From 9f560af8615acbcbbb71c146bad8474e7bbee9c2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robin=20H=C3=BCbner?= <profan@prfn.se>
Date: Sun, 30 Sep 2018 19:58:46 +0200
Subject: [PATCH] hm

---
 source/app.d | 56 +++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 42 insertions(+), 14 deletions(-)

diff --git a/source/app.d b/source/app.d
index 1253f48..739576f 100644
--- a/source/app.d
+++ b/source/app.d
@@ -301,7 +301,7 @@ struct PixelBuffer {
 		out vec4 out_col;
 
 		void main() {
-			float v = texture(tex, frag_uv.st).r;
+			float v = texture(tex, frag_uv.st).r * 255;
 			out_col = vec4(v, v, v, 1.0);
 		}
 
@@ -624,6 +624,13 @@ struct Chip8 {
 	void reset() {
 
 		cpu = cpu.init;
+		stack = stack.init;
+		ram = ram.init;
+		sp = sp.init;
+
+		run_flag = run_flag.init;
+		draw_flag = draw_flag.init;
+
 		screen_buf = screen_buf.init;
 		screen_data = screen_data.init;
 
@@ -666,8 +673,7 @@ struct Chip8 {
 			case 0x2000: // 0x2NNN Calls subroutine at NNN.
 
 				stack[sp++] = cpu.pc;
-				pc_target = cpu.opcode.capture!(0, 12);
-
+				pc_target = cpu.opcode & 0x0FFF;
 				break;
 
 			case 0x3000: // 0x3XNN Skips the next instruction if VX equals NN.
@@ -726,11 +732,25 @@ struct Chip8 {
 						break;
 
 					case 0x0004: // 0x8XY4 Adds VY to VX. VF is set to 1 when there's a carry, and to 0 when there isn't.
-						cpu.v[x] += cpu.v[y]; //TODO carry flag
+						auto vx = cpu.v[x];
+						auto vy = cpu.v[y];
+						if (cast(ushort)vx + cast(ushort)vy > 255) {
+							cpu.v[0xF] = 1;
+						} else { 
+							cpu.v[0xF] = 0;
+						}
+						cpu.v[x] += cpu.v[y];
 						break;
 
 					case 0x0005: // 0x8XY5 VY is subtracted from VX. VF is set to 0 when there's a borrow, and 1 when there isn't.
-						cpu.v[x] -= cpu.v[y]; //TODO borrow flag
+						auto vx = cpu.v[x];
+						auto vy = cpu.v[y];
+						if (vx > vy) {
+							cpu.v[0xF] = 1;
+						} else {
+							cpu.v[0xF] = 0;
+						}
+						cpu.v[x] -= cpu.v[y];
 						break;
 
 					case 0x0006: // 0x8XY6 Shifts VX right by one. VF is set to the value of the least significant bit of VX before the shift.
@@ -738,10 +758,18 @@ struct Chip8 {
 						auto vx = cpu.v[x];
 						cpu.v[0xF] = (vx & 0b10000000) >> 7;
 						cpu.v[x] >>= 1;
+						cpu.v[x] /= 2;
 						break;
 
 					case 0x0007: // 0x8XY7 Sets VX to VY minus VX. VF is set to 0 when there's a borrow, and 1 when there isn't.
-						cpu.v[x] = cast(Register)(cpu.v[y] - cpu.v[x]); // TODO borrow flag
+						auto vx = cpu.v[x];
+						auto vy = cpu.v[y];
+						if (vy > vx) {
+							cpu.v[0xF] = 1;
+						} else {
+							cpu.v[0xF] = 0;
+						}
+						cpu.v[x] = cast(Register)(vy - vx); // TODO borrow flag
 						break;
 
 					case 0x000E: // 0x8XYE Shifts VX left by one. VF is set to the value of the most significant bit of VX before the shift.
@@ -749,6 +777,7 @@ struct Chip8 {
 						auto vx = cpu.v[x];
 						cpu.v[0xF] = (vx & 0b10000000) >> 7;
 						cpu.v[x] <<= 1;
+						cpu.v[x] *= 2;
 						break;
 
 					default: // unhandled for some reason
@@ -762,7 +791,7 @@ struct Chip8 {
 			case 0x9000: // 0x9XYO Skips the next instruction if VX doesn't equal VY.
 
 				if (cpu.v[cpu.opcode.capture!(8, 12)] != cpu.v[cpu.opcode.capture!(4, 8)]) {
-					pc_target += 2; //do skip yes
+					pc_target += 2; // do skip yes
 				}
 
 				break;
@@ -897,7 +926,7 @@ struct Chip8 {
 
 						break;
 
-					default: //unhandled for some reason
+					default: // unhandled for some reason
 						writefln("unknown opcode: 0x%x", cpu.opcode);
 						break;
 
@@ -1012,10 +1041,10 @@ struct Emulator {
 		status.initialize(&this, &emu);
 
 		// debug data
-		emu.screen_buf[0] = 255;
-		emu.screen_buf[64 - 1] = 255;
-		emu.screen_buf[64*32 - 64] = 255;
-		emu.screen_buf[64*32 - 1] = 255;
+		emu.screen_buf[0] = 1;
+		emu.screen_buf[64 - 1] = 1;
+		emu.screen_buf[64*32 - 64] = 1;
+		emu.screen_buf[64*32 - 1] = 1;
 
 		// set up pixel buffer to poke a
 		buf.create(emu.screen_buf.ptr, 64, 32);
@@ -1069,12 +1098,11 @@ struct Emulator {
 
 		int w, h;
 		window.windowSize(w, h);
-
 		if (emu.draw_flag) {
 			buf.update(emu.screen_buf);
 		}
-
 		buf.draw(w, h);
+
 		imgui.newFrame(window);
 
 		status.draw();