/*	$OpenBSD: buf_subs.c,v 1.30 2016/12/20 21:29:08 kettenis Exp $	*/

/*	$NetBSD: buf_subs.c,v 1.5 1995/03/21 09:07:08 cgd Exp $	*/

/*-

 * Copyright (c) 1992 Keith Muller.

 * Copyright (c) 1992, 1993

 *	The Regents of the University of California.  All rights reserved.

 *

 * This code is derived from software contributed to Berkeley by

 * Keith Muller of the University of California, San Diego.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. Neither the name of the University nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

#include <sys/types.h>

#include <sys/stat.h>

#include <stdio.h>

#include <errno.h>

#include <unistd.h>

#include <stdlib.h>

#include <string.h>

#include "pax.h"

#include "extern.h"

/*

 * routines which implement archive and file buffering

 */

#define MINFBSZ		512		/* default block size for hole detect */

#define MAXFLT		10		/* default media read error limit */

/*

 * Need to change bufmem to dynamic allocation when the upper

 * limit on blocking size is removed (though that will violate pax spec)

 * MAXBLK define and tests will also need to be updated.

 */

static char bufmem[MAXBLK+BLKMULT];	/* i/o buffer + pushback id space */

static char *buf;			/* normal start of i/o buffer */

static char *bufend;			/* end or last char in i/o buffer */

static char *bufpt;			/* read/write point in i/o buffer */

int blksz = MAXBLK;			/* block input/output size in bytes */

int wrblksz;				/* user spec output size in bytes */

int maxflt = MAXFLT;			/* MAX consecutive media errors */

int rdblksz;				/* first read blksize (tapes only) */

off_t wrlimit;				/* # of bytes written per archive vol */

off_t wrcnt;				/* # of bytes written on current vol */

off_t rdcnt;				/* # of bytes read on current vol */

/*

 * wr_start()

 *	set up the buffering system to operate in a write mode

 * Return:

 *	0 if ok, -1 if the user specified write block size violates pax spec

 */

int

wr_start(void)

{

	/*

	 * Check to make sure the write block size meets pax specs. If the user

	 * does not specify a blocksize, we use the format default blocksize.

	 * We must be picky on writes, so we do not allow the user to create an

	 * archive that might be hard to read elsewhere. If all ok, we then

	 * open the first archive volume

	 */

			wrblksz, MAXBLK);

	}

		    wrblksz, BLKMULT);

	}

			wrblksz, MAXBLK_POSIX);

	}

	/*

	 * we only allow wrblksz to be used with all archive operations

	 */

/*

 * rd_start()

 *	set up buffering system to read an archive

 * Return:

 *	0 if ok, -1 otherwise

 */

int

rd_start(void)

{

	/*

	 * leave space for the header pushback (see get_arc()). If we are

	 * going to append and user specified a write block size, check it

	 * right away

	 */

				wrblksz, MAXBLK);

		}

			wrblksz, BLKMULT);

		}

	}

	/*

	 * open the archive

	 */

/*

 * cp_start()

 *	set up buffer system for copying within the file system

 */

void

cp_start(void)

{

/*

 * appnd_start()

 *	Set up the buffering system to append new members to an archive that

 *	was just read. The last block(s) of an archive may contain a format

 *	specific trailer. To append a new member, this trailer has to be

 *	removed from the archive. The first byte of the trailer is replaced by

 *	the start of the header of the first file added to the archive. The

 *	format specific end read function tells us how many bytes to move

 *	backwards in the archive to be positioned BEFORE the trailer. Two

 *	different position have to be adjusted, the O.S. file offset (e.g. the

 *	position of the tape head) and the write point within the data we have

 *	stored in the read (soon to become write) buffer. We may have to move

 *	back several records (the number depends on the size of the archive

 *	record and the size of the format trailer) to read up the record where

 *	the first byte of the trailer is recorded. Trailers may span (and

 *	overlap) record boundaries.

 *	We first calculate which record has the first byte of the trailer. We

 *	move the OS file offset back to the start of this record and read it

 *	up. We set the buffer write pointer to be at this byte (the byte where

 *	the trailer starts). We then move the OS file pointer back to the

 *	start of this record so a flush of this buffer will replace the record

 *	in the archive.

 *	A major problem is rewriting this last record. For archives stored

 *	on disk files, this is trivial. However, many devices are really picky

 *	about the conditions under which they will allow a write to occur.

