scemu.c

@@ -14,13 +14,14 @@ enum {
 int		step(void);
 static	u16int	fetch16(void);
 
-u8int	mem[32768];
-u8int	prog[32768];
+u8int	mem[65536];
 u8int	rA, rS, rX, rY, rP;
 u16int	pc;
 
 int	irq, nmi;
 
+u8int	*prog;
+
 void
 usage(void)
 {
@@ -35,18 +36,21 @@ openprog(char *f, vlong *progsiz)
 	long n;
 	Dir *d;
 
-	memset(prog, 0, sizeof prog);
+	prog = nil;
 	if(f == nil)
 		f = "a.out";
 	fd = open(f, OREAD);
 	if(fd < 0)
-		sysfatal("bad program: %r\n");
+		return;
 	d = dirfstat(fd);
 	if(d->length > 32768)
-		sysfatal("bad program: bigger than 32K and no banking support");
+		sysfatal("bad program: bigger than 32K, please shrink it");
 	*progsiz = d->length;
 	free(d);
-	n = read(fd, prog+32768-*progsiz, *progsiz);
+	prog = malloc(*progsiz);
+	if(prog == nil)
+		sysfatal("bad malloc");
+	n = read(fd, prog, *progsiz);
 	if(n != *progsiz)
 		fprint(2, "tried to read %lld bytes, got only %ld bytes\n", *progsiz, n);
 	close(fd);
@@ -69,6 +73,9 @@ main(int argc, char **argv)
 		break;
 	}ARGEND
 	openprog(*argv, &progsiz);
+	if(prog == nil)
+		sysfatal("bad program: %r");
+	memmove(mem+0x8000, prog, progsiz);
 	rP = 0x34;
 	pc = 0xFFFC;
 	pc = fetch16();
@@ -87,65 +94,49 @@ main(int argc, char **argv)
 	}
 }
 
-u8int
-memread(u16int a)
-{
-	if(a < 0x8000)
-		return mem[a];
-	else
-		return prog[a-0x8000];
-}
-
-void
-memwrite(u16int a, u8int v)
-{
-	if(a < 0x8000)
-		mem[a] = v;
-}
-
 static void
 push8(u8int v)
 {
-	memwrite(0x100 | rS--, v);
+	mem[0x100 | rS--] = v;
 }
 
 static void
 push16(u16int v)
 {
-	memwrite(0x100 | rS--, v >> 8);
-	memwrite(0x100 | rS--, v);
+	mem[0x100 | rS--] = v >> 8;
+	mem[0x100 | rS--] = v&0xff;
 }
 
 static u8int
 pop8(void)
 {
-	return memread(0x100 | ++rS);
+	return mem[0x100 | ++rS];
 }
 
 static u16int
 pop16(void)
 {
 	u16int v;
-	
-	v = memread(0x100 | ++rS);
-	v |= memread(0x100 | ++rS) << 8;
+
+	v = mem[0x100 | ++rS];
+	v |= mem[0x100 | ++rS] << 8;
 	return v;
 }
 
 static u8int
 fetch8(void)
 {
-	return memread(pc++);
+	return mem[pc++];
 }
 
 static u16int
 fetch16(void)
 {
-	u16int r;
-	
-	r = memread(pc++);
-	r |= memread(pc++) << 8;
-	return r;
+	u16int v;
+
+	v = fetch8();
+	v |= fetch8() << 8;
+	return v;
 }
 
 static void
@@ -191,8 +182,8 @@ asl(u16int a)
 {
 	u8int v;
 
-	v = memread(a);
 	rP &= ~(Negative | Zero | Carry);
+	v = mem[a];
 	if(v & 0x80)
 		rP |= Carry;
 	v <<= 1;
@@ -200,7 +191,7 @@ asl(u16int a)
 		rP |= Zero;
 	if(v & 0x80)
 		rP |= Negative;
-	memwrite(a, v);
+	mem[a] = v;
 }
 
 static void
@@ -208,13 +199,13 @@ lsr(u16int a)
 {
 	u8int v;
 
-	v = memread(a);
+	v = mem[a];
 	rP &= ~(Negative | Zero | Carry);
 	rP |= v & 1;
 	v >>= 1;
 	if(v == 0) rP |= Zero;
 	if(v & 0x80) rP |= Negative;
-	memwrite(a, v);
+	mem[a] = v;
 }
 
 static void
@@ -222,14 +213,14 @@ rol(u16int a)
 {
 	u8int v, b;
 	
-	v = memread(a);
+	v = mem[a];
 	b = rP & Carry;
 	rP &= ~(Carry | Negative | Zero);
 	if(v & 0x80) rP |= Carry;
 	v = (v << 1) | b;
 	if(v & 0x80) rP |= Negative;
 	if(v == 0) rP |= Zero;
-	memwrite(a, v);
+	mem[a] = v;
 }
 
 static void
@@ -237,14 +228,14 @@ ror(u16int a)
 {
 	u8int v, b;
 	
-	v = memread(a);
+	v = mem[a];
 	b = rP & Carry;
 	rP &= ~(Carry | Negative | Zero);
 	rP |= v & 1;
 	v = (v >> 1) | (b << 7);
 	if(v & 0x80) rP |= Negative;
 	if(v == 0) rP |= Zero;
-	memwrite(a, v);
+	mem[a] = v;
 }
 
 static void
@@ -261,10 +252,10 @@ inc(u16int a)
 {
 	u8int v;
 
-	v = memread(a);
+	v = mem[a];
 	v++;
 	nz(v);
-	memwrite(a, v);
+	mem[a] = v;
 }
 
 static void
@@ -272,10 +263,10 @@ dec(u16int a)
 {
 	u8int v;
 
-	v = memread(a);
+	v = mem[a];
 	v--;
 	nz(v);
-	memwrite(a, v);
+	mem[a] = v;
 }
 
 static int
@@ -299,10 +290,10 @@ aindX(void)
 {
 	u8int r;
 	u16int b;
-	
+
 	r = fetch8() + rX;
-	b = memread(r++);
-	b |= memread(r) << 8;
+	b = mem[r++];
+	b |= mem[r] << 8;
 	return b;
 }
 
@@ -311,11 +302,11 @@ aindY(int *p)
 {
 	u8int r;
 	u16int b;
-	
+
 	r = fetch8();
-	b = memread(r++) + rY;
+	b = mem[r++] + rY;
 	*p = b > 0xFF;
-	b += memread(r) << 8;
+	b += mem[r] << 8;
 	return b;
 }
 
@@ -324,8 +315,8 @@ interrupt(int nmi, int brk)
 {
 	push16(pc);
 	push8(rP | 0x20 | (brk << 4));
-	pc = memread(0xFFFA | (!nmi << 2));
-	pc |= memread(0xFFFB | (!nmi << 2)) << 8;
+	pc = mem[0xFFFA | (!nmi << 2)];
+	pc |= mem[0xFFFB | (!nmi << 2)] << 8;
 	rP |= Interrupt;
 }