/* careful.c --- I/O functions that do error checking.
   Jim Blandy <jimb@cyclic.com> --- February 1995  */

#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

static char *prog_name;

/* Use NAME as the name of the program in future error reports.
   If NAME is a filename containing slashes, only the last component
   of the path is used; this means that you can pass in argv[0], and
   still get clean error messages.
   Return the portion of NAME that will be used in error messages.  */
char *
careful_prog_name (char *name)
{
  prog_name = strrchr (name, '/');
  if (prog_name)
    prog_name++;
  else
    prog_name = name;

  return prog_name;
}


void
check_syscall (int call, char *filename, char *op)
{
  if (call != -1)
    return;

  fprintf (stderr, "%s: %s%s",
	   prog_name,  
	   filename ? filename : "",
	   filename ? ": " : "");
  perror (op);

  exit (2);
}


/* If an error has occured on F, print an error message mentioning
   FILENAME and OP, as with check_syscall, and exit.  If no error has
   occurred on F, simply return.  */
void
check_file (FILE *f, char *filename, char *op)
{
  if (ferror (f))
    check_syscall (-1, filename, op);
}


/* If NAME is null, return DEFALT.
   If NAME is non-null, try to open it with MODE; print an error message
   and exit if this doesn't succeed.  */
FILE *
careful_open (char *name, char *mode, FILE *defalt)
{
  if (name)
    {
      FILE *result = fopen (name, mode);

      if (! result)
	{
	  fprintf (stderr, "%s: ", prog_name);
	  perror (name);
	  exit (2);
	}

      return result;
    }
  else
    return defalt;
}


/* If FILE is neither stdin nor stdout, close it.  */
void
careful_close (FILE *f, char *filename)
{
  check_file (f, filename, "closing file");

  if (f != stdin && f != stdout)
    if (fclose (f) == EOF)
      check_syscall (-1, filename, "closing file");
}