xref: /src/sbin/dump/traverse.c

/*	$NetBSD: traverse.c,v 1.43 2004/03/24 12:28:51 hannken Exp $	*/

/*-
 * Copyright (c) 1980, 1988, 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * 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/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)traverse.c	8.7 (Berkeley) 6/15/95";
#else
__RCSID("$NetBSD: traverse.c,v 1.43 2004/03/24 12:28:51 hannken Exp $");
#endif
#endif /* not lint */

#include <sys/param.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <ufs/ufs/dir.h>
#include <ufs/ufs/dinode.h>
#include <ufs/ffs/fs.h>
#include <ufs/ffs/ffs_extern.h>

#include <protocols/dumprestore.h>

#include <ctype.h>
#include <errno.h>
#include <fts.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "dump.h"

#define	HASDUMPEDFILE	0x1
#define	HASSUBDIRS	0x2

static	int dirindir(ino_t, daddr_t, int, off_t *, u_int64_t *, int);
static	void dmpindir(ino_t, daddr_t, int, off_t *);
static	int searchdir(ino_t, daddr_t, long, off_t, u_int64_t *, int);

/*
 * This is an estimation of the number of TP_BSIZE blocks in the file.
 * It estimates the number of blocks in files with holes by assuming
 * that all of the blocks accounted for by di_blocks are data blocks
 * (when some of the blocks are usually used for indirect pointers);
 * hence the estimate may be high.
 */
int64_t
blockest(union dinode *dp)
{
	int64_t blkest, sizeest;

	/*
	 * dp->di_size is the size of the file in bytes.
	 * dp->di_blocks stores the number of sectors actually in the file.
	 * If there are more sectors than the size would indicate, this just
	 *	means that there are indirect blocks in the file or unused
	 *	sectors in the last file block; we can safely ignore these
	 *	(blkest = sizeest below).
	 * If the file is bigger than the number of sectors would indicate,
	 *	then the file has holes in it.	In this case we must use the
	 *	block count to estimate the number of data blocks used, but
	 *	we use the actual size for estimating the number of indirect
	 *	dump blocks (sizeest vs. blkest in the indirect block
	 *	calculation).
	 */
	blkest = howmany(ufs_fragroundup(ufsib,
	    dbtob((u_int64_t)DIP(dp, blocks))), TP_BSIZE);
	sizeest = howmany(ufs_fragroundup(ufsib, DIP(dp, size)), TP_BSIZE);
	if (blkest > sizeest)
		blkest = sizeest;
	if (DIP(dp, size) > ufsib->ufs_bsize * NDADDR) {
		/* calculate the number of indirect blocks on the dump tape */
		blkest +=
			howmany(sizeest - NDADDR * ufsib->ufs_bsize / TP_BSIZE,
			TP_NINDIR);
	}
	return (blkest + 1);
}

/* Auxiliary macro to pick up files changed since previous dump. */
#define	CHANGEDSINCE(dp, t) \
	(DIP((dp), mtime) >= (t) || DIP((dp), ctime) >= (t))

/* The WANTTODUMP macro decides whether a file should be dumped. */
#ifdef UF_NODUMP
#define	WANTTODUMP(dp) \
	(CHANGEDSINCE(dp, iswap64(spcl.c_ddate)) && \
	 (nonodump || (DIP((dp), flags) & UF_NODUMP) != UF_NODUMP))
#else
#define	WANTTODUMP(dp) CHANGEDSINCE(dp, iswap64(spcl.c_ddate))
#endif

/*
 * Determine if given inode should be dumped
 */
void
mapfileino(ino_t ino, u_int64_t *tape_size, int *dirskipped)
{
	int mode;
	union dinode *dp;

