Function sctp_m_getptr

freebsd/netinet/sctputil.c:3047–3085

* return a pointer to a contiguous piece of data from the given mbuf chain * starting at 'off' for 'len' bytes. If the desired piece spans more than * one mbuf, a copy is made at 'ptr'. caller must ensure that the buffer size * is >= 'len' returns NULL if there there isn't 'len' bytes in the chain. */

 * is >= 'len' returns NULL if there there isn't 'len' bytes in the chain.
 */
caddr_t
sctp_m_getptr(struct mbuf *m, int off, int len, uint8_t *in_ptr)
{
	uint32_t count;
	uint8_t *ptr;

	ptr = in_ptr;
	if ((off < 0) || (len <= 0))
		return (NULL);

	/* find the desired start location */
	while ((m != NULL) && (off > 0)) {
		if (off < SCTP_BUF_LEN(m))
			break;
		off -= SCTP_BUF_LEN(m);
		m = SCTP_BUF_NEXT(m);
	}
	if (m == NULL)
		return (NULL);

	/* is the current mbuf large enough (eg. contiguous)? */
	if ((SCTP_BUF_LEN(m) - off) >= len) {
		return (mtod(m, caddr_t)+off);
	} else {
		/* else, it spans more than one mbuf, so save a temp copy... */
		while ((m != NULL) && (len > 0)) {
			count = min(SCTP_BUF_LEN(m) - off, len);
			memcpy(ptr, mtod(m, caddr_t)+off, count);
			len -= count;
			ptr += count;
			off = 0;
			m = SCTP_BUF_NEXT(m);
		}
		if ((m == NULL) && (len > 0))
			return (NULL);
		else
			return ((caddr_t)in_ptr);
	}
}

struct sctp_paramhdr *
sctp_get_next_param(struct mbuf *m,