WPUQueryBlockingCallback function

The WPUQueryBlockingCallback function returns a pointer to a callback function the service provider should invoke periodically while servicing blocking operations.

Syntax


int WPUQueryBlockingCallback(
  _In_  DWORD              dwCatalogEntryId,
  _Out_ LPBLOCKINGCALLBACK *lplpfnCallback,
  _Out_ PDWORD_PTR         lpdwContext,
  _Out_ LPINT              lpErrno
);

Parameters

dwCatalogEntryId [in]

Descriptor identifying the calling service provider.

lplpfnCallback [out]

Pointer that receives the blocking callback function.

lpdwContext [out]

Pointer that receives a context value that the service provider must pass into the blocking callback.

lpErrno [out]

Pointer to the error code.

Return value

If no error occurs, WPUQueryBlockingCallback returns zero and stores a pointer to a blocking callback function in lpfnCallback and an associated context value in lpdwContext. Otherwise, it returns SOCKET_ERROR, and a specific error code is available in lpErrno.

Error codeMeaning
WSAEFAULT

The lpfnCallback or the lpdwContext parameter is not a valid part of the process address space.

WSAEINVAL

The dwCatalogEntryId parameter is invalid.

 

 

Remarks

The WPUQueryBlockingCallback function returns a pointer to a callback function in lpfnCallback to be invoked periodically during blocking operations. This function also returns a context value in lpdwContext to be passed into the blocking callback.

In Windows, this function can return null in lpfnCallback, indicating that no user defined–blocking hook is installed. In this case, the service provider should use the native Windows synchronization objects to implement blocking.

LPBLOCKINGCALLBACK is defined as follows:


typedef BOOL ( CALLBACK FAR * LPBLOCKINGCALLBACK )( DWORD dwContext );


The blocking callback will return TRUE if the service provider is to continue waiting for the blocking operation to complete. It will return FALSE if the blocking operation has been canceled with the WSPCancelBlockingCall.

Any missing components of the address will default to a reasonable value if possible. For example, a missing port number will default to zero.

Requirements

Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]

Header

Ws2spi.h

See also

WSPCancelBlockingCall

 

 

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