bufr2tac_io.c

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/***************************************************************************
 *   Copyright (C) 2013-2018 by Guillermo Ballester Valor                  *
 *   gbv@ogimet.com                                                        *
 *                                                                         *
 *   This program 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 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program 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 program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
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 ***************************************************************************/
/*!
 \file bufr2tac_io.c
 \brief file with the i/o code for binary bufr2tac
 */
 
#include "bufr2tac.h"
 
/*!
  \fn int read_bufr(unsigned char *bufr, char *filename, int *length)
  \brief read a bufr file as an array of unsigned chars
  \param bufr pointer to an array of unsigned chars. On output it will contain the bufr
  \param filename string with complete pathname of bufr file to read
  \param length On input max length allocated by caller. On output real length of bufr
*/
int read_bufr ( unsigned char *bufr, char *filename, int *length )
{
  int aux;
  size_t n = 0;
  FILE *fp;
 
  /* Open input file */
  if ( ( fp = fopen ( filename, "r" ) ) == NULL )
    {
      fprintf ( stderr, "cannot open file '%s'\n", filename );
      exit ( EXIT_FAILURE );
    }
 
  while ( ( aux = fgetc ( fp ) ) != EOF && ( int ) n < *length )
    bufr[n++] = aux;
  *length = n;
 
  // close the file
  fclose ( fp );
 
  if ( n < 8 ) // we need at least 8 bytes
    return -4;
 
  // check if begins with BUFR
  if ( bufr[0] != 'B' || bufr[1] != 'U' || bufr[2] != 'F' || bufr[3] != 'R' )
    return -1;
 
  // check if end with '7777'
  if ( bufr[n - 4] != '7' || bufr[n - 3] != '7' || bufr[n - 2] != '7'
       || bufr[n - 1] != '7' )
    return -2;
 
  //printf("%d %d\n", n, three_bytes_to_uint(bufr + 4));
  // check about the expected size
  if ( n != three_bytes_to_uint ( bufr + 4 ) )
    return -3;
 
  return 0;
}