596 lines
9.7 KiB
C++
596 lines
9.7 KiB
C++
#include "Chip8.hpp"
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#include <chrono>
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#include <cstdint>
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#include <cstring>
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#include <fstream>
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#include <random>
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const unsigned int FONTSET_SIZE = 80;
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const unsigned int FONTSET_START_ADDRESS = 0x50;
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const unsigned int START_ADDRESS = 0x200;
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uint8_t fontset[FONTSET_SIZE] =
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{
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0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
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0x20, 0x60, 0x20, 0x20, 0x70, // 1
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0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
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0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
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0x90, 0x90, 0xF0, 0x10, 0x10, // 4
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0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
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0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
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0xF0, 0x10, 0x20, 0x40, 0x40, // 7
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0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
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0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
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0xF0, 0x90, 0xF0, 0x90, 0x90, // A
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0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
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0xF0, 0x80, 0x80, 0x80, 0xF0, // C
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0xE0, 0x90, 0x90, 0x90, 0xE0, // D
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0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
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0xF0, 0x80, 0xF0, 0x80, 0x80 // F
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};
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Chip8::Chip8()
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: randGen(std::chrono::system_clock::now().time_since_epoch().count())
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{
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// Initialize PC
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pc = START_ADDRESS;
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// Load fonts into memory
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for (unsigned int i = 0; i < FONTSET_SIZE; ++i)
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{
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memory[FONTSET_START_ADDRESS + i] = fontset[i];
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}
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// Initialize RNG
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randByte = std::uniform_int_distribution<uint8_t>(0, 255U);
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// Set up function pointer table
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table[0x0] = &Chip8::Table0;
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table[0x1] = &Chip8::OP_1nnn;
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table[0x2] = &Chip8::OP_2nnn;
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table[0x3] = &Chip8::OP_3xkk;
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table[0x4] = &Chip8::OP_4xkk;
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table[0x5] = &Chip8::OP_5xy0;
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table[0x6] = &Chip8::OP_6xkk;
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table[0x7] = &Chip8::OP_7xkk;
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table[0x8] = &Chip8::Table8;
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table[0x9] = &Chip8::OP_9xy0;
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table[0xA] = &Chip8::OP_Annn;
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table[0xB] = &Chip8::OP_Bnnn;
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table[0xC] = &Chip8::OP_Cxkk;
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table[0xD] = &Chip8::OP_Dxyn;
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table[0xE] = &Chip8::TableE;
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table[0xF] = &Chip8::TableF;
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for (size_t i = 0; i <= 0xE; i++)
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{
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table0[i] = &Chip8::OP_NULL;
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table8[i] = &Chip8::OP_NULL;
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tableE[i] = &Chip8::OP_NULL;
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}
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table0[0x0] = &Chip8::OP_00E0;
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table0[0xE] = &Chip8::OP_00EE;
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table8[0x0] = &Chip8::OP_8xy0;
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table8[0x1] = &Chip8::OP_8xy1;
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table8[0x2] = &Chip8::OP_8xy2;
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table8[0x3] = &Chip8::OP_8xy3;
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table8[0x4] = &Chip8::OP_8xy4;
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table8[0x5] = &Chip8::OP_8xy5;
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table8[0x6] = &Chip8::OP_8xy6;
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table8[0x7] = &Chip8::OP_8xy7;
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table8[0xE] = &Chip8::OP_8xyE;
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tableE[0x1] = &Chip8::OP_ExA1;
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tableE[0xE] = &Chip8::OP_Ex9E;
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for (size_t i = 0; i <= 0x65; i++)
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{
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tableF[i] = &Chip8::OP_NULL;
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}
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tableF[0x07] = &Chip8::OP_Fx07;
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tableF[0x0A] = &Chip8::OP_Fx0A;
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tableF[0x15] = &Chip8::OP_Fx15;
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tableF[0x18] = &Chip8::OP_Fx18;
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tableF[0x1E] = &Chip8::OP_Fx1E;
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tableF[0x29] = &Chip8::OP_Fx29;
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tableF[0x33] = &Chip8::OP_Fx33;
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tableF[0x55] = &Chip8::OP_Fx55;
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tableF[0x65] = &Chip8::OP_Fx65;
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}
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void Chip8::LoadROM(char const* filename)
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{
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std::ifstream file(filename, std::ios::binary | std::ios::ate);
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if (file.is_open())
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{
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std::streampos size = file.tellg();
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char* buffer = new char[size];
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file.seekg(0, std::ios::beg);
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file.read(buffer, size);
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file.close();
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for (long i = 0; i < size; ++i)
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{
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memory[START_ADDRESS + i] = buffer[i];
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}
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delete[] buffer;
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}
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}
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void Chip8::Cycle()
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{
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// Fetch
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opcode = (memory[pc] << 8u) | memory[pc + 1];
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// Increment the PC before we execute anything
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pc += 2;
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// Decode and Execute
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((*this).*(table[(opcode & 0xF000u) >> 12u]))();
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// Decrement the delay timer if it's been set
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if (delayTimer > 0)
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{
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--delayTimer;
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}
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// Decrement the sound timer if it's been set
