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/bin/pax/buf_subs.c

https://bitbucket.org/freebsd/freebsd-head/
C | 986 lines | 472 code | 80 blank | 434 comment | 136 complexity | 8b231b095f7a8b31e2bb7220ba2e1a60 MD5 | raw file
  1/*-
  2 * Copyright (c) 1992 Keith Muller.
  3 * Copyright (c) 1992, 1993
  4 *	The Regents of the University of California.  All rights reserved.
  5 *
  6 * This code is derived from software contributed to Berkeley by
  7 * Keith Muller of the University of California, San Diego.
  8 *
  9 * Redistribution and use in source and binary forms, with or without
 10 * modification, are permitted provided that the following conditions
 11 * are met:
 12 * 1. Redistributions of source code must retain the above copyright
 13 *    notice, this list of conditions and the following disclaimer.
 14 * 2. Redistributions in binary form must reproduce the above copyright
 15 *    notice, this list of conditions and the following disclaimer in the
 16 *    documentation and/or other materials provided with the distribution.
 17 * 4. Neither the name of the University nor the names of its contributors
 18 *    may be used to endorse or promote products derived from this software
 19 *    without specific prior written permission.
 20 *
 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 31 * SUCH DAMAGE.
 32 */
 33
 34#ifndef lint
 35#if 0
 36static char sccsid[] = "@(#)buf_subs.c	8.2 (Berkeley) 4/18/94";
 37#endif
 38#endif /* not lint */
 39#include <sys/cdefs.h>
 40__FBSDID("$FreeBSD$");
 41
 42#include <sys/types.h>
 43#include <sys/stat.h>
 44#include <errno.h>
 45#include <unistd.h>
 46#include <stdio.h>
 47#include <stdlib.h>
 48#include <string.h>
 49#include "pax.h"
 50#include "extern.h"
 51
 52/*
 53 * routines which implement archive and file buffering
 54 */
 55
 56#define MINFBSZ		512		/* default block size for hole detect */
 57#define MAXFLT		10		/* default media read error limit */
 58
 59/*
 60 * Need to change bufmem to dynamic allocation when the upper
 61 * limit on blocking size is removed (though that will violate pax spec)
 62 * MAXBLK define and tests will also need to be updated.
 63 */
 64static char bufmem[MAXBLK+BLKMULT];	/* i/o buffer + pushback id space */
 65static char *buf;			/* normal start of i/o buffer */
 66static char *bufend;			/* end or last char in i/o buffer */
 67static char *bufpt;			/* read/write point in i/o buffer */
 68int blksz = MAXBLK;			/* block input/output size in bytes */
 69int wrblksz;				/* user spec output size in bytes */
 70int maxflt = MAXFLT;			/* MAX consecutive media errors */
 71int rdblksz;				/* first read blksize (tapes only) */
 72off_t wrlimit;				/* # of bytes written per archive vol */
 73off_t wrcnt;				/* # of bytes written on current vol */
 74off_t rdcnt;				/* # of bytes read on current vol */
 75
 76/*
 77 * wr_start()
 78 *	set up the buffering system to operate in a write mode
 79 * Return:
 80 *	0 if ok, -1 if the user specified write block size violates pax spec
 81 */
 82
 83int
 84wr_start(void)
 85{
 86	buf = &(bufmem[BLKMULT]);
 87	/*
 88	 * Check to make sure the write block size meets pax specs. If the user
 89	 * does not specify a blocksize, we use the format default blocksize.
