ar.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

		if(strcmp(p->name, name) == 0)
			return 1;
	p = (Hashchain*) armalloc(sizeof(Hashchain));
	p->next = hash[h];
	p->name = name;
	hash[h] = p;
	return 0;
}

/*
 *	open an archive and validate its header
 */
int
openar(char *arname, int mode, int errok)
{
	int fd;
	char mbuf[SARMAG];

	fd = open(arname, mode);
	if(fd >= 0){
		if(read(fd, mbuf, SARMAG) != SARMAG || strncmp(mbuf, ARMAG, SARMAG)) {
			fprint(2, "ar: %s not in archive format\n", arname);
			exits("error");
		}
	}else if(!errok){
		fprint(2, "ar: cannot open %s: %r\n", arname);
		exits("error");
	}
	return fd;
}

/*
 *	create an archive and set its header
 */
int
arcreate(char *arname)
{
	int fd;

	fd = create(arname, OWRITE, 0664);
	if(fd < 0){
		fprint(2, "ar: cannot create %s: %r\n", arname);
		exits("error");
	}
	if(write(fd, ARMAG, SARMAG) != SARMAG)
		wrerr();
	return fd;
}

/*
 *		error handling
 */
void
wrerr(void)
{
	perror("ar: write error");
	exits("error");
}

void
rderr(void)
{
	perror("ar: read error");
	exits("error");
}

void
phaseerr(int offset)
{
	fprint(2, "ar: phase error at offset %d\n", offset);
	exits("error");
}

void
usage(void)
{
	fprint(2, "usage: ar [%s][%s] archive files ...\n", opt, man);
	exits("error");
}

/*
 *	read the header for the next archive member
 */
Armember *
getdir(Biobuf *b)
{
	Armember *bp;
	char *cp;
	static char name[ARNAMESIZE+1];

	bp = newmember();
	if(HEADER_IO(Bread, b, bp->hdr)) {
		free(bp);
		return 0;
	}
	if(strncmp(bp->hdr.fmag, ARFMAG, sizeof(bp->hdr.fmag)))
		phaseerr(Boffset(b));
	strncpy(name, bp->hdr.name, sizeof(bp->hdr.name));
	cp = name+sizeof(name)-1;
	while(*--cp==' ')
		;
	cp[1] = '\0';
	file = name;
	bp->date = strtol(bp->hdr.date, 0, 0);
	bp->size = strtol(bp->hdr.size, 0, 0);
	return bp;
}

/*
 *	Copy the file referenced by fd to the temp file
 */
void
armove(Biobuf *b, Arfile *ap, Armember *bp)
{
	char *cp;
	Dir *d;

	d = dirfstat(Bfildes(b));
	if (d == nil) {
		fprint(2, "ar: cannot stat %s\n", file);
		return;
	}
	trim(file, bp->hdr.name, sizeof(bp->hdr.name));
	for (cp = strchr(bp->hdr.name, 0);		/* blank pad on right */
		cp < bp->hdr.name+sizeof(bp->hdr.name); cp++)
			*cp = ' ';
	sprint(bp->hdr.date, "%-12ld", d->mtime);
	sprint(bp->hdr.uid, "%-6d", 0);
	sprint(bp->hdr.gid, "%-6d", 0);
	sprint(bp->hdr.mode, "%-8lo", d->mode);
	sprint(bp->hdr.size, "%-10lld", d->length);
	strncpy(bp->hdr.fmag, ARFMAG, 2);
	bp->size = d->length;
	arread(b, bp, bp->size);
	if (d->length&0x01)
		d->length++;
	if (ap) {
		arinsert(ap, bp);
		ap->size += d->length+SAR_HDR;
	}
	free(d);
}

/*
 *	Copy the archive member at the current offset into the temp file.
 */
void
arcopy(Biobuf *b, Arfile *ap, Armember *bp)
{
	long n;

	n = bp->size;
	if (n & 01)
		n++;
	arread(b, bp, n);
	if (ap) {
		arinsert(ap, bp);
		ap->size += n+SAR_HDR;
	}
}

/*
 *	Skip an archive member
 */
void
skip(Biobuf *bp, vlong len)
{
	if (len & 01)
		len++;
	Bseek(bp, len, 1);
}

/*
 *	Stream the three temp files to an archive
 */
void
install(char *arname, Arfile *astart, Arfile *amiddle, Arfile *aend, int createflag)
{
	int fd;

	if(allobj && dupfound) {
		fprint(2, "%s not changed\n", arname);
		return;
	}
	/* leave note group behind when copying back; i.e. sidestep interrupts */
	rfork(RFNOTEG);

	if(createflag)
		fprint(2, "ar: creating %s\n", arname);
	fd = arcreate(arname);

	if(allobj)
		rl(fd);

	if (astart) {
		arstream(fd, astart);
		arfree(astart);
	}
	if (amiddle) {
		arstream(fd, amiddle);
		arfree(amiddle);
	}
	if (aend) {
		arstream(fd, aend);
		arfree(aend);
	}
	close(fd);
}

void
rl(int fd)
{

	Biobuf b;
	char *cp;
	struct ar_hdr a;
	long len;

