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

/*
 * ar - portable (ascii) format version
 */
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <mach.h>
#include <ar.h>

/*
 *	The algorithm uses up to 3 temp files.  The "pivot member" is the
 *	archive member specified by and a, b, or i option.  The temp files are
 *	astart - contains existing members up to and including the pivot member.
 *	amiddle - contains new files moved or inserted behind the pivot.
 *	aend - contains the existing members that follow the pivot member.
 *	When all members have been processed, function 'install' streams the
 * 	temp files, in order, back into the archive.
 */

typedef struct	Arsymref
{
	char	*name;
	int	type;
	int	len;
	vlong	offset;
	struct	Arsymref *next;
} Arsymref;

typedef struct	Armember	/* Temp file entry - one per archive member */
{
	struct Armember	*next;
	struct ar_hdr	hdr;
	long		size;
	long		date;
	void		*member;
} Armember;

typedef	struct Arfile		/* Temp file control block - one per tempfile */
{
	int	paged;		/* set when some data paged to disk */
	char	*fname;		/* paging file name */
	int	fd;		/* paging file descriptor */
	vlong	size;
	Armember *head;		/* head of member chain */
	Armember *tail;		/* tail of member chain */
	Arsymref *sym;		/* head of defined symbol chain */
} Arfile;

typedef struct Hashchain
{
	char	*name;
	struct Hashchain *next;
} Hashchain;

#define	NHASH	1024

/*
 *	macro to portably read/write archive header.
 *	'cmd' is read/write/Bread/Bwrite, etc.
 */
#define	HEADER_IO(cmd, f, h)	cmd(f, h.name, sizeof(h.name)) != sizeof(h.name)\
				|| cmd(f, h.date, sizeof(h.date)) != sizeof(h.date)\
				|| cmd(f, h.uid, sizeof(h.uid)) != sizeof(h.uid)\
				|| cmd(f, h.gid, sizeof(h.gid)) != sizeof(h.gid)\
				|| cmd(f, h.mode, sizeof(h.mode)) != sizeof(h.mode)\
				|| cmd(f, h.size, sizeof(h.size)) != sizeof(h.size)\
				|| cmd(f, h.fmag, sizeof(h.fmag)) != sizeof(h.fmag)

		/* constants and flags */
char	*man =		"mrxtdpq";
char	*opt =		"uvnbailo";
char	artemp[] =	"/tmp/vXXXXX";
char	movtemp[] =	"/tmp/v1XXXXX";
char	tailtemp[] =	"/tmp/v2XXXXX";
char	symdef[] =	"__.SYMDEF";

int	aflag;				/* command line flags */
int	bflag;
int	cflag;
int	oflag;
int	uflag;
int	vflag;

Arfile *astart, *amiddle, *aend;	/* Temp file control block pointers */
int	allobj = 1;			/* set when all members are object files of the same type */
int	symdefsize;			/* size of symdef file */
int	dupfound;			/* flag for duplicate symbol */
Hashchain	*hash[NHASH];		/* hash table of text symbols */
	
#define	ARNAMESIZE	sizeof(astart->tail->hdr.name)

char	poname[ARNAMESIZE+1];		/* name of pivot member */
char	*file;				/* current file or member being worked on */
Biobuf	bout;
Biobuf bar;

void	arcopy(Biobuf*, Arfile*, Armember*);
int	arcreate(char*);
void	arfree(Arfile*);
void	arinsert(Arfile*, Armember*);
char	*armalloc(int);
void	armove(Biobuf*, Arfile*, Armember*);
void	arread(Biobuf*, Armember*, int);
void	arstream(int, Arfile*);
int	arwrite(int, Armember*);
int	bamatch(char*, char*);
int	duplicate(char*);
Armember *getdir(Biobuf*);
int	getspace(void);
void	install(char*, Arfile*, Arfile*, Arfile*, int);
void	longt(Armember*);
int	match(int, char**);
void	mesg(int, char*);
Arfile	*newtempfile(char*);
Armember *newmember(void);
void	objsym(Sym*, void*);
int	openar(char*, int, int);
int	page(Arfile*);
void	pmode(long);
void	rl(int);
void	scanobj(Biobuf*, Arfile*, long);
void	select(int*, long);
void	setcom(void(*)(char*, int, char**));
void	skip(Biobuf*, vlong);
int	symcomp(void*, void*);
void	trim(char*, char*, int);
void	usage(void);
void	wrerr(void);
void	wrsym(Biobuf*, long, Arsymref*);

void	rcmd(char*, int, char**);		/* command processing */
void	dcmd(char*, int, char**);
void	xcmd(char*, int, char**);
void	tcmd(char*, int, char**);
void	pcmd(char*, int, char**);
void	mcmd(char*, int, char**);
void	qcmd(char*, int, char**);
void	(*comfun)(char*, int, char**);

void
main(int argc, char *argv[])
{
	char *cp;

