Got the sample working

assignment2_handout.c

@@ -49,6 +49,7 @@ typedef struct {
 	int waitingtogodown;    // The number of people waiting to go down
 	semaphore up_arrow;     // People going up wait on this
 	semaphore down_arrow;   // People going down wait on this
+	semaphore queueInteraction; // People can't all press a button at the same time
 } floor_info;
 
 // --------------------------------------------------
@@ -61,20 +62,27 @@ typedef struct {
 	int peopleinlift;             // The number of people in the lift
 	int stops[NFLOORS];           // How many people are going to each floor
 	semaphore stopsem[NFLOORS];   // People in the lift wait on one of these
+	semaphore load;
 } lift_info;
 
 // --------------------------------------------------
 // Some global variables
 // --------------------------------------------------
 floor_info floors[NFLOORS];
+lift_info* targetLift[NFLOORS];
+
+// Bound all printing to this semaphore
+semaphore printSemaphore;
 
 // --------------------------------------------------
 // Print a string on the screen at position (x,y)
 // --------------------------------------------------
 void print_at_xy(int x, int y, const char *s) {
+	semaphore_wait(&printSemaphore);
 	// Move cursor to (x,y)
 	gotoxy(x,y);
 	
+	
 	// Slow things down
 	Sleep(1);
 
@@ -83,6 +91,8 @@ void print_at_xy(int x, int y, const char *s) {
 	
 	// Move cursor out of the way
 	gotoxy(42, NFLOORS+2);
+	fflush(stdout);
+	semaphore_signal(&printSemaphore);
 }
 
 // --------------------------------------------------
@@ -120,7 +130,9 @@ void get_into_lift(lift_info *lift, int direction) {
 		// Check there are people waiting and lift isn't full
 		if(lift->peopleinlift < MAXNOINLIFT && *waiting) {
 			// Add person to the lift
+			semaphore_wait(&lift->load);
 			lift->peopleinlift++;
+			semaphore_signal(&lift->load);
 
 			// Erase the person from the waiting queue
 			print_at_xy(NLIFTS*4+floors[lift->position].waitingtogodown + floors[lift->position].waitingtogoup, NFLOORS-lift->position, " ");
@@ -130,12 +142,8 @@ void get_into_lift(lift_info *lift, int direction) {
 
 			// Wait for person to get into lift
 			Sleep(GETINSPEED);
-			//semaphore_wait(s);
+			targetLift[lift->position] = lift;
-			semaphore_wait(lift->stopsem);
+			semaphore_signal(s);
-			semaphore_signal(lift->stopsem);
-			//--//semaphore_signal(s);
-			// Set lift to enter
-			// Signal passenger to enter
 		 } else {
 			break;
 		}
@@ -157,6 +165,8 @@ void* lift_thread(void *p) {
 	lift.direction = UP;    // Lift starts going up
 	lift.peopleinlift = 0;  // Lift starts empty
 
+	semaphore_create(&lift.load, 1);
+
 	for(i = 0; i < NFLOORS; i++) {
 		lift.stops[i]=0;                        // No passengers waiting
 		semaphore_create(&lift.stopsem[i], 0);  // Initialise semaphores
@@ -169,7 +179,7 @@ void* lift_thread(void *p) {
 	Sleep(rnd(1000));
 
 	// Loop forever
-	while(1 == 1) {
+	while(TRUE) {
 		// Print current position of the lift
 		print_at_xy(no*4+1, NFLOORS-lift.position, lf);
 
@@ -179,14 +189,16 @@ void* lift_thread(void *p) {
 		// Drop off passengers on this floor
 		while (lift.stops[lift.position] != 0) {
 			// One less passenger in lift
+			semaphore_wait(&lift.load);
 			lift.peopleinlift--;
 
 			// One less waiting to get off at this floor
 			lift.stops[lift.position]--;
-			
+			semaphore_signal(&lift.load);
 			// Wait for exit lift delay
 			Sleep(GETOUTSPEED);
-			semaphore_signal(&lift.stopsem[i]);
+			
+			semaphore_signal(&lift.stopsem[lift.position]);
 			// Signal passenger to leave lift			
 
 			// Check if that was the last passenger waiting for this floor
@@ -234,50 +246,54 @@ void* person_thread(void *p) {
 	randomise();
 
