Function m_append

freebsd/kern/uipc_mbuf.c:1180–1217

* Append the specified data to the indicated mbuf chain, * Extend the mbuf chain if the new data does not fit in * existing space. * * Return 1 if able to complete the job; otherwise 0. */

 * Return 1 if able to complete the job; otherwise 0.
 */
int
m_append(struct mbuf *m0, int len, c_caddr_t cp)
{
	struct mbuf *m, *n;
	int remainder, space;

	for (m = m0; m->m_next != NULL; m = m->m_next)
		;
	remainder = len;
	space = M_TRAILINGSPACE(m);
	if (space > 0) {
		/*
		 * Copy into available space.
		 */
		if (space > remainder)
			space = remainder;
		bcopy(cp, mtod(m, caddr_t) + m->m_len, space);
		m->m_len += space;
		cp += space, remainder -= space;
	}
	while (remainder > 0) {
		/*
		 * Allocate a new mbuf; could check space
		 * and allocate a cluster instead.
		 */
		n = m_get(M_NOWAIT, m->m_type);
		if (n == NULL)
			break;
		n->m_len = min(MLEN, remainder);
		bcopy(cp, mtod(n, caddr_t), n->m_len);
		cp += n->m_len, remainder -= n->m_len;
		m->m_next = n;
		m = n;
	}
	if (m0->m_flags & M_PKTHDR)
		m0->m_pkthdr.len += len - remainder;
	return (remainder == 0);
}

/*
 * Apply function f to the data in an mbuf chain starting "off" bytes from