header, " if (not valid) else ""

        # valid = data[4] in PMPacket._valid_bytes
        # msg += "invalid header, expected one of " + ', '.join(hex(s) for s in PMPacket._valid_bytes) +", got: " + hex(data[4]) + ", " if (not valid) else ""
        #valid = valid and ((data[1] == 0x10) or (data[1] == 0xf0))
        #valid = valid and ((data[2] == 0x10) or (data[2] == 0xf0))
        #valid = valid and (data[1] != data[2])
        #msg += "invalid source/target, " if (not valid) else ""

        current_len = len(data)
        expected_len = 5 + data[3]
        valid = valid and (current_len == expected_len)
        msg += "invalid length (is: " + str(current_len) + ", expected: " + str(expected_len) + "), " if (
            not valid) else ""

        checksum = 0
        for i in range(0, len(data) - 1):
            checksum = (checksum + data[i]) & 0xFF

        valid = valid and (checksum == data[-1])
        msg += "invalid checksum (is " + str(checksum) + ", expected: " + str(data[-1]) + "), " if (not valid) else ""

        return valid, msg

    def is_equal(self, packet):
        return self.to_bytes() == packet.to_bytes()

    def to_bytes(self):
        length = len(self._data)

        packet = [self._header_byte, self._dst, self._src, length]
        packet.extend(self._data)

        checksum = 0
        for b in packet:
            checksum = (checksum + b) & 0xFF

        packet.append(checksum)
        return packet

    def to_string(self):
        return array.array('B', self.to_bytes()).tostring()

    def dump(self):
        return "[" + ', '.join(("0x%0.2X" % s) for s in self.to_bytes()) + "], dst: " + hex(
            self._dst) + ", src: " + hex(self._src) + ", len: " + str(len(self._data))

    def get_data(self):
        return self._data

    def get_destination(self):
        return self._dst

    def get_source(self):
        return self._src

    @classmethod
    def dump_header(cls, data):
        print("header [" + ', '.join(hex(s) for s in data) + "], len: " + str(len(data)))