def updateParity(self, dataBits, resolve=False):
'''
Updates data bits and computes parity.
When 32 bits are provided, they are used for parity computation and for
bit inversion.
Parameters
----------
dataBits : numpy.ndarray(dtype=numpy.uint8)
30 or 32 element array
resolve: bool, optional
When specified, bits d23 and d24 of the GPS word are updated to ensure
that parity bits d29 and d30 are zeros.
'''
packed = numpy.packbits(dataBits)
acc = (packed[0] << 24) | (packed[1] << 16) | \
(packed[2] << 8) | packed[3]
if len(dataBits) == 30:
acc >>= 2
elif acc & 0x40000000:
acc ^= 0x3FFFFFC0
dataBits[-30:-6] ^= 1
# D29 = D30*^d1^d3^d5^d6^d7^d9^d10^d14^d15^d16^d17^d18^d21^d22^d24
d29 = parity(acc & 0b01101011101100011111001101000000)
# D30 = D29*^d3^d5^d6^d8^d9^d10^d11^d13^d15^d19^d22^d23^d24
d30 = parity(acc & 0b10001011011110101000100111000000)
if resolve:
if d29:
acc ^= 0x80
d29 = False
d30 = not d30
dataBits[-8] ^= 1
if d30:
acc ^= 0x40
d30 = False
dataBits[-7] ^= 1
# D25 = D29*^d1^d2^d3^d5^d6^d10^d11^d12^d13^d14^d17^d18^d20^d23
dataBits[-6] = parity(acc & 0b10111011000111110011010010000000)
# D26 = D30*^d2^d3^d4^d6^d7^d11^d12^d13^d14^d15^d18^d19^d21^d24
dataBits[-5] = parity(acc & 0b01011101100011111001101001000000)
# D27 = D29*^d1^d3^d4^d5^d7^d8^d12^d13^d14^d15^d16^d19^d20^d22
dataBits[-4] = parity(acc & 0b10101110110001111100111000000000)
# D28 = D30*^d2^d4^d5^d6^d8^d9^d13^d14^d15^d16^d17^d20^d21^d23
dataBits[-3] = parity(acc & 0b01010111011000111110011010000000)
# D29 = D30*^d1^d3^d5^d6^d7^d9^d10^d14^d15^d16^d17^d18^d21^d22^d24
dataBits[-2] = d29
# D30 = D29*^d3^d5^d6^d8^d9^d10^d11^d13^d15^d19^d22^d23^d24
dataBits[-1] = d30
return
def updateParity(self, dataBits):
'''
Updates data bits and computes parity.
When 85 bits are provided, they are used for parity computation and for
bit inversion.
Parameters
----------
dataBits : numpy.ndarray(dtype=numpy.uint8)
85 element array
'''
packed = numpy.packbits(dataBits)
assert len(packed) == 11
hc = _HAMMING_COEFFS
for bIdx in range(8):
p = 0
for i in range(11):
p ^= parity(packed[i] & hc[bIdx][i])
dataBits[-(bIdx + 1)] = p
packed[10] |= p << bIdx
def updateParity(self, dataBits):
'''
Updates data bits and computes parity.
When 85 bits are provided, they are used for parity computation and for
bit inversion.
Parameters
----------
dataBits : numpy.ndarray(dtype=numpy.uint8)
85 element array
'''
packed = numpy.packbits(dataBits)
assert len(packed) == 11
hc = _HAMMING_COEFFS
for bIdx in range(8):
p = 0
for i in range(11):
p ^= parity(packed[i] & hc[bIdx][i])
dataBits[-(bIdx + 1)] = p
packed[10] |= p << bIdx
