ports//devel/plan9port/work/plan9/9pm/src/9/port/sysfile.c

#include <9pm/u.h>
#include <9pm/libc.h>
#include <9pm/fcall.h>
#include <9pm/ns.h>

static void fdclose(Fgrp*, int, int);

static long
bindmount(int ismount, int fd, int afd, char *new, char *old, int flag, char *spec)
{
	int ret;
	Chan *c0, *c1, *volatile ac, *bc;
	struct {
		Chan*	chan;
		Chan*	authchan;
		char*	spec;
		int	flags;
	} mntparam;

	if((flag&~MMASK) || (flag&MORDER) == (MBEFORE|MAFTER))
		error(Ebadarg);

	mntparam.flags = flag & MCACHE;

	if(ismount){
		if(up->pgrp->noattach)
			error(Enoattach);

		ac = nil;
		bc = fdtochan(up->fgrp, fd, ORDWR, 0, 1);
		if(waserror()) {
			if(ac)
				cclose(ac);
			cclose(bc);
			nexterror();
		}
		if(afd >= 0)
			ac = fdtochan(up->fgrp, afd, ORDWR, 0, 1);

		mntparam.chan = bc;
		mntparam.authchan = ac;
		mntparam.spec = spec;

		ret = devno('M', 0);
		c0 = devtab[ret]->attach((char*)&mntparam);

		poperror();
		if(ac)
			cclose(ac);
		cclose(bc);
	}else{
		spec = 0;
		c0 = namec(new, Amount, 0, 0);
	}

	if(waserror()){
		cclose(c0);
		nexterror();
	}

	c1 = namec(old, Amount, 0, 0);
	if(waserror()){
		cclose(c1);
		nexterror();
	}

	ret = cmount(&c0, c1, flag, spec);

	poperror();
	cclose(c1);
	poperror();
	cclose(c0);
	if(ismount)
		fdclose(up->fgrp, fd, 0);
	return ret;
}

static int
growfd(Fgrp *f, int fd)	/* fd is always >= 0 */
{
	Chan **newfd, **oldfd;

	if(fd < f->nfd)
		return 0;
	if(fd >= f->nfd+DELTAFD)
		return -1;	/* out of range */
	if(fd>0 && fd%100 == 0)
		fprint(2, "warning: process exceeds %d file descriptors\n", fd);
	/*
	 * Unbounded allocation is unwise; besides, there are only 16 bits
	 * of fid in 9P
	 */
	if(f->nfd >= 5000){
    Exhausted:
		print("no free file descriptors\n");
		return -1;
	}
	newfd = malloc((f->nfd+DELTAFD)*sizeof(Chan*));
	if(newfd == 0)
		goto Exhausted;
	oldfd = f->fd;
	memmove(newfd, oldfd, f->nfd*sizeof(Chan*));
	f->fd = newfd;
	free(oldfd);
	f->nfd += DELTAFD;
	if(fd > f->maxfd)
		f->maxfd = fd;
	return 1;
}

static void
fdclose(Fgrp *f, int fd, int flag)
{
	int i;
	Chan *c;

	lock(&f->lk);
	c = f->fd[fd];
	if(c == nil){
		/* can happen for users with shared fd tables */
		unlock(&f->lk);
		return;
	}
	if(flag){
		if(c==0 || !(c->flag&flag)) {
			unlock(&f->lk);
			return;
		}
	}
	f->fd[fd] = nil;
	if(fd == f->maxfd)
		for(i=fd; --i>=0 && f->fd[i]==0; )
			f->maxfd = i;
	unlock(&f->lk);
	cclose(c);
}

Chan*
fdtochan(Fgrp *f, int fd, int mode, int chkmnt, int iref)
{
	Chan *c;

	c = 0;
	lock(&f->lk);
	if(fd<0 || f->maxfd<fd || (c = f->fd[fd])==nil) {
		unlock(&f->lk);
		error(Ebadfd);
	}
	if(iref)
		incref(&c->ref);
	unlock(&f->lk);

	if(chkmnt && (c->flag&CMSG))
		goto bad;
	if(mode<0 || c->mode==ORDWR)
		return c;
	if((mode&OTRUNC) && c->mode==OREAD)
		goto bad;
	if((mode&~OTRUNC) != c->mode)
		goto bad;
	return c;
bad:
	if(iref)
		cclose(c);
	error(Ebadusefd);
	return nil; /* shut up compiler */
}

int
fgrpclose(Fgrp *f, int fd)
{
	if(waserror())
		return -1;

	/*
	 * Take no reference on the chan because we don't really need the
	 * data structure, and are calling fdtochan only for error checks.
	 * fdclose takes care of processes racing through here.
	 */
	fdtochan(f, fd, -1, 0, 0);
	fdclose(f, fd, 0);
	poperror();
	return 0;
}

