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2019-chip8-emulator
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This commit is contained in:
Austin Morlan 2019-08-30 18:46:28 -07:00
parent b0dd532971
commit 52c86bee81
Signed by: austin
GPG Key ID: FD6B27654AF5E348
6 changed files with 1053 additions and 0 deletions
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16
CMakeLists.txt Normal file
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cmake_minimum_required(VERSION 3.14)
project(chip8)
set(CMAKE_CXX_STANDARD 11)
find_package(SDL2 REQUIRED)
add_executable(
chip8
Source/Chip8.cpp
Source/Main.cpp
Source/Platform.cpp)
target_compile_options(chip8 PRIVATE -Wall)
target_link_libraries(chip8 PRIVATE SDL2::SDL2)

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Source/Chip8.cpp Normal file
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#include "Chip8.hpp"
#include <chrono>
#include <cstdint>
#include <cstring>
#include <fstream>
#include <random>
const unsigned int FONTSET_SIZE = 80;
const unsigned int FONTSET_START_ADDRESS = 0x50;
const unsigned int START_ADDRESS = 0x200;
uint8_t fontset[FONTSET_SIZE] =
{
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()
: randGen(std::chrono::system_clock::now().time_since_epoch().count())
{
// Initialize PC
pc = START_ADDRESS;
// Load fonts into memory
for (unsigned int i = 0; i < FONTSET_SIZE; ++i)
{
memory[FONTSET_START_ADDRESS + i] = fontset[i];
}
// Initialize RNG
randByte = std::uniform_int_distribution<uint8_t>(0, 255U);
// Set up function pointer table
table[0x0] = &Chip8::Table0;
table[0x1] = &Chip8::OP_1nnn;
table[0x2] = &Chip8::OP_2nnn;
table[0x3] = &Chip8::OP_3xkk;
table[0x4] = &Chip8::OP_4xkk;
table[0x5] = &Chip8::OP_5xy0;
table[0x6] = &Chip8::OP_6xkk;
table[0x7] = &Chip8::OP_7xkk;
table[0x8] = &Chip8::Table8;
table[0x9] = &Chip8::OP_9xy0;
table[0xA] = &Chip8::OP_Annn;
table[0xB] = &Chip8::OP_Bnnn;
table[0xC] = &Chip8::OP_Cxkk;
table[0xD] = &Chip8::OP_Dxyn;
table[0xE] = &Chip8::TableE;
table[0xF] = &Chip8::TableF;
table0[0x0] = &Chip8::OP_00E0;
table0[0xE] = &Chip8::OP_00EE;
table8[0x0] = &Chip8::OP_8xy0;
table8[0x1] = &Chip8::OP_8xy1;
table8[0x2] = &Chip8::OP_8xy2;
table8[0x3] = &Chip8::OP_8xy3;
table8[0x4] = &Chip8::OP_8xy4;
table8[0x5] = &Chip8::OP_8xy5;
table8[0x6] = &Chip8::OP_8xy6;
table8[0x7] = &Chip8::OP_8xy7;
table8[0xE] = &Chip8::OP_8xyE;
tableE[0x1] = &Chip8::OP_ExA1;
tableE[0xE] = &Chip8::OP_Ex9E;
tableF[0x07] = &Chip8::OP_Fx07;
tableF[0x0A] = &Chip8::OP_Fx0A;
tableF[0x15] = &Chip8::OP_Fx15;
tableF[0x18] = &Chip8::OP_Fx18;
tableF[0x1E] = &Chip8::OP_Fx1E;
tableF[0x29] = &Chip8::OP_Fx29;
tableF[0x33] = &Chip8::OP_Fx33;
tableF[0x55] = &Chip8::OP_Fx55;
tableF[0x65] = &Chip8::OP_Fx65;
}
void Chip8::LoadROM(char const* filename)
{
std::ifstream file(filename, std::ios::binary | std::ios::ate);
if (file.is_open())
{
std::streampos size = file.tellg();
char* buffer = new char[size];
file.seekg(0, std::ios::beg);
file.read(buffer, size);
file.close();
for (long i = 0; i < size; ++i)
{
memory[START_ADDRESS + i] = buffer[i];
}
delete[] buffer;
}
}
void Chip8::Cycle()
{
// Fetch
