From e16ec19e3a445c1156c990ed71628fb183332be9 Mon Sep 17 00:00:00 2001 From: jaseg Date: Mon, 12 Oct 2020 20:15:41 +0200 Subject: Initial commit --- tools/reed_solomon.py | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 tools/reed_solomon.py (limited to 'tools/reed_solomon.py') diff --git a/tools/reed_solomon.py b/tools/reed_solomon.py new file mode 100644 index 0000000..c4ca6e4 --- /dev/null +++ b/tools/reed_solomon.py @@ -0,0 +1,91 @@ +import os, sys +import ctypes as C +import argparse +import binascii +import numpy as np +import timeit +import statistics + +lib = C.CDLL('rslib.so') + +lib.rslib_encode.argtypes = [C.c_int, C.c_size_t, C.POINTER(C.c_char), C.POINTER(C.c_char)] +lib.rslib_decode.argtypes = [C.c_int, C.c_size_t, C.POINTER(C.c_char)] +lib.rslib_gexp.argtypes = [C.c_int, C.c_int] +lib.rslib_gexp.restype = C.c_int +lib.rslib_decode.restype = C.c_int +lib.rslib_npar.restype = C.c_size_t + +def npar(): + return lib.rslib_npar() + +def encode(data: bytes, nbits=8): + out = C.create_string_buffer(len(data) + lib.rslib_npar()) + lib.rslib_encode(nbits, len(data), data, out) + return out.raw + +def decode(data: bytes, nbits=8): + inout = C.create_string_buffer(data) + lib.rslib_decode(nbits, len(data), inout) + return inout.raw[:-lib.rslib_npar() - 1] + +def cmdline_func_test(args, print=lambda *args, **kwargs: None, benchmark=False): + st = np.random.RandomState(seed=args.seed) + + lfsr = [lib.rslib_gexp(i, args.bits) for i in range(2**args.bits - 1)] + print('LFSR', len(set(lfsr)), lfsr) + assert all(0 < x < 2**args.bits for x in lfsr) + assert len(set(lfsr)) == 2**args.bits - 1 + + print('Seed', args.seed) + for i in range(args.repeat): + print(f'Run {i}') + test_data = bytes(st.randint(2**args.bits, size=args.message_length, dtype=np.uint8)) + print(' Raw:', binascii.hexlify(test_data).decode()) + encoded = encode(test_data, nbits=args.bits) + print(' Encoded:', binascii.hexlify(encoded).decode()) + + indices = st.permutation(len(encoded)) + encoded = list(encoded) + for pos in indices[:args.errors]: + encoded[pos] = st.randint(2**args.bits) + encoded = bytes(encoded) + print(' Modified:', ''.join(f'\033[91m{b:02x}\033[0m' if pos in indices[:args.errors] else f'{b:02x}' for pos, b in enumerate(encoded))) + + if benchmark: + rpt = 10000 + delta = timeit.timeit('decode(encoded, nbits=args.bits)', + globals={'args': args, 'decode': decode, 'encoded': encoded}, + number=rpt)/rpt + print(f'Decoding runtime: {delta*1e6:.3f}μs') + decoded = decode(encoded, nbits=args.bits) + print(' Decoded:', binascii.hexlify(decoded).decode()) + print(' Delta:', binascii.hexlify( + bytes(x^y for x, y in zip(test_data, decoded)) + ).decode().replace('0', '.')) + assert test_data == decoded + +def cmdline_func_encode(args, **kwargs): + data = np.frombuffer(binascii.unhexlify(args.hex_str), dtype=np.uint8) + # Map 8 bit input to 6 bit symbol string + data = np.packbits(np.pad(np.unpackbits(data).reshape((-1, 6)), ((0,0),(2, 0))).flatten()) + encoded = encode(data.tobytes(), nbits=args.bits) + print('symbol array:', ', '.join(f'0x{x:02x}' for x in encoded)) + print('hex string:', binascii.hexlify(encoded).decode()) + +if __name__ == '__main__': + parser = argparse.ArgumentParser() + cmd_parser = parser.add_subparsers(required=True) + test_parser = cmd_parser.add_parser('test', help='Test reed-solomon implementation') + test_parser.add_argument('-m', '--message-length', type=int, default=6, help='Test message (plaintext) length in bytes') + test_parser.add_argument('-e', '--errors', type=int, default=2, help='Number of byte errors to insert into simulation') + test_parser.add_argument('-r', '--repeat', type=int, default=1000, help='Repeat experiment -r times') + test_parser.add_argument('-b', '--bits', type=int, default=8, help='Symbol bit size') + test_parser.add_argument('-s', '--seed', type=int, default=0, help='Random seed') + test_parser.set_defaults(func=cmdline_func_test) + enc_parser = cmd_parser.add_parser('encode', help='RS-Encode given hex string') + enc_parser.set_defaults(func=cmdline_func_encode) + enc_parser.add_argument('-b', '--bits', type=int, default=8, help='Symbol bit size') + enc_parser.add_argument('hex_str', type=str, help='Input data as hex string') + args = parser.parse_args() + args.func(args) + -- cgit