/*
 *  this assumes that the fgrp is locked
 */
static int
findfreefd(Fgrp *f, int start)
{
	int fd;

	for(fd=start; fd<f->nfd; fd++)
		if(f->fd[fd] == 0)
			break;
	if(fd >= f->nfd && growfd(f, fd) < 0)
		return -1;
	return fd;
}

int
newfd(Chan *c)
{
	int fd;
	Fgrp *f;

	f = up->fgrp;
	lock(&f->lk);
	fd = findfreefd(f, 0);
	if(fd < 0){
		unlock(&f->lk);
		return -1;
	}
	if(fd > f->maxfd)
		f->maxfd = fd;
	f->fd[fd] = c;
	unlock(&f->lk);
	return fd;
}

int
newfdx(Chan *c, int fd)
{
	Fgrp *f;

	if(fd < 0)
		panic("newfdx fd");

	f = up->fgrp;
	lock(&f->lk);
	growfd(f, fd);
	if(fd > f->maxfd)
		f->maxfd = fd;
	f->fd[fd] = c;
	unlock(&f->lk);
	return fd;
}

int
newfd2(int fd[2], Chan *c[2])
{
	Fgrp *f;

	f = up->fgrp;
	lock(&f->lk);
	fd[0] = findfreefd(f, 0);
	if(fd[0] < 0){
		unlock(&f->lk);
		return -1;
	}
	fd[1] = findfreefd(f, fd[0]+1);
	if(fd[1] < 0){
		unlock(&f->lk);
		return -1;
	}
	if(fd[1] > f->maxfd)
		f->maxfd = fd[1];
	f->fd[fd[0]] = c[0];
	f->fd[fd[1]] = c[1];
	unlock(&f->lk);

	return 0;
}

int
openmode(ulong o)
{
	o &= ~(OTRUNC|OCEXEC|ORCLOSE);
	if(o > OEXEC)
		error(Ebadarg);
	if(o == OEXEC)
		return OREAD;
	return o;
}

long
unionread(Chan *c, void *va, long n)
{
	int i;
	Mhead *m;
	Mount *mount;
	long volatile nr;

	qlock(&c->umqlock);
	m = c->umh;
	rlock(&m->lk);
	mount = m->mount;
	/* bring mount in sync with c->uri and c->umc */
	for(i = 0; mount != nil && i < c->uri; i++)
		mount = mount->next;

	nr = 0;
	while(mount != nil) {
		/* Error causes component of union to be skipped */
		if(mount->to && !waserror()) {
			if(c->umc == nil){
				c->umc = cclone(mount->to);
				c->umc = devtab[c->umc->type]->_open(c->umc, OREAD);
			}
	
			nr = devtab[c->umc->type]->_read(c->umc, va, n, c->umc->offset);
			c->umc->offset += nr;
			poperror();
		}
		if(nr > 0)
			break;

		/* Advance to next element */
		c->uri++;
		if(c->umc) {
			cclose(c->umc);
			c->umc = nil;
		}
		mount = mount->next;
	}
	runlock(&m->lk);
	qunlock(&c->umqlock);
	return nr;
}

void
validstat(uchar *s, int n)
{
	int m;
	char buf[64];

	if(statcheck(s, n) < 0)
		error(Ebadstat);
	/* verify that name entry is acceptable */
	s += STATFIXLEN - 4*BIT16SZ;	/* location of first string */
	/*
	 * s now points at count for first string.
	 * if it's too long, let the server decide; this is
	 * only for his protection anyway. otherwise
	 * we'd have to allocate and waserror.
	 */
	m = GBIT16(s);
	s += BIT16SZ;
	if(m+1 > sizeof buf)
		return;
	memmove(buf, s, m);
	buf[m] = '\0';
	/* name could be '/' */
	if(strcmp(buf, "/") != 0)
		validname(buf, 0);
}

int
bind(char *new, char *old, int flags)
{
	long r;

	if(waserror())
		return -1;
	r = bindmount(0, -1, -1, new, old, flags, nil);
	poperror();
	return r;
}

int
chdir(char *path)
{
	Chan *c;

	if(waserror())
		return -1;

	c = namec(path, Atodir, 0, 0);
	cclose(up->dot);
	up->dot = c;
	poperror();
	/* BUG: chdir in underlying os; maybe only at exec */
	return 0;
}

int
close(int fd)
{
	return fgrpclose(getproc()->fgrp, fd);
}

int
create(char *path, int mode, ulong perm)
{
	int fd;
	Chan *volatile c = 0;

	if(waserror()) {
		if(c)
			cclose(c);
		return -1;
	}
	openmode(mode);			/* error check only */
	c = namec(path, Acreate, mode, perm);
	fd = newfd(c);
	if(fd < 0)
		error(Enofd);
	poperror();
	return fd;
}

int
dup(int old, int new)
{
	int fd;
	Chan *oc;
	Fgrp *f = up->fgrp;
	Chan *volatile c = 0;

	if(waserror())
		return -1;

