NAME¶
mbchain
,
mb_init
,
mb_initm
,
mb_done
,
mb_detach
,
mb_fixhdr
,
mb_reserve
,
mb_put_uint8
,
mb_put_uint16be
,
mb_put_uint16le
,
mb_put_uint32be
,
mb_put_uint32le
,
mb_put_int64be
,
mb_put_int64le
,
mb_put_mem
,
mb_put_mbuf
,
mb_put_uio
—
set of functions to build an mbuf chain from various
data types
SYNOPSIS¶
options LIBMCHAIN
kldload
libmchain
#include
<sys/param.h>
#include
<sys/uio.h>
#include
<sys/mchain.h>
int
mb_init
(
struct
mbchain *mbp);
void
mb_initm
(
struct
mbchain *mbp,
struct mbuf *m);
void
mb_done
(
struct
mbchain *mbp);
struct mbuf *
mb_detach
(
struct
mbchain *mbp);
int
mb_fixhdr
(
struct
mbchain *mbp);
caddr_t
mb_reserve
(
struct
mbchain *mbp,
int size);
int
mb_put_uint8
(
struct
mbchain *mbp,
uint8_t x);
int
mb_put_uint16be
(
struct
mbchain *mbp,
uint16_t x);
int
mb_put_uint16le
(
struct
mbchain *mbp,
uint16_t x);
int
mb_put_uint32be
(
struct
mbchain *mbp,
uint32_t x);
int
mb_put_uint32le
(
struct
mbchain *mbp,
uint32_t x);
int
mb_put_int64be
(
struct
mbchain *mbp,
int64_t x);
int
mb_put_int64le
(
struct
mbchain *mbp,
int64_t x);
int
mb_put_mem
(
struct
mbchain *mbp,
c_caddr_t
source,
int
size,
int
type);
int
mb_put_mbuf
(
struct
mbchain *mbp,
struct mbuf *m);
int
mb_put_uio
(
struct
mbchain *mbp,
struct uio
*uiop,
int
size);
DESCRIPTION¶
These functions are used to compose mbuf chains from various data types. The
mbchain structure is used as a working
context and should be initialized with a call to either
mb_init
() or
mb_initm
(). It has the following fields:
- mb_top
- (struct mbuf *) A pointer to the top of
constructed mbuf chain.
- mb_cur
- (struct mbuf *) A pointer to the
currently filled mbuf.
- mb_mleft
- (int) Number of bytes left in the current
mbuf.
- mb_count
- (int) Total number of bytes placed in the
mbuf chain.
- mb_copy
- (mb_copy_t *) User-defined function to
perform a copy into mbuf; useful if any unusual data conversion is
necessary.
- mb_udata
- (void *) User-supplied data which can be
used in the mb_copy function.
mb_done
() function disposes an mbuf chain
pointed to by
mbp->mb_top field and sets
the field to
NULL
.
mb_detach
() function returns the value of
mbp->mb_top field and sets its value to
NULL
.
mb_fixhdr
() recalculates the length of an
mbuf chain and updates the
m_pkthdr.len field
of the first mbuf in the chain. It returns the calculated length.
mb_reserve
() ensures that the object of the
length specified by the
size argument will
fit in the current mbuf (mbuf allocation is performed if necessary), and
advances all pointers as if the real data was placed. Returned value will
point to the beginning of the reserved space. Note that the size of the object
should not exceed
MLEN
bytes.
All
mb_put_*
() functions perform an actual
copy of the data into mbuf chain. Functions which have
le
or
be
suffixes will perform conversion to the little- or big-endian data formats.
mb_put_mem
() function copies
size bytes of data specified by the
source argument to an mbuf chain. The
type argument specifies the method used to
perform a copy, and can be one of the following:
MB_MSYSTEM
- Use
bcopy
() function.
MB_MUSER
- Use copyin(9) function.
MB_MINLINE
- Use an “inline” loop which does not call any function.
MB_MZERO
- Do not copy any data, but just fill the destination with zero bytes.
MB_MCUSTOM
- Call function specified by the
mbp->mb_copy field.
RETURN VALUES¶
All
int functions except
mb_fixhdr
() return zero if successful and
an error code otherwise.
Note: after failure of any function, an mbuf chain
is left in the broken state, and only
mb_done
() function can safely be called to
destroy it.
EXAMPLES¶
struct mbchain *mbp;
struct mbuf *m;
mb_init(mbp);
mb_put_uint8(mbp, 33);
mb_put_uint16le(mbp, length);
m = m_copym(mbp->mb_top, 0, M_COPYALL, M_WAIT);
send(m);
mb_done(mbp);
SEE ALSO¶
mbuf(9),
mdchain(9)
AUTHORS¶
This manual page was written by
Boris Popov
⟨bp@FreeBSD.org⟩.