opcode = (memory[pc] << 8u) | memory[pc + 1];
// Increment the PC before we execute anything
pc += 2;
// Decode and Execute
((*this).*(table[(opcode & 0xF000u) >> 12u]))();
// Decrement the delay timer if it's been set
if (delayTimer > 0)
{
--delayTimer;
}
// Decrement the sound timer if it's been set
if (soundTimer > 0)
{
--soundTimer;
}
}
void Chip8::Table0()
{
((*this).*(table0[opcode & 0x000Fu]))();
}
void Chip8::Table8()
{
((*this).*(table8[opcode & 0x000Fu]))();
}
void Chip8::TableE()
{
((*this).*(tableE[opcode & 0x000Fu]))();
}
void Chip8::TableF()
{
((*this).*(tableF[opcode & 0x00FFu]))();
}
void Chip8::OP_NULL()
{}
void Chip8::OP_00E0()
{
memset(video, 0, VIDEO_HEIGHT * VIDEO_WIDTH);
}
void Chip8::OP_00EE()
{
--sp;
pc = stack[sp];
}
void Chip8::OP_1nnn()
{
uint16_t address = opcode & 0x0FFFu;
pc = address;
}
void Chip8::OP_2nnn()
{
uint16_t address = opcode & 0x0FFFu;
stack[sp] = pc;
++sp;
pc = address;
}
void Chip8::OP_3xkk()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t byte = opcode & 0x00FFu;
if (registers[Vx] == byte)
{
pc += 2;
}
}
void Chip8::OP_4xkk()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t byte = opcode & 0x00FFu;
if (registers[Vx] != byte)
{
pc += 2;
}
}
void Chip8::OP_5xy0()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
if (registers[Vx] == registers[Vy])
{
pc += 2;
}
}
void Chip8::OP_6xkk()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t byte = opcode & 0x00FFu;
registers[Vx] = byte;
}
void Chip8::OP_7xkk()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t byte = opcode & 0x00FFu;
registers[Vx] += byte;
}
void Chip8::OP_8xy0()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
registers[Vx] = registers[Vy];
}
void Chip8::OP_8xy1()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
registers[Vx] |= registers[Vy];
}
void Chip8::OP_8xy2()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
registers[Vx] &= registers[Vy];
}
void Chip8::OP_8xy3()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
registers[Vx] ^= registers[Vy];
}
void Chip8::OP_8xy4()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
uint16_t sum = registers[Vx] + registers[Vy];
if (sum > 255U)
{
registers[0xF] = 1;
}
else
{
registers[0xF] = 0;
}
registers[Vx] = sum & 0xFFu;
}
void Chip8::OP_8xy5()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
if (registers[Vx] > registers[Vy])
{
registers[0xF] = 1;
}
else
{
registers[0xF] = 0;
}
registers[Vx] -= registers[Vy];
}
void Chip8::OP_8xy6()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
// Save LSB in VF
registers[0xF] = (registers[Vx] & 0x1u);
registers[Vx] >>= 1;
}
void Chip8::OP_8xy7()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
if (registers[Vy] > registers[Vx])
{
registers[0xF] = 1;
}
else
{
registers[0xF] = 0;
}
registers[Vx] = registers[Vy] - registers[Vx];
}
void Chip8::OP_8xyE()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
// Save MSB in VF
registers[0xF] = (registers[Vx] & 0x80u) >> 7u;
registers[Vx] <<= 1;
}
void Chip8::OP_9xy0()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
if (registers[Vx] != registers[Vy])
{
pc += 2;
}
}
void Chip8::OP_Annn()