 	// Stay in the building forever
-	while(1) {
+	while(TRUE) {
 		// Work for a while
 		Sleep(rnd(PEOPLESPEED));
 		do {
 			// Randomly pick another floor to go to
 			to = rnd(NFLOORS);
 		} while(to == from);
-
+		semaphore* s;
+		// Wait for our turn to press a button
+		semaphore_wait(&floors[from].queueInteraction);
 		// Check which direction the person is going (UP/DOWN)
 		if(to > from) {
 			// One more person waiting to go up
 			floors[from].waitingtogoup++;
-			
+			semaphore_signal(&floors[from].queueInteraction);
 			// Print person waiting
 			print_at_xy(NLIFTS*4+ floors[from].waitingtogoup +floors[from].waitingtogodown,NFLOORS-from, pr);
-			while (1){
+			s = &floors[from].up_arrow;
-				if (lift->direction == 0){
+			// Wait for a lift to arrive (going up)
-					lift
-				}
-			}
----			// Wait for a lift to arrive (going up)
 		} else {
 			// One more person waiting to go down
 			floors[from].waitingtogodown++;
-			
+			semaphore_signal(&floors[from].queueInteraction);
 			// Print person waiting
 			print_at_xy(NLIFTS*4+floors[from].waitingtogodown+floors[from].waitingtogoup,NFLOORS-from, pr);
-			
+			s = &floors[from].down_arrow;
----			// Wait for a lift to arrive (going down)
+			// Wait for a lift to arrive (going down)
 		}
+		// We've pressed our button
+		
+		semaphore_wait(s);
 		
 		// Which lift we are getting into
----		lift = ;
+		lift = targetLift[from];
 
 		// Add one to passengers waiting for floor
+		// Only one person enters at a time
+		semaphore_wait(&lift->load);
 		lift->stops[to]++;
-
+		semaphore_signal(&lift->load);
 		// Press button if we are the first
 		if(lift->stops[to]==1) {
 			// Print light for destination
 			print_at_xy(lift->no*4+1+2, NFLOORS-to, "-");
 		}
 
----		// Wait until we are at the right floor
+		semaphore_wait(&lift->stopsem[to]);
+		// Wait until we are at the right floor
 
 		// Exit the lift
 		from = to;
@@ -290,12 +306,14 @@ void* person_thread(void *p) {
 //	Print the building on the screen
 // --------------------------------------------------
 void printbuilding(void) {
+
 	// Local variables
 	int l,f;
 
 	// Clear Screen
 	system(clear_screen);
-	
+	// Print the whole building before anything else
+	semaphore_wait(&printSemaphore);
 	// Print Roof
 	printf("%s", tl);
 	for(l = 0; l < NLIFTS-1; l++) {
@@ -322,6 +340,9 @@ void printbuilding(void) {
 
 	// Print Message
 	printf("Lift Simulation - Press CTRL-Break to exit\n");
+	// Ensure buffer is written
+	fflush(stdout);
+	semaphore_signal(&printSemaphore);
 }
 
 // --------------------------------------------------
@@ -330,7 +351,7 @@ void printbuilding(void) {
 int main() {
 	// Local variables
 	unsigned long i;
-
+	semaphore_create(&printSemaphore, 1);
 	// Initialise Building
 	for(i = 0; i < NFLOORS; i++) {
 		// Initialise Floor
@@ -338,6 +359,7 @@ int main() {
 		floors[i].waitingtogodown = 0;
 		semaphore_create(&floors[i].up_arrow, 0);
 		semaphore_create(&floors[i].down_arrow, 0);
+		semaphore_create(&floors[i].queueInteraction, 1); // This initially has one available button press
 	}
 
 	// --- Initialise any other semaphores ---

logic.md

@@ -0,0 +1,20 @@
+# Logic
+## Initial State:
+* Lifts all at the bottom of the building
+* People all outside the building
+    * not waiting on an arrow
+    * not in a lift
+
+## State 1:
+### *These are performed simulataneously*
+---
+* Lift Thread
+    1. Lift waits for a short amount of time (to allow people to enter the building)
+    2. If no one is in the lift, it calls `get_into_lift()`
+    3. `get_into_lift()` checks if someone is waiting on the up arrow semaphore
+    4. Two things must then happen:
+        * First, the lift must update the lift that currently is on that floor
+        * Second, the lift must signal to a passenger that it may enter.
+---
+* Person Thread
+    1.