Platform SDK: Windows Sockets |
The WSPGetOverlappedResult function returns the results of an overlapped operation on the specified socket.
BOOL WSPGetOverlappedResult ( SOCKET s, LPWSAOVERLAPPED lpOverlapped, LPDWORD lpcbTransfer, BOOL fWait, LPDWORD lpdwFlags, LPINT lpErrno );
If WSPGetOverlappedResult succeeds, the return value is TRUE. This means the overlapped operation has completed successfully and the value pointed to by lpcbTransfer has been updated. If WSPGetOverlappedResult returns FALSE, this means that the overlapped operation has not completed or the overlapped operation completed but with errors, or completion status could not be determined due to errors in one or more parameters to WSPGetOverlappedResult. On failure, the value pointed to by lpcbTransfer will not be updated. The lpErrno parameter indicates the cause of the failure (either of WSPGetOverlappedResult or of the associated overlapped operation).
The results reported by the WSPGetOverlappedResult function are those of the specified socket's last overlapped operation to which the specified WSAOVERLAPPED structure was provided, and for which the operation's results were pending. A pending operation is indicated when the function that started the operation returns SOCKET_ERROR, and the lpErrno is WSA_IO_PENDING. When an I/O operation is pending, the function that started the operation resets the hEvent member of the WSAOVERLAPPED structure to the nonsignaled state. Then, when the pending operation has been completed, the system sets the event object to the signaled state.
If the fWait parameter is TRUE, WSPGetOverlappedResult determines whether the pending operation has been completed by blocking and waiting for the event object to be in the signaled state. A client may set the fWait parameter to TRUE only if it selected event-based completion notification when the I/O operation was requested. If another form of notification was selected, the usage of the hEvent member of the WSAOVERLAPPED structure is different, and setting fWait to TRUE causes unpredictable results.
The behavior of WPUCompleteOverlappedRequest places some constraints on how a service provider implements WSPGetOverlappedResult since only the Offset and OffsetHigh members of the WSAOVERLAPPED structure are exclusively controlled by the service provider even though three values (byte count, flags, and error) must be retrieved from the structure by WSPGetOverlappedResult. A service provider may accomplish this any way it chooses as long as it interacts with the behavior of WPUCompleteOverlappedRequest properly. The following description presents a typical implementation:
At the start of overlapped processing, the service provider sets Internal to WSS_OPERATION_IN_PROGRESS.
When the I/O operation is complete, the provider sets OffsetHigh to the Windows Sockets 2 error code resulting from the operation, sets Offset to the flags resulting from the I/O operation, and calls WPUCompleteOverlappedRequest, passing the transfer byte count as one of the parameters. WPUCompleteOverlappedRequest eventually sets InternalHigh to the transfer byte count, then sets Internal to a value other than WSS_OPERATION_IN_PROGRESS.
When WSPGetOverlappedResult is called, the service provider checks Internal. If it is WSS_OPERATION_IN_PROGRESS, the provider waits on the event handle in the hEvent member or returns an error, based on the setting of the fWait flag of WSPGetOverlappedResult. If not in progress, or after completion of waiting, the provider returns the values from InternalHigh, OffsetHigh, and Offset as the transfer count, operation result error code, and flags respectively.
Error code | Meaning |
---|---|
WSAENETDOWN | Network subsystem has failed. |
WSAENOTSOCK | Descriptor is not a socket. |
WSA_INVALID_HANDLE | The hEvent member of the WSAOVERLAPPED structure does not contain a valid event object handle. |
WSA_EINVAL | One of the parameters is unacceptable. |
WSA_IO_INCOMPLETE | The fWait parameter is FALSE and the I/O operation has not yet completed. |
Version: Requires Windows Sockets 2.0.
Header: Declared in Ws2spi.h.
WSPRecv, WSPRecvFrom, WSPSend, WSPSendTo, WSPConnect, WSPAccept, WSPIoctl, WPUCompleteOverlappedRequest