DosTimerAsync

This call starts a timer that runs asynchronously to the thread issuing the request and clears a system semaphore when the specified interval expires.

Syntax
DosTimerAsync (TimeInterval, SemHandle, Handle)

Parameters

 * TimeInterval (ULONG) - input : Number of milliseconds (rounded up to the next clock tick) that passes before the semaphore is cleared.
 * SemHandle (HSEM) - input : Handle of the system semaphore used to communicate the time out to the calling thread. This semaphore should be set by DosSemSet before DosTimerAsync is called.
 * Handle (PHTIMER) - output : Address of the timer handle. This handle may be passed to DosTimerStop to stop this timer before its time interval expires.

Return Code

 * rc (USHORT) - return:Return code descriptions are:
 * 0  NO_ERROR
 * 323 ERROR_TS_SEMHANDLE
 * 324 ERROR_TS_NOTIMER

Remarks
DosTimerAsync is used to wait for a single asynchronous time. The thread waits for the time out by issuing a DosSemWait.

This function is the asynchronous analog of DosSleep. This function allows a thread to start a timer while it is performing another task. This timer can be canceled by calling the DosTimerStop function with the timer handle returned by DosTimerAsync.

If another time out is needed, the semaphore is set and DosTimerAsync is reissued. To ensure reliable detection of the timer expiration, the system semaphore should be set prior to calling DosTimerAsync.

To set a periodic interval timer, see DosTimerStart.

Example Code
The following example sets an asynchronous one-shot timer for one second. It then sets an asynchronous recurring timer with a one-second interval, reporting each time an interval elapses. Finally, it stops the recurring timer. 
 * 1) define INCL_DOSDATETIME
 * 2) define INCL_DOSSEMAPHORES


 * 1) include 


 * 1) define SEM_NAME       "\\SEM\\timer.sem"  /* Semaphore name */
 * 2) define TIME_INTERVAL  1000L               /* Timer interval (in milliseconds) */

main { HSEM      SemHandle; HTIMER   TimerHandle; USHORT   i;  USHORT    rc;

/* Create system semaphore to be used by timers */ DosCreateSem(CSEM_PUBLIC,       /* Ownership - nonexclusive */               &SemHandle,         /* Semaphore handle (returned) */               SEM_NAME);          /* Semaphore name */

/* Set the semaphore, then start a one-shot timer */ if(!DosSemSet(SemHandle))       /* Semaphore handle */ printf("Semaphore set.\n"); if(!(rc=DosTimerAsync(TIME_INTERVAL,   /* Timer interval */                        SemHandle,        /* Semaphore handle */                        &TimerHandle)))   /* Timer handle (returned) */ printf("One shot timer for %f seconds started.\n", TIME_INTERVAL/1000.0);

/* Report when timer expires (other work may be done here) */ if(!DosSemWait(SemHandle,              /* Semaphore handle */ SEM_INDEFINITE_WAIT))   /* Timeout period - indefinite */ printf("Time interval has elapsed.\n");

/* Start a recurring timer */ if(!(rc=DosTimerStart(TIME_INTERVAL,   /* Timer interval */                        SemHandle,        /* Semaphore handle */                        &TimerHandle)))   /* Timer handle (returned) */ printf("Recurring timer with %f second interval started.\n",          TIME_INTERVAL/1000.0); /* */  for(i=1; i<4; i++) if(!DosSemSetWait(SemHandle,            /* Semaphore handle */ SEM_INDEFINITE_WAIT)) /* Timeout period - indefinite */ printf("Recurring timer cleared semaphore %d times.\n", i); if(!(rc=DosTimerStop(TimerHandle)))       /* Timer handle */ printf("Recurring timer has been stopped.\n"); } 

C

 * 1) define INCL_DOSDATETIME

USHORT rc = DosTimerAsync(TimeInterval, SemHandle, Handle);

ULONG  TimeInterval;  /* Interval size (in milliseconds) */ HSEM   SemHandle;     /* System semaphore handle */ PHTIMER Handle;       /* Timer handle (returned) */

USHORT rc;            /* return code */ 

MASM
 EXTRN DosTimerAsync:FAR INCL_DOSDATETIME   EQU 1

PUSH  DWORD   TimeInterval  ;Interval size (in milliseconds) PUSH  DWORD   SemHandle     ;System semaphore handle PUSH@ WORD    Handle        ;Timer handle (returned) CALL  DosTimerAsync

Returns WORD 