p25p1_hdu.c

/*
 * Copyright (C) 2010 DSD Author
 * GPG Key ID: 0x3F1D7FD0 (74EF 430D F7F2 0A48 FCE6  F630 FAA2 635D 3F1D 7FD0)
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

#include "dsd.h"


#include "p25p1_check_hdu.h"

/**
 * Read two bits from the stream of data. Takes into account the periodic occurrence of status bits.
 * Those are discarded.
 */
void
read_dibit (dsd_opts* opts, dsd_state* state, char* output, int* status_count)
{
    int dibit;
    int status;

    if (*status_count == 35) {
        // Status bits now
        status = getDibit (opts, state);
        // TODO: do something useful with the status bits...
        *status_count = 1;
    } else {
        (*status_count)++;
    }

    dibit = getDibit (opts, state);
    output[0] = (1 & (dibit >> 1));      // bit 1
    output[1] = (1 & dibit);             // bit 0
}

/**
 * Read an hex word from the stream of data.
 */
void
read_hex (dsd_opts* opts, dsd_state* state, char* hex, int* status_count)
{
  unsigned int i;

  // Read 3 times a dibit = read 6 bits.
  for (i=0; i<=4; i+=2)
    {
      // We read two bits on each call
      read_dibit(opts, state, hex + i, status_count);
    }
}

/**
 * Read 12 bits from the stream of data. Those are the parity bits that follow each hex word.
 */
static void
read_golay24_parity (dsd_opts* opts, dsd_state* state, char* parity, int* status_count)
{
  unsigned int i;

  // Read 6 times a dibit = read 12 bits.
  for (i=0; i<=10; i+=2)
    {
      // We read two bits on each call
      read_dibit(opts, state, parity + i, status_count);
    }
}

static void
correct_hex_word (dsd_state* state, char* hex, char* parity)
{
  int fixed_errors;
  int irrecoverable_errors;

  irrecoverable_errors = check_and_fix_golay24(hex, parity, &fixed_errors);

  state->debug_header_errors += fixed_errors;
  if (irrecoverable_errors != 0)
    {
      state->debug_header_critical_errors++;
    }
}

/**
 * Read an hex word, its parity bits and attempts to error correct it using the Golay24 algorithm.
 */
static void
read_and_correct_hex_word (dsd_opts* opts, dsd_state* state, char* hex, int* status_count)
{
  char parity[12];

  // Read the hex word
  read_hex (opts, state, hex, status_count);
  // Read the parity
  read_golay24_parity (opts, state, parity, status_count);
  // Use the Golay24 FEC to correct it. This call modifies the content of hex to fix it, hopefully
  correct_hex_word (state, hex, parity);
}

void
processHDU (dsd_opts * opts, dsd_state * state)
{
  char mi[73], mfid[9], algid[9], kid[17], tgid[17], tmpstr[255];
  int dibit, i, j;
  long talkgroup;
  int algidhex, kidhex;
  char hex[6];

  int status_count;
  int status;

  char hex_data[20][6];    // Data in hex-words (6 bit words). A total of 20 hex words.
  char hex_parity[16][6];  // Parity of the data, again in hex-word format. A total of 16 parity hex words.

  int irrecoverable_errors;

  status_count = 35 - 14;

  // Read 20 hex words, correct them using their Golay24 parity data.
  for (i=19; i>=0; i--)
    {
      read_and_correct_hex_word (opts, state, hex, &status_count);
      // Store the corrected hex word into the hex_data store:
      for (j=0; j<6; j++)
        {
          hex_data[i][j] = hex[j];
        }
    }


  // Read the 16 parity hex word. These are used to FEC the 20 hex words using Reed-Solomon.
  for (i=15; i>=0; i--)
    {
      read_and_correct_hex_word (opts, state, hex, &status_count);
      // Store the corrected hex word into the hex_parity store:
      for (j=0; j<6; j++)
        {
          hex_parity[i][j] = hex[j];
        }
    }

  // Use the Reed-Solomon algorithm to correct the data. hex_data is modified in place
  irrecoverable_errors = check_and_fix_redsolomon_36_20_17((char*)hex_data, (char*)hex_parity);
  if (irrecoverable_errors != 0)
    {
      state->debug_header_critical_errors++;
    }

  mi[72] = 0;
  mfid[8] = 0;
  algid[8] = 0;
  kid[16] = 0;
  tgid[16] = 0;

