/* -*- c++ -*- */

/*

 * Copyright 2009 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 <noaa_hrpt_deframer.h>

#include <gr_io_signature.h>

#include <noaa_hrpt.h>

#include <cstring>

#include <cstdio>

#define ST_IDLE   0

#define ST_SYNCED 1

noaa_hrpt_deframer_sptr

noaa_make_hrpt_deframer()

{

  return gnuradio::get_initial_sptr(new noaa_hrpt_deframer());

}

noaa_hrpt_deframer::noaa_hrpt_deframer()

  : gr_block("noaa_hrpt_deframer",

             gr_make_io_signature(1, 1, sizeof(char)),

             gr_make_io_signature(1, 1, sizeof(short)))

{

  set_output_multiple(6); // room for writing full sync when received

  d_mid_bit = true;

  d_last_bit = 0;

  enter_idle();

}

void

noaa_hrpt_deframer::enter_idle()

{

  d_state = ST_IDLE;

}

void

noaa_hrpt_deframer::enter_synced()

{

  d_state = ST_SYNCED;

  d_bit_count = HRPT_BITS_PER_WORD;

  d_word_count = HRPT_MINOR_FRAME_WORDS-HRPT_SYNC_WORDS;

  d_word = 0;

}

int

noaa_hrpt_deframer::general_work(int noutput_items,

                                 gr_vector_int &ninput_items,

                                 gr_vector_const_void_star &input_items,

                                 gr_vector_void_star &output_items)

{

  int ninputs = ninput_items[0];

  const char *in = (const char *)input_items[0];

  unsigned short *out = (unsigned short *)output_items[0];

  int i = 0, j = 0;

  while (i < ninputs && j < noutput_items) {

    char bit = in[i++];

    char diff = bit^d_last_bit;

    d_last_bit = bit;

    // Wait for transition if not synced, otherwise, alternate bits

    if (d_mid_bit && (diff | (d_state == ST_SYNCED))) {

      switch (d_state) {

      case ST_IDLE:

        d_shifter = (d_shifter << 1) | bit; // MSB transmitted first

        if ((d_shifter & 0x0FFFFFFFFFFFFFFFLL) == HRPT_MINOR_FRAME_SYNC) {

          out[j++] = HRPT_SYNC1;

          out[j++] = HRPT_SYNC2;

          out[j++] = HRPT_SYNC3;

          out[j++] = HRPT_SYNC4;

          out[j++] = HRPT_SYNC5;

          out[j++] = HRPT_SYNC6;

          enter_synced();

        }

        break;

      case ST_SYNCED:

        d_word = (d_word << 1) | bit; // MSB transmitted first

        if (--d_bit_count == 0) {

          out[j++] = d_word;

          d_word = 0;

          d_bit_count = HRPT_BITS_PER_WORD;

          if (--d_word_count == 0) {

            enter_idle();

          }

        }

        break;

      default:

        throw std::runtime_error("noaa_hrpt_deframer: bad state\n");

      }

      d_mid_bit = false;

    }

    else {

      d_mid_bit = true;

    }

  }

  consume_each(i);

  return j;

}