osx man page for wr

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

NAME
       WR, wr - get pointer to the write queue for this module or driver

SYNOPSIS
       #include <sys/stream.h>
       #include <sys/ddi.h>

       queue_t *WR(queue_t *q);

INTERFACE LEVEL
       Architecture independent level 1 (DDI/DKI).

PARAMETERS
       q        Pointer to the read queue whose  write queue is to be returned.

DESCRIPTION
       The WR() function accepts a read queue pointer as an argument and returns a pointer to the write queue of the same module.

       CAUTION: Make sure the argument to this function is a pointer to a read queue. WR() will not check for queue type, and a system panic could
       result if the pointer is not to a read queue.

RETURN VALUES
       The pointer to the write queue.

CONTEXT
       WR() can be called from user or interrupt context.

EXAMPLES
       Example 1: Using WR()

       In a STREAMS close(9E) routine, the driver or module is passed a pointer to the read queue.  These usually are set to the  address  of  the
       module-specific data structure for the minor device.

       1   xxxclose(q, flag)
       2       queue_t *q;
       3       int flag;
       4   {
       5             q->q_ptr = NULL;
       6         WR(q)->q_ptr = NULL;
                     . . .
       7   }

SEE ALSO
       close(9E), OTHERQ(9F), RD(9F)

       Writing Device Drivers

       STREAMS Programming Guide

SunOS 5.10                                                          15 Nov 1991                                                             WR(9F)