typedef struct _MUXSEMLIST { /* mxsl */
USHORT cmxs; /* count of MuxSem structures */
MUXSEM amxs[16]; /* MuxSem structure */
} MUXSEMLIST;
typedef struct _MUXSEM { /* mxs */
USHORT zero; /* zero */
HSEM hsem; /* semaphore handle */
} MUXSEM;
#define INCL_DOSSEMAPHORES
USHORT rc = DosMuxSemWait(IndexNbr, ListAddr, Timeout);
PUSHORT IndexNbr; /* Index number of event (returned) */
PVOID ListAddr; /* Semaphore list */
LONG Timeout; /* Timeout (in milliseconds) */
USHORT rc; /* return code */
Example
The following example illustrates notification of events between threads of the same process. The main thread sets two RAM semaphores and invokes two threads, each of which clears one of the semaphores. Meanwhile, the main thread waits for either of the two semaphores to clear, and then resumes execution, indicating the thread that notified first.
#define INCL_DOSPROCESS
#define INCL_DOSSEMAPHORES
#include<os2.h>
#include<stdio.h>
#define NUM_SEMS 2 /* Number of semaphores to wait on */
#define TIMEOUT 2000L /* Timeout period */
#define SLEEPTIME 1000L /* Sleep period for Thread_1 */
#define RETURN_CODE 0 /* Return Code for thread termination */
ULONG RamSem1 = 0L; /* Allocation and initialization of */
ULONG RamSem2 = 0L; /* two RAM semaphores */
ULONG far *RamSem1Handle = &RamSem1; /* Semaphore handles */
ULONG far *RamSem2Handle = &RamSem2;
TID ThreadID[2]; /* Thread Identification */
BYTE ThreadStack1[4000]; /* Thread Stack Area */
BYTE ThreadStack2[4000];
MUXSEMLIST SemList; /* Semaphore list structure */
USHORT IndexNbr; /* Index number for DosMuxSemWait */
USHORT rc; /* Return Code */
VOID APIENTRY Thread_1()
{
USHORT r;
printf("Begin Thread_1. It will sleep for 1 second. \n");
/* Give Thread_2 a chance to execute */
DosSleep(SLEEPTIME); /* Sleep Interval */
if(!(r=DosSemClear(RamSem1Handle))) /* Semaphore handle */
printf("RamSem1 cleared. \n");
DosExit(EXIT_THREAD, /* Action Code */
RETURN_CODE); /* Result Code */
}
VOID APIENTRY Thread_2()
{
USHORT r;
printf("Begin Thread_2. It will try to clear RamSem2 now. \n");
if(!(r=DosSemClear(RamSem2Handle))) /* Semaphore Handle */
printf("RamSem2 cleared. \n");
DosExit(EXIT_THREAD, /* Action Code */
RETURN_CODE); /* Result Code */
}
main()
{
USHORT rc; /* Return Code */
/* Set both semaphores */
if(!(rc=DosSemSet(RamSem1Handle))) /* Semaphore Handle */
printf("RamSem1 set. \n");
if(!(rc=DosSemSet(RamSem2Handle))) /* Semaphore Handle */
printf("RamSem2 set. \n");
/* Initialize Semaphore list structure */
SemList.cmxs = NUM_SEMS; /* Number of semaphores */
SemList.amxs[0].zero = 0; /* This field must be 0 */
SemList.amxs[1].zero = 0; /* This field must be 0 */
SemList.amxs[0].hsem = RamSem1Handle; /* Semaphore handle */
SemList.amxs[1].hsem = RamSem2Handle; /* Semaphore handle */
/* Start the two threads */
if(!(DosCreateThread((PFNTHREAD) Thread_1, /* Thread address */
&ThreadID[0], /* Thread ID
(returned) */
&ThreadStack1[3999]))) /* End of thread
stack */
printf("Thread_1 created. \n");
if(!(DosCreateThread((PFNTHREAD) Thread_2, /* Thread address */
&ThreadID[1], /* Thread ID
(returned) */
&ThreadStack2[3999]))) /* End of thread
stack */
printf("Thread_2 created. \n");
/* Wait for either semaphore to clear; then, indicate which */
/* thread notified first. */
if(!(DosMuxSemWait(&IndexNbr, /* Index of semaphore */
/* cleared (returned) */
&SemList, /* Address of sem. list structure */
TIMEOUT))) /* Timeout period */
printf("Back to main thread; semaphore cleared by Thread%d.\n",
IndexNbr + 1);
}
}