copymsg.9

7号信令功能代码,为开源代码

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.TH COPYMSG 9 "2004/01/12 23:32:59" "LiS-2_16_18-8" "Linux STREAMS DDI/DKI"
.SH NAME
.B copymsg
\- copy a \fISTREAMS\fR message
.SH SYNOPSIS
.PP
.B #include <sys/stream.h>
.HP 8
.BR "struct msgb *" msg " = copymsg(struct msgb *" mp );
.SH DESCRIPTION
.PP
.BR copymsg ()
generates a new copy of each of the message blocks and data blocks and buffers
in the message indicated by
.IR mp ,
and returns a pointer to the new message as
.IR msg .
The new data blocks each have the same type as the copied data blocks and the
.IR b_rptr " and " b_wptr
of each block in the new message are set to the beginning and end of the
copied data from the corresponding blocks in the old message.
.SH "RETURN VALUES"
.PP
Upon success,
.BR copymsg ()
returns a pointer,
.IR msg ,
to the copied message.
.PP
Upon failure,
.BR copymsg ()
returns a
.B NULL
.I msg
pointer.
.SH ERRORS
.PP
When
.BR copymsg ()
fails, it returns a
.B NULL
pointer.
.BR copymsg ()
can fail because the passed in message pointer,
.IR mp ,
is
.BR NULL ;
the size of any of the blocks to be copied has a negative message length (i.e.
the
.I b_wptr
pointer is less than the
.IR b_rptr );
if any of the data blocks are mangled (i.e. the
.I db_lim
pointer is less than the
.IR db_base );
or, memory allocation for any of the copied blocks fails.
.SH CAVEATS
.PP
.B LiS
.[
LiS
.]
copies each block from the copied message on a block by block basis using
.BR copyb (9).
.PP
Because the
.B LiS
.[
LiS
.]
implementaiton of
.BR copyb (9)
fails if the message block has a negative length (i.e.
.I b_wptr
is less than
.IR b_rptr),
.BR copymsg ()
will fail if any of the message blocks in the message to be copied has a
negative length (i.e. the
.I b_wptr
pointer is less than the
.IR b_rptr ),
or if any of the data blocks are mangled (i.e. the
.I db_lim
pointer is less than the
.IR db_base ).
.PP
This does not appear consistent with SVR 4.2 STREAMS.
.[
svr42
.]
.SH "SEE ALSO"
.PP
.BR copyb (9),
.BR dupb "(9) and "
.BR dupmsg (9).
.SH VERSIONS
.PP
.BR copymsg ()
first appeared in SVR 3.
.[
svr3
.]
.\"
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.XX
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.[
svr42
.]
.[
svr4
.]
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$LIST$
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