#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>

/*
 * The following are I/O routines.  This file contains a vanilla C version,
 * which should work anywhere.
 * 
 * NOTES:
 * 
 * - Can be used with an SSD file system.
 * 
 * - Does not do asynchronous transfers
 * 
 * - Does not require an "assign -s bin secondary-storage-filename" as for
 *   FORTRAN
 */

/* opntmp -- Open the specified secondary storage file
 * Calling routine provides:
 *    name = Name of file to be created/opened
 *    size = Size of file in words.
 *
 * Flags:
 *    O_CREAT  = Create the file if it does not exist.
 *    O_RDWR   = Open for reading and writing.
 *    O_TRUNC  = Truncate the file to 0 length if already exists.
 *
 * Returns:
 *    A positive int value (the file descriptor), otherwise it returns
 *    -1 to indicate that the file could not be opened.
 */

int opntmp (char *name, long int size)
{
   return (open (name, O_CREAT | O_RDWR | O_TRUNC, 0640));
}

/* rdtmp -- Read NWORDS words into ARRAY from Input file */

void rdtmp (int fd, char *ARRAY, long int nwords, long int buf)
{
   int  size, nr;

   size = sizeof (long int);
   if ((nr = read (fd, ARRAY, size * nwords)) < 0)
   {
      perror ("<rdtmp> read failed");
      printf("Bytes read  = %d\n", nr);
      exit (1);
   }
   return;
}

/* wrtmp -- Write NWORDS words from ARRAY */

void wrtmp (int fd, char *ARRAY, long int nwords, long int buf)
{
   int  size, nw;

   size = sizeof (long int);
   if ((nw = write (fd, ARRAY, size * nwords)) != (size * nwords))
   {
      perror ("<wrtmp> write failed");
      printf ("Bytes written to file = %d\n", nw);
      exit (1);
   }
   return;
}

/* sktmp -- Seek to word number POS in UNIT */

void sktmp (int fd, long int pos)
{
   long int  size;

   size = sizeof (long int);
   if (lseek (fd, size * pos, 0) != (size * pos))
   {
      perror ("<sktmp> lseek failed");
      exit (1);
   }
   return;
}

/* syntmp -- Make sure previous i/o to this unit is done
 * No action required as asynchronous I/O is not performed by
 * these routines.
 */

void syntmp (int fd, long int buf)
{
   return;
}