int canputnext(queue_t *q);
int bcanputnext(queue_t *q, unsigned char pri);
Architecture independent level 1 (DDI/DKI).
q Pointer to a message queue belonging to the invoking module.
pri Minimum priority level.
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 interference 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); respectively.
See canput(9F) and bcanput(9F) for further details.
1 If the message queue is not full.
0 If the queue is full.
The canputnext() and bcanputnext() functions can be called from user, interrupt, or kernel context.
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.
Writing Device Drivers
STREAMS Programming Guide