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85 lines
2.7 KiB
C
85 lines
2.7 KiB
C
/*
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* Copyright (c) 2007 - 2015 Joseph Gaeddert
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* Copyright (c) 2018 HAW Hamburg
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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/**
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* @ingroup sys_ecc
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* @{
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*
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* @file
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* @brief Repetition code
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*
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* Code referring to Liquid-DSP
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* https://github.com/jgaeddert/liquid-dsp/blob/master/src/fec/src/repetition.c
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*
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* @author Joseph Gaeddert
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* @author Peter Kietzmann <peter.kietzmann@haw.hamburg.de>
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*
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* @}
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "ecc/repetition.h"
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void repetition_encode(unsigned int _dec_msg_len,
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unsigned char *_msg_dec,
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unsigned char *_msg_enc)
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{
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unsigned int i;
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for (i = 0; i < ECC_REPETITION_COUNT; i++) {
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memcpy(&_msg_enc[i * _dec_msg_len], _msg_dec, _dec_msg_len);
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}
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}
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void repetition_decode(unsigned int _dec_msg_len,
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unsigned char *_msg_enc,
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unsigned char *_msg_dec)
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{
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unsigned char s[ECC_REPETITION_COUNT];
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unsigned char bitcnt = 0;
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for (unsigned i = 0; i < _dec_msg_len; i++) {
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/* get all repetitions of a symbol */
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for (int k = 0; k < ECC_REPETITION_COUNT; k++) {
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s[k] = _msg_enc[i + k * _dec_msg_len];
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}
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/* sum all ones for each bit position in a byte */
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for (int j = 0; j < 8; j++) {
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for (int k = 0; k < ECC_REPETITION_COUNT; k++) {
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bitcnt += ((s[k] >> j) & 0x01);
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}
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/* decide for a one if majority says one */
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if (bitcnt > DECODER_MAJORITY) {
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_msg_dec[i] |= (1 << (j));
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}
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else {
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_msg_dec[i] &= ~(1 << (j));
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}
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bitcnt = 0;
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}
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}
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}
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