mbchain(9)

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);
caddrt_
mb_reserve(struct mbchain *mbp, int size);
int
mb_put_uint8(struct mbchain *mbp, ui_nt8t_x);
int
mb_put_uint16be(struct mbchain *mbp, ui_nt16t_x);
int
mb_put_uint16le(struct mbchain *mbp, ui_nt16t_x);
int
mb_put_uint32be(struct mbchain *mbp, ui_nt32t_x);
int
mb_put_uint32le(struct mbchain *mbp, ui_nt32t_x);
int
mb_put_int64be(struct mbchain *mbp, int64t_x);
int
mb_put_int64le(struct mbchain *mbp, int64t_x);
int
mb_put_mem(struct mbchain *mbp, cc_addrt_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:

mbt_op (struct mbuf *) A pointer to the top of con

structed mbuf

chain.

mbc_ur (struct mbuf *) A pointer to the currently

filled mbuf.

mbm_left (int) Number of bytes left in the current mbuf.

mbc_ount (int) Total number of bytes placed in the mbuf

chain.

mbc_opy (mbc_opyt_ *) User-defined function to perform a

copy into

mbuf; useful if any unusual data conversion is

necessary.

mbu_data (void *) User-supplied data which can be used in

the

mbc_opy function.

mb_done() function disposes an mbuf chain pointed to by

mbp->mbt_op field
and sets the field to NULL.

mb_detach() function returns the value of mbp->mbt_op field

and sets its
value to NULL.

mb_fixhdr() recalculates the length of an mbuf chain and up

dates the
mp_kthdr.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 des

tination with

zero bytes.

MB_MCUSTOM Call function specified by the mbp->mbc_opy

field.

RETURN VALUES

All int functions except mb_fixhdr() return zero if success

ful 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_TRYWAIT);
send(m);
mb_done(mbp);

SEE ALSO

mbuf(9), mdchain(9)

AUTHORS

This manual page was written by Boris Popov <bp@FreeB

SD.org>.

BSD February 20, 2001

BSD