pSOSystem System Calls - Read

q_create pSOS+ System Calls
q_create Creates an ordinary message queue.
#include
unsigned long q_create(
char name[4], /* queue name */
unsigned long count, /* queue size */
unsigned long flags, /* queue attributes */
unsigned long *qid /* queue identifier */
)
Description
Arguments
This system call creates an ordinary message queue by allocating and initializing a
Queue Control Block (QCB) according to the specifications supplied with the call.
Like all objects, a queue has a user-assigned name and a pSOS-assigned queue ID
returned by q_create(). Several flag bits specify the characteristics of the
message queue. Tasks can wait for messages either by task priority or strictly FIFO,
and a limit can be optionally set on the maximum number of messages that can be
simultaneously posted at the queue.
name Specifies the user-assigned name of the new message queue.
count If Q_LIMIT is set (see flags, below), then the count argument
specifies the maximum number of messages that can be
simultaneously posted at the queue. If Q_PRIBUF is also set, then the
argument count also specifies the number of buffers set aside from
the system-wide pool of message buffers for the private use of this
queue. If Q_NOLIMIT is set, count is ignored.
flags Specifies the attributes of the queue. flags is formed by OR-ing the
following symbolic constants (one from each pair), which are defined
in . For instance, to specify that the queue is globally
addressable, you place Q_GLOBAL in flags. To specify that the queue
is globally addressable and that tasks are queued by FIFO, you place
Q_GLOBAL and Q_FIFO in flags, using the following syntax:
Q_GLOBAL | Q_FIFO
1-74 pSOSystem System Calls