samestr.9

7号信令功能代码,为开源代码

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.\" @(#) SAMESTR.9,v 1.1.4.1 2004/01/12 23:32:57 brian Exp
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.TH SAMESTR 9 "2004/01/12 23:32:57" "LiS-2_16_18-8" "Linux STREAMS DDI/DKI"
.SH NAME
.B SAMESTR
\- test for \fISTREAMS\fR pipe or fifo
.SH SYNOPSIS
.PP
.B #include <sys/stream.h>
.HP 8
.BI "int " retval " = SAMESTR(" q );
.SH DESCRIPTION
.PP
.BR SAMESTR ()
tests whether the next queue belongs to the same stream as the specified
queue
.IR q .
.BR SAMESTR ()
can be used to detect whether or not
.I q
belongs to a
.BR pipe (3)
or a
.BR fifo (4).
.SH "RETURN VALUES"
.PP
.BR SAMESTR ()
returns true (1) if the next queue from the specified queue,
.IR q->q_next ,
belongs to the same stream (read or write) as the specified queue
.IR q .
In this case, the queue
.I q
is not a
.BR pipe (3)
or
.BR fifo (4).
.PP
.BR SAMESTR ()
returns false (0) if the next queue from the specified queue,
.IR q->q_next ,
belongs to a different stream (read or write) as the specified queue
.IR q .
In this case, the queue
.I q
is a
.BR pipe (3)
or
.BR fifo (4).
.SH ERRORS
.PP
When
.BR SAMESTR ()
fails, it returns
zero (0).
.BR SAMESTR ()
fails when the queue pointer
.I q
is
.BR NULL ;
.I q
does not point to a valid queue structure;
.I q->q_next
is
.BR NULL ;
.I q->q_next
does not point to a valid queue structure.
.SH CAVEATS
.PP
.B LiS
.[
LiS
.]
implements
.BR SAMESTR ()
as a function rather than as the more obvious
macro:
.sp
.nf
#define SAMESTR(__q) (__q->q_flag & QREADR) == (__q->q_next->q_flag & QREADR)
.fi
.PP
The
.B LiS
.[
LiS
.]
function call is inefficient, particularly as this function is called often
and regularly.
.SH "SEE ALSO"
.PP
.BR RD (9),
.BR WR (9),
.BR OTHER (9).
.SH VERSIONS
.PP
This manpage was written for
.B LiS\c
.
.[
LiS
.]
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