/* -*- c++ -*- */
/*
 * Copyright 2016 Free Software Foundation, Inc.
 *
 * This 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.
 *
 * This software 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 this software; 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 "catv_reed_solomon_enc_bb_impl.h"
#include <gnuradio/io_signature.h>

namespace gr {
namespace dtv {

catv_reed_solomon_enc_bb::sptr catv_reed_solomon_enc_bb::make()
{
    return gnuradio::get_initial_sptr(new catv_reed_solomon_enc_bb_impl());
}

/*
 * The private constructor
 */
catv_reed_solomon_enc_bb_impl::catv_reed_solomon_enc_bb_impl()
    : gr::block("catv_reed_solomon_enc_bb",
                gr::io_signature::make(1, 1, sizeof(unsigned char)),
                gr::io_signature::make(1, 1, sizeof(unsigned char)))
{
    set_output_multiple(128);
    init_rs();
}

/*
 * Our virtual destructor.
 */
catv_reed_solomon_enc_bb_impl::~catv_reed_solomon_enc_bb_impl() {}

void catv_reed_solomon_enc_bb_impl::init_rs()
{
    unsigned char x;
    int i, j;

    gf_exp[0] = 1;
    gf_log[1] = 0;

    x = 1;
    for (i = 1; i < 127; i++) {
        x <<= 1;
        if (x & 0x80) {
            x = (x & 0x7F) ^ 0x09;
        }
        gf_exp[i] = x;
        gf_log[x] = i;
    }
    for (; i < 256; i++) {
        gf_exp[i] = gf_exp[i - 127];
    }

    for (i = 0; i < 128; i++) {
        for (j = 0; j < 128; j++) {
            if ((i == 0) || (j == 0)) {
                gf_mul_table[i][j] = 0;
            } else {
                gf_mul_table[i][j] = gf_exp[gf_log[i] + gf_log[j]];
            }
        }
    }
}

unsigned char
catv_reed_solomon_enc_bb_impl::gf_poly_eval(unsigned char* p, int len, unsigned char x)
{
    unsigned char y = p[0];
    int i;

    for (i = 1; i < len; i++) {
        y = gf_mul_table[y][x] ^ p[i];
    }
    return y;
}

void catv_reed_solomon_enc_bb_impl::reed_solomon_enc(const unsigned char* message,
                                                     unsigned char* output)
{
    // Generator polynomial from p.7 of ANSI/SCTE 07 2013
    unsigned char g[] = {
        1, gf_exp[52], gf_exp[116], gf_exp[119], gf_exp[61], gf_exp[15]
    };
    int i, j;

    memcpy(output, message, 122);
    memset(output + 122, 0, 6);

    for (i = 0; i < 122; i++) {
        for (j = 1; j < 6; j++) {
            output[i + j] ^= gf_mul_table[output[i]][g[j]];
        }
        output[i] = message[i];
    }

    output[127] = gf_poly_eval(output, 127, gf_exp[6]);
}

void catv_reed_solomon_enc_bb_impl::forecast(int noutput_items,
                                             gr_vector_int& ninput_items_required)
{
    ninput_items_required[0] = (noutput_items / 128) * 122;
}

int catv_reed_solomon_enc_bb_impl::general_work(int noutput_items,
                                                gr_vector_int& ninput_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 j = 0;

    for (int i = 0; i < noutput_items; i += 128) {
        reed_solomon_enc(in + j, out + i);
        j += 122;
    }

    // Tell runtime system how many input items we consumed on
    // each input stream.
    consume_each(j);

    // Tell runtime system how many output items we produced.
    return noutput_items;
}

} /* namespace dtv */
} /* namespace gr */