  // Now put the corrected data on the DSD structures

  mi[ 0] = hex_data[19][0] + '0';
  mi[ 1] = hex_data[19][1] + '0';
  mi[ 2] = hex_data[19][2] + '0';
  mi[ 3] = hex_data[19][3] + '0';
  mi[ 4] = hex_data[19][4] + '0';
  mi[ 5] = hex_data[19][5] + '0';

  mi[ 6] = hex_data[18][0] + '0';
  mi[ 7] = hex_data[18][1] + '0';
  mi[ 8] = hex_data[18][2] + '0';
  mi[ 9] = hex_data[18][3] + '0';
  mi[10] = hex_data[18][4] + '0';
  mi[11] = hex_data[18][5] + '0';

  mi[12] = hex_data[17][0] + '0';
  mi[13] = hex_data[17][1] + '0';
  mi[14] = hex_data[17][2] + '0';
  mi[15] = hex_data[17][3] + '0';
  mi[16] = hex_data[17][4] + '0';
  mi[17] = hex_data[17][5] + '0';

  mi[18] = hex_data[16][0] + '0';
  mi[19] = hex_data[16][1] + '0';
  mi[20] = hex_data[16][2] + '0';
  mi[21] = hex_data[16][3] + '0';
  mi[22] = hex_data[16][4] + '0';
  mi[23] = hex_data[16][5] + '0';

  mi[24] = hex_data[15][0] + '0';
  mi[25] = hex_data[15][1] + '0';
  mi[26] = hex_data[15][2] + '0';
  mi[27] = hex_data[15][3] + '0';
  mi[28] = hex_data[15][4] + '0';
  mi[29] = hex_data[15][5] + '0';

  mi[30] = hex_data[14][0] + '0';
  mi[31] = hex_data[14][1] + '0';
  mi[32] = hex_data[14][2] + '0';
  mi[33] = hex_data[14][3] + '0';
  mi[34] = hex_data[14][4] + '0';
  mi[35] = hex_data[14][5] + '0';

  mi[36] = hex_data[13][0] + '0';
  mi[37] = hex_data[13][1] + '0';
  mi[38] = hex_data[13][2] + '0';
  mi[39] = hex_data[13][3] + '0';
  mi[40] = hex_data[13][4] + '0';
  mi[41] = hex_data[13][5] + '0';

  mi[42] = hex_data[12][0] + '0';
  mi[43] = hex_data[12][1] + '0';
  mi[44] = hex_data[12][2] + '0';
  mi[45] = hex_data[12][3] + '0';
  mi[46] = hex_data[12][4] + '0';
  mi[47] = hex_data[12][5] + '0';

  mi[48] = hex_data[11][0] + '0';
  mi[49] = hex_data[11][1] + '0';
  mi[50] = hex_data[11][2] + '0';
  mi[51] = hex_data[11][3] + '0';
  mi[52] = hex_data[11][4] + '0';
  mi[53] = hex_data[11][5] + '0';

  mi[54] = hex_data[10][0] + '0';
  mi[55] = hex_data[10][1] + '0';
  mi[56] = hex_data[10][2] + '0';
  mi[57] = hex_data[10][3] + '0';
  mi[58] = hex_data[10][4] + '0';
  mi[59] = hex_data[10][5] + '0';

  mi[60] = hex_data[9][0] + '0';
  mi[61] = hex_data[9][1] + '0';
  mi[62] = hex_data[9][2] + '0';
  mi[63] = hex_data[9][3] + '0';
  mi[64] = hex_data[9][4] + '0';
  mi[65] = hex_data[9][5] + '0';

  mi[66] = hex_data[8][0] + '0';
  mi[67] = hex_data[8][1] + '0';
  mi[68] = hex_data[8][2] + '0';
  mi[69] = hex_data[8][3] + '0';
  mi[70] = hex_data[8][4] + '0';
  mi[71] = hex_data[8][5] + '0';

  mfid[0]  = hex_data[7][0] + '0';
  mfid[1]  = hex_data[7][1] + '0';
  mfid[2]  = hex_data[7][2] + '0';
  mfid[3]  = hex_data[7][3] + '0';
  mfid[4]  = hex_data[7][4] + '0';
  mfid[5]  = hex_data[7][5] + '0';