	/*
	 * Close after dup'ing, so date > #d/1 works
	 */
	c = fdtochan(up->fgrp, old, -1, 0, 1);
	fd = new;
	if(fd != -1){
		lock(&f->lk);
		if(fd<0 || growfd(f, fd)<0) {
			unlock(&f->lk);
			cclose(c);
			error(Ebadfd);
		}
		if(fd > f->maxfd)
			f->maxfd = fd;

		oc = f->fd[fd];
		f->fd[fd] = c;
		unlock(&f->lk);
		if(oc)
			cclose(oc);
	}else{
		if(waserror()) {
			cclose(c);
			nexterror();
		}
		fd = newfd(c);
		if(fd < 0)
			error(Enofd);
		poperror();
	}

	poperror();
	return fd;
}

int
fd2path(int fd, char *buf, int nbuf)
{
	Chan *c;
	char *s;

	if(waserror())
		return -1;
	c = fdtochan(up->fgrp, fd, -1, 0, 1);
	poperror();
	if(c->name == nil)
		s = "<null>";
	else
		s = c->name->s;
	utfecpy(buf, buf+nbuf, s);
	cclose(c);
	return 0;
}

int
fstat(int fd, uchar *buf, int n)
{
	Chan *volatile c = 0;

	if(waserror()) {
		if(c)
			cclose(c);
		return -1;
	}
	c = fdtochan(up->fgrp, fd, -1, 0, 1);
	n = devtab[c->type]->_stat(c, buf, n);
	poperror();
	cclose(c);
	return n;
}

int
fwstat(int fd, uchar *buf, int n)
{
	Chan *volatile c = 0;

	if(waserror()) {
		if(c)
			cclose(c);
		return -1;
	}
	validstat(buf, n);
	c = fdtochan(up->fgrp, fd, -1, 1, 1);
	n = devtab[c->type]->_wstat(c, buf, n);
	poperror();
	cclose(c);
	return n;
}

int
mount(int fd, int afd, char *old, int flags, char *spec)
{
	long r;

	if(waserror())
		return -1;
	r = bindmount(1, fd, afd, nil, old, flags, spec);
	poperror();
	return r;
}

int
open(char *path, int mode)
{
	int fd;
	Chan *volatile c = 0;

	if(waserror()){
		if(c)
			cclose(c);
		return -1;
	}
	openmode(mode);				/* error check only */
	c = namec(path, Aopen, mode, 0);
	fd = newfd((Chan*)c);
	if(fd < 0)
		error(Enofd);
	poperror();
	return fd;
}

int
unmount(char *old, char *new)
{
	Chan *volatile cmount = 0, *volatile cmounted = 0;

	if(waserror()) {
		if(cmount)
			cclose(cmount);
		if(cmounted)
			cclose(cmounted);
		return -1;
	}
	cmount = namec(new, Aopen, OREAD, 0);
	if(old != nil){
		/*
		 * This has to be namec(..., Aopen, ...) because
		 * if arg[0] is something like /srv/cs or /fd/0,
		 * opening it is the only way to get at the real
		 * Chan underneath.
		 */
		cmounted = namec(old, Aopen, OREAD, 0);
		poperror();
	}

	cunmount(cmount, cmounted);
	poperror();	
	cclose(cmount);
	if(cmounted)
		cclose(cmounted);
	return 0;
}

long
pread(int fd, void *va, long n, vlong offset)
{
	int dir;
	vlong off;
	Chan *volatile c = 0;

	if(waserror()) {
		if(c)
			cclose(c);
		return -1;
	}
	c = fdtochan(up->fgrp, fd, OREAD, 1, 1);

	dir = c->qid.type&QTDIR;
	/*
	 * The offset is passed through on directories, normally. sysseek complains but
	 * pread is used by servers and e.g. exportfs that shouldn't need to worry about this issue.
	 */

	if(offset == (vlong)-1)	/* use and maintain channel's offset */
		off = c->offset;
	else
		off = offset;

	if(off < 0)
		error(Enegoff);

	if(dir && c->umh)
		n = unionread(c, va, n);
	else
		n = devtab[c->type]->_read(c, va, n, off);

	if(offset == (vlong)-1){
		lock(&c->lk);
		c->offset += n;
		unlock(&c->lk);
	}

	poperror();
	cclose(c);

	return n;
}

long
read(int fd, void *va, long n)
{
	return pread(fd, va, n, (vlong)-1);
}

int
remove(char *path)
{
	Chan *volatile c = 0;

	if(waserror()) {
		if(c != nil){
			c->type = 0;	/* see below */
			cclose(c);
		}
		return -1;
	}
	c = namec(path, Aremove, 0, 0);
	devtab[c->type]->_remove(c);

