DosOpenMutexSem

From EDM2
Jump to: navigation, search

Syntax

rc = DosOpenMutexSem( pszSemaphoreName, 
                      phmtxSemaphore );

Parameters

PSZ pszSemaphoreName (input)
This is a pointer to a null-terminated string containing the name of the semaphore to gain access to. If pszSemaphoreName equals NULL then the

handle contained in phmtxSemaphore will be used.

PHMTX phmtxSemaphore (input/output)
This is a pointer to the HMTX containing the handle of the semaphore to be opened. If the semaphore is to be opened by name using pszSemaphoreName then the input value of phmtxSemaphore must be NULL or

ERROR_INVALID_PARAMETER will be returned. On successful return of this function, phmtxSemaphore will point to a mutex handle (HMTX) containing the opened semaphore.

Returns

APIRET rc

The following values can be returned

0 NO_ERROR Semaphore opened successfully
6 ERROR_INVALID_HANDLE Error, The value in phmtxSemaphore does not point to a valid semaphore
8 ERROR_NOT_ENOUGH_MEMORY Error, The system memory limit has been exceeded
87 ERROR_INVALID_PARAMETER Error, One or more parameters is not recognized, See parameters above
105 ERROR_SEM_OWNER_DIED Error, The process that owns the semaphore has died before releasing it, DosQueryMutexSem can determine which process died
123 ERROR_INVALID_NAME Error, The name pointed to by pszSemaphoreName has been rejected by the file system
187 ERROR_SEM_NOT_FOUND Error, There is no semaphore with the name in pszSemaphoreName
291 ERROR_TOO_MANY_OPENS Error, The usage count for the semaphore in question has exceeded the system limit of 65535

Usage Explanation

DosOpenMutexSem gains access to a shared semaphore for the calling process. When access is granted to the calling process, DosOpenMutexSem increments, by one (1), the usage count for the semaphore pointed to by phmtxSemaphore or named in pszSemaphoreName.

Sample Code

#define INCL_DOSSEMAPHORES
#include <os2.h>

UCHAR SemName[15];
PHMTX phmtxMySemaphore= NULL; /* pointer to my semaphore handle */

	/* a shared mutex semaphore is successfully created in another process */
	/* its name happens to be \SEM32\MySem */

	strcpy(SemName,"\\SEM32\\MySem");

	rc = DosOpenMutexSem(SemName, phmtxMySemaphore);

	if (rc != 0)
	{
	  /* We got an error to take care of. */
	}
	else
	{
	  /* The semaphore was successfully opened */
	  /* it may be accessed via the handle pointer, phmtxMySemaphore */
	}

See Also