 90	 * We must be picky on writes, so we do not allow the user to create an
 91	 * archive that might be hard to read elsewhere. If all ok, we then
 92	 * open the first archive volume
 93	 */
 94	if (!wrblksz)
 95		wrblksz = frmt->bsz;
 96	if (wrblksz > MAXBLK) {
 97		paxwarn(1, "Write block size of %d too large, maximum is: %d",
 98			wrblksz, MAXBLK);
 99		return(-1);
100	}
101	if (wrblksz % BLKMULT) {
102		paxwarn(1, "Write block size of %d is not a %d byte multiple",
103		    wrblksz, BLKMULT);
104		return(-1);
105	}
106	if (wrblksz > MAXBLK_POSIX) {
107		paxwarn(0, "Write block size of %d larger than POSIX max %d, archive may not be portable",
108			wrblksz, MAXBLK_POSIX);
109		return(-1);
110	}
111
112	/*
113	 * we only allow wrblksz to be used with all archive operations
114	 */
115	blksz = rdblksz = wrblksz;
116	if ((ar_open(arcname) < 0) && (ar_next() < 0))
117		return(-1);
118	wrcnt = 0;
119	bufend = buf + wrblksz;
120	bufpt = buf;
121	return(0);
122}
123
124/*
125 * rd_start()
126 *	set up buffering system to read an archive
127 * Return:
128 *	0 if ok, -1 otherwise
129 */
130
131int
132rd_start(void)
133{
134	/*
135	 * leave space for the header pushback (see get_arc()). If we are
136	 * going to append and user specified a write block size, check it
137	 * right away
138	 */
139	buf = &(bufmem[BLKMULT]);
140	if ((act == APPND) && wrblksz) {
141		if (wrblksz > MAXBLK) {
142			paxwarn(1,"Write block size %d too large, maximum is: %d",
143				wrblksz, MAXBLK);
144			return(-1);
145		}
146		if (wrblksz % BLKMULT) {
147			paxwarn(1, "Write block size %d is not a %d byte multiple",
148			wrblksz, BLKMULT);
149			return(-1);
150		}
151	}
152
153	/*
154	 * open the archive
155	 */
156	if ((ar_open(arcname) < 0) && (ar_next() < 0))
157		return(-1);
158	bufend = buf + rdblksz;
159	bufpt = bufend;
160	rdcnt = 0;
161	return(0);
162}
163
164/*
165 * cp_start()
166 *	set up buffer system for copying within the file system
167 */
168
169void
170cp_start(void)
171{
172	buf = &(bufmem[BLKMULT]);
173	rdblksz = blksz = MAXBLK;
174}
175
176/*
177 * appnd_start()
178 *	Set up the buffering system to append new members to an archive that
179 *	was just read. The last block(s) of an archive may contain a format
180 *	specific trailer. To append a new member, this trailer has to be
181 *	removed from the archive. The first byte of the trailer is replaced by
182 *	the start of the header of the first file added to the archive. The
183 *	format specific end read function tells us how many bytes to move
184 *	backwards in the archive to be positioned BEFORE the trailer. Two
185 *	different positions have to be adjusted, the O.S. file offset (e.g. the
186 *	position of the tape head) and the write point within the data we have
187 *	stored in the read (soon to become write) buffer. We may have to move
188 *	back several records (the number depends on the size of the archive
189 *	record and the size of the format trailer) to read up the record where
190 *	the first byte of the trailer is recorded. Trailers may span (and
191 *	overlap) record boundaries.
192 *	We first calculate which record has the first byte of the trailer. We
193 *	move the OS file offset back to the start of this record and read it
194 *	up. We set the buffer write pointer to be at this byte (the byte where
195 *	the trailer starts). We then move the OS file pointer back to the
196 *	start of this record so a flush of this buffer will replace the record
197 *	in the archive.
198 *	A major problem is rewriting this last record. For archives stored
199 *	on disk files, this is trivial. However, many devices are really picky
200 *	about the conditions under which they will allow a write to occur.
201 *	Often devices restrict the conditions where writes can be made writes,
202 *	so it may not be feasible to append archives stored on all types of
203 *	devices.
204 * Return:
205 *	0 for success, -1 for failure
206 */
207
208int
209appnd_start(off_t skcnt)
210{
211	int res;
212	off_t cnt;
213
214	if (exit_val != 0) {
215		paxwarn(0, "Cannot append to an archive that may have flaws.");
216		return(-1);
217	}
218	/*
219	 * if the user did not specify a write blocksize, inherit the size used
220	 * in the last archive volume read. (If a is set we still use rdblksz
221	 * until next volume, cannot shift sizes within a single volume).
