# -*- coding: utf-8 -*-
"""
    CRC Funktionen

"""
from six.moves import range


def build_codetable(poly):
    """
    Builds an ascii codetable for a polynome to be used by a crc
    checksum.
    """
    crc_table = []
    for i in range(256):
        crc = i
        for j in range(1, 9):
            if (crc & 1) == 1:
                crc = int(crc / 2.0) ^ poly
            else:
                crc = int(crc / 2.0)
        crc_table += [crc]
    return crc_table


def crc_checksum(something, poly=33800):
    """
        makes a crc checksum with any given polynome, building the table
        every time.
    """
    crc_table = build_codetable(poly)
    crc = 0
    for i in something:
        hb = int(crc / 256.0)
        lb = crc - (256 * hb)
        crc = crc_table[lb ^ ord(i)] ^ hb
    return crc


#: poly = 0x8408
TABLE_XMODEM16 = [
    0, 4489, 8978, 12955, 17956, 22445, 25910, 29887, 35912,
    40385, 44890, 48851, 51820, 56293, 59774, 63735, 4225, 264,
    13203, 8730, 22181, 18220, 30135, 25662, 40137, 36160, 49115,
    44626, 56045, 52068, 63999, 59510, 8450, 12427, 528, 5017,
    26406, 30383, 17460, 21949, 44362, 48323, 36440, 40913, 60270,
    64231, 51324, 55797, 12675, 8202, 4753, 792, 30631, 26158,
    21685, 17724, 48587, 44098, 40665, 36688, 64495, 60006, 55549,
    51572, 16900, 21389, 24854, 28831, 1056, 5545, 10034, 14011,
    52812, 57285, 60766, 64727, 34920, 39393, 43898, 47859, 21125,
    17164, 29079, 24606, 5281, 1320, 14259, 9786, 57037, 53060,
    64991, 60502, 39145, 35168, 48123, 43634, 25350, 29327, 16404,
    20893, 9506, 13483, 1584, 6073, 61262, 65223, 52316, 56789,
    43370, 47331, 35448, 39921, 29575, 25102, 20629, 16668, 13731,
    9258, 5809, 1848, 65487, 60998, 56541, 52564, 47595, 43106,
    39673, 35696, 33800, 38273, 42778, 46739, 49708, 54181, 57662,
    61623, 2112, 6601, 11090, 15067, 20068, 24557, 28022, 31999,
    38025, 34048, 47003, 42514, 53933, 49956, 61887, 57398, 6337,
    2376, 15315, 10842, 24293, 20332, 32247, 27774, 42250, 46211,
    34328, 38801, 58158, 62119, 49212, 53685, 10562, 14539, 2640,
    7129, 28518, 32495, 19572, 24061, 46475, 41986, 38553, 34576,
    62383, 57894, 53437, 49460, 14787, 10314, 6865, 2904, 32743,
    28270, 23797, 19836, 50700, 55173, 58654, 62615, 32808, 37281,
    41786, 45747, 19012, 23501, 26966, 30943, 3168, 7657, 12146,
    16123, 54925, 50948, 62879, 58390, 37033, 33056, 46011, 41522,
    23237, 19276, 31191, 26718, 7393, 3432, 16371, 11898, 59150,
    63111, 50204, 54677, 41258, 45219, 33336, 37809, 27462, 31439,
    18516, 23005, 11618, 15595, 3696, 8185, 63375, 58886, 54429,
    50452, 45483, 40994, 37561, 33584, 31687, 27214, 22741, 18780,
    15843, 11370, 7921, 3960]


def crc_xmodem16(something):
    """
        short for hardcoded 0x8408 (XMODEM-16) crc checksum from a predefined
        codetable.
    """
    crc_table = TABLE_XMODEM16
    crc = 0
    for i in something:
        hb = int(crc / 256.0)
        lb = crc - (256 * hb)
        crc = crc_table[lb ^ ord(i)] ^ hb
    return crc