{
uint16_t address = opcode & 0x0FFFu;
index = address;
}
void Chip8::OP_Bnnn()
{
uint16_t address = opcode & 0x0FFFu;
pc = registers[0] + address;
}
void Chip8::OP_Cxkk()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t byte = opcode & 0x00FFu;
registers[Vx] = randByte(randGen) & byte;
}
void Chip8::OP_Dxyn()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t Vy = (opcode & 0x00F0u) >> 4u;
uint8_t height = opcode & 0x000Fu;
// Wrap if going beyond screen boundaries
uint8_t xPos = registers[Vx] % VIDEO_WIDTH;
uint8_t yPos = registers[Vy] % VIDEO_HEIGHT;
registers[0xF] = 0;
for (unsigned int row = 0; row < height; ++row)
{
uint8_t spriteByte = memory[index + row];
for (unsigned int col = 0; col < 8; ++col)
{
uint8_t spritePixel = spriteByte & (0x80u >> col);
uint32_t* screenPixel = &video[(yPos + row) * VIDEO_WIDTH + (xPos + col)];
// Sprite pixel is on
if (spritePixel)
{
// Screen pixel also on - collision
if (*screenPixel == 0xFFFFFFFF)
{
registers[0xF] = 1;
}
// Effectively XOR with the sprite pixel
*screenPixel ^= 0xFFFFFFFF;
}
}
}
}
void Chip8::OP_Ex9E()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t key = registers[Vx];
if (keypad[key])
{
pc += 2;
}
}
void Chip8::OP_ExA1()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t key = registers[Vx];
if (!keypad[key])
{
pc += 2;
}
}
void Chip8::OP_Fx07()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
registers[Vx] = delayTimer;
}
void Chip8::OP_Fx0A()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
if (keypad[0])
{
registers[Vx] = 0;
}
else if (keypad[1])
{
registers[Vx] = 1;
}
else if (keypad[2])
{
registers[Vx] = 2;
}
else if (keypad[3])
{
registers[Vx] = 3;
}
else if (keypad[4])
{
registers[Vx] = 4;
}
else if (keypad[5])
{
registers[Vx] = 5;
}
else if (keypad[6])
{
registers[Vx] = 6;
}
else if (keypad[7])
{
registers[Vx] = 7;
}
else if (keypad[8])
{
registers[Vx] = 8;
}
else if (keypad[9])
{
registers[Vx] = 9;
}
else if (keypad[10])
{
registers[Vx] = 10;
}
else if (keypad[11])
{
registers[Vx] = 11;
}
else if (keypad[12])
{
registers[Vx] = 12;
}
else if (keypad[13])
{
registers[Vx] = 13;
}
else if (keypad[14])
{
registers[Vx] = 14;
}
else if (keypad[15])
{
registers[Vx] = 15;
}
else
{
pc -= 2;
}
}
void Chip8::OP_Fx15()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
delayTimer = registers[Vx];
}
void Chip8::OP_Fx18()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
soundTimer = registers[Vx];
}
void Chip8::OP_Fx1E()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
index += registers[Vx];
}
void Chip8::OP_Fx29()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t digit = registers[Vx];
index = FONTSET_START_ADDRESS + (5 * digit);
}
void Chip8::OP_Fx33()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
uint8_t value = registers[Vx];
// Ones-place
memory[index + 2] = value % 10;
value /= 10;
// Tens-place
memory[index + 1] = value % 10;
value /= 10;
// Hundreds-place
memory[index] = value % 10;
}
void Chip8::OP_Fx55()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
for (uint8_t i = 0; i <= Vx; ++i)
{
memory[index + i] = registers[i];
}
}
void Chip8::OP_Fx65()
