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Diffstat (limited to 'src/chip8.cpp')
| -rw-r--r-- | src/chip8.cpp | 520 |
1 files changed, 520 insertions, 0 deletions
diff --git a/src/chip8.cpp b/src/chip8.cpp new file mode 100644 index 0000000..94573f0 --- /dev/null +++ b/src/chip8.cpp @@ -0,0 +1,520 @@ +#include "chip8.hpp" + +#include <fstream> +#include <iostream> +#include <cstdint> +#include <chrono> + +const uint32_t FONTSET_START_ADDRESS = 0x050; +const uint32_t ROM_START_ADDRESS = 0x200; + +const uint32_t FONTSET_SIZE = 0x0a0 - FONTSET_START_ADDRESS; + +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() { + pc = ROM_START_ADDRESS; + + for (uint32_t i = 0; i < FONTSET_SIZE; i++) { + memory[FONTSET_START_ADDRESS + i] = fontset[i]; + } + + randGen = std::default_random_engine( + std::chrono::system_clock::now() + .time_since_epoch() + .count() + ); + randByte = std::uniform_int_distribution<uint8_t>(0, 255U); + + SetupTable(); +} + +void Chip8::SetupTable() { + for (size_t i = 0; i <= sizeof(table0) / sizeof(table0[0]); i++) { + table0[i] = &Chip8::OP_NULL; + table8[i] = &Chip8::OP_NULL; + tableE[i] = &Chip8::OP_NULL; + } + + for (size_t i = 0; i <= sizeof(tableF) / sizeof(tableF[0]); i++) { + tableF[i] = &Chip8::OP_NULL; + } + + 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::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::Cycle() { + // Fetch + opcode = (memory[pc] << 8u) | memory[pc + 1]; + pc += 2; + + // Decode and Execute + ((*this).*(table[(opcode & 0xF000u) >> 12u]))(); + + // Decrement delay timer + if (delayTimer > 0) { + delayTimer--; + } + + if (soundTimer > 0) { + --soundTimer; + } +} + +void Chip8::LoadROM(const char* filename) { + // Open file as binary stream and seek to the end + std::ifstream file(filename, std::ios::binary | std::ios::ate); + + if (file.is_open()) { + // Get file size + std::streampos size = file.tellg(); + // Allocate buffer + char* buffer = new char[size]; + + // Seek to the beginning + file.seekg(0, std::ios::beg); + // Populate the buffer + file.read(buffer, size); + file.close(); + + // Load ROM contents into Chip8's memory, from 0x200 + for (uint64_t i = 0; i < size; i++) { + memory[ROM_START_ADDRESS + i] = buffer[i]; + } + + // Free the buffer + delete[] buffer; + } +} + +// NULL: NOP +// Do nothing +void Chip8::OP_NULL() {} + +// 00E0: CLS +// Clear the display +void Chip8::OP_00E0() { + for (uint32_t i = 0; i < sizeof(video) / sizeof(video[0]); i++) { + video[i] = 0; + } +}; + +// 00EE: RET +// Return from a subroutine +void Chip8::OP_00EE() { + sp--; + pc = stack[sp]; +} + +// 1nnn: JP addr +// Jump to location nnn +void Chip8::OP_1nnn() { + uint16_t address = opcode & 0x0FFFu; + pc = address; +} + +// 2nnn: CALL addr +// Call subroutine at nnn +void Chip8::OP_2nnn() { + uint16_t address = opcode & 0x0FFFu; + stack[sp] = pc; + sp++; + pc = address; +} + +// 3xkk: SE Vx, byte +// Skip next instruction if Vx = kk +void Chip8::OP_3xkk() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t byte = opcode & 0x00FFu; + + if (registers[Vx] == byte) + pc += 2; +} + +// 4xkk: SNE Vx, byte +// Skip next instruction if Vx != kk +void Chip8::OP_4xkk() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t byte = opcode & 0x00FFu; + + if (registers[Vx] != byte) + pc += 2; +} + +// 5xy0: SE Vx, Vy +// Skip next instruction if Vx == Vy +void Chip8::OP_5xy0() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + if (registers[Vx] == registers[Vy]) + pc += 2; +} + +// 6xkk: LD Vx, byte +// Set Vx = kk +void Chip8::OP_6xkk() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t byte = opcode & 0x00FFu; + + registers[Vx] = byte; +} + +// 7xkk: ADD Vx, byte +// Set Vx += kk +void Chip8::OP_7xkk() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t byte = opcode & 0x00FFu; + + registers[Vx] += byte; +} + +// 8xy0: LD Vx, Vy +// Set Vx = Vy +void Chip8::OP_8xy0() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + registers[Vx] = registers[Vy]; +} + +// 8xy1: OR