// This file contains the logic necessary to open a 'unique number' file
// grab the number it contains, and then increment the number inside
// the file before closing the file.

#include <iostream.h>
#include <fstream.h>
#include <stdio.h>
#include "unique_id.h"
#include "errors.h"




int get_unique_id()
  {
  static char* filename = "unique_number";
  ifstream f_in;
  ofstream f_out;
  int current; // the current value of the unique number

  // read in the current value of the unique number

  f_in.open(filename);
  if (!f_in) 
    { 
    strcpy(fatal_err_function, "get_unique_number");
    sprintf(fatal_err_msg, "unable to open %s to read", filename); 
    fatal_error();
    }

  f_in >> current;
  if (current < 1)
    { 
    strcpy(fatal_err_function, "unique_id::initialize");
    sprintf(fatal_err_msg, "file %s has invalid value %d", 
            filename, current); 
    fatal_error();
    }
    
  f_in.close();

  // write out the next value of the unique number to the file

  f_out.open(filename);
  if (!f_out) 
    { 
    strcpy(fatal_err_function, "get_unique_number");
    sprintf(fatal_err_msg, "unable to open %s to write", filename); 
    fatal_error();
    }

  f_out << (current+1);
  f_out.close();

  return current;
  }