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/* -*- c++ -*- */
/*
* Copyright 2008,2010,2012 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* GNU Radio is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "additive_scrambler_bb_impl.h"
#include <gnuradio/io_signature.h>
namespace gr {
namespace digital {
additive_scrambler_bb::sptr
additive_scrambler_bb::make (int mask, int seed,
int len, int count,
int bits_per_byte,
const std::string &reset_tag_key)
{
return gnuradio::get_initial_sptr(new additive_scrambler_bb_impl
(mask, seed, len, count, bits_per_byte, reset_tag_key));
}
additive_scrambler_bb_impl::additive_scrambler_bb_impl(int mask,
int seed,
int len,
int count,
int bits_per_byte,
const std::string &reset_tag_key)
: sync_block("additive_scrambler_bb",
io_signature::make(1, 1, sizeof(unsigned char)),
io_signature::make(1, 1, sizeof(unsigned char))),
d_lfsr(mask, seed, len),
d_count(reset_tag_key.empty() ? count : -1),
d_bytes(0), d_len(len), d_seed(seed),
d_bits_per_byte(bits_per_byte), d_reset_tag_key(pmt::string_to_symbol(reset_tag_key))
{
if (d_count < -1) {
throw std::invalid_argument("count must be non-negative!");
}
if (d_bits_per_byte < 1 || d_bits_per_byte > 8) {
throw std::invalid_argument("bits_per_byte must be in [1, 8]");
}
}
additive_scrambler_bb_impl::~additive_scrambler_bb_impl()
{
}
int
additive_scrambler_bb_impl::mask() const
{
return d_lfsr.mask();
}
int
additive_scrambler_bb_impl::seed() const
{
return d_seed;
}
int
additive_scrambler_bb_impl::len() const
{
return d_len;
}
int
additive_scrambler_bb_impl::count() const
{
return d_count;
}
int additive_scrambler_bb_impl::_get_next_reset_index(int noutput_items, int last_reset_index /* = -1 */)
{
int reset_index = noutput_items; // This is a value that gets never reached in the for loop
if (d_count == -1) {
std::vector<gr::tag_t> tags;
get_tags_in_range(tags, 0, nitems_read(0), nitems_read(0)+noutput_items, d_reset_tag_key);
for (unsigned i = 0; i < tags.size(); i++) {
int reset_pos = tags[i].offset - nitems_read(0);
if (reset_pos < reset_index && reset_pos > last_reset_index) {
reset_index = reset_pos;
};
}
} else {
if (last_reset_index == -1) {
reset_index = d_count - d_bytes;
} else {
reset_index = last_reset_index + d_count;
}
}
return reset_index;
}
int
additive_scrambler_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];
int reset_index = _get_next_reset_index(noutput_items);
for(int i = 0; i < noutput_items; i++) {
unsigned char scramble_byte = 0x00;
for (int k = 0; k < d_bits_per_byte; k++) {
scramble_byte ^= (d_lfsr.next_bit() << k);
}
out[i] = in[i] ^ scramble_byte;
d_bytes++;
if (i == reset_index) {
d_lfsr.reset();
d_bytes = 0;
reset_index = _get_next_reset_index(noutput_items, reset_index);
}
}
return noutput_items;
}
} /* namespace digital */
} /* namespace gr */
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