Function fdcopy

freebsd/kern/kern_descrip.c:2329–2359

* Copy a filedesc structure. A NULL pointer in returns a NULL reference, * this is to ease callers, not catch errors. */

 * this is to ease callers, not catch errors.
 */
struct filedesc *
fdcopy(struct filedesc *fdp)
{
	struct filedesc *newfdp;
	struct filedescent *nfde, *ofde;
	int i, lastfile;

	MPASS(fdp != NULL);

	newfdp = fdinit(fdp, true, &lastfile);
	/* copy all passable descriptors (i.e. not kqueue) */
	newfdp->fd_freefile = -1;
	for (i = 0; i <= lastfile; ++i) {
		ofde = &fdp->fd_ofiles[i];
		if (ofde->fde_file == NULL ||
		    (ofde->fde_file->f_ops->fo_flags & DFLAG_PASSABLE) == 0 ||
		    !fhold(ofde->fde_file)) {
			if (newfdp->fd_freefile == -1)
				newfdp->fd_freefile = i;
			continue;
		}
		nfde = &newfdp->fd_ofiles[i];
		*nfde = *ofde;
		filecaps_copy(&ofde->fde_caps, &nfde->fde_caps, true);
		fdused_init(newfdp, i);
	}
	if (newfdp->fd_freefile == -1)
		newfdp->fd_freefile = i;
	FILEDESC_SUNLOCK(fdp);
	return (newfdp);
}

/*
 * Copy a pwddesc structure.