WPUQueryBlockingCallback function (ws2spi.h)

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

[in] dwCatalogEntryId

Descriptor identifying the calling service provider.

[out] lplpfnCallback

Pointer that receives the blocking callback function.

[out] lpdwContext

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

[out] lpErrno

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 code Meaning
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

Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header ws2spi.h

See also

WSPCancelBlockingCall