76 static int can_unlnk = 0;		/* do we unlink null archives?  */
88  *	Note: we may be called with name == NULL on the first open only.
183 	 * make sure we beyond any doubt that we only can unlink 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()
305 	 * 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()
357 	 * and we have already determined the archive format.  in ar_close()
376 	 * If we have not determined the format yet, we just say how many bytes  in ar_close()
377 	 * we have skipped over looking for a header to id. There is no way we  in ar_close()
414 	 * we only drain from a pipe/socket. Other devices can be closed  in ar_drain()
415 	 * without reading up to end of file. We sure hope that pipe is closed  in ar_drain()
416 	 * on the other side so we will get an EOF.  in ar_drain()
433  *	For all archive devices we are already positioned at the place we want
445 	 * we must make sure the trailer is rewritten on append, ar_next()  in ar_set_wr()
456 	 * Ok we have an archive in a regular file. If we were rewriting a  in ar_set_wr()
457 	 * file, we must get rid of all the stuff after the current offset  in ar_set_wr()
470  *	check if the last volume in the archive allows appends. We cannot check
471  *	this until we are ready to write since there is no spec that says all
474  *	0 if we can append, -1 otherwise.
495  *	supplied buffer. When dealing with tapes we may not always be able to
496  *	read what we want.
513 	 * how we read must be based on device type  in ar_read()
520 			 * sized records so we leave blksz == MAXBLK. The  in ar_read()
529 				 * any record after the first, we probably have  in ar_read()
531 				 * (we are getting multiple records in a single  in ar_read()
550 		 * be trusted at all. So when we are dealing with character  in ar_read()
551 		 * devices and pipes we just take what they have ready for us  in ar_read()
563 	 * We are in trouble at this point, something is broken...  in ar_read()
603 	 * write broke, see what we can do with it. We try to send any partial  in ar_write()
646 		 * see if we reached the end of media, if so force a change to  in ar_write()
655 		 * we cannot fix errors to these devices  in ar_write()
662 	 * if this is a block aligned archive format, we may have a bad archive  in ar_write()
664 	 * we can deal with the mis-aligned data, it violates spec and other  in ar_write()
675 	 * If we were trying to rewrite the trailer and it didn't work, we  in ar_write()
713 	 * we need to go to the next volume not try a resync.  in ar_rdsync()
728 		 * if the last i/o was a successful data transfer, we assume  in ar_rdsync()
729 		 * the fault is just a bad record on the tape that we are now  in ar_rdsync()
730 		 * past. If we did not get any data since the last resync try  in ar_rdsync()
781  *	bytes as supported by the device. If we cannot move the requested
799 	 * we cannot move forward at EOF or error  in ar_fow()
806 	 * the media without reading to it. With tapes we cannot be sure of the  in ar_fow()
807 	 * number of physical blocks to skip (we do not know physical block  in ar_fow()
808 	 * size at this point), so we must only read forward on tapes!  in ar_fow()
814 	 * figure out where we are in the archive  in ar_fow()
818 	 	 * we can be asked to move farther than there are bytes in this  in ar_fow()
839  *	count as supported by the device. With tapes drives we RESET rdblksz to
841  *	NOTE: We should only be called to move backwards so we can rewrite the
855 	 * make sure we do not have try to reverse on a flawed archive  in ar_rev()
879 		 * high probability of failure as we really do not know the  in ar_rev()
880 		 * true attributes of the device we are talking to (the device  in ar_rev()
882 		 * First we figure out where we are in the archive.  in ar_rev()
892 		 * we may try to go backwards past the start when the archive  in ar_rev()
893 		 * is only a single record. If this happens and we are on a  in ar_rev()
894 		 * multi volume archive, we need to go to the end of the  in ar_rev()
919 		 * tape size, we cannot do the move (this should never happen).  in ar_rev()
920 		 * (We also cannot handle trailers spread over two vols).  in ar_rev()
921 		 * get_phys() also makes sure we are in front of the filemark.  in ar_rev()
935 		 * if no movement is required, just return (we must be after  in ar_rev()
942 		 * ok we have to move. Make sure the tape drive can do it.  in ar_rev()
970  *	Determine the physical block size on a tape drive. We need the physical
971  *	block size so we know how many bytes we skip over when we move with
972  *	mtio commands. We also make sure we are BEFORE THE TAPE FILEMARK when
994 		 * we know we are at file mark when we get back a 0 from  in get_phys()
1006 	 * move backwards over the file mark so we are at the end of the  in get_phys()
1017 	 * move backwards so we are in front of the last record and read it to  in get_phys()
1049 	 * set lstrval so we know that the filemark has not been seen  in get_phys()
1060 	 * make sure we can move backwards over the padding. (this should  in get_phys()
1070 	 * we were first called (if required).  in get_phys()
1085  *	we may allow the media to be changed. Otherwise a new archive is
1087  *	read on tty input, we must quit pax.
1100 	 * WE MUST CLOSE THE DEVICE. A lot of devices must see last close, (so  in ar_next()
1102 	 * also be called via a signal handler, so we must prevent a race.  in ar_next()
1116 	 * if i/o is on stdin or stdout, we cannot reopen it (we do not know  in ar_next()
1160 				 * we are to continue with the same device  in ar_next()