222	 */
223	if (!wrblksz)
224		wrblksz = blksz = rdblksz;
225	else
226		blksz = rdblksz;
227
228	/*
229	 * make sure that this volume allows appends
230	 */
231	if (ar_app_ok() < 0)
232		return(-1);
233
234	/*
235	 * Calculate bytes to move back and move in front of record where we
236	 * need to start writing from. Remember we have to add in any padding
237	 * that might be in the buffer after the trailer in the last block. We
238	 * travel skcnt + padding ROUNDED UP to blksize.
239	 */
240	skcnt += bufend - bufpt;
241	if ((cnt = (skcnt/blksz) * blksz) < skcnt)
242		cnt += blksz;
243	if (ar_rev((off_t)cnt) < 0)
244		goto out;
245
246	/*
247	 * We may have gone too far if there is valid data in the block we are
248	 * now in front of, read up the block and position the pointer after
249	 * the valid data.
250	 */
251	if ((cnt -= skcnt) > 0) {
252		/*
253		 * watch out for stupid tape drives. ar_rev() will set rdblksz
254		 * to be real physical blocksize so we must loop until we get
255		 * the old rdblksz (now in blksz). If ar_rev() fouls up the
256		 * determination of the physical block size, we will fail.
257		 */
258		bufpt = buf;
259		bufend = buf + blksz;
260		while (bufpt < bufend) {
261			if ((res = ar_read(bufpt, rdblksz)) <= 0)
262				goto out;
263			bufpt += res;
264		}
265		if (ar_rev((off_t)(bufpt - buf)) < 0)
266			goto out;
267		bufpt = buf + cnt;
268		bufend = buf + blksz;
269	} else {
270		/*
271		 * buffer is empty
272		 */
273		bufend = buf + blksz;
274		bufpt = buf;
275	}
276	rdblksz = blksz;
277	rdcnt -= skcnt;
278	wrcnt = 0;
279
280	/*
281	 * At this point we are ready to write. If the device requires special
282	 * handling to write at a point were previously recorded data resides,
283	 * that is handled in ar_set_wr(). From now on we operate under normal
284	 * ARCHIVE mode (write) conditions
285	 */
286	if (ar_set_wr() < 0)
287		return(-1);
288	act = ARCHIVE;
289	return(0);
290
291    out:
292	paxwarn(1, "Unable to rewrite archive trailer, cannot append.");
293	return(-1);
294}
295	
296/*
297 * rd_sync()
298 *	A read error occurred on this archive volume. Resync the buffer and
299 *	try to reset the device (if possible) so we can continue to read. Keep
300 *	trying to do this until we get a valid read, or we reach the limit on
301 *	consecutive read faults (at which point we give up). The user can
302 *	adjust the read error limit through a command line option.
303 * Returns:
304 *	0 on success, and -1 on failure
305 */
306
307int
308rd_sync(void)
309{
310	int errcnt = 0;
311	int res;
312
313	/*
314	 * if the user says bail out on first fault, we are out of here...
315	 */
316	if (maxflt == 0)
317		return(-1);
318	if (act == APPND) {
319		paxwarn(1, "Unable to append when there are archive read errors.");
320		return(-1);
321	}
322
323	/*
324	 * poke at device and try to get past media error
325	 */
326	if (ar_rdsync() < 0) {
327		if (ar_next() < 0)
328			return(-1);
329		else
330			rdcnt = 0;
331	}
332
333	for (;;) {
334		if ((res = ar_read(buf, blksz)) > 0) {
335			/*
336			 * All right! got some data, fill that buffer
337			 */
338			bufpt = buf;
339			bufend = buf + res;
340			rdcnt += res;
341			return(0);
342		}
343
344		/*
345		 * Oh well, yet another failed read...
346		 * if error limit reached, ditch. o.w. poke device to move past
347		 * bad media and try again. if media is badly damaged, we ask
348		 * the poor (and upset user at this point) for the next archive
349		 * volume. remember the goal on reads is to get the most we
350		 * can extract out of the archive.
