DosQueryMuxWaitSem: Difference between revisions

Latest revision as of 18:54, 1 December 2018

DosQueryMuxWaitSem returns the semaphore records of the MuxWait semaphore referred to by hmuxSemaphore.

Syntax

rc = DosQueryMuxWaitSem( hmuxSemaphore,
                         pulSemaphoreRecords,
                         pSemaphoreRecord,
                         pflAttributes );

Parameters

HMUX hmuxSemaphore (input): The handle of the MuxWait semaphore to be queried.
PULONG pulSemaphoreRecords (input/output): For input, this points to a ULONG that contains the number of SEMRECORDs that may be returned in the SEMRECORD structure pointed to by

pSemaphoreRecord.

If this value is not enough to contain all SEMRECORDs from the MuxWait list then ERROR_PARAM_TOO_SMALL is returned and this value points to the number of records in the MuxWait list. For output, this value points to the number of SEMRECORDs actually returned.

PSEMRECORD pSemaphoreRecord (output)

A pointer to a buffer that will get the SEMRECORDs.

PULONG pflAttributes (output)

The attribute flags that were specified when this MuxWait semaphore was created.

DC_SEM_SHARED indicates the semaphore is shared.
DCMW_WAIT_ANY indicates the semaphore will unblock if any of the semaphores in the MuxWait list either post or release.
DCMW_WAIT_ALL indicates the semaphore will unblock only if all of the semaphores in the MuxWait list either post or release.

Returns

APIRET rc: The following values can be returned; 0: NO_ERROR - Operation successful; 6: ERROR_INVALID_HANDLE - Error, The value in phmuxSemaphore 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, Both pszSemaphoreName and phmuxSemaphore may be NULL; 105: ERROR_SEM_OWNER_DIED - Error, The owner of the semaphore has died without freeing the semaphore; 289: ERROR_PARAM_TOO_SMALL - Error, The value pointed to by pulSemaphoreRecords is too small

Gotchas

The process calling DosQueryMuxWaitSem must first obtain access to the semaphore in question or ERROR_INVALID_HANDLE will be returned.

Sample Code

#define INCL_DOSSEMAPHORES
#include <os2.h>

HMUX      hmuxMySemaphore;   /* my semaphore handle */
ULONG     ulNumSemRecords=1; /* will get the request count for the sem */
SEMRECORD SemRecord;         /* single SEMRECORD structure */
PULONG    pflAttribs;        /* pointer to attribute flags */

 /* access is gained to the semaphore in question
    either by DosCreateMuxWaitSem or by DosOpenMuxWaitSem
    its handle is placed in hmuxMySemaphore */

	rc = DosQueryMuxWaitSem( hmuxMySemaphore,
	                         ulNumSemRecords,
	                        &SemRecord,
	                        &pflAttribs );

	if (rc != 0)
	{
	  /* We got an error to take care of. */
	}

@@ Line 19: / Line 19: @@
 === Returns ===
- APIRET rc
+;APIRET rc:The following values can be returned
-The following values can be returned
+:0: NO_ERROR - Operation successful
-{|class="wikitable"
+:6: ERROR_INVALID_HANDLE - Error, The value in ''phmuxSemaphore'' does not point to a valid semaphore
-|-
+:8: ERROR_NOT_ENOUGH_MEMORY - Error, The system memory limit has been exceeded
-|0
+:87: ERROR_INVALID_PARAMETER - Error, One or more parameters is not recognized, See parameters above, Both ''pszSemaphoreName'' and ''phmuxSemaphore'' may be NULL
-|NO_ERROR
+:105: ERROR_SEM_OWNER_DIED - Error, The owner of the semaphore has died without freeing the semaphore
-|Operation
+:289: ERROR_PARAM_TOO_SMALL - Error, The value pointed to by ''pulSemaphoreRecords'' is too small
-successful
-|-
-|6
-|ERROR_INVALID_HANDLE
-|Error, The value in ''phmuxSemaphore'' 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,
-Both ''pszSemaphoreName'' and ''phmuxSemaphore'' may be NULL
-|-
-|105
-|ERROR_SEM_OWNER_DIED
-|Error, The owner of the semaphore has died without freeing the
-semaphore
-|-
-|289
-|ERROR_PARAM_TOO_SMALL
-|Error, The value pointed to by ''pulSemaphoreRecords'' is too
-small
-|}
-=== Include Info ===
- #define INCL_DOSSEMAPHORES
- #include <os2.h>
 === Gotchas ===
@@ Line 63: / Line 33: @@
 <pre>
 #define INCL_DOSSEMAPHORES
-#include
+#include <os2.h>
-HMUX  hmuxMySemaphore;     /* my semaphore handle */
+HMUX      hmuxMySemaphore;   /* my semaphore handle */
-ULONG ulNumSemRecords=1;   /* will get the request count for the sem */
+ULONG     ulNumSemRecords=1; /* will get the request count for the sem */
-SEMRECORD SemRecord;       /* single SEMRECORD structure */
+SEMRECORD SemRecord;         /* single SEMRECORD structure */
-PULONG pflAttribs;         /* pointer to attribute flags */
+PULONG    pflAttribs;        /* pointer to attribute flags */
-	/* access is gained to the semaphore in question */
+ /* access is gained to the semaphore in question
-	/* either by DosCreateMuxWaitSem ... */
+    either by DosCreateMuxWaitSem or by DosOpenMuxWaitSem
-	/* ... or by DosOpenMuxWaitSem */
+    its handle is placed in hmuxMySemaphore */
-	/* its handle is placed in hmuxMySemaphore */
-	rc = DosQueryMuxWaitSem(  hmuxMySemaphore,
+	rc = DosQueryMuxWaitSem( hmuxMySemaphore,
-	                          ulNumSemRecords,
+	                         ulNumSemRecords,
-	                          &SemRecord,
+	                        &SemRecord,
-	                          &pflAttribs );
+	                        &pflAttribs );
 	if (rc != 0)