139 lines
6.5 KiB
Python
Executable File
139 lines
6.5 KiB
Python
Executable File
#!/usr/bin/env python
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#
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# This work is licensed under the Creative Attribution-NonCommercial-ShareAlike
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# 3.0 Unported License.To view a copy of this license, visit
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# http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to
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# Creative Commons, 444 Castro Street, Suite 900, Mountain View,
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# California, 94041, USA.
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from __future__ import print_function
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from bitarray import bitarray
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# Does anybody read this stuff? There's a PEP somewhere that says I should do this.
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__author__ = 'Cortney T. Buffington, N0MJS'
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__copyright__ = 'Copyright (c) 2016 Cortney T. Buffington, N0MJS and the K0USY Group'
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__credits__ = 'Jonathan Naylor, G4KLX'
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__license__ = 'Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported'
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__maintainer__ = 'Cort Buffington, N0MJS'
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__email__ = 'n0mjs@me.com'
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#------------------------------------------------------------------------------
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# Hamming 15,11,3 routines
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#------------------------------------------------------------------------------
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# ENCODER- returns a bitarray object containing the hamming checksums
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def enc_hamming_15113(_data):
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csum = bitarray(4)
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csum[0] = _data[0] ^ _data[1] ^ _data[2] ^ _data[3] ^ _data[5] ^ _data[7] ^ _data[8]
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csum[1] = _data[1] ^ _data[2] ^ _data[3] ^ _data[4] ^ _data[6] ^ _data[8] ^ _data[9]
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csum[2] = _data[2] ^ _data[3] ^ _data[4] ^ _data[5] ^ _data[7] ^ _data[9] ^ _data[10]
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csum[3] = _data[0] ^ _data[1] ^ _data[2] ^ _data[4] ^ _data[6] ^ _data[7] ^ _data[10]
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return csum
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# DECODER - Returns a tuple of (decoded data, True if an error was corrected)
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def dec_hamming_15113(_data):
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chk0 = _data[0] ^ _data[1] ^ _data[2] ^ _data[3] ^ _data[5] ^ _data[7] ^ _data[8]
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chk1 = _data[1] ^ _data[2] ^ _data[3] ^ _data[4] ^ _data[6] ^ _data[8] ^ _data[9]
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chk2 = _data[2] ^ _data[3] ^ _data[4] ^ _data[5] ^ _data[7] ^ _data[9] ^ _data[10]
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chk3 = _data[0] ^ _data[1] ^ _data[2] ^ _data[4] ^ _data[6] ^ _data[7] ^ _data[10]
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n = 0
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error = False
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n |= 0x01 if chk0 != _data[11] else 0x00
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n |= 0x02 if chk1 != _data[12] else 0x00
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n |= 0x04 if chk2 != _data[13] else 0x00
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n |= 0x08 if chk3 != _data[14] else 0x00
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if n == 0x01: _data[11] = not _data[11]; return (_data, True)
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if n == 0x02: _data[12] = not _data[12]; return (_data, True)
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if n == 0x04: _data[13] = not _data[13]; return (_data, True)
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if n == 0x08: _data[14] = not _data[14]; return (_data, True)
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if n == 0x0f: _data[0] = not _data[0]; return (_data, True)
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if n == 0x07: _data[1] = not _data[1]; return (_data, True)
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if n == 0x0b: _data[2] = not _data[2]; return (_data, True)
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if n == 0x03: _data[3] = not _data[3]; return (_data, True)
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if n == 0x0d: _data[4] = not _data[4]; return (_data, True)
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if n == 0x05: _data[5] = not _data[5]; return (_data, True)
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if n == 0x09: _data[6] = not _data[6]; return (_data, True)
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if n == 0x0e: _data[7] = not _data[7]; return (_data, True)
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if n == 0x06: _data[8] = not _data[8]; return (_data, True)
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if n == 0x0a: _data[9] = not _data[9]; return (_data, True)
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if n == 0x0c: _data[10] = not _data[10]; return (_data, True)
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return (_data, False)
