[dpdk-dev] [PATCH 08/10] librte_mbuf: Add rte_pktmbuf_mtod_offset()
Olivier MATZ
olivier.matz at 6wind.com
Fri Jun 19 17:58:59 CEST 2015
On 04/29/2015 06:15 PM, Cyril Chemparathy wrote:
> There are a number of instances in the code where rte_pktmbuf_mtod() is used
> to get the mbuf data pointer, only to add an offset before casting the result
> to some other header type. This patch adds a new rte_pktmbuf_mtod_offset()
> macro to eliminate these awful double cast situations.
>
> Signed-off-by: Cyril Chemparathy <cchemparathy at ezchip.com>
> ---
> lib/librte_mbuf/rte_mbuf.h | 20 +++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 5ddd8dd..e8f1bf4 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -54,6 +54,7 @@
> */
>
> #include <stdint.h>
> +#include <rte_common.h>
> #include <rte_mempool.h>
> #include <rte_memory.h>
> #include <rte_atomic.h>
> @@ -1071,6 +1072,23 @@ static inline struct rte_mbuf *rte_pktmbuf_lastseg(struct rte_mbuf *m)
> }
>
> /**
> + * A macro that points to an offset into the data in the mbuf.
> + *
> + * The returned pointer is cast to type t. Before using this
> + * function, the user must ensure that m_headlen(m) is large enough to
> + * read its data.
Small comment here: m_headlen(m) should be replaced by "the length of
the first segment". Indeed, there is no m_headlen() function (I see that
it is coming from a copy/paste of the mtod() comment). Could you
also fix it by the way?
> + *
> + * @param m
> + * The packet mbuf.
> + * @param o
> + * The offset into the mbuf data.
> + * @param t
> + * The type to cast the result into.
> + */
> +#define rte_pktmbuf_mtod_offset(m, t, o) \
> + ((t)((char *)(m)->buf_addr + (m)->data_off + (o)))
> +
> +/**
> * A macro that points to the start of the data in the mbuf.
> *
> * The returned pointer is cast to type t. Before using this
> @@ -1082,7 +1100,7 @@ static inline struct rte_mbuf *rte_pktmbuf_lastseg(struct rte_mbuf *m)
> * @param t
> * The type to cast the result into.
> */
> -#define rte_pktmbuf_mtod(m, t) ((t)((char *)(m)->buf_addr + (m)->data_off))
> +#define rte_pktmbuf_mtod(m, t) rte_pktmbuf_mtod_offset(m, t, 0)
>
> /**
> * A macro that returns the length of the packet.
>
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