	Binit(&b, fd, OWRITE);
	Bseek(&b,seek(fd,0,1), 0);

	len = symdefsize;
	if(len&01)
		len++;
	sprint(a.date, "%-12ld", time(0));
	sprint(a.uid, "%-6d", 0);
	sprint(a.gid, "%-6d", 0);
	sprint(a.mode, "%-8lo", 0644L);
	sprint(a.size, "%-10ld", len);
	strncpy(a.fmag, ARFMAG, 2);
	strcpy(a.name, symdef);
	for (cp = strchr(a.name, 0);		/* blank pad on right */
		cp < a.name+sizeof(a.name); cp++)
			*cp = ' ';
	if(HEADER_IO(Bwrite, &b, a))
			wrerr();

	len += Boffset(&b);
	if (astart) {
		wrsym(&b, len, astart->sym);
		len += astart->size;
	}
	if(amiddle) {
		wrsym(&b, len, amiddle->sym);
		len += amiddle->size;
	}
	if(aend)
		wrsym(&b, len, aend->sym);

	if(symdefsize&0x01)
		Bputc(&b, 0);
	Bterm(&b);
}

/*
 *	Write the defined symbols to the symdef file
 */
void
wrsym(Biobuf *bp, long offset, Arsymref *as)
{
	int off;

	while(as) {
		Bputc(bp, as->type);
		off = as->offset+offset;
		Bputc(bp, off);
		Bputc(bp, off>>8);
		Bputc(bp, off>>16);
		Bputc(bp, off>>24);
		if (Bwrite(bp, as->name, as->len+1) != as->len+1)
			wrerr();
		as = as->next;
	}
}

/*
 *	Check if the archive member matches an entry on the command line.
 */
int
match(int count, char **files)
{
	int i;
	char name[ARNAMESIZE+1];

	for(i=0; i<count; i++) {
		if(files[i] == 0)
			continue;
		trim(files[i], name, ARNAMESIZE);
		if(strncmp(name, file, ARNAMESIZE) == 0) {
			file = files[i];
			files[i] = 0;
			return 1;
		}
	}
	return 0;
}

/*
 *	compare the current member to the name of the pivot member
 */
int
bamatch(char *file, char *pivot)
{
	static int state = 0;

	switch(state)
	{
	case 0:			/* looking for position file */
		if (aflag) {
			if (strncmp(file, pivot, ARNAMESIZE) == 0)
				state = 1;
		} else if (bflag) {
			if (strncmp(file, pivot, ARNAMESIZE) == 0) {
				state = 2;	/* found */
				return 1;
			}
		}
		break;
	case 1:			/* found - after previous file */
		state = 2;
		return 1;
	case 2:			/* already found position file */
		break;
	}
	return 0;
}

/*
 *	output a message, if 'v' option was specified
 */
void
mesg(int c, char *file)
{

	if(vflag)
		Bprint(&bout, "%c - %s\n", c, file);
}

/*
 *	isolate file name by stripping leading directories and trailing slashes
 */
void
trim(char *s, char *buf, int n)
{
	char *p;

	for(;;) {
		p = strrchr(s, '/');
		if (!p) {		/* no slash in name */
			strncpy(buf, s, n);
			return;
		}
		if (p[1] != 0) {	/* p+1 is first char of file name */
			strncpy(buf, p+1, n);
			return;
		}
		*p = 0;			/* strip trailing slash */
	}
}

/*
 *	utilities for printing long form of 't' command
 */
#define	SUID	04000
#define	SGID	02000
#define	ROWN	0400
#define	WOWN	0200
#define	XOWN	0100
#define	RGRP	040
#define	WGRP	020
#define	XGRP	010
#define	ROTH	04
#define	WOTH	02
#define	XOTH	01
#define	STXT	01000

void
longt(Armember *bp)
{
	char *cp;

	pmode(strtoul(bp->hdr.mode, 0, 8));
	Bprint(&bout, "%3ld/%1ld", strtol(bp->hdr.uid, 0, 0), strtol(bp->hdr.gid, 0, 0));
	Bprint(&bout, "%7ld", bp->size);
	cp = ctime(bp->date);
	Bprint(&bout, " %-12.12s %-4.4s ", cp+4, cp+24);
}

int	m1[] = { 1, ROWN, 'r', '-' };
int	m2[] = { 1, WOWN, 'w', '-' };
int	m3[] = { 2, SUID, 's', XOWN, 'x', '-' };
int	m4[] = { 1, RGRP, 'r', '-' };
int	m5[] = { 1, WGRP, 'w', '-' };
int	m6[] = { 2, SGID, 's', XGRP, 'x', '-' };
int	m7[] = { 1, ROTH, 'r', '-' };
int	m8[] = { 1, WOTH, 'w', '-' };
int	m9[] = { 2, STXT, 't', XOTH, 'x', '-' };

