fcp.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

#include <u.h>
#include <libc.h>
#define	DEFB	(8*1024)
#define	Nwork	16

int	failed;
int	gflag;
int	uflag;
int	xflag;
void	copy(char *from, char *to, int todir);
int	copy1(int fdf, int fdt, char *from, char *to);
void	worker(int fdf, int fdt, char *from, char *to);
vlong	nextoff(void);
void	failure(void *, char *note);

QLock	lk;
vlong	off;

void
main(int argc, char *argv[])
{
	Dir *dirb;
	int todir, i;

	ARGBEGIN {
	case 'g':
		gflag++;
		break;
	case 'u':
		uflag++;
		gflag++;
		break;
	case 'x':
		xflag++;
		break;
	default:
		goto usage;
	} ARGEND

	todir=0;
	if(argc < 2)
		goto usage;
	dirb = dirstat(argv[argc-1]);
	if(dirb!=nil && (dirb->mode&DMDIR))
		todir=1;
	if(argc>2 && !todir){
		fprint(2, "fcp: %s not a directory\n", argv[argc-1]);
		exits("bad usage");
	}
	for(i=0; i<argc-1; i++)
		copy(argv[i], argv[argc-1], todir);
	if(failed)
		exits("errors");
	exits(0);

usage:
	fprint(2, "usage:\tfcp [-gux] fromfile tofile\n");
	fprint(2, "\tfcp [-x] fromfile ... todir\n");
	exits("usage");
}

int
samefile(Dir *a, char *an, char *bn)
{
	Dir *b;
	int ret;

	ret = 0;
	b=dirstat(bn);
	if(b != nil)
	if(b->qid.type==a->qid.type)
	if(b->qid.path==a->qid.path)
	if(b->qid.vers==a->qid.vers)
	if(b->dev==a->dev)
	if(b->type==a->type){
		fprint(2, "fcp: %s and %s are the same file\n", an, bn);
		ret = 1;
	}
	free(b);
	return ret;
}

void
copy(char *from, char *to, int todir)
{
	Dir *dirb, dirt;
	char name[256];
	int fdf, fdt, mode;

	if(todir){
		char *s, *elem;
		elem=s=from;
		while(*s++)
			if(s[-1]=='/')
				elem=s;
		sprint(name, "%s/%s", to, elem);
		to=name;
	}

	if((dirb=dirstat(from))==nil){
		fprint(2,"fcp: can't stat %s: %r\n", from);
		failed = 1;
		return;
	}
	mode = dirb->mode;
	if(mode&DMDIR){
		fprint(2, "fcp: %s is a directory\n", from);
		free(dirb);
		failed = 1;
		return;
	}
	if(samefile(dirb, from, to)){
		free(dirb);
		failed = 1;
		return;
	}
	mode &= 0777;
	fdf=open(from, OREAD);
	if(fdf<0){
		fprint(2, "fcp: can't open %s: %r\n", from);
		free(dirb);
		failed = 1;
		return;
	}
	fdt=create(to, OWRITE, mode);
	if(fdt<0){
		fprint(2, "fcp: can't create %s: %r\n", to);
		close(fdf);
		free(dirb);
		failed = 1;
		return;
	}
	if(copy1(fdf, fdt, from, to)==0 && (xflag || gflag || uflag)){
		nulldir(&dirt);
		if(xflag){
			dirt.mtime = dirb->mtime;
			dirt.mode = dirb->mode;
		}
		if(uflag)
			dirt.uid = dirb->uid;
		if(gflag)
			dirt.gid = dirb->gid;
		if(dirfwstat(fdt, &dirt) < 0)
			fprint(2, "fcp: warning: can't wstat %s: %r\n", to);
	}			
	free(dirb);
	close(fdf);
	close(fdt);
}

int
copy1(int fdf, int fdt, char *from, char *to)
{
	int i, n, rv, pid[Nwork];
	Waitmsg *w;

	n = 0;
	off = 0;
	for(i=0; i<Nwork; i++){
		switch(pid[n] = rfork(RFPROC|RFMEM)){
		case 0:
			notify(failure);
			worker(fdf, fdt, from, to);
		case -1:
			break;
		default:
			n++;
			break;
		}
	}
	if(n == 0){
		fprint(2, "fcp: rfork: %r\n");
		failed = 1;
		return -1;
	}

	rv = 0;
	while((w = wait()) != nil){
		if(w->msg[0]){
			rv = -1;
			failed = 1;
			for(i=0; i<n; i++)
				if(pid[i] > 0)
					postnote(PNPROC, pid[i], "failure");
		}
		free(w);
	}
	return rv;
}

void
worker(int fdf, int fdt, char *from, char *to)
{
	char buf[DEFB], *bp;
	long len, n;
	vlong o;

	len = sizeof(buf);
	bp = buf;
	o = nextoff();

	while(n = pread(fdf, bp, len, o)){
		if(n < 0){
			fprint(2, "reading %s at %lld: %r\n", from, o);
			_exits("bad");
		}
		if(pwrite(fdt, buf, n, o) != n){
			fprint(2, "writing %s: %r\n", to);
			_exits("bad");
		}
		bp += n;
		o += n;
		len -= n;
		if(len == 0){
			len = sizeof buf;
			bp = buf;
			o = nextoff();
		}
	}
	_exits(nil);
}

vlong
nextoff(void)
{
	vlong o;

	qlock(&lk);
	o = off;
	off += DEFB;
	qunlock(&lk);

	return o;
}

void
failure(void*, char *note)
{
	if(strcmp(note, "failure") == 0)
		_exits(nil);
	noted(NDFLT);
}