74 static int can_unlnk = 0;		/* do we unlink null archives?  */
78 int force_one_volume;			/* 1 if we ignore volume changes */
88  *	Note: we may be called with name == NULL on the first open only.
183 	 * make sure beyond any doubt that we can unlink only regular files  in ar_open()
184 	 * we created  in ar_open()
189 	 * if we are writing, we are done  in ar_open()
199 	 * On all new archive volumes, we shift to wrblksz (if the user  in ar_open()
200 	 * specified one, otherwise we will continue to use rdblksz). We  in ar_open()
210 		 * that support variable sized records, we must make large  in ar_open()
211 		 * reads to make sure we get the entire record, otherwise we  in ar_open()
212 		 * will just get the first part of the record (up to size we  in ar_open()
214 		 * multiple records in a single read. We really do not care  in ar_open()
215 		 * what the physical record size is UNLESS we are going to  in ar_open()
216 		 * append. (We will need the physical block size to rewrite  in ar_open()
217 		 * the trailer). Only when we are appending do we go to the  in ar_open()
228 		 * block size, we use that to read. Under append, we must  in ar_open()
229 		 * always keep blksz == rdblksz. Otherwise we go ahead and use  in ar_open()
244 		 * For performance go for large reads when we can without harm  in ar_open()
254 		 * we must always keep blksz == rdblksz  in ar_open()
261 		 * See if we can find the blocking factor from the file size  in ar_open()
267 		 * When we cannot find a match, we may have a flawed archive.  in ar_open()
272 		 * for performance go for large reads when we can  in ar_open()
293  *	If in_sig is set we're in a signal handler and can't flush stdio.
308 	 * Close archive file. This may take a LONG while on tapes (we may be  in ar_close()
320 	 * if nothing was written to the archive (and we created it), we remove  in ar_close()
362 	 * and we have already determined the archive format.  in ar_close()
381 	 * If we have not determined the format yet, we just say how many bytes  in ar_close()
382 	 * we have skipped over looking for a header to id. there is no way we  in ar_close()
418 	 * we only drain from a pipe/socket. Other devices can be closed  in ar_drain()
419 	 * without reading up to end of file. We sure hope that pipe is closed  in ar_drain()
420 	 * on the other side so we will get an EOF.  in ar_drain()
437  *	For all archive devices we are already positioned at the place we want
449 	 * we must make sure the trailer is rewritten on append, ar_next()  in ar_set_wr()
460 	 * Ok we have an archive in a regular file. If we were rewriting a  in ar_set_wr()
461 	 * file, we must get rid of all the stuff after the current offset  in ar_set_wr()
474  *	check if the last volume in the archive allows appends. We cannot check
475  *	this until we are ready to write since there is no spec that says all
478  *	0 if we can append, -1 otherwise.
499  *	supplied buffer. When dealing with tapes we may not always be able to
500  *	read what we want.
517 	 * how we read must be based on device type  in ar_read()
524 			 * sized records so we leave blksz == MAXBLK. The  in ar_read()
533 				 * any record after the first, we probably have  in ar_read()
535 				 * (we are getting multiple records in a single  in ar_read()
554 		 * be trusted at all. So when we are dealing with character  in ar_read()
555 		 * devices and pipes we just take what they have ready for us  in ar_read()
567 	 * We are in trouble at this point, something is broken...  in ar_read()
607 	 * write broke, see what we can do with it. We try to send any partial  in ar_write()
650 		 * see if we reached the end of media, if so force a change to  in ar_write()
659 		 * we cannot fix errors to these devices  in ar_write()
666 	 * if this is a block aligned archive format, we may have a bad archive  in ar_write()
668 	 * we can deal with the mis-aligned data, it violates spec and other  in ar_write()
679 	 * If we were trying to rewrite the trailer and it didn't work, we  in ar_write()
717 	 * we need to go to the next volume not try a resync  in ar_rdsync()
732 		 * if the last i/o was a successful data transfer, we assume  in ar_rdsync()
733 		 * the fault is just a bad record on the tape that we are now  in ar_rdsync()
734 		 * past. If we did not get any data since the last resync try  in ar_rdsync()
785  *	bytes as supported by the device. If we cannot move the requested
803 	 * we cannot move forward at EOF or error  in ar_fow()
810 	 * the media without reading to it. With tapes we cannot be sure of the  in ar_fow()
811 	 * number of physical blocks to skip (we do not know physical block  in ar_fow()
812 	 * size at this point), so we must only read forward on tapes!  in ar_fow()
818 	 * figure out where we are in the archive  in ar_fow()
822 		 * we can be asked to move farther than there are bytes in this  in ar_fow()
843  *	count as supported by the device. With tapes drives we RESET rdblksz to
845  *	NOTE: We should only be called to move backwards so we can rewrite the
859 	 * make sure we do not have try to reverse on a flawed archive  in ar_rev()
883 		 * high probability of failure as we really do not know the  in ar_rev()
884 		 * true attributes of the device we are talking to (the device  in ar_rev()
886 		 * First we figure out where we are in the archive.  in ar_rev()
896 		 * we may try to go backwards past the start when the archive  in ar_rev()
897 		 * is only a single record. If this happens and we are on a  in ar_rev()
898 		 * multi-volume archive, we need to go to the end of the  in ar_rev()
923 		 * tape size, we cannot do the move (this should never happen).  in ar_rev()
924 		 * (We also cannot handle trailers spread over two vols.)  in ar_rev()
925 		 * get_phys() also makes sure we are in front of the filemark.  in ar_rev()
939 		 * if no movement is required, just return (we must be after  in ar_rev()
946 		 * ok we have to move. Make sure the tape drive can do it.  in ar_rev()
974  *	Determine the physical block size on a tape drive. We need the physical
975  *	block size so we know how many bytes we skip over when we move with
976  *	mtio commands. We also make sure we are BEFORE THE TAPE FILEMARK when
998 		 * we know we are at file mark when we get back a 0 from  in get_phys()
1010 	 * move backwards over the file mark so we are at the end of the  in get_phys()
1021 	 * move backwards so we are in front of the last record and read it to  in get_phys()
1053 	 * set lstrval so we know that the filemark has not been seen  in get_phys()
1064 	 * make sure we can move backwards over the padding. (this should  in get_phys()
1074 	 * we were first called (if required).  in get_phys()
1089  *	we may allow the media to be changed. Otherwise a new archive is
1091  *	read on tty input, we must quit pax.
1104 	 * WE MUST CLOSE THE DEVICE. A lot of devices must see last close, (so  in ar_next()
1106 	 * also be called via a signal handler, so we must prevent a race.  in ar_next()
1120 	 * if i/o is on stdin or stdout, we cannot reopen it (we do not know  in ar_next()
1164 				 * we are to continue with the same device  in ar_next()