	Binit(&bout, 1, OWRITE);
	if(argc < 3)
		usage();
	for (cp = argv[1]; *cp; cp++) {
		switch(*cp) {
		case 'a':	aflag = 1;	break;
		case 'b':	bflag = 1;	break;
		case 'c':	cflag = 1;	break;
		case 'd':	setcom(dcmd);	break;
		case 'i':	bflag = 1;	break;
		case 'l':
				strcpy(artemp, "vXXXXX");
				strcpy(movtemp, "v1XXXXX");
				strcpy(tailtemp, "v2XXXXX");
				break;
		case 'm':	setcom(mcmd);	break;
		case 'o':	oflag = 1;	break;
		case 'p':	setcom(pcmd);	break;
		case 'q':	setcom(qcmd);	break;
		case 'r':	setcom(rcmd);	break;
		case 't':	setcom(tcmd);	break;
		case 'u':	uflag = 1;	break;
		case 'v':	vflag = 1;	break;
		case 'x':	setcom(xcmd);	break;
		default:
			fprint(2, "ar: bad option `%c'\n", *cp);
			exits("error");
		}
	}
	if (aflag && bflag) {
		fprint(2, "ar: only one of 'a' and 'b' can be specified\n");
		usage();
	}
	if(aflag || bflag) {
		trim(argv[2], poname, sizeof(poname));
		argv++;
		argc--;
		if(argc < 3)
			usage();
	}
	if(comfun == 0) {
		if(uflag == 0) {
			fprint(2, "ar: one of [%s] must be specified\n", man);
			usage();
		}
		setcom(rcmd);
	}
	cp = argv[2];
	argc -= 3;
	argv += 3;
	(*comfun)(cp, argc, argv);	/* do the command */
	cp = 0;
	while (argc--) {
		if (*argv) {
			fprint(2, "ar: %s not found\n", *argv);
			cp = "error";
		}
		argv++;
	}
	exits(cp);
}
/*
 *	select a command
 */
void
setcom(void (*fun)(char *, int, char**))
{

	if(comfun != 0) {
		fprint(2, "ar: only one of [%s] allowed\n", man);
		usage();
	}
	comfun = fun;
}
/*
 *	perform the 'r' and 'u' commands
 */
void
rcmd(char *arname, int count, char **files)
{
	int fd;
	int i;
	Arfile *ap;
	Armember *bp;
	Dir *d;
	Biobuf *bfile;

	fd = openar(arname, ORDWR, 1);
	if (fd >= 0) {
		Binit(&bar, fd, OREAD);
		Bseek(&bar,seek(fd,0,1), 1);
	}
	astart = newtempfile(artemp);
	ap = astart;
	aend = 0;
	for(i = 0; fd >= 0; i++) {
		bp = getdir(&bar);
		if (!bp)
			break;
		if (bamatch(file, poname)) {		/* check for pivot */
			aend = newtempfile(tailtemp);
			ap = aend;
		}
			/* pitch symdef file */
		if (i == 0 && strcmp(file, symdef) == 0) {
			skip(&bar, bp->size);
			continue;
		}
		if (count && !match(count, files)) {
			scanobj(&bar, ap, bp->size);
			arcopy(&bar, ap, bp);
			continue;
		}
		bfile = Bopen(file, OREAD);
		if (!bfile) {
			if (count != 0)
				fprint(2, "ar: cannot open %s\n", file);
			scanobj(&bar, ap, bp->size);
			arcopy(&bar, ap, bp);
			continue;
		}
		d = dirfstat(Bfildes(bfile));
		if(d == nil)
			fprint(2, "ar: cannot stat %s: %r\n", file);
		if (uflag && (d==nil || d->mtime <= bp->date)) {
			scanobj(&bar, ap, bp->size);
			arcopy(&bar, ap, bp);
			Bterm(bfile);
			free(d);
			continue;
		}
		mesg('r', file);
		skip(&bar, bp->size);
		scanobj(bfile, ap, d->length);
		free(d);
		armove(bfile, ap, bp);
		Bterm(bfile);
	}
	if(fd >= 0)
		close(fd);
		/* copy in remaining files named on command line */
	for (i = 0; i < count; i++) {
		file = files[i];
		if(file == 0)
			continue;
		files[i] = 0;
		bfile = Bopen(file, OREAD);
		if (!bfile)
			fprint(2, "ar: %s cannot open\n", file);
		else {
			mesg('a', file);
			d = dirfstat(Bfildes(bfile));
			if (d == nil)
				fprint(2, "can't stat %s\n", file);
			else {
				scanobj(bfile, astart, d->length);
				armove(bfile, astart, newmember());
				free(d);
			}
			Bterm(bfile);
		}
	}
	if(fd < 0 && !cflag)
		install(arname, astart, 0, aend, 1);	/* issue 'creating' msg */
	else
		install(arname, astart, 0, aend, 0);
}