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if (soundTimer > 0)
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{
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--soundTimer;
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}
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}
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void Chip8::Table0()
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{
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((*this).*(table0[opcode & 0x000Fu]))();
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}
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void Chip8::Table8()
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{
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((*this).*(table8[opcode & 0x000Fu]))();
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}
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void Chip8::TableE()
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{
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((*this).*(tableE[opcode & 0x000Fu]))();
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}
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void Chip8::TableF()
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{
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((*this).*(tableF[opcode & 0x00FFu]))();
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}
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void Chip8::OP_NULL()
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{}
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void Chip8::OP_00E0()
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{
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memset(video, 0, sizeof(video));
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}
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void Chip8::OP_00EE()
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{
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--sp;
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pc = stack[sp];
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}
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void Chip8::OP_1nnn()
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{
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uint16_t address = opcode & 0x0FFFu;
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pc = address;
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}
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void Chip8::OP_2nnn()
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{
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uint16_t address = opcode & 0x0FFFu;
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stack[sp] = pc;
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++sp;
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pc = address;
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}
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void Chip8::OP_3xkk()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t byte = opcode & 0x00FFu;
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if (registers[Vx] == byte)
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{
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pc += 2;
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}
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}
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void Chip8::OP_4xkk()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t byte = opcode & 0x00FFu;
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if (registers[Vx] != byte)
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{
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pc += 2;
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}
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}
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void Chip8::OP_5xy0()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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if (registers[Vx] == registers[Vy])
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{
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pc += 2;
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}
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}
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void Chip8::OP_6xkk()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t byte = opcode & 0x00FFu;
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registers[Vx] = byte;
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}
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void Chip8::OP_7xkk()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t byte = opcode & 0x00FFu;
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registers[Vx] += byte;
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}
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void Chip8::OP_8xy0()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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registers[Vx] = registers[Vy];
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}
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void Chip8::OP_8xy1()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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registers[Vx] |= registers[Vy];
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}
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void Chip8::OP_8xy2()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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registers[Vx] &= registers[Vy];
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}
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void Chip8::OP_8xy3()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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registers[Vx] ^= registers[Vy];
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}
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void Chip8::OP_8xy4()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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uint16_t sum = registers[Vx] + registers[Vy];
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if (sum > 255U)
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{
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registers[0xF] = 1;
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}
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else
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{
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registers[0xF] = 0;
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}
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registers[Vx] = sum & 0xFFu;
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}
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void Chip8::OP_8xy5()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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if (registers[Vx] > registers[Vy])
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{
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registers[0xF] = 1;
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}
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else
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{
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registers[0xF] = 0;
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}
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registers[Vx] -= registers[Vy];
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}
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void Chip8::OP_8xy6()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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// Save LSB in VF
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registers[0xF] = (registers[Vx] & 0x1u);
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registers[Vx] >>= 1;
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}
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void Chip8::OP_8xy7()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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if (registers[Vy] > registers[Vx])
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{
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registers[0xF] = 1;
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}
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else
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{
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registers[0xF] = 0;
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}
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registers[Vx] = registers[Vy] - registers[Vx];
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}
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void Chip8::OP_8xyE()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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// Save MSB in VF
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registers[0xF] = (registers[Vx] & 0x80u) >> 7u;
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registers[Vx] <<= 1;
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}
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void Chip8::OP_9xy0()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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if (registers[Vx] != registers[Vy])
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{
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pc += 2;
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}
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}
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void Chip8::OP_Annn()
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{
