CreateWaitableTimer
[New
- Windows NT]
The CreateWaitableTimer
function creates a waitable timer object.
HANDLE CreateWaitableTimer(
|
LPSECURITY_ATTRIBUTES lpTimerAttributes, |
// pointer to
security attributes |
|
BOOL bManualReset, |
// flag for manual
reset state |
|
LPCTSTR lpTimerName |
// pointer to timer
object name |
|
); |
|
Parameters
lpTimerAttributes
Pointer to a SECURITY_ATTRIBUTES structure that specifies a
security descriptor for the new timer object and determines whether child
processes can inherit the returned handle. If lpTimerAttributes is NULL,
the timer object gets a default security descriptor and the handle cannot be
inherited.
bManualReset
Specifies the
timer type. If bManualReset is TRUE, the timer is a manual-reset
notification timer. Otherwise, the timer is a synchronization timer.
lpTimerName
Points to a
null-terminated string specifying the name of the timer object. The name is
limited to MAX_PATH characters and can contain any character except the
backslash path-separator character (\). Name comparison is case sensitive.
If the string specified in the lpTimerName parameter matches the
name of an existing named timer object, the call returns successfully and the GetLastError function returns
ERROR_ALREADY_EXISTS.
If lpTimerName is NULL, the timer object is created without a
name.
If lpTimerName matches the name of an existing event, semaphore,
mutex, or file-mapping object, the function fails and GetLastError
returns ERROR_INVALID_HANDLE. This occurs because event, semaphore, mutex,
file-mapping, and waitable-timer objects share the same name space.
Return Values
If the
function succeeds, the return value is a handle to the timer object. If the
named timer object exists before the function call, GetLastError returns
ERROR_ALREADY_EXISTS. Otherwise, GetLastError returns zero.
If the
function fails, the return value is NULL. To get extended error information,
call GetLastError.
Remarks
The handle
returned by CreateWaitableTimer is created with the TIMER_ALL_ACCESS
access right. This handle can be used in any function that requires a handle to
a timer object.
Any thread of
the calling process can specify the timer object handle in a call to one of the
wait functions.
Multiple
processes can have handles to the same timer object, enabling use of the object
for interprocess synchronization.
A process created by the CreateProcess function can inherit a
handle to a timer object if the lpTimerAttributes parameter of CreateWaitableTimer
enables inheritance.
A process can specify the timer
object handle in a call to the DuplicateHandle function. The resulting
handle can be used by another process.
A process can specify the name
of a timer object in a call to the OpenWaitableTimer or CreateWaitableTimer
function.
Use the CloseHandle
function to close the handle. The system closes the handle automatically when
the process terminates. The timer object is destroyed when its last handle has
been closed.
See Also