	/*
	 * Skip inode if we've already marked it for dumping
	 */
	if (TSTINO(ino, usedinomap))
		return;
	dp = getino(ino);
	if ((mode = (DIP(dp, mode) & IFMT)) == 0)
		return;
	/*
	 * Put all dirs in dumpdirmap, inodes that are to be dumped in the
	 * used map. All inode but dirs who have the nodump attribute go
	 * to the usedinomap.
	 */
	SETINO(ino, usedinomap);
	if (mode == IFDIR)
		SETINO(ino, dumpdirmap);
	if (WANTTODUMP(dp)) {
		SETINO(ino, dumpinomap);
		if (mode != IFREG && mode != IFDIR && mode != IFLNK)
			*tape_size += 1;
		else
			*tape_size += blockest(dp);
		return;
	}
	if (mode == IFDIR) {
#ifdef UF_NODUMP
		if (!nonodump && (DIP(dp, flags) & UF_NODUMP))
			CLRINO(ino, usedinomap);
#endif
		*dirskipped = 1;
	}
}

/*
 * Dump pass 1.
 *
 * Walk the inode list for a file system to find all allocated inodes
 * that have been modified since the previous dump time. Also, find all
 * the directories in the file system.
 * disk may be NULL if dirv is NULL.
 */
int
mapfiles(ino_t maxino, u_int64_t *tape_size, char *diskname, char * const *dirv)
{
	int anydirskipped = 0;

	if (dirv != NULL) {
		char	 curdir[MAXPATHLEN];
		FTS	*dirh;
		FTSENT	*entry;
		int	 d;

		if (getcwd(curdir, sizeof(curdir)) == NULL) {
			msg("Can't determine cwd: %s\n", strerror(errno));
			dumpabort(0);
		}
		if ((dirh = fts_open(dirv, FTS_PHYSICAL|FTS_SEEDOT|FTS_XDEV,
		    		    NULL)) == NULL) {
			msg("fts_open failed: %s\n", strerror(errno));
			dumpabort(0);
		}
		while ((entry = fts_read(dirh)) != NULL) {
			switch (entry->fts_info) {
			case FTS_DNR:		/* an error */
			case FTS_ERR:
			case FTS_NS:
				msg("Can't fts_read %s: %s\n", entry->fts_path,
				    strerror(errno));
			case FTS_DP:		/* already seen dir */
				continue;
			}
			mapfileino(entry->fts_statp->st_ino, tape_size,
			    &anydirskipped);
		}
		(void)fts_close(dirh);

		/*
		 * Add any parent directories
		 */
		for (d = 0 ; dirv[d] != NULL ; d++) {
			char path[MAXPATHLEN];

			if (dirv[d][0] != '/')
				(void)snprintf(path, sizeof(path), "%s/%s",
				    curdir, dirv[d]);
			else
				(void)snprintf(path, sizeof(path), "%s",
				    dirv[d]);
			while (strcmp(path, diskname) != 0) {
				char *p;
				struct stat sb;

				if (*path == '\0')
					break;
				if ((p = strrchr(path, '/')) == NULL)
					break;
				if (p == path)
					break;
				*p = '\0';
				if (stat(path, &sb) == -1) {
					msg("Can't stat %s: %s\n", path,
					    strerror(errno));
					break;
				}
				mapfileino(sb.st_ino, tape_size, &anydirskipped);
			}
		}

		/*
		 * Ensure that the root inode actually appears in the
		 * file list for a subdir
		 */
		mapfileino(ROOTINO, tape_size, &anydirskipped);
	} else {
		fs_mapinodes(maxino, tape_size, &anydirskipped);
	}
	/*
	 * Restore gets very upset if the root is not dumped,
	 * so ensure that it always is dumped.
	 */
	SETINO(ROOTINO, dumpinomap);
	return (anydirskipped);
}