{
uint8_t Vx = (opcode & 0x0F00u) >> 8u;
for (uint8_t i = 0; i <= Vx; ++i)
{
registers[i] = memory[index + i];
}
}

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#pragma once
#include <cstdint>
#include <random>
const unsigned int KEY_COUNT = 16;
const unsigned int MEMORY_SIZE = 4096;
const unsigned int REGISTER_COUNT = 16;
const unsigned int STACK_LEVELS = 16;
const unsigned int VIDEO_HEIGHT = 32;
const unsigned int VIDEO_WIDTH = 64;
class Chip8
{
public:
Chip8();
void LoadROM(char const* filename);
void Cycle();
uint8_t keypad[KEY_COUNT]{};
uint32_t video[VIDEO_WIDTH * VIDEO_HEIGHT]{};
private:
void Table0();
void Table8();
void TableE();
void TableF();
// Do nothing
void OP_NULL();
// CLS
void OP_00E0();
// RET
void OP_00EE();
// JP address
void OP_1nnn();
// CALL address
void OP_2nnn();
// SE Vx, byte
void OP_3xkk();
// SNE Vx, byte
void OP_4xkk();
// SE Vx, Vy
void OP_5xy0();
// LD Vx, byte
void OP_6xkk();
// ADD Vx, byte
void OP_7xkk();
// LD Vx, Vy
void OP_8xy0();
// OR Vx, Vy
void OP_8xy1();
// AND Vx, Vy
void OP_8xy2();
// XOR Vx, Vy
void OP_8xy3();
// ADD Vx, Vy
void OP_8xy4();
// SUB Vx, Vy
void OP_8xy5();
// SHR Vx
void OP_8xy6();
// SUBN Vx, Vy
void OP_8xy7();
// SHL Vx
void OP_8xyE();
// SNE Vx, Vy
void OP_9xy0();
// LD I, address
void OP_Annn();
// JP V0, address
void OP_Bnnn();
// RND Vx, byte
void OP_Cxkk();
// DRW Vx, Vy, height
void OP_Dxyn();
// SKP Vx
void OP_Ex9E();
// SKNP Vx
void OP_ExA1();
// LD Vx, DT
void OP_Fx07();
// LD Vx, K
void OP_Fx0A();
// LD DT, Vx
void OP_Fx15();
// LD ST, Vx
void OP_Fx18();
// ADD I, Vx
void OP_Fx1E();
// LD F, Vx
void OP_Fx29();
// LD B, Vx
void OP_Fx33();
// LD [I], Vx
void OP_Fx55();
// LD Vx, [I]
void OP_Fx65();
uint8_t memory[MEMORY_SIZE]{};
uint8_t registers[REGISTER_COUNT]{};
uint16_t index{};
uint16_t pc{};
uint8_t delayTimer{};
uint8_t soundTimer{};
uint16_t stack[STACK_LEVELS]{};
uint8_t sp{};
uint16_t opcode{};
std::default_random_engine randGen;
std::uniform_int_distribution<uint8_t> randByte;
typedef void (Chip8::*Chip8Func)();
Chip8Func table[0xF + 1]{&Chip8::OP_NULL};
Chip8Func table0[0xE + 1]{&Chip8::OP_NULL};
Chip8Func table8[0xE + 1]{&Chip8::OP_NULL};
Chip8Func tableE[0xE + 1]{&Chip8::OP_NULL};
Chip8Func tableF[0x65 + 1]{&Chip8::OP_NULL};
};

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#include "Chip8.hpp"
#include "Platform.hpp"
#include <chrono>
#include <iostream>
int main(int argc, char** argv)
{
if (argc != 4)
{
std::cerr << "Usage: " << argv[0] << " <Scale> <Delay> <ROM>\n";
std::exit(EXIT_FAILURE);
}
int videoScale = std::stoi(argv[1]);
int cycleDelay = std::stoi(argv[2]);
char const* romFilename = argv[3];
Platform platform("CHIP-8 Emulator", VIDEO_WIDTH * videoScale, VIDEO_HEIGHT * videoScale, VIDEO_WIDTH, VIDEO_HEIGHT);
Chip8 chip8;
chip8.LoadROM(romFilename);
int videoPitch = sizeof(chip8.video[0]) * VIDEO_WIDTH;
auto lastCycleTime = std::chrono::high_resolution_clock::now();
bool quit = false;
while (!quit)
{
quit = platform.ProcessInput(chip8.keypad);
auto currentTime = std::chrono::high_resolution_clock::now();
