Copyright (c) 2001 Boris Popov
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$FreeBSD: releng/10.2/share/man/man9/mdchain.9 231564 2012-02-12 18:29:56Z ed $
.Dd February 28, 2001 .Dt MDCHAIN 9 .Os .Sh NAME .Nm mdchain , .Nm md_initm , .Nm md_done , .Nm md_append_record , .Nm md_next_record , .Nm md_get_uint8 , .Nm md_get_uint16 , .Nm md_get_uint16be , .Nm md_get_uint16le , .Nm md_get_uint32 , .Nm md_get_uint32be , .Nm md_get_uint32le , .Nm md_get_int64 , .Nm md_get_int64be , .Nm md_get_int64le , .Nm md_get_mem , .Nm md_get_mbuf , .Nm md_get_uio .Nd "set of functions to dissect an mbuf chain to various data types" .Sh SYNOPSIS .Cd options LIBMCHAIN .Li kldload libmchain
p n sys/param.h n sys/uio.h n sys/mchain.h .Ft void .Fn md_initm "struct mdchain *mdp" "struct mbuf *m" .Ft void .Fn md_done "struct mdchain *mdp" .Ft void .Fn md_append_record "struct mdchain *mdp" "struct mbuf *top" .Ft int .Fn md_next_record "struct mdchain *mdp" .Ft int .Fn md_get_uint8 "struct mdchain *mdp" "uint8_t *x" .Ft int .Fn md_get_uint16 "struct mdchain *mdp" "uint16_t *x" .Ft int .Fn md_get_uint16be "struct mdchain *mdp" "uint16_t *x" .Ft int .Fn md_get_uint16le "struct mdchain *mdp" "uint16_t *x" .Ft int .Fn md_get_uint32 "struct mdchain *mdp" "uint32_t *x" .Ft int .Fn md_get_uint32be "struct mdchain *mdp" "uint32_t *x" .Ft int .Fn md_get_uint32le "struct mdchain *mdp" "uint32_t *x" .Ft int .Fn md_get_int64 "struct mdchain *mdp" "int64_t *x" .Ft int .Fn md_get_int64be "struct mdchain *mdp" "int64_t *x" .Ft int .Fn md_get_int64le "struct mdchain *mdp" "int64_t *x" .Ft int .Fn md_get_mem "struct mdchain *mdp" "caddr_t target" "int size" "int type" .Ft int .Fn md_get_mbuf "struct mdchain *mdp" "int size" "struct mbuf **m" .Ft int .Fn md_get_uio "struct mdchain *mdp" "struct uio *uiop" "int size" .Sh DESCRIPTION These functions are used to decompose mbuf chains to various data types. The .Vt mdchain structure is used as a working context and should be initialized through a call of the .Fn mb_initm function. It has the following fields: l -tag -width "md_top" t Va "md_top"
q Vt "struct mbuf *" A pointer to the top of the parsed mbuf chain. t Va md_cur
q Vt "struct mbuf *" A pointer to the currently parsed mbuf. t Va md_pas
q Vt int Offset in the current mbuf. .El
p The .Fn md_done function disposes of an mbuf chain pointed to by the .Fa mdp->md_top field and sets the field to .Dv NULL .
p The .Fn md_append_record appends a new mbuf chain using .Va m_nextpkt field to form a single linked list of mbuf chains. If the .Fa mdp->md_top field is .Dv NULL , then this function behaves exactly as the .Fn md_initm function.
p The .Fn md_next_record function extracts the next mbuf chain and disposes the current one, if any. For a new mbuf chain it calls the .Fn md_initm function. If there is no data left the function returns .Er ENOENT .
p All .Fn md_get_* functions perform an actual copy of the data from an mbuf chain. Functions which have .Cm le or .Cm be suffixes will perform conversion to the little- or big-endian data formats.
p .Fn md_get_mem function copies .Fa size bytes of data specified by the .Fa source argument from an mbuf chain. The .Fa type argument specifies the method used to perform a copy, and can be one of the following: l -tag -width ".Dv MB_MINLINE" t Dv MB_MSYSTEM Use the .Fn bcopy function. t Dv MB_MUSER Use the .Xr copyin 9 function. t Dv MB_MINLINE Use an .Dq inline loop which does not call any function. .El
p If .Fa target is .Dv NULL , an actual copy is not performed and the function just skips the given number of bytes. .Sh RETURN VALUES All .Ft int functions return zero if successful, otherwise an error code is returned.
p .Em Note : after failure of any function, an mbuf chain is left in the broken state and only the .Fn md_done function can safely be called to destroy it. .Sh EXAMPLES d -literal 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); .Ed .Sh SEE ALSO .Xr mbchain 9 , .Xr mbuf 9 .Sh AUTHORS This manual page was written by .An Boris Popov Aq bp@FreeBSD.org .