	/*
	 * Remove clunks the fid, but we need to recover the Chan
	 * so fake it up.  rootclose() is known to be a nop.
	 */
	c->type = 0;
	poperror();
	cclose(c);
	return 0;
}

vlong
seek(int fd, vlong off, int whence)
{
	int n;
	Dir dir;
	Chan *volatile c = 0;
	uchar buf[sizeof(Dir)+100];

	if(waserror()) {
		if(c)
			cclose(c);
		return -1;
	}

	c = fdtochan(up->fgrp, fd, -1, 1, 1);
	if(c->qid.type & QTDIR)
		error(Eisdir);
	if(devtab[c->type]->dc == '|')
		error(Eisstream);

	switch(whence) {
	case 0:
		if((c->qid.type & QTDIR) && off != 0)
			error(Eisdir);
		if(off < 0)
			error(Enegoff);
		lock(&c->lk);	/* vlong assignment is not atomic */
		c->offset = off;
		unlock(&c->lk);
		break;

	case 1:
		if(c->qid.type & QTDIR)
			error(Eisdir);
		lock(&c->lk);	/* read/write update */
		off += c->offset;
		if(off < 0){
			unlock(&c->lk);
			error(Enegoff);
		}
		c->offset = off;
		unlock(&c->lk);
		break;

	case 2:
		if(c->qid.type & QTDIR)
			error(Eisdir);
		n = devtab[c->type]->_stat(c, buf, sizeof buf);
		if(convM2D(buf, n, &dir, nil) == 0)
			error("internal error: stat error in seek");
		off += dir.length;
		if(off < 0)
			error(Enegoff);
		lock(&c->lk);	/* vlong assignment is not atomic */
		c->offset = off;
		unlock(&c->lk);
		break;

	default:
		error(Ebadarg);
	}
	c->uri = 0;
	c->dri = 0;
	cclose(c);
	poperror();
	return off;
}

int
stat(char *path, uchar *buf, int n)
{
	Chan *volatile c = 0;

	if(waserror()){
		if(c)
			cclose(c);
		return -1;
	}
	c = namec(path, Aaccess, 0, 0);
	n = devtab[c->type]->_stat(c, buf, n);
	poperror();
	cclose(c);
	return n;
}

long
pwrite(int fd, void *va, long n, vlong offset)
{
	long m;
	vlong off;
	Chan *volatile c = 0;

	if(waserror()){
		dprint(PmDebugFd, "pwrite error %s\n", getproc()->err);
		if(offset == (vlong)-1 && c != nil){
			lock(&c->lk);
			c->offset -= n;
			unlock(&c->lk);
		}
		if(c){
			cclose(c);
			if(devtab[c->type]->dc == (Rune)'|')
				error("write on closed pipe");
		}
		return -1;
	}

	c = fdtochan(up->fgrp, fd, OWRITE, 1, 1);
	if(c->qid.type & QTDIR)
		error(Eisdir);

	if(offset == (vlong)-1){
		lock(&c->lk);
		off = c->offset;
		c->offset += n;
		unlock(&c->lk);
	}else
		off = offset;

	if(off < 0)
		error(Enegoff);

	dprint(PmDebugFd, "pwrite dev %C\n", devtab[c->type]->dc);
	m = devtab[c->type]->_write(c, va, n, off);

	if(offset == (vlong)-1 && m < n){
		lock(&c->lk);
		c->offset -= n - m;
		unlock(&c->lk);
	}

	poperror();
	cclose(c);

	return n;
}

long
write(int fd, void *va, long n)
{
	return pwrite(fd, va, n, (vlong)-1);
}

int
wstat(char *path, uchar *buf, int n)
{
	Chan *volatile c = 0;

	if(waserror()) {
		if(c)
			cclose(c);
		return -1;
	}
	validstat(buf, n);
	c = namec(path, Aaccess, 0, 0);
	n = devtab[c->type]->_wstat(c, buf, n);
	poperror();
	cclose(c);
	return n;
}

int
iounit(int fd)
{
	Chan *c;

	if(waserror())
		return -1;
	c = fdtochan(up->fgrp, fd, -1, 1, 0);
	return c->iounit;
}
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