freebsd man page for canputnext

canputnext(9F)						   Kernel Functions for Drivers 					    canputnext(9F)

NAME

       canputnext, bcanputnext - test for room in next module's message queue

SYNOPSIS

       #include <sys/stream.h>

       int canputnext(queue_t *q);

       int bcanputnext(queue_t *q, unsigned char pri);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       q	Pointer to a message queue belonging to the invoking module.

       pri	Minimum priority level.

DESCRIPTION

       The  invocation	canputnext(q); is an atomic equivalent of the canput(q->q_next); routine. That is, the STREAMS framework provides whatever
       mutual exclusion is necessary to insure that dereferencing q through its q_next field and then invoking canput(9F) proceeds without  inter-
       ference from other threads.

       bcanputnext(q, pri); is the equivalent of the bcanput(q->q_next, pri); routine.

       canputnext(q);  and  bcanputnext(q,  pri);  should  always be used in preference to canput(q->q_next); and bcanput(q->q_next, pri); respec-
       tively.

       See canput(9F) and bcanput(9F) for further details.

RETURN VALUES

       1	If the message queue is not full.

       0	If the queue is full.

CONTEXT

       canputnext() and bcanputnext() can be called from user or interrupt context.

WARNINGS

       Drivers are responsible for both testing a queue with canputnext() or bcanputnext() and refraining from placing a message on the  queue	if
       the queue is full.

SEE ALSO

       bcanput(9F), canput(9F)

       Writing Device Drivers

       STREAMS Programming Guide

SunOS 5.10							    31 Jan 1993 						    canputnext(9F)