Usenet 1994 October/usenetsourcesnewsgroupsinfomagicoctober1994disk2.iso/misc/volume22/ftape/part01/ftaperead.c

C/C++ Source or Header | 1991-09-04 | 6KB | 211 lines

#ifndef lint
static char sccs_id[] = "@(#)2.4  ftaperead.c 91/09/03 FAST TAPE";
#endif
/*
 * Original author: Kari Yli-Kuha, SQ Consulting Ltd.
 * Address: Kanslerinkatu 8, 33720 Tampere, Finland
 * Phone: [phone]
 *
 * Reads tape blocks to shared memory buffers.
 *
 * Handles tape changing if we're attached to terminal, otherwise exits.
 */

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include "ftape.h"

extern void perror(), exit();
extern char *strrchr();
extern int  errno;

extern struct SHBUF *shbuf;   /* shared memory */
static struct SHBUF *buf;     /* current buffer */
static int  nbuf = 0;         /* buffer counter */
static void quit();           /* signal catching */
static char *progname;        /* name of this program */

/*
 * main
 */
main(argc, argv)
int argc;
char  *argv[];
{
  extern int  optind;         /* option index */
  extern char *optarg;        /* option's argument */
  int opt;                    /* current option */
  char *tape_device = TAPE;   /* default tape device */
  int shbufs = SHBUFS;        /* default # of buffers */
  int debug = 0;              /* default: nodebug mode */
  int fdtape;                 /* tape file desciptor */
  int end = 0;                /* flag to stop reading */
  FILE * ttyin, *ttyout;      /* terminal (if any) */
  char *cp;                   /* local pointer */
  int n;                      /* local counter */

  progname = ((cp = strrchr (argv[0], '/')) ? cp+1 : argv[0]);

  /*
   * options
   */
  while ( (opt = getopt(argc, argv, "dn:f:")) != EOF ) {
    switch (opt) {
    case 'n':      /* # of buffers */
      shbufs = atoi(optarg);
      if (shbufs <= 0) {
        (void) fprintf (stderr, "%s: too few buffers: %d\n", progname, shbufs);
    exit(1);
      }
      break;
    case 'f':
      tape_device = optarg;
      break;
    case 'd':
      debug++;
      break;
    default:      /* unknown option */
      (void) fprintf (stderr, "%s: unknown option -- %c\n", progname, opt);
      exit(1);
      break;
    }
  }

  /* catch signals */
  for (n = 0; n < NSIG; n++)
    (void) signal (n, quit);

  /*
   * Try to attach to terminal if possible.
   * It may not be possible if we're running in background
   * or started by 'cron'. In that case tty{in,out} == NULL
   */
  ttyin = fopen ("/dev/tty", "r");
  ttyout = fopen ("/dev/tty", "w");

  /* shared memory should already be created - attach to it */
  if (attach_shared(tape_device) == -1)
    exit (1);

  if ((fdtape = open(tape_device, O_RDONLY)) == -1) {
    (void) fprintf (stderr, "%s: cannot open tape, errno %d\n"
            , progname, errno);
    exit (1);
  }

  /* READING LOOP */
  nbuf = 0;
  buf = shbuf;
  end = 0;
  while (!end) {
    semdown (BUFFERS_FREE, 1);

    errno = 0; /* clear errno, read doesn't do it */
    buf->nread = read (fdtape, buf->buf, SHBUFSIZE*512);

    switch (buf->nread) {
    case 0:  /* end of archive */
      DEBUG fprintf (ttyout, "\n%s: READ %d bytes, errno %d\n",
             progname, buf->nread, errno);

      semup (BUFFERS_AVAIL, 1);
      end = 1;
      break;

    case -1: /* End Of Media with no data */
      DEBUG fprintf (ttyout, "\n%s: READ %d bytes, errno %d\n",
             progname, buf->nread, errno);
      (void) close(fdtape);
      /*
       * If we're attached to a terminal ask user to change the tape.
       * otherwise exit.
       */
      if (ttyin && ttyout)
        fdtape = change_tape(ttyin, ttyout, tape_device);
      else {
        (void) fprintf (stderr, "Reached end of medium.\n");
        (void) fprintf (stderr, "No controlling terminal. Exit.\n");
        quit(-1);
      }
      break; /* continue reading to the same buffer */

    case SHBUFSIZE*512: /* OK, buffer read */
    default:     /*
         * EOM or smaller buffer at end of archive (EOA).
         * We simply pass the data on and check it during the
         * next read cycle.
         * If we're at EOA, next read should give "0" bytes.
         * If we're at EOM, next read should give "-1" bytes
         */
      DEBUG fprintf (ttyout, "%s: READ %d bytes, errno %d     \r",
             progname, buf->nread, errno), fflush(ttyout);

      semup (BUFFERS_AVAIL, 1);

      /* next buffer */
      nbuf++; buf++;
      if (nbuf >= shbufs) {
    nbuf = 0;
    buf = shbuf;
      }

      break;
    }
  }
  return (0);
}

/*
 * quit is called either by a signal interrupt (sig > 0) or
 * explicitly (sig < 0).
 *
 * Signal interrupt is written to stderr
 */
static void quit (sig)
int sig;
{
  if (sig > 0)
    fprintf (stderr, "%s: exit signal %d\n", progname, sig);
  buf->nread = 0;
  semup (BUFFERS_AVAIL, 1);
  exit (1);
}

/*
 * change_tape
 */
change_tape(ttyin, ttyout, device)
FILE *ttyin, *ttyout;
char *device;
{
  static char inbuf[BUFSIZ];
  int (fdtape);

  (void) fprintf (ttyout, "\nReached end of medium.\n");
  (void) fprintf (ttyout, "Change tape after the light is off.\n");
  while (1) {
    (void) fprintf (ttyout, "Press 'y' <RETURN> to continue: ");

    fgets (inbuf, sizeof(inbuf), ttyin);  /* read tty */

    if (tolower(inbuf[0]) != 'y') {
      (void) fprintf (ttyout, "\007"); /* BEEP - illegal reply */
      continue;
    }

    if ((fdtape = open(device, O_RDONLY)) != -1)
      break; /* succeeded opening tape */

    (void) fprintf (ttyout, "\007Could not open tape for reading.\n");
    (void) fprintf (ttyout, "Check if it's properly installed.\n");
    continue;
  }
  return fdtape;
}