#define INCL_DOSPROCESS USHORT rc = DosSetPrty(Scope, PriorityClass, PriorityDelta, ID); USHORT Scope; /* Indicate scope of change */ USHORT PriorityClass; /* Priority class to set */ SHORT PriorityDelta; /* Priority delta to apply */ USHORT ID; /* Process or thread ID */ USHORT rc; /* return code */
Example
The following example illustrates how to obtain the priority of a thread and how to change the priority. The main thread creates Thread2 and allows it to begin executing. Thread2 iterates through a loop that prints a line and then sleeps, relinquishing its time slice to the main thread. After one or two iterations by Thread2, the main thread obtains Thread2's priority information and prints it. It then raises Thread2's priority to fixed-high, and increments the level by ten. Since Thread2 is now at a high priority, it immediately finishes its remaining iterations before relinquishing control on a long sleep; at this point, the main thread re-examines Thread2's priority and reports its new priority level. In this example, it is helpful to understand how the DosSleep calls are used either to relinquish control of the processor, or to keep a thread alive (see DosTimerAsync or DosTimerStart for alternatives to DosSleep).
#define INCL_DOSPROCESS
#include <os2.h>
#define PRTYC_FIXEDHIGH 4 /* Priority class: fixed-high */
#define PRTY_DELTA 10 /* Priority delta: increase
by 10 */
#define SEGSIZE 4000 /* Number of bytes requested in
segment */
#define ALLOCFLAGS 0 /* Segment allocation flags - no
sharing */
#define SLEEPSHORT 0L /* Sleep interval -
5 milliseconds */
#define SLEEPLONG 20L /* Sleep interval -
75 milliseconds */
#define RETURN_CODE 0 /* Return code for DosExit() */
VOID APIENTRY Thread2()
{
USHORT i;
/* Loop with four iterations */
for(i=1; i<5; i++)
{
printf("In Thread2, i is now %d\n", i);
/** Sleep to relinquish time slice to main thread **/
DosSleep(SLEEPSHORT); /* Sleep interval */
}
DosExit(EXIT_THREAD, /* Action code - end a thread */
RETURN_CODE); /* Return code */
}
main()
{
USHORT Priority; /* Thread priority */
USHORT Class; /* Priority class */
USHORT Level; /* Priority level */
SEL ThreadStackSel; /* Segment selector for thread stack */
PBYTE StackEnd; /* Ptr. to end of thread stack */
USHORT rc;
/* Allocate segment for thread stack; this is better than just */
/* declaring an array of bytes to use as a stack. Make pointer eos. */
rc = DosAllocSeg(SEGSIZE, /* Number of bytes
requested */
&ThreadStackSel, /* Segment selector
(returned) */
ALLOCFLAGS); /* Allocation flags */
StackEnd = MAKEP(ThreadStackSel, SEGSIZE-1);
/* Start Thread2 */
if(!(DosCreateThread((PFNTHREAD) Thread2, /* Thread address */
&ThreadID, /* Thread ID (returned) */
StackEnd))) /* End of thread stack */
printf("Thread2 created.\n");
/** Sleep to allow Thread2 to execute **/
if(!(DosSleep(SLEEPLONG))) /* Sleep interval */
printf("Slept a little to let Thread2 execute.\n");
/** Obtain Thread2's priority information and report it **/
if(!(rc=DosGetPrty(PRTYS_THREAD, /* Scope - single
thread */
&Priority, /* Address to put
priority */
ThreadID))) /* ID - thread ID */
{
/* Extract priority class and level information */
Class = HIBYTE(Priority);
Level = LOBYTE(Priority);
printf("Thread2: ID is %d, Priority Class is %d and Level is %d\n",
ThreadID, Class, Level);
}
/** Raise Thread2's priority **/
if(!(rc=DosSetPrty(PRTYS_THREAD, /* Scope - single thread */
PRTYC_FIXEDHIGH, /* Prty class -
fixed-high */
PRTY_DELTA, /* Prty delta - increase
by 10 */
ThreadID))) /* ID - thread ID */
{
/* Obtain Thread2' new priority information and report it */
rc=DosGetPrty(PRTYS_THREAD, /* Scope - single thread */
&Priority, /* Address to put
priority */
ThreadID); /* ID - thread ID */
/* Extract priority class and level information */
Class = HIBYTE(Priority);
Level = LOBYTE(Priority);
printf("Thread2: ID is %d, New Priority Class is %d and Level is %d\n",
ThreadID, Class, Level);
}
}