@@ -21,5 +21,8 @@ cc -std=c89 -DNO_SDL -DDEBUG -Wall -Wno-unknown-pragmas -Wpedantic -Wshadow -Wex

 # cc uxn.c emulator.c -std=c89 -Os -DNDEBUG -g0 -s -Wall -Wno-unknown-pragmas -L/usr/local/lib -lSDL2 -o bin/emulator

 # run

+if [ "${#}" -gt 0 ]; then

+	exec ./run.sh "${@}"

+fi

 ./bin/assembler projects/software/noodle.usm bin/boot.rom

 ./bin/emulator bin/boot.rom

@@ -412,6 +412,131 @@ file_poke(Uxn *u, Uint16 ptr, Uint8 b0, Uint8 b1)

 	return b1;

 }

+static void

+stack_diff(Stack *old, Stack *new, char *title)

+{

+	size_t i;

+	printf("%6s: ", title);

+	for (i = 0;; ++i) {

+		if (i < old->ptr) {

+			if (i < new->ptr) {

+				if (old->dat[i] == new->dat[i]) {

+					printf(" \033[0m%02x", new->dat[i]);

+				}

+				else {

+					printf(" \033[0;31m%02x\033[33;1m%02x", old->dat[i], new->dat[i]);

+				}

+			}

+			else { /* only in old stack */

+				printf(" \033[0;31m%02x", old->dat[i]);

+			}

+		}

+		else {

+			if (i < new->ptr) { /* only in new stack */

+				printf(" \033[33;1m%02x", new->dat[i]);

+			}

+			else { /* in neither stack, end of loop */

+				break;

+			}

+		}

+	}

+	printf("\033[0m\n");

+}

+

+static void

+memory_diff(Uint8 *old, Uint8 *new, size_t start, size_t end)

+{

+	size_t i, j;

+	for (i = start; i < end; i += 0x10) {

+		int changes = 0;

+		for (j = i; j < i + 0x10; ++j ) {

+			if (old[j] != new[j]) {

+				changes = 1;

+				break;

+			}

+		}

+		if (!changes) continue;

+		printf("0x%04lx:  ", i);

+		for (j = i; j < i + 0x10; ++j) {

+			printf("\033[%sm%02x", old[j] == new[j] ? "0" : "33;1", new[j]);

+			if (j % 2) putchar(' ');

+		}

+		printf("  ");

+		for (j = i; j < i + 0x10; ++j) {

+			printf("\033[%sm%c", old[j] == new[j] ? "0" : "33;1",

+				(new[j] < ' ' || new[j] > '~') ? '.' : new[j]);

+		}

+		printf("\033[0m\n");

+	}

+}

+

+Uint8

+debug_poke(Uxn *u, Uint16 ptr, Uint8 b0, Uint8 b1)

+{

+	size_t i;

+	(void)ptr;

+	switch (b0) {

+		case 0x08: /* stack */

+			printf("pc %04x working stack:", u->ram.ptr);

+			for (i = 0; i < u->wst.ptr; ++i) {

+				printf(" %02x", u->wst.dat[i]);

+			}

+			printf(", return stack: ");

+			for (i = 0; i < u->rst.ptr; ++i) {

+				printf(" %02x", u->rst.dat[i]);

+			}

+			printf("\n");

+			if (b1 && b1 != u->wst.ptr) {

+				printf("length %d failed to match %d!\n", b1, u->wst.ptr);

+				exit(1);

+			}

+			break;

+		case 0x09: /* snapshot */

+			if (u->snapshot != NULL) {

+				if (!(b1 & 0x01)) {

+					stack_diff(&u->snapshot->wst, &u->wst, "work");

+				}

+				if (!(b1 & 0x02)) {

+					stack_diff(&u->snapshot->rst, &u->rst, "return");

+				}

+				if (!(b1 & 0x04)) {

+					memory_diff(u->snapshot->ram.dat, u->ram.dat, 0, PAGE_DEVICE);

+					memory_diff(u->snapshot->ram.dat, u->ram.dat, PAGE_DEVICE + 0x0100, 0x10000);

+				}

+			}

+			{

+				int want_snapshot = !(b1 & 0x80);

+				if (want_snapshot) {

+					if (u->snapshot == NULL) {

+						u->snapshot = malloc(sizeof(*u));

+					}

+					for (i = 0; i < sizeof(*u); ++i) {

+						((char *) u->snapshot)[i] = ((char *) u)[i];

+					}

+				}

+				printf("pc 0x%04x snapshot%s taken\n", u->counter, want_snapshot ? "" : " not");

+			}

+			break;

+		case 0x0a: /* exit */

+			printf("Exited after 0x%04x cycles.\n", u->counter);

+			exit(b1);

+			break;

+		case 0x0f: /* test mode */

+			u->test_mode = b1;

+			printf("Test mode is now 0x%02x: ", u->test_mode);

+			if (b1 & 0x01) {

+				printf("BRK resets stacks to zero length");

+			}

+			else {

+				printf("all test mode features disabled");

+			}

+			printf("\n");

+			break;

+	}

+	fflush(stdout);

+	return b1;

+}

+

 Uint8

 system_poke(Uxn *u, Uint16 ptr, Uint8 b0, Uint8 b1)

 {

@@ -468,6 +593,10 @@ start(Uxn *u)

 			}

 		}

 #endif

+		if (u->test_mode & 0x01) {

+			u->wst.ptr = 0;

+			u->rst.ptr = 0;

+		}

 		evaluxn(u, u->vframe);

 #ifndef NO_SDL

 		if(screen.reqdraw)

@@ -504,7 +633,7 @@ main(int argc, char **argv)

 	portuxn(&u, "empty", ppnil);

 	portuxn(&u, "empty", ppnil);

 	portuxn(&u, "empty", ppnil);

-	portuxn(&u, "empty", ppnil);

+	portuxn(&u, "debug", debug_poke);

 	portuxn(&u, "system", system_poke);

 	/* Write screen size to dev/screen */

@@ -5,6 +5,7 @@

 |0140 ;Keys { key 1 }

 |0150 ;Mouse { x 2 y 2 state 1 chord 1 }

 |0160 ;File { pad 8 name 2 length 2 load 2 save 2 }

+|01E0 ;Debug { pad 8 stack 1 snapshot 1 exit 1 pad 4 test_mode 1 }

 |01F0 .RESET .FRAME .ERROR ( vectors )

 |01F8 [ f07c f0e2 f0c2 ]   ( palette )

@@ -22,10 +23,10 @@

 	TEST #01 #02 ADD #03 EQU PASS? [ add-result ]

 	TEST #01 #02 ADD #ff EQU PASS? [ this-test-fails ]

-	( infinite loop: change to HCF when implemented )

-	TEST #fd JMP

+	TEST #00 =Debug.exit

 @RESET

+	#01 =Debug.test_mode

 	,tests #0001 SUB2 =current-test

 	BRK

@@ -40,11 +40,12 @@ typedef struct Device {

 } Device;

 typedef struct Uxn {

-	Uint8 literal, status, devices;

+	Uint8 literal, status, devices, test_mode;

 	Uint16 counter, vreset, vframe, verror;

 	Stack wst, rst, *src, *dst;

 	Memory ram;

 	Device dev[16];

+	struct Uxn *snapshot;

 } Uxn;

 void setflag(Uint8 *status, char flag, int b);