float dt = std::chrono::duration<float, std::chrono::milliseconds::period>(currentTime - lastCycleTime).count();
if (dt > cycleDelay)
{
lastCycleTime = currentTime;
chip8.Cycle();
platform.Update(chip8.video, videoPitch);
}
}
return 0;
}

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Source/Platform.cpp Normal file
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#include "Platform.hpp"
#include <SDL2/SDL.h>
Platform::Platform(char const* title, int windowWidth, int windowHeight, int textureWidth, int textureHeight)
{
SDL_Init(SDL_INIT_VIDEO);
window = SDL_CreateWindow(title, 0, 0, windowWidth, windowHeight, SDL_WINDOW_SHOWN);
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
texture = SDL_CreateTexture(
renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_STREAMING, textureWidth, textureHeight);
}
Platform::~Platform()
{
SDL_DestroyTexture(texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
}
void Platform::Update(void const* buffer, int pitch)
{
SDL_UpdateTexture(texture, nullptr, buffer, pitch);
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture, nullptr, nullptr);
SDL_RenderPresent(renderer);
}
bool Platform::ProcessInput(uint8_t* keys)
{
bool quit = false;
SDL_Event event;
while (SDL_PollEvent(&event))
{
switch (event.type)
{
case SDL_QUIT:
{
quit = true;
} break;
case SDL_KEYDOWN:
{
switch (event.key.keysym.sym)
{
case SDLK_ESCAPE:
{
quit = true;
} break;
case SDLK_x:
{
keys[0] = 1;
} break;
case SDLK_1:
{
keys[1] = 1;
} break;
case SDLK_2:
{
keys[2] = 1;
} break;
case SDLK_3:
{
keys[3] = 1;
} break;
case SDLK_q:
{
keys[4] = 1;
} break;
case SDLK_w:
{
keys[5] = 1;
} break;
case SDLK_e:
{
keys[6] = 1;
} break;
case SDLK_a:
{
keys[7] = 1;
} break;
case SDLK_s:
{
keys[8] = 1;
} break;
case SDLK_d:
{
keys[9] = 1;
} break;
case SDLK_z:
{
keys[0xA] = 1;
} break;
case SDLK_c:
{
keys[0xB] = 1;
} break;
case SDLK_4:
{
keys[0xC] = 1;
} break;
case SDLK_r:
{
keys[0xD] = 1;
} break;
case SDLK_f:
{
keys[0xE] = 1;
} break;
case SDLK_v:
{
keys[0xF] = 1;
} break;
}
} break;
case SDL_KEYUP:
{
switch (event.key.keysym.sym)
{
case SDLK_x:
{
keys[0] = 0;
} break;
case SDLK_1:
{
keys[1] = 0;
} break;
case SDLK_2:
{
keys[2] = 0;
} break;
case SDLK_3:
{
keys[3] = 0;
} break;
case SDLK_q:
{
keys[4] = 0;
} break;
case SDLK_w:
{
keys[5] = 0;
} break;
case SDLK_e:
{
keys[6] = 0;
} break;
case SDLK_a:
{
keys[7] = 0;
} break;
case SDLK_s:
{
keys[8] = 0;
} break;
case SDLK_d:
{
keys[9] = 0;
} break;
case SDLK_z:
{
keys[0xA] = 0;
} break;
case SDLK_c:
{
keys[0xB] = 0;
} break;
case SDLK_4:
{
keys[0xC] = 0;
} break;
case SDLK_r:
{
keys[0xD] = 0;
} break;
case SDLK_f:
{
keys[0xE] = 0;
} break;
case SDLK_v:
{
keys[0xF] = 0;
} break;
}
} break;
}
}
return quit;
}

23
Source/Platform.hpp Normal file
View File

@ -0,0 +1,23 @@
#pragma once
#include <cstdint>
class SDL_Window;
class SDL_Renderer;
class SDL_Texture;
class Platform
{
public:
Platform(char const* title, int windowWidth, int windowHeight, int textureWidth, int textureHeight);
~Platform();
void Update(void const* buffer, int pitch);
bool ProcessInput(uint8_t* keys);
private:
SDL_Window* window{};
SDL_Renderer* renderer{};
SDL_Texture* texture{};
};