User`s guide

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WinHLLAPICancelBlockingCall( )
This function cancels any outstanding blocking operation for its thread. Any outstanding blocked call
canceled will cause an error code of WHLLCANCEL to be generated. Examples of blocking calls are
WinHLLAPI with function number set to GETKEY, WAIT, PAUSE, SENDFILE or RECEIVEFILE.
You should use WinHLLAPIAsync( ) instead of the blocking versions of these functions.
Under Windows NT, a multi-threaded application may have multiple blocking operations outstanding;
but only one per thread. To distinguish between multiple outstanding calls,
WinHLLAPICancelBlockingCall cancels the outstanding operation on the current (i.e. calling)
application thread if one exists; otherwise it fails. By default under Windows NT, WinHLLAPI will
suspend the calling application thread while an operation is outstanding. As a result, the thread on
which the blocking operation was initiated will not regain control ( and hence will not be able to issue a
call to WinHLLAPICancelBlockingCall) unless a blocking hook is registered for the thread using
WinHLLAPISetBlockingHook. This condition does not apply to Windows version 3.x since
applications only have one effective thread and the default blocking hook is registered by default.
int WinHLLAPICancelBlockingCall(void)
The return value indicates whether the cancellation request was successful. It is zero if the operation
was successful; otherwise it is one of the following return codes:
WHLLINVALID Indicates that there is no outstanding blocking call.
See also: WinHLLAPICancelAsyncRequest( )
Syntax
Returns