ar_io.c

早期freebsd实现

		 * deal with the end of file (it will go to next volume by
		 * itself)
	 	 */
		if ((mpos = cpos + sksz) > arsb.st_size) {
			*skipped = arsb.st_size - cpos;
			mpos = arsb.st_size;
		} else
			*skipped = sksz;
		if (lseek(arfd, mpos, SEEK_SET) >= 0)
			return(0);
	}
	syswarn(1, errno, "Foward positioning operation on archive failed");
	lstrval = -1;
	return(-1);
}

/*
 * ar_rev()
 *	move the i/o position within the archive backwards the specified byte
 *	count as supported by the device. With tapes drives we RESET rdblksz to
 *	the PHYSICAL blocksize.
 *	NOTE: We should only be called to move backwards so we can rewrite the
 *	last records (the trailer) of an archive (APPEND).
 * Return:
 *	0 if moved the requested distance, -1 on complete failure
 */

#if __STDC__
int
ar_rev(off_t sksz)
#else
int
ar_rev(sksz)
	off_t sksz;
#endif
{
	off_t cpos;
        struct mtop mb;
	register int phyblk; 

	/*
	 * make sure we do not have try to reverse on a flawed archive
	 */
	if (lstrval < 0)
		return(lstrval);

	switch(artyp) {
	case ISPIPE:
		if (sksz <= 0) 
			break;
		/*
		 * cannot go backwards on these critters
		 */
		warn(1, "Reverse positioning on pipes is not supported.");
		lstrval = -1;
		return(-1);
	case ISREG:
	case ISBLK:
	case ISCHR:
	default:
		if (sksz <= 0)
			break;

		/*
		 * For things other than files, backwards movement has a very
		 * high probability of failure as we really do not know the
		 * true attributes of the device we are talking to (the device
		 * may not even have the ability to lseek() in any direction).
		 * First we figure out where we are in the archive.
		 */
		if ((cpos = lseek(arfd, (off_t)0L, SEEK_CUR)) < 0) {
			syswarn(1, errno,
			   "Unable to obtain current archive byte offset");
			lstrval = -1;
			return(-1);
		}

		/*
		 * we may try to go backwards past the start when the archive
		 * is only a single record. If this hapens and we are on a
		 * multi volume archive, we need to go to the end of the
		 * previous volume and continue our movement backwards from
		 * there.
		 */
		if ((cpos -= sksz) < (off_t)0L) {
			if (arvol > 1) {
				/*
				 * this should never happen
				 */
				warn(1,"Reverse position on previous volume.");
				lstrval = -1;
				return(-1);
			}
			cpos = (off_t)0L;
		}
		if (lseek(arfd, cpos, SEEK_SET) < 0) {
			syswarn(1, errno, "Unable to seek archive backwards");
			lstrval = -1;
			return(-1);
		}
		break;
	case ISTAPE:
		/*
	 	 * Calculate and move the proper number of PHYSICAL tape
		 * blocks. If the sksz is not an even multiple of the physical
		 * tape size, we cannot do the move (this should never happen).
		 * (We also cannot handler trailers spread over two vols).
		 * get_phys() also makes sure we are in front of the filemark.
	 	 */
		if ((phyblk = get_phys()) <= 0) {
			lstrval = -1;
			return(-1);
		}

		/*
		 * make sure future tape reads only go by physical tape block
		 * size (set rdblksz to the real size).
		 */
		rdblksz = phyblk;

		/*
		 * if no movement is required, just return (we must be after
		 * get_phys() so the physical blocksize is properly set)
		 */
		if (sksz <= 0)
			break;

		/*
		 * ok we have to move. Make sure the tape drive can do it.
		 */
		if (sksz % phyblk) {
			warn(1,
			    "Tape drive unable to backspace requested amount");
			lstrval = -1;
			return(-1);
		}

		/*
		 * move backwards the requested number of bytes
		 */
		mb.mt_op = MTBSR;
		mb.mt_count = sksz/phyblk;
		if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
			syswarn(1,errno, "Unable to backspace tape %d blocks.",
			    mb.mt_count);
			lstrval = -1;
			return(-1);
		}
		break;
	}
	lstrval = 1;
	return(0);
}