/*
 * Dump pass 2.
 *
 * Scan each directory on the file system to see if it has any modified
 * files in it. If it does, and has not already been added to the dump
 * list (because it was itself modified), then add it. If a directory
 * has not been modified itself, contains no modified files and has no
 * subdirectories, then it can be deleted from the dump list and from
 * the list of directories. By deleting it from the list of directories,
 * its parent may now qualify for the same treatment on this or a later
 * pass using this algorithm.
 */
int
mapdirs(ino_t maxino, u_int64_t *tape_size)
{
	union dinode *dp, di;
	int i, isdir, nodump;
	char *map;
	ino_t ino;
	off_t filesize;
	int ret, change = 0;
	daddr_t blk;

	isdir = 0;		/* XXX just to get gcc to shut up */
	for (map = dumpdirmap, ino = 1; ino < maxino; ino++) {
		if (((ino - 1) % NBBY) == 0)	/* map is offset by 1 */
			isdir = *map++;
		else
			isdir >>= 1;
		/*
		 * If dir has been removed from the used map, it's either
		 * because it had the nodump flag, or it inherited it from
		 * its parent. A directory can't be in dumpinomap if
		 * not in usedinomap, but we have to go throuh it anyway
		 * to propagate the nodump attribute.
		 */
		nodump = (TSTINO(ino, usedinomap) == 0);
		if ((isdir & 1) == 0 ||
		    (TSTINO(ino, dumpinomap) && nodump == 0))
			continue;

		dp = getino(ino);
		/*
		 * inode buf may be changed in searchdir().
		 */
		if (is_ufs2)
			di.dp2 = dp->dp2;
		else
			di.dp1 = dp->dp1;
		filesize = DIP(&di, size);
		for (ret = 0, i = 0; filesize > 0 && i < NDADDR; i++) {
			if (is_ufs2)
				blk = iswap64(di.dp2.di_db[i]);
			else
				blk = iswap32(di.dp1.di_db[i]);
			if (blk != 0)
				ret |= searchdir(ino, blk,
					(long)ufs_dblksize(ufsib, &di, i),
					filesize, tape_size, nodump);
			if (ret & HASDUMPEDFILE)
				filesize = 0;
			else
				filesize -= ufsib->ufs_bsize;
		}
		for (i = 0; filesize > 0 && i < NIADDR; i++) {
			if (is_ufs2)
				blk = iswap64(di.dp2.di_ib[i]);
			else
				blk = iswap32(di.dp1.di_ib[i]);
			if (blk == 0)
				continue;
			ret |= dirindir(ino, blk, i, &filesize,
			    tape_size, nodump);
		}
		if (ret & HASDUMPEDFILE) {
			SETINO(ino, dumpinomap);
			*tape_size += blockest(&di);
			change = 1;
			continue;
		}
		if (nodump) {
			if (ret & HASSUBDIRS)
				change = 1; /* subdirs have inherited nodump */
			CLRINO(ino, dumpdirmap);
		} else if ((ret & HASSUBDIRS) == 0) {
			if (!TSTINO(ino, dumpinomap)) {
				CLRINO(ino, dumpdirmap);
				change = 1;
			}
		}
	}
	return (change);
}

/*
 * Read indirect blocks, and pass the data blocks to be searched
 * as directories. Quit as soon as any entry is found that will
 * require the directory to be dumped.
 */
static int
dirindir(ino_t ino, daddr_t blkno, int ind_level, off_t *filesize,
	u_int64_t *tape_size, int nodump)
{
	int ret = 0;
	int i;
	union {
		int64_t i64[MAXBSIZE / sizeof (int64_t)];
		int32_t i32[MAXBSIZE / sizeof (int32_t)];
	} idblk;

	bread(fsatoda(ufsib, blkno), (char *)&idblk, (int)ufsib->ufs_bsize);
	if (ind_level <= 0) {
		for (i = 0; *filesize > 0 && i < ufsib->ufs_nindir; i++) {
			if (is_ufs2)
				blkno = iswap64(idblk.i64[i]);
			else
				blkno = iswap32(idblk.i32[i]);
			if (blkno != 0)
				ret |= searchdir(ino, blkno,
				    ufsib->ufs_bsize, *filesize,
				    tape_size, nodump);
			if (ret & HASDUMPEDFILE)
				*filesize = 0;
			else
				*filesize -= ufsib->ufs_bsize;
		}
		return (ret);
	}
	ind_level--;
	for (i = 0; *filesize > 0 && i < ufsib->ufs_nindir; i++) {
		if (is_ufs2)
			blkno = iswap64(idblk.i64[i]);
		else
			blkno = iswap32(idblk.i32[i]);
		if (blkno != 0)
			ret |= dirindir(ino, blkno, ind_level, filesize,
			    tape_size, nodump);
	}
	return (ret);
}

