@@ -10,6 +10,10 @@ cc uxn.c -std=c89 -Os -DNDEBUG -g0 -s -Wall -Wno-unknown-pragmas -o uxn

 ## Assembly Syntax

+- `:label`, a named offset

+- `+literal`, a numeric value

+- `.pointer`, pointer to a label

+

 ```

 < comment >

@@ -30,31 +34,16 @@ $01 < pointer8 >

 :label ADD RTS

 ```

-## Design

-

-### CPU

-

-- Build stack with pointer

-- Print stack

-- Build memory

-

-### PPU

-

-### Assembly

-

-#### Addressing 

-

-- `label`, a named offset[TODO]

-- `literal`, a numeric value

-- `pointer`, pointer to an address[TODO]

-

-### Assembler

-

-

-### Emulator

-

-- SDL Layer

+## TODOs

+- Implement addressing

+- Implement 16 bits operations

+- Jumps should be relative

+- Catch overflow/underflow

+- Implement literals like `[2]`, and `[ 2 3 ]`.

+- Audo-detect literals length.

+- SDL Layer Emulator

+- Build PPU

 ## Refs

@@ -1,5 +1,18 @@

 < comment >

-[3 1 2 3 ] pop dup swp ovr rot 

+.deep JSR [4 6 7 8 9 ] BRK

-brk

+:deep

+	[2 1 2 ] 

+	.deeper JSR 

+	RTS

+

+:deeper

+	[3 3 4 5 ] 

+	.deeperyet JSR

+	RTS

+

+:deeperyet

+	[2 aa bb ]

+	RTS

+	

\ No newline at end of file

@@ -24,8 +24,9 @@ typedef struct {

 	Uint8 literal;

 	Uint8 status, counter;

 	Uint8 memory[STACK_DEPTH];

-	Uint8 mptr, sptr;

+	Uint8 mptr, sptr, rsptr;

 	Uint8 stack[STACK_DEPTH];

+	Uint8 rstack[STACK_DEPTH];

 	Uint8 address[STACK_DEPTH];

 } Computer;

@@ -61,20 +62,66 @@ echo(Uint8 *s, Uint8 len, char *name)

 	printf("\n\n");

 }

-#pragma mark - Operations

+void

+spush(Uint8 v)

+{

+	cpu.stack[cpu.sptr++] = v;

+}

+

+Uint8

+spop(void)

+{

+	return cpu.stack[--cpu.sptr];

+}

 void

-op_push(Uint8 *s, Uint8 *ptr, Uint8 v)

+rspush(Uint8 v)

 {

-	s[(*ptr)++] = v;

+	cpu.rstack[cpu.rsptr++] = v;

 }

 Uint8

-op_pop(Uint8 *s, Uint8 *ptr)

+rspop(void)

 {

-	return s[--*ptr];

+	return cpu.rstack[--cpu.rsptr];

 }

+#pragma mark - Operations

+

+/* clang-format off */

+

+void op_brk() { setflag(FLAG_HALT, 1); }

+void op_lit() { cpu.literal += cpu.memory[cpu.mptr++]; }

+void op_nop() { }

+void op_drp() { spop(); }

+void op_dup() { spush(cpu.stack[cpu.sptr - 1]); }

+void op_swp() { Uint8 b = spop(), a = spop(); spush(b); spush(a); }

+void op_ovr() { spush(cpu.stack[cpu.sptr - 2]); }

+void op_rot() { Uint8 c = spop(),b = spop(),a = spop(); spush(b); spush(c); spush(a); }

