Leitores e escritores: solução equânime

 

 
class FairRW {

		 TicketQueue waiting;

		 int ticket = 0, nw = 0, nr = 0;

		 key mutex;

		 void requestRead() {

		 		 lock(mutex);

		 		 while((nw > 0)  (!waiting.iAmTheBest(myTicket))) {

		 		 		 waiting.enter(myTicket, mutex);

		 		 }

		 		 nr++;

		 		 waiting.ok(myTicket);

		 		 unlock(mutex);

		 }

		 void requestWrite() {

		 		 lock(mutex);

		 		 while((nw + nr > 0) 

		 		 		 		 (!waiting.iAmTheBest(myTicket))) {

		 		 		 waiting.enter(myTicket, mutex);

		 		 }

		 		 nw++;

		 		 waiting.ok(myTicket);

		 		 unlock(mutex);

		 }