/*
 * Scan a disk block containing directory information looking to see if
 * any of the entries are on the dump list and to see if the directory
 * contains any subdirectories.
 */
static int
searchdir(ino_t dino, daddr_t blkno, long size, off_t filesize,
	u_int64_t *tape_size, int nodump)
{
	struct direct *dp;
	union dinode *ip;
	long loc, ret = 0;
	char *dblk;
	ino_t ino;

	dblk = malloc(size);
	if (dblk == NULL)
		quit("searchdir: cannot allocate directory memory.\n");
	bread(fsatoda(ufsib, blkno), dblk, (int)size);
	if (filesize < size)
		size = filesize;
	for (loc = 0; loc < size; ) {
		dp = (struct direct *)(dblk + loc);
		if (dp->d_reclen == 0) {
			msg("corrupted directory, inumber %d\n", dino);
			break;
		}
		loc += iswap16(dp->d_reclen);
		if (dp->d_ino == 0)
			continue;
		if (dp->d_name[0] == '.') {
			if (dp->d_name[1] == '\0')
				continue;
			if (dp->d_name[1] == '.' && dp->d_name[2] == '\0')
				continue;
		}
		ino = iswap32(dp->d_ino);
		if (nodump) {
			ip = getino(ino);
			if (TSTINO(ino, dumpinomap)) {
				CLRINO(ino, dumpinomap);
				*tape_size -= blockest(ip);
			}
			/*
			 * Add back to dumpdirmap and remove from usedinomap
			 * to propagate nodump.
			 */
			if ((DIP(ip, mode) & IFMT) == IFDIR) {
				SETINO(ino, dumpdirmap);
				CLRINO(ino, usedinomap);
				ret |= HASSUBDIRS;
			}
		} else {
			if (TSTINO(ino, dumpinomap)) {
				ret |= HASDUMPEDFILE;
				if (ret & HASSUBDIRS)
					break;
			}
			if (TSTINO(ino, dumpdirmap)) {
				ret |= HASSUBDIRS;
				if (ret & HASDUMPEDFILE)
					break;
			}
		}
	}
	free(dblk);
	return (ret);
}

/*
 * Dump passes 3 and 4.
 *
 * Dump the contents of an inode to tape.
 */
void
dumpino(union dinode *dp, ino_t ino)
{
	int ind_level, cnt;
	off_t size;
	char buf[TP_BSIZE];
	daddr_t blk;
	void *shortlink;

	if (newtape) {
		newtape = 0;
		dumpmap(dumpinomap, TS_BITS, ino);
	}
	CLRINO(ino, dumpinomap);
	if (!is_ufs2) {
		if (needswap)
			ffs_dinode1_swap(&dp->dp1, &spcl.c_dinode);
		else
			spcl.c_dinode = dp->dp1;
	} else {
		if (needswap)
			ffs_dinode2_swap(&dp->dp2, &dp->dp2);
		spcl.c_mode = dp->dp2.di_mode;
		spcl.c_size = dp->dp2.di_size;
		spcl.c_atime = dp->dp2.di_atime;
		spcl.c_atimensec = dp->dp2.di_atimensec;
		spcl.c_mtime = dp->dp2.di_mtime;
		spcl.c_mtimensec = dp->dp2.di_mtimensec;
		spcl.c_birthtime = dp->dp2.di_birthtime;
		spcl.c_birthtimensec = dp->dp2.di_birthnsec;
		spcl.c_rdev = dp->dp2.di_rdev;
		spcl.c_file_flags = dp->dp2.di_flags;
		spcl.c_uid = dp->dp2.di_uid;
		spcl.c_gid = dp->dp2.di_gid;
	}
	spcl.c_type = iswap32(TS_INODE);
	spcl.c_count = 0;
	switch (DIP(dp, mode) & IFMT) {

