IHostIoCompletionManager::GetHostOverlappedSize Method

Gets the size of any custom data the host intends to append to I/O requests.


HRESULT GetHostOverlappedSize (  
    [out] DWORD *pcbSize  


[out] A pointer to the number of bytes that the common language runtime (CLR) should allocate in addition to the size of the Win32 OVERLAPPED object.

Return Value

HRESULT Description
S_OK GetHostOverlappedSize returned successfully.
HOST_E_CLRNOTAVAILABLE The CLR has not been loaded into a process, or the CLR is in a state in which it cannot run managed code or process the call successfully.
HOST_E_TIMEOUT The call timed out.
HOST_E_NOT_OWNER The caller does not own the lock.
HOST_E_ABANDONED An event was canceled while a blocked thread or fiber was waiting on it.
E_FAIL An unknown catastrophic failure occurred. When a method returns E_FAIL, the CLR is no longer usable within the process. Subsequent calls to hosting methods return HOST_E_CLRNOTAVAILABLE.


All asynchronous I/O calls to Windows Platform APIs take a Win32 OVERLAPPED object, which provides information such as the file pointer position. To maintain state, applications that make asynchronous I/O calls typically add custom data to the structure. GetHostOverlappedSize and IHostIoCompletionManager::InitializeHostOverlapped provide an opportunity for the host to include such custom data.

The CLR calls the GetHostOverlappedSize method to determine the size of the custom data that the host intends to append to the OVERLAPPED object.


GetHostOverlappedSize is called only once. The host's custom data must be the same size for every I/O request.


The size of the OVERLAPPED object itself is not included in the value of pcbSize.

For more information about the OVERLAPPED structure, see the Windows Platform documentation.


Platforms: See System Requirements.

Header: MSCorEE.h

Library: Included as a resource in MSCorEE.dll

.NET Framework Versions: Available since 2.0

See Also

ICLRIoCompletionManager Interface
IHostIoCompletionManager Interface