void
dcmd(char *arname, int count, char **files)
{
	Armember *bp;
	int fd, i;

	if (!count)
		return;
	fd = openar(arname, ORDWR, 0);
	Binit(&bar, fd, OREAD);
	Bseek(&bar,seek(fd,0,1), 1);
	astart = newtempfile(artemp);
	for (i = 0; bp = getdir(&bar); i++) {
		if(match(count, files)) {
			mesg('d', file);
			skip(&bar, bp->size);
			if (strcmp(file, symdef) == 0)
				allobj = 0;
		} else if (i == 0 && strcmp(file, symdef) == 0)
				skip(&bar, bp->size);
		else {
			scanobj(&bar, astart, bp->size);
			arcopy(&bar, astart, bp);
		}
	}
	close(fd);
	install(arname, astart, 0, 0, 0);
}

void
xcmd(char *arname, int count, char **files)
{
	int fd, f, mode, i;
	Armember *bp;
	Dir dx;

	fd = openar(arname, OREAD, 0);
	Binit(&bar, fd, OREAD);
	Bseek(&bar,seek(fd,0,1), 1);
	i = 0;
	while (bp = getdir(&bar)) {
		if(count == 0 || match(count, files)) {
			mode = strtoul(bp->hdr.mode, 0, 8) & 0777;
			f = create(file, OWRITE, mode);
			if(f < 0) {
				fprint(2, "ar: %s cannot create\n", file);
				skip(&bar, bp->size);
			} else {
				mesg('x', file);
				arcopy(&bar, 0, bp);
				if (write(f, bp->member, bp->size) < 0)
					wrerr();
				if(oflag) {
					nulldir(&dx);
					dx.atime = bp->date;
					dx.mtime = bp->date;
					if(dirwstat(file, &dx) < 0)
						perror(file);
				}
				free(bp->member);
				close(f);
			}
			free(bp);
			if (count && ++i >= count)
				break;
		} else {
			skip(&bar, bp->size);
			free(bp);
		}
	}
	close(fd);
}
void
pcmd(char *arname, int count, char **files)
{
	int fd;
	Armember *bp;

	fd = openar(arname, OREAD, 0);
	Binit(&bar, fd, OREAD);
	Bseek(&bar,seek(fd,0,1), 1);
	while(bp = getdir(&bar)) {
		if(count == 0 || match(count, files)) {
			if(vflag)
				print("\n<%s>\n\n", file);
			arcopy(&bar, 0, bp);
			if (write(1, bp->member, bp->size) < 0)
				wrerr();
		} else
			skip(&bar, bp->size);
		free(bp);
	}
	close(fd);
}
void
mcmd(char *arname, int count, char **files)
{
	int fd, i;
	Arfile *ap;
	Armember *bp;

	if (count == 0)
		return;
	fd = openar(arname, ORDWR, 0);
	Binit(&bar, fd, OREAD);
	Bseek(&bar,seek(fd,0,1), 1);
	astart = newtempfile(artemp);
	amiddle = newtempfile(movtemp);
	aend = 0;
	ap = astart;
	for (i = 0; bp = getdir(&bar); i++) {
		if (bamatch(file, poname)) {
			aend = newtempfile(tailtemp);
			ap = aend;
		}
		if(match(count, files)) {
			mesg('m', file);
			scanobj(&bar, amiddle, bp->size);
			arcopy(&bar, amiddle, bp);
		} else
			/*
			 * pitch the symdef file if it is at the beginning
			 * of the archive and we aren't inserting in front
			 * of it (ap == astart).
			 */
		if (ap == astart && i == 0 && strcmp(file, symdef) == 0)
			skip(&bar, bp->size);
		else {
			scanobj(&bar, ap, bp->size);
			arcopy(&bar, ap, bp);
		}
	}
	close(fd);
	if (poname[0] && aend == 0)
		fprint(2, "ar: %s not found - files moved to end.\n", poname);
	install(arname, astart, amiddle, aend, 0);
}
void
tcmd(char *arname, int count, char **files)
{
	int fd;
	Armember *bp;
	char name[ARNAMESIZE+1];