+void op_jmp() { cpu.mptr = spop(); }

+void op_jsr() { rspush(cpu.mptr); cpu.mptr = spop(); }

+void op_jeq() { if(getflag(FLAG_ZERO)) cpu.mptr = spop(); }

+void op_rts() {	cpu.mptr = rspop(); }

+void op_equ() { setflag(FLAG_ZERO, spop() == spop()); }

+void op_neq() { setflag(FLAG_ZERO, spop() != spop()); }

+void op_lth() {	setflag(FLAG_ZERO, spop() < spop()); }

+void op_gth() {	setflag(FLAG_ZERO, spop() > spop()); }

+void op_and() {	spush(spop() & spop()); }

+void op_ora() {	spush(spop() | spop()); }

+void op_rol() { spush(spop() << 1); }

+void op_ror() { spush(spop() >> 1); }

+void op_add() { spush(spop() + spop()); }

+void op_sub() { spush(spop() - spop()); }

+void op_mul() { spush(spop() * spop()); }

+void op_div() { spush(spop() / spop()); }

+

+void (*ops[])(void) = {

+	op_brk, op_lit, op_nop, op_drp, op_dup, op_swp, op_ovr, op_rot, 

+	op_jmp, op_jsr, op_jeq, op_rts, op_equ, op_neq, op_gth, op_lth, 

+	op_and, op_ora, op_rol, op_ror, op_add, op_sub, op_mul, op_div};

+

+/* clang-format on */

+

 void

 reset(void)

 {

@@ -105,42 +152,13 @@ void

 eval()

 {

 	Uint8 instr = cpu.memory[cpu.mptr++];

-	Uint8 a, b, c;

 	if(cpu.literal > 0) {

-		printf("push: %02x[%d](%d)\n", instr, cpu.literal, cpu.sptr);

-		op_push(cpu.stack, &cpu.sptr, instr);

+		spush(instr);

 		cpu.literal--;

 		return;

 	}

-	switch(instr) {

-	case 0x0: setflag(FLAG_HALT, 1); break;

-	case 0x1: cpu.literal += cpu.memory[cpu.mptr++]; break;

-	case 0x2: printf("??\n"); break;

-	case 0x3: /* pop */

-		op_pop(cpu.stack, &cpu.sptr);

-		break;

-	case 0x4: /* dup */

-		op_push(cpu.stack, &cpu.sptr, cpu.stack[cpu.sptr - 1]);

-		break;

-	case 0x5: /* swp */

-		b = op_pop(cpu.stack, &cpu.sptr);

-		a = op_pop(cpu.stack, &cpu.sptr);

-		op_push(cpu.stack, &cpu.sptr, b);

-		op_push(cpu.stack, &cpu.sptr, a);

-		break;

-	case 0x6: /* ovr */

-		op_push(cpu.stack, &cpu.sptr, cpu.stack[cpu.sptr - 2]);

-		break;

-	case 0x7: /* rot */

-		c = op_pop(cpu.stack, &cpu.sptr);

-		b = op_pop(cpu.stack, &cpu.sptr);

-		a = op_pop(cpu.stack, &cpu.sptr);

-		op_push(cpu.stack, &cpu.sptr, b);

-		op_push(cpu.stack, &cpu.sptr, c);

-		op_push(cpu.stack, &cpu.sptr, a);

-		break;

-	default: printf("Unknown instruction: #%02x\n", instr);

-	}

+	if(instr < 24)

+		(*ops[instr])();

 }

 void

@@ -12,6 +12,7 @@ WITH REGARD TO THIS SOFTWARE.

 */

 #define PRGLEN 256

+#define LABELIDLEN 32

 typedef unsigned char Uint8;

@@ -20,7 +21,13 @@ typedef struct {

 	Uint8 data[PRGLEN];

 } Program;

-char labels[256][16];

+typedef struct {

+	Uint8 addr;

+	char name[LABELIDLEN];

+} Label;

+

+int labelslen;

+Label labels[256];

 char opcodes[][4] = {

 	"BRK",

@@ -40,6 +47,14 @@ char opcodes[][4] = {

 	"NEQ",

 	"LTH",

 	"GTH",

+	"---",

+	"---",

+	"---",

+	"---",

+	"ADD",

+	"SUB",

+	"MUL",

+	"DIV"

