mdchain, md_initm, md_done, md_append_record, md_next_record, md_get_uint8, md_get_uint16,

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

Debian                                          February 28, 2001                                     MDCHAIN(9)

       These  functions  are used to decompose mbuf chains to various data types.  The mdchain structure is used
       as a working context and should be initialized through a call of the mb_initm()  function.   It  has  the
       following fields:

       md_top  (structmbuf*) A pointer to the top of the parsed mbuf chain.

       md_cur  (structmbuf*) A pointer to the currently parsed mbuf.

       md_pas  (int) Offset in the current mbuf.

       The  md_done()  function disposes of an mbuf chain pointed to by the mdp->md_top field and sets the field
       to NULL.

       The md_append_record() appends a new mbuf chain using m_nextpkt field to form a  single  linked  list  of
       mbuf  chains.   If  the  mdp->md_top  field is NULL, then this function behaves exactly as the md_initm()
       function.

       The md_next_record() function extracts the next mbuf chain and disposes the current one, if any.   For  a
       new mbuf chain it calls the md_initm() function.  If there is no data left the function returns ENOENT.

       All  md_get_*() functions perform an actual copy of the data from an mbuf chain.  Functions which have le
       or be suffixes will perform conversion to the little- or big-endian data formats.

       md_get_mem() function copies size bytes of data specified by the source argument from an mbuf chain.  The
       type argument specifies the method used to perform a copy, and can be one of the following:

       MB_MSYSTEM  Use the bcopy() function.

       MB_MUSER    Use the copyin(9) function.

       MB_MINLINE  Use an “inline” loop which does not call any function.

       If target is NULL, an actual copy is not performed and the function just skips the given number of bytes.

       struct mdchain *mdp;
       struct mbuf *m;
       uint16_t length;
       uint8_t byte;

       receive(so, &m);
       md_initm(mdp, m);
       if (md_get_uint8(mdp, &byte) != 0 ||
           md_get_uint16le(mdp, &length) != 0)
               error = EBADRPC;
       mb_done(mdp);

       mdchain,    md_initm,    md_done,    md_append_record,   md_next_record,   md_get_uint8,   md_get_uint16,
       md_get_uint16be,  md_get_uint16le,   md_get_uint32,   md_get_uint32be,   md_get_uint32le,   md_get_int64,
       md_get_int64be, md_get_int64le, md_get_mem, md_get_mbuf, md_get_uio — set of functions to dissect an mbuf
       chain to various data types

       All int functions return zero if successful, otherwise an error code is returned.

       Note: after failure of any function, an mbuf chain is left in the broken state  and  only  the  md_done()
       function can safely be called to destroy it.

mbchain(9), mbuf(9)

optionsLIBMCHAINkldloadlibmchain#include<sys/param.h>#include<sys/uio.h>#include<sys/mchain.h>voidmd_initm(structmdchain*mdp, structmbuf*m);

       voidmd_done(structmdchain*mdp);

       voidmd_append_record(structmdchain*mdp, structmbuf*top);

       intmd_next_record(structmdchain*mdp);

       intmd_get_uint8(structmdchain*mdp, uint8_t*x);

       intmd_get_uint16(structmdchain*mdp, uint16_t*x);

       intmd_get_uint16be(structmdchain*mdp, uint16_t*x);

       intmd_get_uint16le(structmdchain*mdp, uint16_t*x);

       intmd_get_uint32(structmdchain*mdp, uint32_t*x);

       intmd_get_uint32be(structmdchain*mdp, uint32_t*x);

       intmd_get_uint32le(structmdchain*mdp, uint32_t*x);

       intmd_get_int64(structmdchain*mdp, int64_t*x);

       intmd_get_int64be(structmdchain*mdp, int64_t*x);

       intmd_get_int64le(structmdchain*mdp, int64_t*x);

       intmd_get_mem(structmdchain*mdp, caddr_ttarget, intsize, inttype);

       intmd_get_mbuf(structmdchain*mdp, intsize, structmbuf**m);

       intmd_get_uio(structmdchain*mdp, structuio*uiop, intsize);