	fd = openar(arname, OREAD, 0);
	Binit(&bar, fd, OREAD);
	Bseek(&bar,seek(fd,0,1), 1);
	while(bp = getdir(&bar)) {
		if(count == 0 || match(count, files)) {
			if(vflag)
				longt(bp);
			trim(file, name, ARNAMESIZE);
			Bprint(&bout, "%s\n", name);
		}
		skip(&bar, bp->size);
		free(bp);
	}
	close(fd);
}
void
qcmd(char *arname, int count, char **files)
{
	int fd, i;
	Armember *bp;
	Biobuf *bfile;

	if(aflag || bflag) {
		fprint(2, "ar: abi not allowed with q\n");
		exits("error");
	}
	fd = openar(arname, ORDWR, 1);
	if (fd < 0) {
		if(!cflag)
			fprint(2, "ar: creating %s\n", arname);
		fd = arcreate(arname);
	}
	Binit(&bar, fd, OREAD);
	Bseek(&bar,seek(fd,0,1), 1);
	/* leave note group behind when writing archive; i.e. sidestep interrupts */
	rfork(RFNOTEG);
	Bseek(&bar, 0, 2);
	bp = newmember();
	for(i=0; i<count && files[i]; i++) {
		file = files[i];
		files[i] = 0;
		bfile = Bopen(file, OREAD);
		if(!bfile)
			fprint(2, "ar: %s cannot open\n", file);
		else {
			mesg('q', file);
			armove(bfile, 0, bp);
			if (!arwrite(fd, bp))
				wrerr();
			free(bp->member);
			bp->member = 0;
			Bterm(bfile);
		}
	}
	free(bp);
	close(fd);
}

/*
 *	extract the symbol references from an object file
 */
void
scanobj(Biobuf *b, Arfile *ap, long size)
{
	int obj;
	vlong offset;
	Dir *d;
	static int lastobj = -1;

	if (!allobj)			/* non-object file encountered */
		return;
	offset = Boffset(b);
	obj = objtype(b, 0);
	if (obj < 0) {			/* not an object file */
		allobj = 0;
		d = dirfstat(Bfildes(b));
		if (d != nil && d->length == 0)
			fprint(2, "ar: zero length file %s\n", file);
		free(d);
		Bseek(b, offset, 0);
		return;
	}
	if (lastobj >= 0 && obj != lastobj) {
		fprint(2, "ar: inconsistent object file %s\n", file);
		allobj = 0;
		Bseek(b, offset, 0);
		return;
	}
	lastobj = obj;
	if (!readar(b, obj, offset+size, 0)) {
		fprint(2, "ar: invalid symbol reference in file %s\n", file);
		allobj = 0;
		Bseek(b, offset, 0);
		return;
	}
	Bseek(b, offset, 0);
	objtraverse(objsym, ap);
}

/*
 *	add text and data symbols to the symbol list
 */
void
objsym(Sym *s, void *p)
{
	int n;
	Arsymref *as;
	Arfile *ap;

	if (s->type != 'T' &&  s->type != 'D')
		return;
	ap = (Arfile*)p;
	as = (Arsymref*)armalloc(sizeof(Arsymref));
	as->offset = ap->size;
	n = strlen(s->name);
	as->name = armalloc(n+1);
	strcpy(as->name, s->name);
	if(s->type == 'T' && duplicate(as->name)) {
		dupfound = 1;
		fprint(2, "duplicate text symbol: %s\n", as->name);
		free(as->name);
		free(as);
		return;
	}
	as->type = s->type;
	symdefsize += 4+(n+1)+1;
	as->len = n;
	as->next = ap->sym;
	ap->sym = as;
}

/*
 *	Check the symbol table for duplicate text symbols
 */
int
duplicate(char *name)
{
	Hashchain *p;
	char *cp;
	int h;

	h = 0;
	for(cp = name; *cp; h += *cp++)
		h *= 1119;
	if(h < 0)
		h = ~h;
	h %= NHASH;

	for(p = hash[h]; p; p = p->next)