 *	Often devices restrict the conditions where writes can be made,

 *	so it may not be feasible to append archives stored on all types of

 *	devices.

 * Return:

 *	0 for success, -1 for failure

 */

int

appnd_start(off_t skcnt)

{

	int res;

	off_t cnt;

	}

	/*

	 * if the user did not specify a write blocksize, inherit the size used

	 * in the last archive volume read. (If a is set we still use rdblksz

	 * until next volume, cannot shift sizes within a single volume).

	 */

	else

		blksz = rdblksz;

	/*

	 * make sure that this volume allows appends

	 */

	/*

	 * Calculate bytes to move back and move in front of record where we

	 * need to start writing from. Remember we have to add in any padding

	 * that might be in the buffer after the trailer in the last block. We

	 * travel skcnt + padding ROUNDED UP to blksize.

	 */

		goto out;

	/*

	 * We may have gone too far if there is valid data in the block we are

	 * now in front of, read up the block and position the pointer after

	 * the valid data.

	 */

		/*

		 * watch out for stupid tape drives. ar_rev() will set rdblksz

		 * to be real physical blocksize so we must loop until we get

		 * the old rdblksz (now in blksz). If ar_rev() fouls up the

		 * determination of the physical block size, we will fail.

		 */

				goto out;

		}

			goto out;

		/*

		 * buffer is empty

		 */

	}

	/*

	 * At this point we are ready to write. If the device requires special

	 * handling to write at a point were previously recorded data resides,

	 * that is handled in ar_set_wr(). From now on we operate under normal

	 * ARCHIVE mode (write) conditions

	 */

    out:

/*

 * rd_sync()

 *	A read error occurred on this archive volume. Resync the buffer and

 *	try to reset the device (if possible) so we can continue to read. Keep

 *	trying to do this until we get a valid read, or we reach the limit on

 *	consecutive read faults (at which point we give up). The user can

 *	adjust the read error limit through a command line option.

 * Returns:

 *	0 on success, and -1 on failure

 */

int

rd_sync(void)

{

	int errcnt = 0;

	int res;

	/*

	 * if the user says bail out on first fault, we are out of here...

	 */

	}

	/*

	 * poke at device and try to get past media error

	 */

		else

	}

			/*

			 * All right! got some data, fill that buffer

			 */

		}

		/*

		 * Oh well, yet another failed read...

		 * if error limit reached, ditch. o.w. poke device to move past

		 * bad media and try again. if media is badly damaged, we ask

		 * the poor (and upset user at this point) for the next archive

		 * volume. remember the goal on reads is to get the most we

		 * can extract out of the archive.

		 */

			continue;

			break;

		errcnt = 0;

	}

}

/*

 * pback()

 *	push the data used during the archive id phase back into the I/O

 *	buffer. This is required as we cannot be sure that the header does NOT

 *	overlap a block boundary (as in the case we are trying to recover a

 *	flawed archived). This was not designed to be used for any other

 *	purpose. (What software engineering, HA!)

 *	WARNING: do not even THINK of pback greater than BLKMULT, unless the

 *	pback space is increased.

 */

void

pback(char *pt, int cnt)

{

/*

 * rd_skip()

 *	skip forward in the archive during a archive read. Used to get quickly

 *	past file data and padding for files the user did NOT select.

 * Return:

 *	0 if ok, -1 failure, and 1 when EOF on the archive volume was detected.

 */

int

rd_skip(off_t skcnt)

{

	off_t res;

	off_t cnt;

	/*

	 * consume what data we have in the buffer. If we have to move forward

	 * whole records, we call the low level skip function to see if we can

	 * move within the archive without doing the expensive reads on data we

	 * do not want.

	 */

	/*

	 * if skcnt is now 0, then no additional i/o is needed

	 */

	/*

	 * We have to read more, calculate complete and partial record reads

	 * based on rdblksz. we skip over "cnt" complete records

	 */

	/*

	 * if the skip fails, we will have to resync. ar_fow will tell us

	 * how much it can skip over. We will have to read the rest.

	 */

	/*

	 * what is left we have to read (which may be the whole thing if

	 * ar_fow() told us the device can only read to skip records);

	 */

		/*

		 * if the read fails, we will have to resync

		 */

	}

/*

 * wr_fin()

 *	flush out any data (and pad if required) the last block. We always pad

 *	with zero (even though we do not have to). Padding with 0 makes it a

 *	lot easier to recover if the archive is damaged. zero padding SHOULD

 *	BE a requirement....

