NTDLL: implement NtSignalAndWaitForSingleObject

[Robert Shearman]

Mike McCormack wrote:

>
>> I think this is a little ugly. I'd prefer to see this code do a 
>> switch on obj->ops and call the relevant function with the raw object 
>> instead of a handle.
>
>
> I know it's ugly; I rewrote that bit three times, including once with 
> an ops->signal() method.  Implementing a object operation requires 
> that the 3 operations are consistent.  For example, the access flags 
> required to perform must be consistent, so the get_handle_obj can be 
> done only once.  Unfortunately, semaphores and event flags require 
> different permissions to execute ops->signal().


Ok, I see the problem now. The only alternative I can think of is to try 
to open the object with the GENERIC_WRITE access right and implement 
generic mappings for each object (these mappings are really needed 
anyway for other situaitons).

>> This seems to be pretty similar to select_on. Would it not be 
>> possible to use that function instead of duplicating that code?
>
>
> I considered that.  The problem is that we would have to signal the 
> object in the middle of the setup for select_on().  That means passing 
> new parameters to select_on(), and that function already looks a 
> little busy.


You could refactor the function so that the wait_on bit is separate. 
That seems to be the only thing you have to do before signalling the object.

Rob