On 30 Mar 2010, at 01:58, jiani1012 wrote:
> Hi,all
> A problem puzzled me in ath code. The following code in function
> ath_node_alloc( ) shows the space allocated to an,
>
>> struct ath_ratectrl {
>> size_t arc_space; /* space required for per-node state */
>> };
>
>> const size_t space = sizeof(struct ath_node) + sc->sc_rc->arc_space;
>> struct ath_node *an;
>> an = malloc(space, M_80211_NODE, M_NOWAIT|M_ZERO);
>
> but in the two lines below ,what is (an)[1]? Where is the initialization of
> (an)[1]? What does it contain? Can you show me? and how to get the content of
> sn?
>
>> struct sample_node *sn = ATH_NODE_SAMPLE(an); /*in sample.c*/
>> #define ATH_NODE_SAMPLE(an) ((struct sample_node *)&(an)[1]) /*in
>> sample.h*/
>
> Otherwise, the struct ath_ratectrl has been used in structures ath_softc,
> sample_softc and so on. Is there any relations between them?
Think about memory in the following way:
an[0] .................................. an[1] ...................
struct ath_node struct sample_node
Indexing an[1] gives the address past the end of struct ath_node, which is the
start address of struct sample_node.
--
Rui Paulo
_______________________________________________
freebsd-net@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