351		 */
352		if ((maxflt > 0) && (++errcnt > maxflt))
353			paxwarn(0,"Archive read error limit (%d) reached",maxflt);
354		else if (ar_rdsync() == 0)
355			continue;
356		if (ar_next() < 0)
357			break;
358		rdcnt = 0;
359		errcnt = 0;
360	}
361	return(-1);
362}
363
364/*
365 * pback()
366 *	push the data used during the archive id phase back into the I/O
367 *	buffer. This is required as we cannot be sure that the header does NOT
368 *	overlap a block boundary (as in the case we are trying to recover a
369 *	flawed archived). This was not designed to be used for any other
370 *	purpose. (What software engineering, HA!)
371 *	WARNING: do not even THINK of pback greater than BLKMULT, unless the
372 *	pback space is increased.
373 */
374
375void
376pback(char *pt, int cnt)
377{
378	bufpt -= cnt;
379	memcpy(bufpt, pt, cnt);
380	return;
381}
382
383/*
384 * rd_skip()
385 *	skip forward in the archive during an archive read. Used to get quickly
386 *	past file data and padding for files the user did NOT select.
387 * Return:
388 *	0 if ok, -1 failure, and 1 when EOF on the archive volume was detected.
389 */
390
391int
392rd_skip(off_t skcnt)
393{
394	off_t res;
395	off_t cnt;
396	off_t skipped = 0;
397
398	/*
399	 * consume what data we have in the buffer. If we have to move forward
400	 * whole records, we call the low level skip function to see if we can
401	 * move within the archive without doing the expensive reads on data we
402	 * do not want.
403	 */
404	if (skcnt == 0)
405		return(0);
406	res = MIN((bufend - bufpt), skcnt);
407	bufpt += res;
408	skcnt -= res;
409
410	/*
411	 * if skcnt is now 0, then no additional i/o is needed
412	 */
413	if (skcnt == 0)
414		return(0);
415
416	/*
417	 * We have to read more, calculate complete and partial record reads
418	 * based on rdblksz. we skip over "cnt" complete records
419	 */
420	res = skcnt%rdblksz;
421	cnt = (skcnt/rdblksz) * rdblksz;
422
423	/*
424	 * if the skip fails, we will have to resync. ar_fow will tell us
425	 * how much it can skip over. We will have to read the rest.
426	 */
427	if (ar_fow(cnt, &skipped) < 0)
428		return(-1);
429	res += cnt - skipped;
430	rdcnt += skipped;
431
432	/*
433	 * what is left we have to read (which may be the whole thing if
434	 * ar_fow() told us the device can only read to skip records);
435	 */
436	while (res > 0L) {
437		cnt = bufend - bufpt;
438		/*
439		 * if the read fails, we will have to resync
440		 */
441		if ((cnt <= 0) && ((cnt = buf_fill()) < 0))
442			return(-1);
443		if (cnt == 0)
444			return(1);
445		cnt = MIN(cnt, res);
446		bufpt += cnt;
447		res -= cnt;
448	}
449	return(0);
450}
451
452/*
453 * wr_fin()
454 *	flush out any data (and pad if required) the last block. We always pad
455 *	with zero (even though we do not have to). Padding with 0 makes it a
456 *	lot easier to recover if the archive is damaged. zero padding SHOULD
457 *	BE a requirement....
458 */
459
460void
461wr_fin(void)
462{
463	if (bufpt > buf) {
464		memset(bufpt, 0, bufend - bufpt);
465		bufpt = bufend;
466		(void)buf_flush(blksz);
467	}
468}
469
470/*
471 * wr_rdbuf()
472 *	fill the write buffer from data passed to it in a buffer (usually used
473 *	by format specific write routines to pass a file header). On failure we
474 *	punt. We do not allow the user to continue to write flawed archives.
475 *	We assume these headers are not very large (the memory copy we use is
476 *	a bit expensive).
