@@ -20,7 +20,8 @@ static const char *errors[] = {

 	"Working-stack overflow",

 	"Return-stack overflow",

 	"Working-stack division by zero",

-	"Return-stack division by zero"};

+	"Return-stack division by zero",

+	"Execution timeout"};

 static void

 system_print(Stack *s, char *name)

@@ -30,16 +30,25 @@ WITH REGARD TO THIS SOFTWARE.

 #define DEVW8(x, y) { dev->dat[(x) & 0xf] = y; dev->deo(dev, (x) & 0x0f); }

 #define DEVW(d, x, y) { dev = (d); if(bs) { DEVW8((x), (y) >> 8); DEVW8((x) + 1, (y)); } else { DEVW8((x), (y)) } }

 #define WARP(x) { if(bs) pc = (x); else pc += (Sint8)(x); }

+#define LIMIT 0x40000 /* around 3 ms */

 int

 uxn_eval(Uxn *u, Uint16 pc)

 {

 	unsigned int a, b, c, j, k, bs, instr, errcode;

+	unsigned int limit = LIMIT;

 	Uint8 kptr, *sp;

 	Stack *src, *dst;

 	Device *dev;

 	if(!pc || u->dev[0].dat[0xf]) return 0;

 	while((instr = u->ram[pc++])) {

+		if(!limit--) {

+			if(!uxn_interrupt()) {

+				errcode = 6;

+				goto timeout;

+			}

+			limit = LIMIT;

+		}

 		/* Return Mode */

 		if(instr & 0x40) {

 			src = &u->rst; dst = &u->wst;

@@ -101,6 +110,7 @@ err:

 	/* set 1 in errcode if it involved the return stack instead of the working stack */

 	/*        (stack overflow & ( opcode was STH / JSR )) ^ Return Mode */

 	errcode |= ((errcode >> 1 & ((instr & 0x1e) == 0x0e)) ^ instr >> 6) & 1;

+timeout:

 	return uxn_halt(u, errcode, pc - 1);

 }

@@ -47,6 +47,7 @@ typedef struct Uxn {

 int uxn_boot(Uxn *u, Uint8 *ram);

 int uxn_eval(Uxn *u, Uint16 pc);

+int uxn_interrupt(void);

 int uxn_halt(Uxn *u, Uint8 error, Uint16 addr);

 Device *uxn_port(Uxn *u, Uint8 id, Uint8 (*deifn)(Device *, Uint8), void (*deofn)(Device *, Uint8));

 #endif /* UXN_UXN_H */

@@ -101,6 +101,12 @@ load(Uxn *u, char *filepath)

 	return 1;

 }

+int

+uxn_interrupt(void)

+{

+	return 1;

+}

+

 static int

 start(Uxn *u)

 {

@@ -32,6 +32,7 @@ WITH REGARD TO THIS SOFTWARE.

 #define WIDTH 64 * 8

 #define HEIGHT 40 * 8

 #define PAD 4

+#define TIMEOUT_FRAMES 10

 static SDL_Window *gWindow;

 static SDL_Texture *gTexture;

@@ -43,7 +44,7 @@ static SDL_Rect gRect;

 static Device *devscreen, *devmouse, *devctrl, *devaudio0, *devfile0;

 static Uint8 zoom = 1;

-static Uint32 stdin_event, audio0_event, redraw_event;

+static Uint32 stdin_event, audio0_event, redraw_event, interrupt_event;

 static int

 error(char *msg, const char *err)

@@ -89,12 +90,19 @@ stdin_handler(void *p)

 static int

 redraw_handler(void *p)

 {

-	SDL_Event event;

+	int dropped_frames = 0;

+	SDL_Event event, interrupt;

 	event.type = redraw_event;

+	interrupt.type = interrupt_event;

 	for(;;) {

 		SDL_Delay(16);

-		if(SDL_HasEvent(redraw_event) == SDL_FALSE)

+		if(SDL_HasEvent(redraw_event) == SDL_FALSE) {

 			SDL_PushEvent(&event);

+			dropped_frames = 0;

+		}

+		else if(++dropped_frames == TIMEOUT_FRAMES) {

+			SDL_PushEvent(&interrupt);

+		}

 	}

 	return 0;

 	(void)p;

@@ -169,6 +177,7 @@ init(void)

 	stdin_event = SDL_RegisterEvents(1);

 	audio0_event = SDL_RegisterEvents(POLYPHONY);

 	redraw_event = SDL_RegisterEvents(1);

+	interrupt_event = SDL_RegisterEvents(1);

 	SDL_CreateThread(stdin_handler, "stdin", NULL);

 	SDL_CreateThread(redraw_handler, "redraw", NULL);

 	SDL_StartTextInput();

@@ -467,6 +476,12 @@ run(Uxn *u)

 	return error("SDL_WaitEvent", SDL_GetError());

 }

+int

+uxn_interrupt(void)

+{

+	return SDL_PeepEvents(NULL, 1, SDL_GETEVENT, interrupt_event, interrupt_event) < 1;

+}

+

 int

 main(int argc, char **argv)

 {