 	/* */};

 Program p;

@@ -56,6 +71,16 @@ scmp(char *a, char *b) /* string compare */

 	return 0;

 }

+char *

+scpy(char *src, char *dst, int len) /* string copy */

+{

+	int i = 0;

+	while((dst[i] = src[i]) && i < len - 2)

+		i++;

+	dst[i + 1] = '\0';

+	return dst;

+}

+

 char *

 suca(char *s) /* string to uppercase */

 {

@@ -72,7 +97,7 @@ sihx(char *s)

 	int i = 0;

 	char c;

 	while((c = s[i++]))

-		if(!(c >= '0' && c <= '9') && !(c >= 'A' && c <= 'F'))

+		if(!(c >= '0' && c <= '9') && !(c >= 'a' && c <= 'f') && !(c >= 'A' && c <= 'F'))

 			return 0;

 	return 1;

 }

@@ -87,6 +112,8 @@ shex(char *s) /* string to num */

 			n = n * 16 + (c - '0');

 		else if(c >= 'A' && c <= 'F')

 			n = n * 16 + 10 + (c - 'A');

+		else if(c >= 'a' && c <= 'f')

+			n = n * 16 + 10 + (c - 'f');

 	return n;

 }

@@ -101,7 +128,10 @@ addprg(Uint8 hex)

 void

 addlabel(char *id, Uint8 addr)

 {

-	printf("new label: %s=%02x\n", id, addr);

+	Label *l = &labels[labelslen++];

+	scpy(suca(id), l->name, LABELIDLEN);

+	l->addr = addr;

+	printf("new label: %s=%02x\n", l->name, l->addr);

 }

 void

@@ -110,16 +140,39 @@ addconst(char *id, Uint8 value)

 	printf("new const: %s=%02x\n", id, value);

 }

+Label *

+findlabel(char *s)

+{

+	int i;

+	for(i = 0; i < labelslen; ++i)

+		if(scmp(labels[i].name, s))

+			return &labels[i];

+	return NULL;

+}

+

 Uint8

 findop(char *s)

 {

 	int i;

-	for(i = 0; i < 16; ++i)

+	for(i = 0; i < 24; ++i)

 		if(scmp(opcodes[i], s))

 			return i;

 	return 0;

 }

+int

+getlength(char *w)

+{

+	if(findop(w) || scmp(w, "BRK")) return 1;

+	if(w[0] == '.') return 3;

+	if(w[0] == ':') return 0;

+	if(w[0] == '[') return 2;

+	if(sihx(w)) return 1;

+	if(w[0] == ']') return 0;

+	printf("Unknown length %s\n", w);

+	return 0;

+}

+

 int

 comment(char *w, int *skip)

 {

@@ -136,10 +189,12 @@ void

 pass1(FILE *f)

 {

 	int skip = 0;

+	int addr = 0;

 	char word[64];

 	while(fscanf(f, "%s", word) == 1) {

-		if(comment(word, &skip))

-			continue;

+		if(comment(word, &skip)) continue;

+		if(word[0] == ':') addlabel(word + 1, addr);

+		addr += getlength(word);

 	}

 	rewind(f);

 }

@@ -151,6 +206,8 @@ pass2(FILE *f)

 	char word[64];

 	while(fscanf(f, "%s", word) == 1) {

 		Uint8 op;

+		Label *l;

+		if(word[0] == ':') continue;

 		suca(word);

 		if(comment(word, &skip)) continue;

 		if(word[0] == ']') continue;

@@ -167,7 +224,11 @@ pass2(FILE *f)

 			addprg(shex(word));

 		else if(scmp(word, "BRK"))

 			addprg(0x00);

-		else

+		else if((l = findlabel(word + 1))) {

+			addprg(0x01);

+			addprg(1);

+			addprg(l->addr);

+		} else

 			printf("unknown: %s\n", word);

 	}

 }