477 * Return:
478 *	0 if buffer was filled ok, -1 o.w. (buffer flush failure)
479 */
480
481int
482wr_rdbuf(char *out, int outcnt)
483{
484	int cnt;
485
486	/*
487	 * while there is data to copy copy into the write buffer. when the
488	 * write buffer fills, flush it to the archive and continue
489	 */
490	while (outcnt > 0) {
491		cnt = bufend - bufpt;
492		if ((cnt <= 0) && ((cnt = buf_flush(blksz)) < 0))
493			return(-1);
494		/*
495		 * only move what we have space for
496		 */
497		cnt = MIN(cnt, outcnt);
498		memcpy(bufpt, out, cnt);
499		bufpt += cnt;
500		out += cnt;
501		outcnt -= cnt;
502	}
503	return(0);
504}
505
506/*
507 * rd_wrbuf()
508 *	copy from the read buffer into a supplied buffer a specified number of
509 *	bytes. If the read buffer is empty fill it and continue to copy.
510 *	usually used to obtain a file header for processing by a format
511 *	specific read routine.
512 * Return
513 *	number of bytes copied to the buffer, 0 indicates EOF on archive volume,
514 *	-1 is a read error
515 */
516
517int
518rd_wrbuf(char *in, int cpcnt)
519{
520	int res;
521	int cnt;
522	int incnt = cpcnt;
523
524	/*
525	 * loop until we fill the buffer with the requested number of bytes
526	 */
527	while (incnt > 0) {
528		cnt = bufend - bufpt;
529		if ((cnt <= 0) && ((cnt = buf_fill()) <= 0)) {
530			/*
531			 * read error, return what we got (or the error if
532			 * no data was copied). The caller must know that an
533			 * error occurred and has the best knowledge what to
534			 * do with it
535			 */
536			if ((res = cpcnt - incnt) > 0)
537				return(res);
538			return(cnt);
539		}
540
541		/*
542		 * calculate how much data to copy based on whats left and
543		 * state of buffer
544		 */
545		cnt = MIN(cnt, incnt);
546		memcpy(in, bufpt, cnt);
547		bufpt += cnt;
548		incnt -= cnt;
549		in += cnt;
550	}
551	return(cpcnt);
552}
553
554/*
555 * wr_skip()
556 *	skip forward during a write. In other words add padding to the file.
557 *	we add zero filled padding as it makes flawed archives much easier to
558 *	recover from. the caller tells us how many bytes of padding to add
559 *	This routine was not designed to add HUGE amount of padding, just small
560 *	amounts (a few 512 byte blocks at most)
561 * Return:
562 *	0 if ok, -1 if there was a buf_flush failure
563 */
564
565int
566wr_skip(off_t skcnt)
567{
568	int cnt;
569
570	/*
571	 * loop while there is more padding to add
572	 */
573	while (skcnt > 0L) {
574		cnt = bufend - bufpt;
575		if ((cnt <= 0) && ((cnt = buf_flush(blksz)) < 0))
576			return(-1);
577		cnt = MIN(cnt, skcnt);
578		memset(bufpt, 0, cnt);
579		bufpt += cnt;
580		skcnt -= cnt;
581	}
582	return(0);
583}
584
585/*
586 * wr_rdfile()
587 *	fill write buffer with the contents of a file. We are passed an open
588 *	file descriptor to the file and the archive structure that describes the
589 *	file we are storing. The variable "left" is modified to contain the
590 *	number of bytes of the file we were NOT able to write to the archive.
591 *	it is important that we always write EXACTLY the number of bytes that
592 *	the format specific write routine told us to. The file can also get
593 *	bigger, so reading to the end of file would create an improper archive,
594 *	we just detect this case and warn the user. We never create a bad
595 *	archive if we can avoid it. Of course trying to archive files that are
596 *	active is asking for trouble. It we fail, we pass back how much we
597 *	could NOT copy and let the caller deal with it.
598 * Return:
599 *	0 ok, -1 if archive write failure. a short read of the file returns a
600 *	0, but "left" is set to be greater than zero.
