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The OS/2 API Project
DosWaitEventSem
[ Syntax |
Params |
Returns |
Include |
Usage |
Structs |
Gotchas |
Code |
Also ]
Syntax
rc = DosWaitEventSem( hevSemaphore,
ulTimeOut );
Parameters
- HEV hevSemaphore (input)
- The handle of the semaphore wait on.
- ULONG ulTimeout (input)
- The number of milliseconds the function will wait before
returning.
- Set to SEM_IMMEDIATE_RETURN (0), the function will
return immediately regardless of whether or not the semaphore
is posted.
- Set to SEM_INDEFINITE_WAIT (-1), the function will
block indefinitely (forever) until the semaphore is posted.
Returns
- APIRET rc
- The following values can be returned
| 0 | NO_ERROR | Successfully waited for the event semaphore to be posted to |
| 6 | ERROR_INVALID_HANDLE | Error, The value in phevSemaphore does not point to a valid semaphore, The calling process must first have access to the semaphore in question |
| 8 | ERROR_NOT_ENOUGH_MEMORY | Error, The system memory limit has been exhausted |
| 95 | ERROR_INTERRUPT | Error, The thread has become unblocked by an external event such as an exception, ownership has not been obtained |
| 640 | ERROR_TIMEOUT | Error, The caller was blocked for ulTimeout milliseconds but no post was issued within this time limit, Time has expired |
Include Info
#define INCL_DOSSEMAPHORES
#include <os2.h>
Usage Explanation
DosWaitEventSem blocks until the specified event semaphore is posted.
Event semaphores are edge-triggered. This means that if the semaphore is
posted and reset before a waiting thread has a chance to run, the waiting
thread will still act as though the semaphore is posted.
Relevant Structures
Gotchas
The process calling DosWaitEventSem must first obtain access to
the semaphore in question or ERROR_INVALID_HANDLE will be returned.
If the thread to be blocked, waiting on an event semaphore, is a PM thread,
WinWaitEventSem should be used instead
of DosWaitEventSem. This will allow the message queue thread to continue
processing.
Sample Code
<![CDATA[
#define INCL_DOSSEMAPHORES
#include <os2.h>
HEV hevMySemaphore; /* MySemaphore handle */
ULONG TimeOut= -1; /* the number of milliseconds the */
/* the caller will block for the sem */
/* this example will block forever */
/* access is gained to the semaphore in question */
/* either by DosCreateEventSem ... */
/* ... or by DosOpenEventSem */
/* its handle is placed in hevMySemaphore */
rc = DosWaitEventSem(hevMySemaphore, TimeOut);
if (rc != 0)
{
/* We got an error to take care of. */
}
]]>
See Also
DosCloseEventSem,
DosCreateEventSem,
DosOpenEventSem,
DosPostEventSem
DosQueryEventSem,
DosResetEventSem,
WinWaitEventSem
Author
Joe Phillips -
jaiger@eng2.uconn.edu
Additions
Last modified June 19/1996
Please send all errors, comments, and suggestions to:
timur@vnet.ibm.com
The OS/2 API Project |
DosWaitEventSem |