/*
 * get_phys()
 *	Determine the physical block size on a tape drive. We need the physical
 *	block size so we know how many bytes we skip over when we move with 
 *	mtio commands. We also make sure we are BEFORE THE TAPE FILEMARK when
 *	return.
 *	This is one really SLOW routine...
 * Return:
 *	physical block size if ok (ok > 0), -1 otherwise
 */

#if __STDC__
static int
get_phys(void)
#else
static int
get_phys()
#endif
{
	register int padsz = 0;
	register int res;
	register int phyblk;
	struct mtop mb;
	char scbuf[MAXBLK];

	/*
	 * move to the file mark, and then back up one record and read it.
	 * this should tell us the physical record size the tape is using.
	 */
	if (lstrval == 1) {
		/*
		 * we know we are at file mark when we get back a 0 from
		 * read()
		 */
		while ((res = read(arfd, scbuf, sizeof(scbuf))) > 0)
			padsz += res;
		if (res < 0) {
			syswarn(1, errno, "Unable to locate tape filemark.");
			return(-1);
		}
	}

	/*
	 * move backwards over the file mark so we are at the end of the
	 * last record.
	 */
	mb.mt_op = MTBSF;
	mb.mt_count = 1;
	if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
		syswarn(1, errno, "Unable to backspace over tape filemark.");
		return(-1);
	}

	/*
	 * move backwards so we are in front of the last record and read it to
	 * get physical tape blocksize.
	 */
	mb.mt_op = MTBSR;
	mb.mt_count = 1;
	if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
		syswarn(1, errno, "Unable to backspace over last tape block.");
		return(-1);
	}
	if ((phyblk = read(arfd, scbuf, sizeof(scbuf))) <= 0) {
		syswarn(1, errno, "Cannot determine archive tape blocksize.");
		return(-1);
	}

	/*
	 * read foward to the file mark, then back up in front of the filemark
	 * (this is a bit paranoid, but should be safe to do).
	 */
	while ((res = read(arfd, scbuf, sizeof(scbuf))) > 0)
		;
	if (res < 0) {
		syswarn(1, errno, "Unable to locate tape filemark.");
		return(-1);
	}
	mb.mt_op = MTBSF;
	mb.mt_count = 1;
	if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
		syswarn(1, errno, "Unable to backspace over tape filemark.");
		return(-1);
	}

	/*
	 * set lstrval so we know that the filemark has not been seen
	 */
	lstrval = 1;

	/*
	 * return if there was no padding
	 */
	if (padsz == 0)
		return(phyblk);

	/*
	 * make sure we can move backwards over the padding. (this should
	 * never fail).
	 */
	if (padsz % phyblk) {
		warn(1, "Tape drive unable to backspace requested amount");
		return(-1);
	}

	/*
	 * move backwards over the padding so the head is where it was when
	 * we were first called (if required).
	 */
	mb.mt_op = MTBSR;
	mb.mt_count = padsz/phyblk;
	if (ioctl(arfd, MTIOCTOP, &mb) < 0) {
		syswarn(1,errno,"Unable to backspace tape over %d pad blocks",
		    mb.mt_count);
		return(-1);
	}
	return(phyblk);
}

/*
 * ar_next()
 *	prompts the user for the next volume in this archive. For some devices
 *	we may allow the media to be changed. Otherwise a new archive is
 *	prompted for. By pax spec, if there is no controlling tty or an eof is
 *	read on tty input, we must quit pax.
 * Return:
 *	0 when ready to continue, -1 when all done
 */

#if __STDC__
int
ar_next(void)
#else
int
ar_next()
#endif
{
	char buf[PAXPATHLEN+2];
	static int freeit = 0;
	sigset_t o_mask;