	case 0:
		/*
		 * Freed inode.
		 */
		return;

	case IFLNK:
		/*
		 * Check for short symbolic link.
		 */
		if (DIP(dp, size) > 0 &&
#ifdef FS_44INODEFMT
		    (DIP(dp, size) < ufsib->ufs_maxsymlinklen ||
		     (ufsib->ufs_maxsymlinklen == 0 && DIP(dp, blocks) == 0))
#else
		    DIP(dp, blocks) == 0
#endif
			) {
			spcl.c_addr[0] = 1;
			spcl.c_count = iswap32(1);
			writeheader(ino);
			if (is_ufs2)
				shortlink = dp->dp2.di_db;
			else
				shortlink = dp->dp1.di_db;
			memmove(buf, shortlink, DIP(dp, size));
			buf[DIP(dp, size)] = '\0';
			writerec(buf, 0);
			return;
		}
		/* fall through */

	case IFDIR:
	case IFREG:
		if (DIP(dp, size) > 0)
			break;
		/* fall through */

	case IFIFO:
	case IFSOCK:
	case IFCHR:
	case IFBLK:
		writeheader(ino);
		return;

	default:
		msg("Warning: undefined file type 0%o\n", DIP(dp, mode) & IFMT);
		return;
	}
	if (DIP(dp, size) > NDADDR * ufsib->ufs_bsize)
		cnt = NDADDR * ufsib->ufs_frag;
	else
		cnt = howmany(DIP(dp, size), ufsib->ufs_fsize);
	if (is_ufs2)
		blksout64(&dp->dp2.di_db[0], cnt, ino);
	else
		blksout32(&dp->dp1.di_db[0], cnt, ino);

	if ((size = DIP(dp, size) - NDADDR * ufsib->ufs_bsize) <= 0)
		return;
	for (ind_level = 0; ind_level < NIADDR; ind_level++) {
		if (is_ufs2)
			blk = iswap64(dp->dp2.di_ib[ind_level]);
		else
			blk = iswap32(dp->dp1.di_ib[ind_level]);
		dmpindir(ino, blk, ind_level, &size);
		if (size <= 0)
			return;
	}
}

/*
 * Read indirect blocks, and pass the data blocks to be dumped.
 */
static void
dmpindir(ino_t ino, daddr_t blk, int ind_level, off_t *size)
{
	int i, cnt;
	union {
		int32_t i32[MAXBSIZE / sizeof (int32_t)];
		int64_t i64[MAXBSIZE / sizeof (int64_t)];
	} idblk;
	daddr_t iblk;


	if (blk != 0)
		bread(fsatoda(ufsib, blk), (char *)&idblk,
			(int) ufsib->ufs_bsize);
	else
		memset(&idblk, 0, (int)ufsib->ufs_bsize);
	if (ind_level <= 0) {
		if (*size < ufsib->ufs_nindir * ufsib->ufs_bsize)
			cnt = howmany(*size, ufsib->ufs_fsize);
		else
			cnt = ufsib->ufs_nindir * ufsib->ufs_frag;
		*size -= ufsib->ufs_nindir * ufsib->ufs_bsize;
		if (is_ufs2)
			blksout64(&idblk.i64[0], cnt, ino);
		else
			blksout32(&idblk.i32[0], cnt, ino);
		return;
	}
	ind_level--;
	for (i = 0; i < ufsib->ufs_nindir; i++) {
		if (is_ufs2)
			iblk = iswap64(idblk.i64[i]);
		else
			iblk = iswap32(idblk.i32[i]);
		dmpindir(ino, iblk, ind_level, size);
		if (*size <= 0)
			return;
	}
}

