apps,nanos-lite,proc: press F12 to change game

apps/nanos-lite/src/device.c

@@ -15,6 +15,10 @@ size_t read_events(void *buf) {
   char keydown_char = (key & 0x8000 ? 'd' : 'u');
   key &= ~0x8000;
   if (key != _KEY_NONE) {
+    if (key == _KEY_F12 && keydown_char == 'u') {
+      extern void change_game(void);
+      change_game();
+    }
     return sprintf(buf, "k%c %s\n", keydown_char, names[key]) - 1;
   }
   else {

apps/nanos-lite/src/main.c

@@ -26,6 +26,7 @@ int main() {
 
   load_prog("/bin/pal");
   load_prog("/bin/hello");
+  load_prog("/bin/litenes");
 
   _trap();
 

apps/nanos-lite/src/proc.c

@@ -22,12 +22,18 @@ void load_prog(const char *filename) {
 }
 
 static int cnt = 0;
+static PCB* game_pcb = &pcb[0];
+
+void change_game() {
+  Log("game change!");
+  game_pcb = (game_pcb == &pcb[0] ? &pcb[2] : &pcb[0]);
+}
 
 _RegSet* schedule(_RegSet *prev) {
   // when current == NULL at the very beginning, it will not cover
   // any valid data, so it will be safe to write to memory near NULL
   current->tf = prev;
-  if (current == &pcb[0]) {
+  if (current == game_pcb) {
     cnt ++;
     if (cnt == 200) {
       current = &pcb[1];
@@ -35,7 +41,7 @@ _RegSet* schedule(_RegSet *prev) {
     }
   }
   else {
-    current = &pcb[0];
+    current = game_pcb;
   }
   _switch(&current->as);
   return current->tf;