def encode(input_octets, rate_index):
service_bits = np.zeros(16, int)
data_bits = util.shiftout(input_octets, 8)
data_bits = np.r_[service_bits, data_bits, crc.FCS(data_bits)]
signal_subcarriers = subcarriersFromBits(plcp_bits(wifi_802_11_rates[rate_index], input_octets.size+4), wifi_802_11_rates[0], 0)
data_subcarriers = subcarriersFromBits(data_bits, wifi_802_11_rates[rate_index], 0x5d)
return ofdm.encode(signal_subcarriers, data_subcarriers)
def lut_bootstrap(b, new_L):
global L, _lut, M, s, M_L, m
M = b.size-1
if L is None:
fn = lambda a: util.shiftin(remainder1(a, b)[::-1], M)[0]
else:
fn = lambda a: remainder5(a, True)
lut = np.empty(1<<new_L, int)
for i in xrange(lut.size):
lut[i] = fn(np.r_[util.shiftout(np.r_[i], new_L)[::-1], np.zeros(M, int)])
_lut = lut
L = new_L
s = M-L
M_L = M/L
m = (1<<M)-1
def FCS(calculationFields):
k = calculationFields.size
return 1 & ~remainder(
np.r_[np.ones(32, int), np.zeros(k, int)]
^ np.r_[calculationFields, np.zeros(32, int)], G)
def checkFCS(frame):
k = frame.size
x = remainder(
np.r_[np.ones(32, int), np.zeros(k, int)]
^ np.r_[frame, np.zeros(32, int)], G)
return all(x == correct_remainder)
remainder = lambda a, b: remainder5(a)
# The FCS field is transmitted commencing with the coefficient of the highest-order term.
# polynomial from x^32 down to x^0: 0b100000100110000010001110110110111
CRC32_802_11_FCS_G = 0b100000100110000010001110110110111
CRC32_802_11_FCS_remainder = 0b11000111000001001101110101111011
G = util.shiftout(np.r_[CRC32_802_11_FCS_G], 33)[::-1]
correct_remainder = util.shiftout(np.r_[CRC32_802_11_FCS_remainder], 32)[::-1]
L = None
fn = 'crc_lut_16'
if not lut_load(fn):
lut_bootstrap(G, 8)
lut_bootstrap(G, 16)
lut_dump(fn)
def plcp_bits(rate, octets):
plcp_rate = util.rev(rate.encoding, 4)
plcp = plcp_rate | (octets << 5)
parity = (util.mul(plcp, 0x1FFFF) >> 16) & 1
plcp |= parity << 17
return util.shiftout(np.array([plcp]), 18)
with open(fn, 'rb') as f:
_lut, M, L, s, M_L, m = pickle.load(f)
return True
except:
return False
def FCS(calculationFields):
k = calculationFields.size
return 1 & ~remainder(np.r_[np.ones(32, int), np.zeros(k, int)] ^ np.r_[calculationFields, np.zeros(32, int)], G)
def checkFCS(frame):
k = frame.size
x = remainder(np.r_[np.ones(32, int), np.zeros(k, int)] ^ np.r_[frame, np.zeros(32, int)], G)
return all(x == correct_remainder)
remainder = lambda a, b: remainder5(a)
# The FCS field is transmitted commencing with the coefficient of the highest-order term.
# polynomial from x^32 down to x^0: 0b100000100110000010001110110110111
CRC32_802_11_FCS_G = 0b100000100110000010001110110110111
CRC32_802_11_FCS_remainder = 0b11000111000001001101110101111011
G = util.shiftout(np.r_[CRC32_802_11_FCS_G], 33)[::-1]
correct_remainder = util.shiftout(np.r_[CRC32_802_11_FCS_remainder], 32)[::-1]
L = None
fn = 'crc_lut_16'
if not lut_load(fn):
lut_bootstrap(G, 8)
lut_bootstrap(G, 16)
lut_dump(fn)
