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/* -*- c++ -*- */
/*
* Copyright 2006,2010,2012 Free Software Foundation, Inc.
* Copyright 2021 Daniel Estevez <daniel@destevez.net>
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "diff_decoder_bb_impl.h"
#include <gnuradio/io_signature.h>
#include <stdexcept>
namespace gr {
namespace digital {
diff_decoder_bb::sptr diff_decoder_bb::make(unsigned int modulus,
enum diff_coding_type coding)
{
return gnuradio::make_block_sptr<diff_decoder_bb_impl>(modulus, coding);
}
diff_decoder_bb_impl::diff_decoder_bb_impl(unsigned int modulus,
enum diff_coding_type coding)
: sync_block("diff_decoder_bb",
io_signature::make(1, 1, sizeof(unsigned char)),
io_signature::make(1, 1, sizeof(unsigned char))),
d_modulus(modulus),
d_coding(coding)
{
if (d_coding == DIFF_NRZI && d_modulus != 2) {
throw std::runtime_error("diff_decoder: NRZI only supported with modulus 2");
}
set_history(2); // need to look at two inputs
}
diff_decoder_bb_impl::~diff_decoder_bb_impl() {}
int diff_decoder_bb_impl::work(int noutput_items,
gr_vector_const_void_star& input_items,
gr_vector_void_star& output_items)
{
const unsigned char* in = (const unsigned char*)input_items[0];
unsigned char* out = (unsigned char*)output_items[0];
in += 1; // ensure that in[-1] is valid
unsigned modulus = d_modulus;
if (d_coding == DIFF_NRZI) {
for (int i = 0; i < noutput_items; i++) {
out[i] = ~(in[i] ^ in[i - 1]) & 1;
}
} else if (modulus == 2) {
// optimized implementation for modulus 2
for (int i = 0; i < noutput_items; i++) {
out[i] = (in[i] ^ in[i - 1]) & 1;
}
} else {
// implementation for modulus != 2
for (int i = 0; i < noutput_items; i++) {
out[i] = (in[i] - in[i - 1]) % modulus;
}
}
return noutput_items;
}
} /* namespace digital */
} /* namespace gr */
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