601 */
602
603int
604wr_rdfile(ARCHD *arcn, int ifd, off_t *left)
605{
606	int cnt;
607	int res = 0;
608	off_t size = arcn->sb.st_size;
609	struct stat sb;
610
611	/*
612	 * while there are more bytes to write
613	 */
614	while (size > 0L) {
615		cnt = bufend - bufpt;
616		if ((cnt <= 0) && ((cnt = buf_flush(blksz)) < 0)) {
617			*left = size;
618			return(-1);
619		}
620		cnt = MIN(cnt, size);
621		if ((res = read(ifd, bufpt, cnt)) <= 0)
622			break;
623		size -= res;
624		bufpt += res;
625	}
626
627	/*
628	 * better check the file did not change during this operation
629	 * or the file read failed.
630	 */
631	if (res < 0)
632		syswarn(1, errno, "Read fault on %s", arcn->org_name);
633	else if (size != 0L)
634		paxwarn(1, "File changed size during read %s", arcn->org_name);
635	else if (fstat(ifd, &sb) < 0)
636		syswarn(1, errno, "Failed stat on %s", arcn->org_name);
637	else if (arcn->sb.st_mtime != sb.st_mtime)
638		paxwarn(1, "File %s was modified during copy to archive",
639			arcn->org_name);
640	*left = size;
641	return(0);
642}
643
644/*
645 * rd_wrfile()
646 *	extract the contents of a file from the archive. If we are unable to
647 *	extract the entire file (due to failure to write the file) we return
648 *	the numbers of bytes we did NOT process. This way the caller knows how
649 *	many bytes to skip past to find the next archive header. If the failure
650 *	was due to an archive read, we will catch that when we try to skip. If
651 *	the format supplies a file data crc value, we calculate the actual crc
652 *	so that it can be compared to the value stored in the header
653 * NOTE:
654 *	We call a special function to write the file. This function attempts to
655 *	restore file holes (blocks of zeros) into the file. When files are
656 *	sparse this saves space, and is a LOT faster. For non sparse files
657 *	the performance hit is small. As of this writing, no archive supports
658 *	information on where the file holes are.
659 * Return:
660 *	0 ok, -1 if archive read failure. if we cannot write the entire file,
661 *	we return a 0 but "left" is set to be the amount unwritten
662 */
663
664int
665rd_wrfile(ARCHD *arcn, int ofd, off_t *left)
666{
667	int cnt = 0;
668	off_t size = arcn->sb.st_size;
669	int res = 0;
670	char *fnm = arcn->name;
671	int isem = 1;
672	int rem;
673	int sz = MINFBSZ;
674	struct stat sb;
675	u_long crc = 0L;
676
677	/*
678	 * pass the blocksize of the file being written to the write routine,
679	 * if the size is zero, use the default MINFBSZ
680	 */
681	if (fstat(ofd, &sb) == 0) {
682		if (sb.st_blksize > 0)
683			sz = (int)sb.st_blksize;
684	} else
685		syswarn(0,errno,"Unable to obtain block size for file %s",fnm);
686	rem = sz;
687	*left = 0L;
688
689	/*
690	 * Copy the archive to the file the number of bytes specified. We have
691	 * to assume that we want to recover file holes as none of the archive
692	 * formats can record the location of file holes.
693	 */
694	while (size > 0L) {
695		cnt = bufend - bufpt;
696		/*
697		 * if we get a read error, we do not want to skip, as we may
698		 * miss a header, so we do not set left, but if we get a write
699		 * error, we do want to skip over the unprocessed data.
700		 */
701		if ((cnt <= 0) && ((cnt = buf_fill()) <= 0))
702			break;
703		cnt = MIN(cnt, size);
704		if ((res = file_write(ofd,bufpt,cnt,&rem,&isem,sz,fnm)) <= 0) {
705			*left = size;
706			break;
707		}
708
709		if (docrc) {
710			/*
711			 * update the actual crc value
712			 */
713			cnt = res;
714			while (--cnt >= 0)
715				crc += *bufpt++ & 0xff;
716		} else
717			bufpt += res;
718		size -= res;
719	}
720
721	/*
722	 * if the last block has a file hole (all zero), we must make sure this
723	 * gets updated in the file. We force the last block of zeros to be
724	 * written. just closing with the file offset moved forward may not put
725	 * a hole at the end of the file.
