• Patrick Jeeves (73/73) Nov 21 2014 So I've been using an event range rather than an event loop or

"Patrick Jeeves" <pdj9 pitt.edu> writes:

So I've been using an event range rather than an event loop or 
event/listener system; because I realized I could process events 
more effectively using a recursive descent parser on them.  So I 
made this class to strip the events into different ranges and 
send them to different parsers:

auto demultiplex(alias attrFunc, string functional, Range)(Range 
r)
{
	alias attr = std.functional.unaryFun!(attrFunc);
	alias T    = ElementType!(Range);
	
	struct SlaveRange {
	private T**               _front;
	private Fiber _fiber;		
		this(T ** it) {	
			_front = it;
			_fiber = Fiber.getThis();
		}
		
		 property bool empty() const { return *_front is null; }
		 property T    front() const { return *(*_front); }
		          void popFront()    { _fiber.call(); }
	}
		
	struct MasterRange {
		private SlaveRange        _slave;
		private Range             _input;
		private T                 _cur;
		private T               * _front;
		private Fiber _fiber;
		
		private void run() {
			mixin("_slave." ~ functional ~ ";");
		}
		
		private void call() {
			if(_fiber.state != Fiber.State.TERM)
				_fiber.call();
		}
		
		this(Range ins) {
			_input = ins;
			_fiber = new Fiber(&run);
			_slave = &_front;
			popFront();
			_front = &_cur;
		}
		
		 property T    front() const { return *_front; }
		 property bool empty() const { return _front is null; }		
		
		void popFront()    {
			while(!_input.empty) {
				_cur = _input.front;
				_input.popFront();
				
				final switch(attr(_cur)) {
				case -1: break;
				case  0: return;
				case  1: call(); break;
				case  2: call(); return;
				}
			}			
			_front = null;
		}
	}

	return MasterRange(r);
}

the problem is that when the SlaveRange is constructed it needs 
to know the current fiber, but if it isn't called from a fiber 
then it returns null and can't switch back.  And I can't use 
yeild because I don't want to return to the calling fiber, that 
doesn't help me.