	/*
	 * WE MUST CLOSE THE DEVICE. A lot of devices must see last close, (so
	 * things like writing EOF etc will be done) (Watch out ar_close() can
	 * also be called via a signal handler, so we must prevent a race.
	 */
	if (sigprocmask(SIG_BLOCK, &s_mask, &o_mask) < 0)
		syswarn(0, errno, "Unable to set signal mask");
	ar_close();
	if (sigprocmask(SIG_SETMASK, &o_mask, (sigset_t *)NULL) < 0)
		syswarn(0, errno, "Unable to restore signal mask");

	if (done || !wr_trail)
		return(-1);

	tty_prnt("\nATTENTION! %s archive volume change required.\n", argv0);

	/*
	 * if i/o is on stdin or stdout, we cannot reopen it (we do not know
	 * the name), the user will be forced to type it in.
	 */
	if (strcmp(arcname, STDO) && strcmp(arcname, STDN) && (artyp != ISREG)
	    && (artyp != ISPIPE)) {
		if (artyp == ISTAPE) {
			tty_prnt("%s ready for archive tape volume: %d\n",
				arcname, arvol);
			tty_prnt("Load the NEXT TAPE on the tape drive");
		} else {
			tty_prnt("%s ready for archive volume: %d\n",
				arcname, arvol);
			tty_prnt("Load the NEXT STORAGE MEDIA (if required)");
		}

		if ((act == ARCHIVE) || (act == APPND))
			tty_prnt(" and make sure it is WRITE ENABLED.\n");
		else
			tty_prnt("\n");

		for(;;) {
			tty_prnt("Type \"y\" to continue, \".\" to quit %s,",
				argv0);
			tty_prnt(" or \"s\" to switch to new device.\nIf you");
			tty_prnt(" cannot change storage media, type \"s\"\n");
			tty_prnt("Is the device ready and online? > ");

			if ((tty_read(buf,sizeof(buf))<0) || !strcmp(buf,".")){
				done = 1;
				lstrval = -1;
				tty_prnt("Quitting %s!\n", argv0);
				vfpart = 0;
				return(-1);
			}

			if ((buf[0] == '\0') || (buf[1] != '\0')) {
				tty_prnt("%s unknown command, try again\n",buf);
				continue;
			}

			switch (buf[0]) {
			case 'y':
			case 'Y':
				/*
				 * we are to continue with the same device
				 */
				if (ar_open(arcname) >= 0) 
					return(0);
				tty_prnt("Cannot re-open %s, try again\n",
					arcname);
				continue;
			case 's':
			case 'S':
				/*
				 * user wants to open a different device
				 */
				tty_prnt("Switching to a different archive\n");
				break;
			default:
				tty_prnt("%s unknown command, try again\n",buf);
				continue;
			}
			break;
		}
	} else
		tty_prnt("Ready for archive volume: %d\n", arvol);

	/*
	 * have to go to a different archive
	 */
	for (;;) {
		tty_prnt("Input archive name or \".\" to quit %s.\n", argv0);
		tty_prnt("Archive name > ");

		if ((tty_read(buf, sizeof(buf)) < 0) || !strcmp(buf, ".")) {
			done = 1;
			lstrval = -1;
			tty_prnt("Quitting %s!\n", argv0);
			vfpart = 0;
			return(-1);
		}
		if (buf[0] == '\0') {
			tty_prnt("Empty file name, try again\n");
			continue;
		}
                if (!strcmp(buf, "..")) {
                        tty_prnt("Illegal file name: .. try again\n");
                        continue;
                }
		if (strlen(buf) > PAXPATHLEN) {
			tty_prnt("File name too long, try again\n");
			continue;
		}

		/*
		 * try to open new archive
		 */
		if (ar_open(buf) >= 0) {
			if (freeit) {
				(void)free(arcname);
				freeit = 0;
			}
			if ((arcname = strdup(buf)) == NULL) {
				done = 1;
				lstrval = -1;
				warn(0, "Cannot save archive name.");
				return(-1);
			}
			freeit = 1;
			break;
		}
		tty_prnt("Cannot open %s, try again\n", buf);
		continue;
	}
	return(0);
}