NAME    [Toc]    [Back]

     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    [Toc]    [Back]

     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, u_int8_t x);

     int
     mb_put_uint16be(struct mbchain *mbp, u_int16_t x);

     int
     mb_put_uint16le(struct mbchain *mbp, u_int16_t x);

     int
     mb_put_uint32be(struct mbchain *mbp, u_int32_t x);

     int
     mb_put_uint32le(struct mbchain *mbp, u_int32_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    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     mbuf(9), mdchain(9)

AUTHORS    [Toc]    [Back]

     This manual page was written by Boris Popov <bp@FreeBSD.org>.


FreeBSD 5.2.1		       February 20, 2001		 FreeBSD 5.2.1