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Chip8.cpp
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Chip8.cpp
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//
// Created by JULIA BALAJAN on 19/04/2017.
//
#include "Chip8.h"
#include <fstream>
#include <sstream>
#include <iostream>
const uint8_t Chip8::font_set[80] =
{
0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
0x20, 0x60, 0x20, 0x20, 0x70, // 1
0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
0x90, 0x90, 0xF0, 0x10, 0x10, // 4
0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
0xF0, 0x10, 0x20, 0x40, 0x40, // 7
0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
0xF0, 0x90, 0xF0, 0x90, 0x90, // A
0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
0xF0, 0x80, 0x80, 0x80, 0xF0, // C
0xE0, 0x90, 0x90, 0x90, 0xE0, // D
0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
0xF0, 0x80, 0xF0, 0x80, 0x80 // F
};
Chip8::Chip8(Drawer *drawer) : rnd_(std::random_device()()) {
add_observer(drawer);
clear_();
}
void Chip8::emulate_cycle() {
exec_inst_();
if (delay_timer > 0) {
--delay_timer;
}
if (sound_timer > 0) {
AudioManager::instance().beep();
--sound_timer;
}
}
void Chip8::clear_() {
PC_ = 0x200;
opcode_ = 0;
I_ = 0;
SP_ = 0;
delay_timer = 0;
sound_timer = 0;
screen_updated = true;
state_ = RUNNING;
clear_screen_();
std::fill_n(&stack_[0], 12, 0);
std::fill_n(&V_[0], 0x10, 0);
std::fill_n(&mem_[0], 0x1000, 0);
// Load the font set
for (int i = 0; i < 80; ++i)
mem_[i] = font_set[i];
}
void Chip8::draw() {
if (screen_updated) {
screen_updated = false;
notify(&vga_mem_[0]);
}
}
void Chip8::load_program(const std::string &src) {
int i = 0x200;
for(std::ifstream f(src, std::ios::binary); f.good(); )
mem_[i++ & 0xFFF] = f.get();
}
uint8_t Chip8::get_rnd_num_() {
static std::uniform_int_distribution<uint8_t> dst(0, 255);
return dst(rnd_);
}
inline
void Chip8::clear_screen_() {
std::fill_n(&vga_mem_[0], W * H / BITS_IN_BYTE, 0);
}
void Chip8::exec_inst_() {
uint16_t nnn,
kk,
x,
y,
n;
opcode_ = mem_[PC_ & 0xFFF] << 8 | mem_[(PC_ + 1) & 0xFFF];
switch(opcode_ & 0xF000) {
case 0x0000:
switch(opcode_ & 0x00FF) {
case 0x00E0:
clear_screen_();
PC_ += 2;
break;
case 0x00EE:
PC_ = stack_[SP_];
--SP_;
PC_ += 2;
break;
}
break;
case 0x1000:
nnn = opcode_ & 0x0FFF;
PC_ = nnn;
break;
case 0x2000:
nnn = opcode_ & 0x0FFF;
stack_[++SP_] = PC_;
PC_ = nnn;
break;
case 0x3000:
x = (opcode_ & 0x0F00) >> 8;
kk = opcode_ & 0x00FF;
if (V_[x] == kk)
PC_ += 2;
PC_ += 2;
break;
case 0x4000:
x = (opcode_ & 0x0F00) >> 8;
kk = opcode_ & 0x00FF;
if (V_[x] != kk)
PC_ += 2;
PC_ += 2;
break;
case 0x5000:
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
if (V_[x] == V_[y])
PC_ += 2;
PC_ += 2;
break;
case 0x6000:
x = (opcode_ & 0x0F00) >> 8;
kk = opcode_ & 0x00FF;
V_[x] = kk;
PC_ += 2;
break;
case 0x7000:
x = (opcode_ & 0x0F00) >> 8;
kk = opcode_ & 0x00FF;
V_[x] += kk;
PC_ += 2;
break;
case 0x8000:
switch(opcode_ & 0x000F) {
case 0x0000:
{
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
V_[x] = V_[y];
PC_ += 2;
}
break;
case 0x0001:
{
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
V_[x] = V_[x] | V_[y];
PC_ += 2;
}
break;
case 0x0002:
{
