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CreateEvent
The CreateEvent function creates or opens a named or unnamed event object. HANDLE CreateEvent( LPSECURITY_ATTRIBUTES lpEventAttributes, BOOL bManualReset, BOOL bInitialState, LPCTSTR lpName ); Parameters
Return ValuesIf the function succeeds, the return value is a handle to the event object. If the named event object existed before the function call, the function returns a handle to the existing object and GetLastError returns ERROR_ALREADY_EXISTS. If the function fails, the return value is NULL. To get extended error information, call GetLastError. RemarksThe handle returned by CreateEvent has the EVENT_ALL_ACCESS access right and can be used in any function that requires a handle to an event object. For more information, see Synchronization Object Security and Access Rights. Any thread of the calling process can specify the event-object handle in a call to one of the wait functions. The single-object wait functions return when the state of the specified object is signaled. The multiple-object wait functions can be instructed to return either when any one or when all of the specified objects are signaled. When a wait function returns, the waiting thread is released to continue its execution. The initial state of the event object is specified by the bInitialState parameter. Use the SetEvent function to set the state of an event object to signaled. Use the ResetEvent function to reset the state of an event object to nonsignaled. When the state of a manual-reset event object is signaled, it remains signaled until it is explicitly reset to nonsignaled by the ResetEvent function. Any number of waiting threads, or threads that subsequently begin wait operations for the specified event object, can be released while the object's state is signaled. When the state of an auto-reset event object is signaled, it remains signaled until a single waiting thread is released; the system then automatically resets the state to nonsignaled. If no threads are waiting, the event object's state remains signaled. Multiple processes can have handles of the same event object, enabling use of the object for interprocess synchronization. The following object-sharing mechanisms are available:
Use the CloseHandle function to close the handle. The system closes the handle automatically when the process terminates. The event object is destroyed when its last handle has been closed. Windows 95/98/Me: CreateEventW is supported by the Microsoft Layer for Unicode. To use this, you must add certain files to your application, as outlined in Microsoft Layer for Unicode on Windows 95/98/Me Systems. Example CodeFor an example that uses CreateEvent, see Using Event Objects.RequirementsWindows NT/2000/XP: Included in Windows NT 3.1 and
later. See AlsoSynchronization Overview, Synchronization Functions, CloseHandle, CreateProcess, DuplicateHandle, OpenEvent, ResetEvent, SECURITY_ATTRIBUTES, SetEvent, Object Names ![]() Platform SDK Release: August
2002
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