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mbuf.9: Document mtodo

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mtodo() accepts an mbuf and offset and returns a void * pointer to the
requested offset into the mbuf's associated data.  Similar to mtod(),
no bounds checking is performed.

Reviewed by:	imp, markj
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D43215
This commit is contained in:
John Baldwin 2023-12-28 11:17:22 -08:00
parent 10ed63fc06
commit 854e1fd692
2 changed files with 20 additions and 5 deletions
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1
share/man/man9/Makefile
View file

@ -1516,6 +1516,7 @@ MLINKS+=\
mbuf.9 m_pullup.9 \ mbuf.9 m_pullup.9 \
mbuf.9 m_split.9 \ mbuf.9 m_split.9 \
mbuf.9 mtod.9 \ mbuf.9 mtod.9 \
mbuf.9 mtodo.9 \
mbuf.9 M_TRAILINGSPACE.9 \ mbuf.9 M_TRAILINGSPACE.9 \
mbuf.9 m_unshare.9 \ mbuf.9 m_unshare.9 \
mbuf.9 M_WRITABLE.9 mbuf.9 M_WRITABLE.9

24
share/man/man9/mbuf.9
View file

@ -22,7 +22,7 @@
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE. .\" SUCH DAMAGE.
.\" .\"
.Dd August 8, 2021 .Dd December 28, 2023
.Dt MBUF 9 .Dt MBUF 9
.Os .Os
.\" .\"
@ -52,7 +52,10 @@
.Fc .Fc
.\" .\"
.Ss Mbuf utility macros .Ss Mbuf utility macros
.Ft type
.Fn mtod "struct mbuf *mbuf" "type" .Fn mtod "struct mbuf *mbuf" "type"
.Ft void *
.Fn mtodo "struct mbuf *mbuf" "offset"
.Fn M_ALIGN "struct mbuf *mbuf" "u_int len" .Fn M_ALIGN "struct mbuf *mbuf" "u_int len"
.Fn MH_ALIGN "struct mbuf *mbuf" "u_int len" .Fn MH_ALIGN "struct mbuf *mbuf" "u_int len"
.Ft int .Ft int
@ -394,6 +397,14 @@ It is advisable to ensure that there is enough contiguous data in
See See
.Fn m_pullup .Fn m_pullup
for details. for details.
.It Fn mtodo mbuf offset
Return a data pointer at an offset (in bytes) into the data attached to
.Fa mbuf .
Returns a
.Ft void *
pointer .
.Sy Note :
The caller must ensure that the offset is in bounds of the attached data.
.It Fn MGET mbuf how type .It Fn MGET mbuf how type
Allocate an Allocate an
.Vt mbuf .Vt mbuf
@ -773,7 +784,9 @@ in the
are contiguous and lay in the data area of are contiguous and lay in the data area of
.Fa mbuf , .Fa mbuf ,
so they are accessible with so they are accessible with
.Fn mtod mbuf type . .Fn mtod
or
.Fn mtodo .
.Fa len .Fa len
must be smaller than, or equal to, the size of an must be smaller than, or equal to, the size of an
.Vt mbuf cluster . .Vt mbuf cluster .
@ -787,12 +800,13 @@ to the data contained in the returned mbuf is stored in
If If
.Fa offsetp .Fa offsetp
is NULL, the region may be accessed using is NULL, the region may be accessed using
.Fn mtod mbuf type . .Fn mtod mbuf type
or
.Fn mtodo mbuf 0 .
If If
.Fa offsetp .Fa offsetp
is non-NULL, the region may be accessed using is non-NULL, the region may be accessed using
.Fn mtod mbuf uint8_t .Fn mtodo mbuf *offsetp .
+ *offsetp.
The region of the mbuf chain between its beginning and The region of the mbuf chain between its beginning and
.Fa offset .Fa offset
is not modified, therefore it is safe to hold pointers to data within is not modified, therefore it is safe to hold pointers to data within