 */

void

wr_fin(void)

{

/*

 * wr_rdbuf()

 *	fill the write buffer from data passed to it in a buffer (usually used

 *	by format specific write routines to pass a file header). On failure we

 *	punt. We do not allow the user to continue to write flawed archives.

 *	We assume these headers are not very large (the memory copy we use is

 *	a bit expensive).

 * Return:

 *	0 if buffer was filled ok, -1 o.w. (buffer flush failure)

 */

int

wr_rdbuf(char *out, int outcnt)

{

	int cnt;

	/*

	 * while there is data to copy copy into the write buffer. when the

	 * write buffer fills, flush it to the archive and continue

	 */

		/*

		 * only move what we have space for

		 */

	}

/*

 * rd_wrbuf()

 *	copy from the read buffer into a supplied buffer a specified number of

 *	bytes. If the read buffer is empty fill it and continue to copy.

 *	usually used to obtain a file header for processing by a format

 *	specific read routine.

 * Return

 *	number of bytes copied to the buffer, 0 indicates EOF on archive volume,

 *	-1 is a read error

 */

int

rd_wrbuf(char *in, int cpcnt)

{

	int res;

	int cnt;

	int incnt = cpcnt;

	/*

	 * loop until we fill the buffer with the requested number of bytes

	 */

			/*

			 * read error, return what we got (or the error if

			 * no data was copied). The caller must know that an

			 * error occurred and has the best knowledge what to

			 * do with it

			 */

		}

		/*

		 * calculate how much data to copy based on whats left and

		 * state of buffer

		 */

	}

/*

 * wr_skip()

 *	skip forward during a write. In other words add padding to the file.

 *	we add zero filled padding as it makes flawed archives much easier to

 *	recover from. the caller tells us how many bytes of padding to add

 *	This routine was not designed to add HUGE amount of padding, just small

 *	amounts (a few 512 byte blocks at most)

 * Return:

 *	0 if ok, -1 if there was a buf_flush failure

 */

int

wr_skip(off_t skcnt)

{

	int cnt;

	/*

	 * loop while there is more padding to add

	 */

	}

/*

 * wr_rdfile()

 *	fill write buffer with the contents of a file. We are passed an	open

 *	file descriptor to the file an the archive structure that describes the

 *	file we are storing. The variable "left" is modified to contain the

 *	number of bytes of the file we were NOT able to write to the archive.

 *	it is important that we always write EXACTLY the number of bytes that

 *	the format specific write routine told us to. The file can also get

 *	bigger, so reading to the end of file would create an improper archive,

 *	we just detect this case and warn the user. We never create a bad

 *	archive if we can avoid it. Of course trying to archive files that are

 *	active is asking for trouble. It we fail, we pass back how much we

 *	could NOT copy and let the caller deal with it.

 * Return:

 *	0 ok, -1 if archive write failure. a short read of the file returns a

 *	0, but "left" is set to be greater than zero.

 */

int

wr_rdfile(ARCHD *arcn, int ifd, off_t *left)

{

	int cnt;

	int res = 0;

	/*

	 * while there are more bytes to write

	 */

		}

			break;

	}

	/*

	 * better check the file did not change during this operation

	 * or the file read failed.

	 */

/*

 * rd_wrfile()

 *	extract the contents of a file from the archive. If we are unable to

 *	extract the entire file (due to failure to write the file) we return

 *	the numbers of bytes we did NOT process. This way the caller knows how

 *	many bytes to skip past to find the next archive header. If the failure

 *	was due to an archive read, we will catch that when we try to skip. If

 *	the format supplies a file data crc value, we calculate the actual crc

 *	so that it can be compared to the value stored in the header

 * NOTE:

 *	We call a special function to write the file. This function attempts to

 *	restore file holes (blocks of zeros) into the file. When files are

 *	sparse this saves space, and is a LOT faster. For non sparse files

 *	the performance hit is small. As of this writing, no archive supports

 *	information on where the file holes are.

 * Return:

 *	0 ok, -1 if archive read failure. if we cannot write the entire file,

 *	we return a 0 but "left" is set to be the amount unwritten

 */

int

rd_wrfile(ARCHD *arcn, int ofd, off_t *left)

{

	int cnt = 0;

	int res = 0;

	int sz = MINFBSZ;

	u_int32_t crc = 0;

	/*

	 * pass the blocksize of the file being written to the write routine,

	 * if the size is zero, use the default MINFBSZ

	 */

	} else

	/*

	 * Copy the archive to the file the number of bytes specified. We have

	 * to assume that we want to recover file holes as none of the archive

	 * formats can record the location of file holes.

