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MBCHAIN (9) | Kernel routines | Unix Manual Pages | :man

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"

CONTENTS

Synopsis
Description
Return Values
Examples
See Also
Authors

SYNOPSIS


.Cd options LIBMCHAIN kldload libmchain


.In sys/param.h
.In sys/uio.h
.In 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

These functions are used to compose mbuf chains from various data types. The
.Vt 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" (Vt "struct mbuf *") A pointer to the top of constructed mbuf chain.
mb_cur (Vt "struct mbuf *") A pointer to the currently filled mbuf.
mb_mleft (Vt int) Number of bytes left in the current mbuf.
mb_count (Vt int) Total number of bytes placed in the mbuf chain.
mb_copy (Vt "mb_copy_t *") User-defined function to perform a copy into mbuf; useful if any unusual data conversion is necessary.
mb_udata (Vt "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

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


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


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