NAME
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 typesSYNOPSIS
options LIBMCHAINkldload
libmchain
#include <sys/param.h>
#include <sys/uio.h>
#include <sys/mchain.h> void
md_initm(struct mdchain *mdp, struct mbuf *m); void
md_done(struct mdchain *mdp); void
md_append_record(struct mdchain *mdp, struct mbuf *top); int
md_next_record(struct mdchain *mdp); int
md_get_uint8(struct mdchain *mdp, uint8_t *x); int
md_get_uint16(struct mdchain *mdp, uint16_t *x); int
md_get_uint16be(struct mdchain *mdp, uint16_t *x); int
md_get_uint16le(struct mdchain *mdp, uint16_t *x); int
md_get_uint32(struct mdchain *mdp, uint32_t *x); int
md_get_uint32be(struct mdchain *mdp, uint32_t *x); int
md_get_uint32le(struct mdchain *mdp, uint32_t *x); int
md_get_int64(struct mdchain *mdp, int64_t *x); int
md_get_int64be(struct mdchain *mdp, int64_t *x); int
md_get_int64le(struct mdchain *mdp, int64_t *x); int
md_get_mem(struct mdchain *mdp, caddr_t target, int size, int type); int
md_get_mbuf(struct mdchain *mdp, int size, struct mbuf **m); int
md_get_uio(struct mdchain *mdp, struct uio *uiop, int size);
DESCRIPTION
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
- (struct mbuf *) A pointer to the top of the parsed mbuf chain.
- md_cur
- (struct mbuf *) A pointer to the currently parsed mbuf.
- md_pas
- (int) Offset in the current mbuf.
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.
NULL, an actual copy is not performed and
the function just skips the given number of bytes.
RETURN VALUES
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.EXAMPLES
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);
SEE ALSO
mbchain(9), mbuf(9)AUTHORS
This manual page was written by Boris Popov <[email protected]>.| February 28, 2001 | Debian |