int	*m[] = { m1, m2, m3, m4, m5, m6, m7, m8, m9};

void
pmode(long mode)
{
	int **mp;

	for(mp = &m[0]; mp < &m[9];)
		select(*mp++, mode);
}

void
select(int *ap, long mode)
{
	int n;

	n = *ap++;
	while(--n>=0 && (mode&*ap++)==0)
		ap++;
	Bputc(&bout, *ap);
}

/*
 *	Temp file I/O subsystem.  We attempt to cache all three temp files in
 *	core.  When we run out of memory we spill to disk.
 *	The I/O model assumes that temp files:
 *		1) are only written on the end
 *		2) are only read from the beginning
 *		3) are only read after all writing is complete.
 *	The architecture uses one control block per temp file.  Each control
 *	block anchors a chain of buffers, each containing an archive member.
 */
Arfile *
newtempfile(char *name)		/* allocate a file control block */
{
	Arfile *ap;

	ap = (Arfile *) armalloc(sizeof(Arfile));
	ap->fname = name;
	return ap;
}

Armember *
newmember(void)			/* allocate a member buffer */
{
	return (Armember *)armalloc(sizeof(Armember));
}

void
arread(Biobuf *b, Armember *bp, int n)	/* read an image into a member buffer */
{
	int i;

	bp->member = armalloc(n);
	i = Bread(b, bp->member, n);
	if (i < 0) {
		free(bp->member);
		bp->member = 0;
		rderr();
	}
}

/*
 * insert a member buffer into the member chain
 */
void
arinsert(Arfile *ap, Armember *bp)
{
	bp->next = 0;
	if (!ap->tail)
		ap->head = bp;
	else
		ap->tail->next = bp;
	ap->tail = bp;
}

/*
 *	stream the members in a temp file to the file referenced by 'fd'.
 */
void
arstream(int fd, Arfile *ap)
{
	Armember *bp;
	int i;
	char buf[8192];

	if (ap->paged) {		/* copy from disk */
		seek(ap->fd, 0, 0);
		for (;;) {
			i = read(ap->fd, buf, sizeof(buf));
			if (i < 0)
				rderr();
			if (i == 0)
				break;
			if (write(fd, buf, i) != i)
				wrerr();
		}
		close(ap->fd);
		ap->paged = 0;
	}
		/* dump the in-core buffers */
	for (bp = ap->head; bp; bp = bp->next) {
		if (!arwrite(fd, bp))
			wrerr();
	}
}

/*
 *	write a member to 'fd'.
 */
int
arwrite(int fd, Armember *bp)
{
	int len;

	if(HEADER_IO(write, fd, bp->hdr))
		return 0;
	len = bp->size;
	if (len & 01)
		len++;
	if (write(fd, bp->member, len) != len)
		return 0;
	return 1;
}

/*
 *	Spill a member to a disk copy of a temp file
 */
int
page(Arfile *ap)
{
	Armember *bp;

	bp = ap->head;
	if (!ap->paged) {		/* not yet paged - create file */
		ap->fname = mktemp(ap->fname);
		ap->fd = create(ap->fname, ORDWR|ORCLOSE, 0600);
		if (ap->fd < 0) {
			fprint(2,"ar: can't create temp file\n");
			return 0;
		}
		ap->paged = 1;
	}
	if (!arwrite(ap->fd, bp))	/* write member and free buffer block */
		return 0;
	ap->head = bp->next;
	if (ap->tail == bp)
		ap->tail = bp->next;
	free(bp->member);
	free(bp);
	return 1;
}

/*
 *	try to reclaim space by paging.  we try to spill the start, middle,
 *	and end files, in that order.  there is no particular reason for the
 *	ordering.
 */
int
getspace(void)
{
	if (astart && astart->head && page(astart))
			return 1;
	if (amiddle && amiddle->head && page(amiddle))
			return 1;
	if (aend && aend->head && page(aend))
			return 1;
	return 0;
}

void
arfree(Arfile *ap)		/* free a member buffer */
{
	Armember *bp, *next;

	for (bp = ap->head; bp; bp = next) {
		next = bp->next;
		if (bp->member)
			free(bp->member);
		free(bp);
	}
	free(ap);
}

/*
 *	allocate space for a control block or member buffer.  if the malloc
 *	fails we try to reclaim space by spilling previously allocated
 *	member buffers.
 */
char *
armalloc(int n)
{
	char *cp;

	do {
		cp = malloc(n);
		if (cp) {
			memset(cp, 0, n);
			return cp;
		}
	} while (getspace());
	fprint(2, "ar: out of memory\n");
	exits("malloc");
	return 0;
}