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#------------------------------------------------------------------------------
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# Hamming 13,9,3 routines
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#------------------------------------------------------------------------------
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# ENCODER - returns a bitarray object containing the hamming checksums
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def enc_hamming_1393(_data):
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csum = bitarray(4)
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csum[0] = _data[0] ^ _data[1] ^ _data[3] ^ _data[5] ^ _data[6]
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csum[1] = _data[0] ^ _data[1] ^ _data[2] ^ _data[4] ^ _data[6] ^ _data[7]
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csum[2] = _data[0] ^ _data[1] ^ _data[2] ^ _data[3] ^ _data[5] ^ _data[7] ^ _data[8]
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csum[3] = _data[0] ^ _data[2] ^ _data[4] ^ _data[5] ^ _data[8]
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return csum
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# DECODER - Returns a tuple of (decoded data, True if an error was corrected)
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def dec_hamming_1393(_data):
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chk0 = _data[0] ^ _data[1] ^ _data[3] ^ _data[5] ^ _data[6]
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chk1 = _data[0] ^ _data[1] ^ _data[2] ^ _data[4] ^ _data[6] ^ _data[7]
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chk2 = _data[0] ^ _data[1] ^ _data[2] ^ _data[3] ^ _data[5] ^ _data[7] ^ _data[8]
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chk3 = _data[0] ^ _data[2] ^ _data[4] ^ _data[5] ^ _data[8]
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n = 0
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error = False
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n |= 0x01 if chk0 != _data[9] else 0x00
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n |= 0x02 if chk1 != _data[10] else 0x00
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n |= 0x04 if chk2 != _data[11] else 0x00
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n |= 0x08 if chk3 != _data[12] else 0x00
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if n == 0x01: _data[9] = not _data[9]; return (_data, True)
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if n == 0x02: _data[10] = not _data[10]; return (_data, True)
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if n == 0x04: _data[11] = not _data[11]; return (_data, True)
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if n == 0x08: _data[12] = not _data[12]; return (_data, True)
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if n == 0x0f: _data[0] = not _data[0]; return (_data, True)
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if n == 0x07: _data[1] = not _data[1]; return (_data, True)
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if n == 0x0b: _data[2] = not _data[2]; return (_data, True)
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if n == 0x03: _data[3] = not _data[3]; return (_data, True)
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if n == 0x0d: _data[4] = not _data[4]; return (_data, True)
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if n == 0x05: _data[5] = not _data[5]; return (_data, True)
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if n == 0x09: _data[6] = not _data[6]; return (_data, True)
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if n == 0x0e: _data[7] = not _data[7]; return (_data, True)
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if n == 0x06: _data[8] = not _data[8]; return (_data, True)
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return (_data, False)
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#------------------------------------------------------------------------------
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# Used to execute the module directly to run built-in tests
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#------------------------------------------------------------------------------
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if __name__ == '__main__':
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# Validation Example
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# Good
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_data = bitarray('0000000000000000000100000011101000000000000000000000110001110011000000100100111110011010110111100101111001011010110101101100010110100110000110000111100111010011101101000010101001110000100101010100')
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# Bad
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_data = bitarray('0000000000000000000110000011101000000000000000000000110001110011000000100100111110011010110111100101111001011010110101101100010110100110000110000111100111010011101101000010101001110000100101010100')
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rows = (_data[1:16],_data[16:31],_data[31:46],_data[46:61],_data[61:76],_data[76:91],_data[91:106],_data[106:121],_data[121:136])
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for row in rows:
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print('original data:', row[0:11], 'original parity:', row[11:15])
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hamming_dec = dec_hamming_15113(row[0:15])
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code = hamming_dec[0]
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error = hamming_dec[1]
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print('return data: ', code[0:11], 'return parity: ', code[11:15], 'return error:', error)
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print('calculated parity:', enc_hamming_15113(row[0:11]))
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print() |