	 */

		/*

		 * if we get a read error, we do not want to skip, as we may

		 * miss a header, so we do not set left, but if we get a write

		 * error, we do want to skip over the unprocessed data.

		 */

			break;

		}

			/*

			 * update the actual crc value

			 */

			cnt = res;

		} else

	}

	/*

	 * if the last block has a file hole (all zero), we must make sure this

	 * gets updated in the file. We force the last block of zeros to be

	 * written. just closing with the file offset moved forward may not put

	 * a hole at the end of the file.

	 */

	/*

	 * if we failed from archive read, we do not want to skip

	 */

	/*

	 * some formats record a crc on file data. If so, then we compare the

	 * calculated crc to the crc stored in the archive

	 */

/*

 * cp_file()

 *	copy the contents of one file to another. used during -rw phase of pax

 *	just as in rd_wrfile() we use a special write function to write the

 *	destination file so we can properly copy files with holes.

 */

void

cp_file(ARCHD *arcn, int fd1, int fd2)

{

	int cnt;

	off_t cpcnt = 0;

	int res = 0;

	int no_hole = 0;

	int sz = MINFBSZ;

	/*

	 * check for holes in the source file. If none, we will use regular

	 * write instead of file write.

	 */

	/*

	 * pass the blocksize of the file being written to the write routine,

	 * if the size is zero, use the default MINFBSZ

	 */

	} else

	/*

	 * read the source file and copy to destination file until EOF

	 */

			break;

		else

			break;

	}

	/*

	 * check to make sure the copy is valid.

	 */

	/*

	 * if the last block has a file hole (all zero), we must make sure this

	 * gets updated in the file. We force the last block of zeros to be

	 * written. just closing with the file offset moved forward may not put

	 * a hole at the end of the file.

	 */

/*

 * buf_fill()

 *	fill the read buffer with the next record (or what we can get) from

 *	the archive volume.

 * Return:

 *	Number of bytes of data in the read buffer, -1 for read error, and

 *	0 when finished (user specified termination in ar_next()).

 */

int

buf_fill(void)

{

	int cnt;

	static int fini = 0;

		/*

		 * try to fill the buffer. on error the next archive volume is

		 * opened and we try again.

		 */

		}

		/*

		 * errors require resync, EOF goes to next archive

		 * but in case we have not determined yet the format,

		 * this means that we have a very short file, so we

		 * are done again.

		 */

			break;

		}

	}

/*

 * buf_flush()

 *	force the write buffer to the archive. We are passed the number of

 *	bytes in the buffer at the point of the flush. When we change archives

 *	the record size might change. (either larger or smaller).

 * Return:

 *	0 if all is ok, -1 when a write error occurs.

 */

int

buf_flush(int bufcnt)

{

	int cnt;

	int push = 0;

	int totcnt = 0;

	/*

	 * if we have reached the user specified byte count for each archive

	 * volume, prompt for the next volume. (The non-standard -R flag).

	 * NOTE: If the wrlimit is smaller than wrcnt, we will always write

	 * at least one record. We always round limit UP to next blocksize.

	 */

			wrcnt = 0;

		}

		wrcnt = 0;

		/*

		 * The new archive volume might have changed the size of the

		 * write blocksize. if so we figure out if we need to write

		 * (one or more times), or if there is now free space left in

		 * the buffer (it is no longer full). bufcnt has the number of

		 * bytes in the buffer, (the blocksize, at the point we were

		 * CALLED). Push has the amount of "extra" data in the buffer

		 * if the block size has shrunk from a volume change.

		 */

	}

	/*

	 * We have enough data to write at least one archive block

	 */

	for (;;) {

		/*

		 * write a block and check if it all went out ok

		 */

			/*

			 * the write went ok

			 */

				/* we have extra data to push to the front.

				 * check for more than 1 block of push, and if

				 * so we loop back to write again

				 */

				}

			} else

			/*

			 * Oh drat we got a partial write!

			 * if format does not care about alignment let it go,

			 * we warned the user in ar_write().... but this means

			 * the last record on this volume violates pax spec....

			 */

			break;

		}

		/*

		 * All done, go to next archive

		 */

			break;

		/*

		 * The new archive volume might also have changed the block

		 * size. if so, figure out if we have too much or too little

		 * data for using the new block size

		 */