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uint16_t address = opcode & 0x0FFFu;
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index = address;
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}
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void Chip8::OP_Bnnn()
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{
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uint16_t address = opcode & 0x0FFFu;
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pc = registers[0] + address;
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}
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void Chip8::OP_Cxkk()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t byte = opcode & 0x00FFu;
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registers[Vx] = randByte(randGen) & byte;
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}
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void Chip8::OP_Dxyn()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t Vy = (opcode & 0x00F0u) >> 4u;
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uint8_t height = opcode & 0x000Fu;
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// Wrap if going beyond screen boundaries
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uint8_t xPos = registers[Vx] % VIDEO_WIDTH;
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uint8_t yPos = registers[Vy] % VIDEO_HEIGHT;
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registers[0xF] = 0;
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for (unsigned int row = 0; row < height; ++row)
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{
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uint8_t spriteByte = memory[index + row];
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for (unsigned int col = 0; col < 8; ++col)
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{
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uint8_t spritePixel = spriteByte & (0x80u >> col);
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uint32_t* screenPixel = &video[(yPos + row) * VIDEO_WIDTH + (xPos + col)];
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// Sprite pixel is on
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if (spritePixel)
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{
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// Screen pixel also on - collision
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if (*screenPixel == 0xFFFFFFFF)
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{
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registers[0xF] = 1;
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}
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// Effectively XOR with the sprite pixel
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*screenPixel ^= 0xFFFFFFFF;
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}
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}
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}
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}
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void Chip8::OP_Ex9E()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t key = registers[Vx];
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if (keypad[key])
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{
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pc += 2;
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}
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}
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void Chip8::OP_ExA1()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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uint8_t key = registers[Vx];
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if (!keypad[key])
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{
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pc += 2;
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}
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}
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void Chip8::OP_Fx07()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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registers[Vx] = delayTimer;
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}
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void Chip8::OP_Fx0A()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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if (keypad[0])
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{
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registers[Vx] = 0;
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}
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else if (keypad[1])
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{
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registers[Vx] = 1;
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}
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else if (keypad[2])
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{
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registers[Vx] = 2;
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}
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else if (keypad[3])
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{
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registers[Vx] = 3;
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}
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else if (keypad[4])
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{
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registers[Vx] = 4;
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}
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else if (keypad[5])
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{
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registers[Vx] = 5;
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}
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else if (keypad[6])
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{
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registers[Vx] = 6;
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}
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else if (keypad[7])
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{
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registers[Vx] = 7;
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}
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else if (keypad[8])
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{
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registers[Vx] = 8;
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}
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else if (keypad[9])
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{
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registers[Vx] = 9;
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}
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else if (keypad[10])
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{
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registers[Vx] = 10;
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}
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else if (keypad[11])
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{
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registers[Vx] = 11;
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}
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else if (keypad[12])
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{
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registers[Vx] = 12;
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}
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else if (keypad[13])
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{
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registers[Vx] = 13;
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}
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else if (keypad[14])
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{
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registers[Vx] = 14;
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}
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else if (keypad[15])
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{
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registers[Vx] = 15;
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}
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else
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{
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pc -= 2;
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}
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}
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void Chip8::OP_Fx15()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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delayTimer = registers[Vx];
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}
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void Chip8::OP_Fx18()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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soundTimer = registers[Vx];
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}
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void Chip8::OP_Fx1E()
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{
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uint8_t Vx = (opcode & 0x0F00u) >> 8u;
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index += registers[Vx];
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}
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|
|
|
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];
|
|
}
|
|
}
|