726	 */
727	if (isem && (arcn->sb.st_size > 0L))
728		file_flush(ofd, fnm, isem);
729
730	/*
731	 * if we failed from archive read, we do not want to skip
732	 */
733	if ((size > 0L) && (*left == 0L))
734		return(-1);
735
736	/*
737	 * some formats record a crc on file data. If so, then we compare the
738	 * calculated crc to the crc stored in the archive
739	 */
740	if (docrc && (size == 0L) && (arcn->crc != crc))
741		paxwarn(1,"Actual crc does not match expected crc %s",arcn->name);
742	return(0);
743}
744
745/*
746 * cp_file()
747 *	copy the contents of one file to another. used during -rw phase of pax
748 *	just as in rd_wrfile() we use a special write function to write the
749 *	destination file so we can properly copy files with holes.
750 */
751
752void
753cp_file(ARCHD *arcn, int fd1, int fd2)
754{
755	int cnt;
756	off_t cpcnt = 0L;
757	int res = 0;
758	char *fnm = arcn->name;
759	int no_hole = 0;
760	int isem = 1;
761	int rem;
762	int sz = MINFBSZ;
763	struct stat sb;
764
765	/*
766	 * check for holes in the source file. If none, we will use regular
767	 * write instead of file write.
768	 */
769	 if (((off_t)(arcn->sb.st_blocks * BLKMULT)) >= arcn->sb.st_size)
770		++no_hole;
771
772	/*
773	 * pass the blocksize of the file being written to the write routine,
774	 * if the size is zero, use the default MINFBSZ
775	 */
776	if (fstat(fd2, &sb) == 0) {
777		if (sb.st_blksize > 0)
778			sz = sb.st_blksize;
779	} else
780		syswarn(0,errno,"Unable to obtain block size for file %s",fnm);
781	rem = sz;
782
783	/*
784	 * read the source file and copy to destination file until EOF
785	 */
786	for(;;) {
787		if ((cnt = read(fd1, buf, blksz)) <= 0)
788			break;
789		if (no_hole)
790			res = write(fd2, buf, cnt);
791		else
792			res = file_write(fd2, buf, cnt, &rem, &isem, sz, fnm);
793		if (res != cnt)
794			break;
795		cpcnt += cnt;
796	}
797
798	/*
799	 * check to make sure the copy is valid.
800	 */
801	if (res < 0)
802		syswarn(1, errno, "Failed write during copy of %s to %s",
803			arcn->org_name, arcn->name);
804	else if (cpcnt != arcn->sb.st_size)
805		paxwarn(1, "File %s changed size during copy to %s",
806			arcn->org_name, arcn->name);
807	else if (fstat(fd1, &sb) < 0)
808		syswarn(1, errno, "Failed stat of %s", arcn->org_name);
809	else if (arcn->sb.st_mtime != sb.st_mtime)
810		paxwarn(1, "File %s was modified during copy to %s",
811			arcn->org_name, arcn->name);
812
813	/*
814	 * if the last block has a file hole (all zero), we must make sure this
815	 * gets updated in the file. We force the last block of zeros to be
816	 * written. just closing with the file offset moved forward may not put
817	 * a hole at the end of the file.
818	 */
819	if (!no_hole && isem && (arcn->sb.st_size > 0L))
820		file_flush(fd2, fnm, isem);
821	return;
822}
823
824/*
825 * buf_fill()
826 *	fill the read buffer with the next record (or what we can get) from
827 *	the archive volume.
828 * Return:
829 *	Number of bytes of data in the read buffer, -1 for read error, and
830 *	0 when finished (user specified termination in ar_next()).
831 */
832
833int
834buf_fill(void)
835{
836	int cnt;
837	static int fini = 0;
838
839	if (fini)
840		return(0);
841
842	for(;;) {
843		/*
844		 * try to fill the buffer. on error the next archive volume is
845		 * opened and we try again.
