Function sbuf_new

freebsd/kern/subr_sbuf.c:195–254

* Initialize an sbuf. * If buf is non-NULL, it points to a static or already-allocated string * big enough to hold at least length characters. */

 * big enough to hold at least length characters.
 */
struct sbuf *
sbuf_new(struct sbuf *s, char *buf, int length, int flags)
{

	KASSERT(length >= 0,
	    ("attempt to create an sbuf of negative length (%d)", length));
	KASSERT((flags & ~SBUF_USRFLAGMSK) == 0,
	    ("%s called with invalid flags", __func__));
	KASSERT((flags & SBUF_AUTOEXTEND) || length >= SBUF_MINSIZE,
	    ("sbuf buffer %d smaller than minimum %d bytes", length,
	    SBUF_MINSIZE));

	flags &= SBUF_USRFLAGMSK;

	/*
	 * Allocate 'DYNSTRUCT' sbuf from the heap, if NULL 's' was provided.
	 */
	if (s == NULL) {
		s = SBMALLOC(sizeof(*s),
		    (flags & SBUF_NOWAIT) ?  M_NOWAIT : M_WAITOK);
		if (s == NULL)
			goto out;
		SBUF_SETFLAG(s, SBUF_DYNSTRUCT);
	} else {
		/*
		 * DYNSTRUCT SBMALLOC sbufs are allocated with M_ZERO, but
		 * user-provided sbuf objects must be initialized.
		 */
		memset(s, 0, sizeof(*s));
	}

	s->s_flags |= flags;
	s->s_size = length;
	s->s_buf = buf;
	/*
	 * Never-written sbufs do not need \n termination.
	 */
	SBUF_SETFLAG(s, SBUF_DRAINATEOL);

	/*
	 * Allocate DYNAMIC, i.e., heap data buffer backing the sbuf, if no
	 * buffer was provided.
	 */
	if (s->s_buf == NULL) {
		if (SBUF_CANEXTEND(s))
			s->s_size = sbuf_extendsize(s->s_size);
		s->s_buf = SBMALLOC(s->s_size, SBUF_MALLOCFLAG(s));
		if (s->s_buf == NULL)
			goto out;
		SBUF_SETFLAG(s, SBUF_DYNAMIC);
	}

out:
	if (s != NULL && s->s_buf == NULL) {
		if (SBUF_ISDYNSTRUCT(s))
			SBFREE(s);
		s = NULL;
	}