Function m_align

freebsd/sys/mbuf.h:1136–1148

* Set the m_data pointer of a newly allocated mbuf to place an object of the * specified size at the end of the mbuf, longword aligned. * * NB: Historically, we had M_ALIGN(), MH_ALIGN(), and MEXT_ALIGN() as * separate macros, each asserting that it was called at the proper moment. * This required callers to themselves test the storage type and call the * right one. Rather than require call

 * decisions, we centralize here.
 */
static __inline void
m_align(struct mbuf *m, int len)
{
#ifdef INVARIANTS
	const char *msg = "%s: not a virgin mbuf";
#endif
	int adjust;

	KASSERT(m->m_data == M_START(m), (msg, __func__));

	adjust = M_SIZE(m) - len;
	m->m_data += adjust &~ (sizeof(long)-1);
}

#define	M_ALIGN(m, len)		m_align(m, len)
#define	MH_ALIGN(m, len)	m_align(m, len)