  mfid[6]  = hex_data[6][0] + '0';
  mfid[7]  = hex_data[6][1] + '0';
  algid[0] = hex_data[6][2] + '0';  // The important algorithm ID. This indicates whether the data is
  algid[1] = hex_data[6][3] + '0';  // encrypted and if so what is the encryption algorithm used.
  algid[2] = hex_data[6][4] + '0';  // A code 0x80 here means that the data is unencrypted.
  algid[3] = hex_data[6][5] + '0';

  algid[4] = hex_data[5][0] + '0';
  algid[5] = hex_data[5][1] + '0';
  algid[6] = hex_data[5][2] + '0';
  algid[7] = hex_data[5][3] + '0';
  kid[ 0]  = hex_data[5][4] + '0';
  kid[ 1]  = hex_data[5][5] + '0';

  kid[ 2]  = hex_data[4][0] + '0';  // The encryption key ID
  kid[ 3]  = hex_data[4][1] + '0';
  kid[ 4]  = hex_data[4][2] + '0';
  kid[ 5]  = hex_data[4][3] + '0';
  kid[ 6]  = hex_data[4][4] + '0';
  kid[ 7]  = hex_data[4][5] + '0';

  kid[ 8]  = hex_data[3][0] + '0';
  kid[ 9]  = hex_data[3][1] + '0';
  kid[10]  = hex_data[3][2] + '0';
  kid[11]  = hex_data[3][3] + '0';
  kid[12]  = hex_data[3][4] + '0';
  kid[13]  = hex_data[3][5] + '0';

  kid[14]  = hex_data[2][0] + '0';
  kid[15]  = hex_data[2][1] + '0';
  tgid[ 0] = hex_data[2][2] + '0';  // Talk group ID
  tgid[ 1] = hex_data[2][3] + '0';
  tgid[ 2] = hex_data[2][4] + '0';
  tgid[ 3] = hex_data[2][5] + '0';

  tgid[ 4] = hex_data[1][0] + '0';
  tgid[ 5] = hex_data[1][1] + '0';
  tgid[ 6] = hex_data[1][2] + '0';
  tgid[ 7] = hex_data[1][3] + '0';
  tgid[ 8] = hex_data[1][4] + '0';
  tgid[ 9] = hex_data[1][5] + '0';

  tgid[10] = hex_data[0][0] + '0';
  tgid[11] = hex_data[0][1] + '0';
  tgid[12] = hex_data[0][2] + '0';
  tgid[13] = hex_data[0][3] + '0';
  tgid[14] = hex_data[0][4] + '0';
  tgid[15] = hex_data[0][5] + '0';

  state->p25kid = strtol(kid, NULL, 2);

  skipDibit (opts, state, 5);
  status = getDibit (opts, state);
  //TODO: Do something useful with the status bits...

  if (opts->p25enc == 1)
    {
      algidhex = strtol (algid, NULL, 2);
      kidhex = strtol (kid, NULL, 2);
      printf ("mi: %s algid: $%x kid: $%x\n", mi, algidhex, kidhex);
    }
  if (opts->p25lc == 1)
    {
      printf ("mfid: %s tgid: %s ", mfid, tgid);
      if (opts->p25tg == 0)
        {
          printf ("\n");
        }
    }

  j = 0;
  if (strcmp (mfid, "10010000") == 0)
    {
      for (i = 4; i < 16; i++)
        {
          if (state->tgcount < 24)
            {
              state->tg[state->tgcount][j] = tgid[i];
            }
          tmpstr[j] = tgid[i];
          j++;
        }
      tmpstr[12] = '0';
      tmpstr[13] = '0';
      tmpstr[14] = '0';
      tmpstr[15] = '0';
    }
  else
    {
      for (i = 0; i < 16; i++)
        {
          if (state->tgcount < 24)
            {
              state->tg[state->tgcount][j] = tgid[i];
            }
          tmpstr[j] = tgid[i];
          j++;
        }
    }
  tmpstr[16] = 0;
  talkgroup = strtol (tmpstr, NULL, 2);
  state->lasttg = talkgroup;
  if (state->tgcount < 24)
    {
      state->tgcount = state->tgcount + 1;
    }
  if (opts->p25tg == 1)
    {
      printf ("tg: %li\n", talkgroup);
    }
}