846		 */
847		if ((cnt = ar_read(buf, blksz)) > 0) {
848			bufpt = buf;
849			bufend = buf + cnt;
850			rdcnt += cnt;
851			return(cnt);
852		}
853
854		/*
855		 * errors require resync, EOF goes to next archive
856		 */
857		if (cnt < 0)
858			break;
859		if (ar_next() < 0) {
860			fini = 1;
861			return(0);
862		}
863		rdcnt = 0;
864	}
865	exit_val = 1;
866	return(-1);
867}
868
869/*
870 * buf_flush()
871 *	force the write buffer to the archive. We are passed the number of
872 *	bytes in the buffer at the point of the flush. When we change archives
873 *	the record size might change. (either larger or smaller).
874 * Return:
875 *	0 if all is ok, -1 when a write error occurs.
876 */
877
878int
879buf_flush(int bufcnt)
880{
881	int cnt;
882	int push = 0;
883	int totcnt = 0;
884
885	/*
886	 * if we have reached the user specified byte count for each archive
887	 * volume, prompt for the next volume. (The non-standard -R flag).
888	 * NOTE: If the wrlimit is smaller than wrcnt, we will always write
889	 * at least one record. We always round limit UP to next blocksize.
890	 */
891	if ((wrlimit > 0) && (wrcnt > wrlimit)) {
892		paxwarn(0, "User specified archive volume byte limit reached.");
893		if (ar_next() < 0) {
894			wrcnt = 0;
895			exit_val = 1;
896			return(-1);
897		}
898		wrcnt = 0;
899
900		/*
901		 * The new archive volume might have changed the size of the
902		 * write blocksize. if so we figure out if we need to write
903		 * (one or more times), or if there is now free space left in
904		 * the buffer (it is no longer full). bufcnt has the number of
905		 * bytes in the buffer, (the blocksize, at the point we were
906		 * CALLED). Push has the amount of "extra" data in the buffer
907		 * if the block size has shrunk from a volume change.
908		 */
909		bufend = buf + blksz;
910		if (blksz > bufcnt)
911			return(0);
912		if (blksz < bufcnt)
913			push = bufcnt - blksz;
914	}
915
916	/*
917	 * We have enough data to write at least one archive block
918	 */
919	for (;;) {
920		/*
921		 * write a block and check if it all went out ok
922		 */
923		cnt = ar_write(buf, blksz);
924		if (cnt == blksz) {
925			/*
926			 * the write went ok
927			 */
928			wrcnt += cnt;
929			totcnt += cnt;
930			if (push > 0) {
931				/* we have extra data to push to the front.
932				 * check for more than 1 block of push, and if
933				 * so we loop back to write again
934				 */
935				memcpy(buf, bufend, push);
936				bufpt = buf + push;
937				if (push >= blksz) {
938					push -= blksz;
939					continue;
940				}
941			} else
942				bufpt = buf;
943			return(totcnt);
944		} else if (cnt > 0) {
945			/*
946			 * Oh drat we got a partial write!
947			 * if format doesn't care about alignment let it go,
948			 * we warned the user in ar_write().... but this means
949			 * the last record on this volume violates pax spec....
950			 */
951			totcnt += cnt;
952			wrcnt += cnt;
953			bufpt = buf + cnt;
954			cnt = bufcnt - cnt;
955			memcpy(buf, bufpt, cnt);
956			bufpt = buf + cnt;
957			if (!frmt->blkalgn || ((cnt % frmt->blkalgn) == 0))
958				return(totcnt);
959			break;
960		}
961
962		/*
963		 * All done, go to next archive
964		 */
965		wrcnt = 0;
966		if (ar_next() < 0)
967			break;
968
969		/*
970		 * The new archive volume might also have changed the block
971		 * size. if so, figure out if we have too much or too little
972		 * data for using the new block size
973		 */
974		bufend = buf + blksz;
975		if (blksz > bufcnt)
976			return(0);
977		if (blksz < bufcnt)
978			push = bufcnt - blksz;
979	}
980
981	/*
982	 * write failed, stop pax. we must not create a bad archive!
983	 */
984	exit_val = 1;
985	return(-1);
986}