/*
 * Collect up the data into tape record sized buffers and output them.
 */
void
blksout32(int32_t *blkp, int frags, ino_t ino)
{
	int32_t *bp;
	int i, j, count, blks, tbperdb;

	blks = howmany(frags * ufsib->ufs_fsize, TP_BSIZE);
	tbperdb = ufsib->ufs_bsize >> tp_bshift;
	for (i = 0; i < blks; i += TP_NINDIR) {
		if (i + TP_NINDIR > blks)
			count = blks;
		else
			count = i + TP_NINDIR;
		for (j = i; j < count; j++)
			if (blkp[j / tbperdb] != 0)
				spcl.c_addr[j - i] = 1;
			else
				spcl.c_addr[j - i] = 0;
		spcl.c_count = iswap32(count - i);
		writeheader(ino);
		bp = &blkp[i / tbperdb];
		for (j = i; j < count; j += tbperdb, bp++)
			if (*bp != 0) {
				if (j + tbperdb <= count)
					dumpblock(iswap32(*bp), (int)ufsib->ufs_bsize);
				else
					dumpblock(iswap32(*bp), (count - j) * TP_BSIZE);
			}
		spcl.c_type = iswap32(TS_ADDR);
	}
}

void
blksout64(int64_t *blkp, int frags, ino_t ino)
{
	int64_t *bp;
	int i, j, count, blks, tbperdb;

	blks = howmany(frags * ufsib->ufs_fsize, TP_BSIZE);
	tbperdb = ufsib->ufs_bsize >> tp_bshift;
	for (i = 0; i < blks; i += TP_NINDIR) {
		if (i + TP_NINDIR > blks)
			count = blks;
		else
			count = i + TP_NINDIR;
		for (j = i; j < count; j++)
			if (blkp[j / tbperdb] != 0)
				spcl.c_addr[j - i] = 1;
			else
				spcl.c_addr[j - i] = 0;
		spcl.c_count = iswap32(count - i);
		writeheader(ino);
		bp = &blkp[i / tbperdb];
		for (j = i; j < count; j += tbperdb, bp++)
			if (*bp != 0) {
				if (j + tbperdb <= count)
					dumpblock(iswap64(*bp), (int)ufsib->ufs_bsize);
				else
					dumpblock(iswap64(*bp), (count - j) * TP_BSIZE);
			}
		spcl.c_type = iswap32(TS_ADDR);
	}
}

/*
 * Dump a map to the tape.
 */
void
dumpmap(char *map, int type, ino_t ino)
{
	int i;
	char *cp;

	spcl.c_type = iswap32(type);
	spcl.c_count = iswap32(howmany(mapsize * sizeof(char), TP_BSIZE));
	writeheader(ino);
	for (i = 0, cp = map; i < iswap32(spcl.c_count); i++, cp += TP_BSIZE)
		writerec(cp, 0);
}

/*
 * Write a header record to the dump tape.
 */
void
writeheader(ino_t ino)
{
	int32_t sum, cnt, *lp;

	spcl.c_inumber = iswap32(ino);
	if (is_ufs2)
		spcl.c_magic = iswap32(FS_UFS2_MAGIC);
	else {
		spcl.c_magic = iswap32(NFS_MAGIC);
		spcl.c_old_date = iswap32(iswap64(spcl.c_date));
		spcl.c_old_ddate = iswap32(iswap64(spcl.c_ddate));
		spcl.c_old_tapea = iswap32(iswap64(spcl.c_tapea));
		spcl.c_old_firstrec = iswap32(iswap64(spcl.c_firstrec));
	}
	spcl.c_checksum = 0;
	lp = (int32_t *)&spcl;
	sum = 0;
	cnt = sizeof(union u_spcl) / (4 * sizeof(int32_t));
	while (--cnt >= 0) {
		sum += iswap32(*lp++);
		sum += iswap32(*lp++);
		sum += iswap32(*lp++);
		sum += iswap32(*lp++);
	}
	spcl.c_checksum = iswap32(CHECKSUM - sum);
	writerec((char *)&spcl, 1);
}