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
V_[x] = V_[x] & V_[y];
PC_ += 2;
}
break;
case 0x0003:
{
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
V_[x] = V_[x] ^ V_[y];
PC_ += 2;
}
break;
case 0x0004:
{
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
uint16_t sum = V_[x] + V_[y];
if (sum > 255)
V_[0xF] = 1;
else
V_[0xF] = 0;
V_[x] = sum & 0x00FF;
PC_ += 2;
}
break;
case 0x0005:
{
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
if (V_[x] > V_[y])
V_[0xF] = 1;
else
V_[0xF] = 0;
V_[x] = V_[x] - V_[y];
PC_ += 2;
}
break;
case 0x0006:
{
x = (opcode_ & 0x0F00) >> 8;
V_[0xF] = V_[x] & 0x1;
V_[x] >>= 1;
PC_ += 2;
}
break;
case 0x0007:
{
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
if (V_[y] > V_[x])
V_[0xF] = 1;
else
V_[0xF] = 0;
V_[x] = V_[y] - V_[x];
PC_ += 2;
}
break;
case 0x000E:
{
x = (opcode_ & 0x0F00) >> 8;
V_[0xF] = V_[x] >> 7;
V_[x] <<= 1;
PC_ += 2;
}
break;
}
break;
case 0x9000:
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
if (V_[x] != V_[y])
PC_ += 2;
PC_ += 2;
break;
case 0xA000:
nnn = opcode_ & 0x0FFF;
I_ = nnn;
PC_ += 2;
break;
case 0xB000:
nnn = opcode_ & 0x0FFF;
PC_ = nnn + V_[0x0];
break;
case 0xC000:
x = (opcode_ & 0x0F00) >> 8;
kk = opcode_ & 0x00FF;
V_[x] = get_rnd_num_() & kk;
PC_ += 2;
break;
case 0xD000:
{
x = (opcode_ & 0x0F00) >> 8;
y = (opcode_ & 0x00F0) >> 4;
n = opcode_ & 0x000F;
V_[0xF] = 0;
for (int y_iter = 0; y_iter < n; ++y_iter) {
uint8_t sprite_row = mem_[I_ + y_iter];
for (int i = 0; i < BITS_IN_BYTE; ++i) {
int x_iter = (i + V_[x]);
int bit_iter = x_iter % 8;
if (sprite_row & (0x80 >> i)) {
if ((vga_mem_[(y_iter + V_[y]) * (W / BITS_IN_BYTE) + ((x_iter) / BITS_IN_BYTE)] >> (7 - bit_iter)) & 1)
V_[0xF] = 1;
vga_mem_[(y_iter + V_[y]) * (W / BITS_IN_BYTE) + ((x_iter) / BITS_IN_BYTE)] ^= (1 << bit_iter);
}
}
}
screen_updated = true;
PC_ += 2;
}
break;
case 0xE000:
switch (opcode_ & 0x00FF) {
case 0x009E:
x = (opcode_ & 0x0F00) >> 8;
if(key_[V_[x]])
PC_ += 2;
PC_+= 2;
break;
case 0x00A1:
x = (opcode_ & 0x0F00) >> 8;
if(!key_[V_[x]])
PC_ += 2;
PC_+= 2;
break;
}
break;
case 0xF000:
switch(opcode_ & 0x00FF) {
case 0x0007:
{
x = (opcode_ & 0x0F00) >> 8;
V_[x] = delay_timer;
PC_ += 2;
}
break;
case 0x000A:
{
x = (opcode_ & 0x0F00) >> 8;
waiting_reg_ = &V_[x];
state_ = WAITING;
PC_ += 2;
}
break;
case 0x0015:
{
x = (opcode_ & 0x0F00) >> 8;
delay_timer = V_[x];
PC_ += 2;
}
break;
case 0x0018:
{
x = (opcode_ & 0x0F00) >> 8;
sound_timer = V_[x];
PC_ += 2;
}
break;
case 0x001E:
{
x = (opcode_ & 0x0F00) >> 8;
I_ += V_[x];
PC_ += 2;
}
break;
case 0x0029:
{
x = (opcode_ & 0x0F00) >> 8;
I_ = V_[x] * 5;
PC_ += 2;
}
break;
case 0x0033:
{
x = (opcode_ & 0x0F00) >> 8;
mem_[I_] = V_[x] / 100;
mem_[I_ + 1] = (V_[x] / 10) % 10;
mem_[I_ + 2] = (V_[x] % 100) % 10;
PC_ += 2;
}
break;
case 0x0055:
{
x = (opcode_ & 0x0F00) >> 8;
for (int i = 0; i <= x; ++i)
mem_[I_ + i] = V_[i];
PC_ += 2;
}
break;
case 0x0065:
{
x = (opcode_ & 0x0F00) >> 8;
for (int i = 0; i <= x; ++i)
V_[i] = mem_[I_ + i];
PC_ += 2;
}
break;
}
break;
default:
{
std::stringstream ss;
ss << "Unknown opcode of value: 0x" << std::hex << opcode_;
std::runtime_error(ss.str());
}
break;
}
}
CPU_state Chip8::get_state() const {
return state_;
}