costat

costat

Return Coprocess Status

SYNOPSIS
DESCRIPTION
RETURN VALUE
CAUTION
EXAMPLE

SYNOPSIS

#include <coproc.h>

int costat(coproc_t id);

DESCRIPTION

The costat function returns information about the status of a coprocess. The id argument is the ID of the coprocess whose status is desired.

RETURN VALUE

The value returned by costat is one of the symbolic constants STARTING , ACTIVE , BUSY , IDLE , or ENDED . These constants have the following significance:

STARTING: indicates that the coprocess has been created by a call to costart but has never been cocalled.
ACTIVE: indicates that the coprocess is the one currently running.
BUSY: indicates that the coprocess has cocalled another coprocess and therefore has been suspended by the cocall function. A BUSY coprocess cannot be cocalled itself.
IDLE: indicates that the coprocess is suspended by a call to coreturn . The coprocess will not execute again until it is cocalled.
ENDED: indicates that the coprocess has terminated.

CAUTION

The effects of passing an invalid coprocess ID to costat are unpredictable. Usually, this causes the value ENDED to be returned.

EXAMPLE

#include <stddef.h>
#include <coproc.h>
#include <stdlib.h>

coproc_t err_proc;

/* Cocall the coprocess whose ID is in the variable err_proc. But  */
/* abort instead if that coprocess cannot be legally cocalled.     */
switch (costat(err_proc)) {
   case STARTED:
   case IDLE:
      cocall(err_proc,NULL);       /* Call the error coprocess if  */
      break;                       /* this is legal.               */
   default:
      abort();                     /* Abort if error coprocess not */
}                                 /* available for cocall.         */

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