Vx, Vy +// Set Vx = Vx OR Vy +void Chip8::OP_8xy1() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + registers[Vx] |= registers[Vy]; +} + +// 8xy2: AND Vx, Vy +// Set Vx = Vx AND Vy +void Chip8::OP_8xy2() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + registers[Vx] &= registers[Vy]; +} + +// 8xy3: XOR Vx, Vy +// Set Vx = Vx XOR Vy +void Chip8::OP_8xy3() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + registers[Vx] ^= registers[Vy]; +} + +// 8xy4: ADD Vx, Vy +// Set Vx += Vy, set VF = carry +void Chip8::OP_8xy4() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + uint16_t sum = registers[Vx] + registers[Vy]; + + if (sum > 255u) { + registers[0xF] = 1; + } else { + registers[0xF] = 0; + } + + registers[Vx] = sum & 0xFFu; +} + +// 8xy5: SUB Vx, Vy +// Set Vx -= Vy, set VF = NOT borrow +void Chip8::OP_8xy5() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + if (registers[Vx] > registers[Vy]) { + registers[0xF] = 1; + } else { + registers[0xF] = 0; + } + + registers[Vx] -= registers[Vy]; +} + +// 8xy6: SHR Vx +// Set Vx = Vx SHR 1 +void Chip8::OP_8xy6() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + + // Save LSB in VF + registers[0xF] = (registers[Vx] & 0x1u); + + registers[Vx] >>= 1; +} + +// 8xy7: SUBN Vx, Vy +// Set Vy -= Vx, set VF = NOT borrow +void Chip8::OP_8xy7() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + if (registers[Vy] > registers[Vx]) { + registers[0xF] = 1; + } else { + registers[0xF] = 0; + } + + registers[Vx] = registers[Vy] - registers[Vx]; +} + +// 8xyE: SHL Vx +// Set Vx = Vx SHL 1 +void Chip8::OP_8xyE() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + + // Save LSB in VF + registers[0xF] = (registers[Vx] & 0x80u) >> 7u; + + registers[Vx] <<= 1; +} + +// 9xy0: SNE Vx, Vy +// Skip next instruction if Vx != Vy +void Chip8::OP_9xy0() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 4u; + + if (registers[Vx] != registers[Vy]) + pc += 2; +} + +// Annn: LD I, addr +// Set I = nnn +void Chip8::OP_Annn() { + uint16_t address = opcode & 0x0FFFu; + index = address; +} + +// Bnnn: JP V0, addr +// Jump to location nnn + V0 +void Chip8::OP_Bnnn() { + uint16_t address = opcode & 0x0FFFu; + pc = registers[0x0] + address; +} + +// Cxkk: RND Vx, byte +// Set Vx = random byte AND kk +void Chip8::OP_Cxkk() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t byte = opcode & 0x00FFu; + + registers[Vx] = randByte(randGen) & byte; +} + +// Dxyn: DRW Vx, Vy, nibble +// Display n-byte sprite starting at memory location I at (Vx, Vy), set VF = collision +void Chip8::OP_Dxyn() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t Vy = (opcode & 0x00FFu) >> 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 (uint32_t row = 0; row < height; ++row) { + uint8_t spriteByte = memory[index + row]; + for (uint32_t col = 0; col < 8; ++col) { + uint8_t spritePixel = spriteByte & (0x80u >> col); + uint32_t* screenPixel = &video[(yPos + row) * VIDEO_WIDTH + (xPos + col)]; + + if (spritePixel) { + if(*screenPixel == 0xFFFFFFFF) + registers[0xF] = 1; + *screenPixel ^= 0xFFFFFFFF; + } + } + } +} + +// Ex9E: SKP Vx +// Skip next instruction if key with the value of Vx is pressed +void Chip8::OP_Ex9E() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t key = registers[Vx]; + + if (keypad[key]) + pc += 2; +} + +// ExA1: SKNP Vx +// Skip next instruction if key with the value of Vx is not pressed +void Chip8::OP_ExA1() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t key = registers[Vx]; + + if (!keypad[key]) + pc += 2; +} + +// Fx07: LD Vx, DT +// Set Vx = delay timer value +void Chip8::OP_Fx07() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + registers[Vx] = delayTimer; +} + +// Fx0A: LD Vx, K +// Wait for a key press, store the value of the key in Vx +void Chip8::OP_Fx0A() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + for (uint16_t i = 0; i < 16; i++) { + if (keypad[i]) { + registers[Vx] = static_cast<uint8_t>(i); + return; + } + } + + pc -= 2; +} + +// Fx15: LD DT, Vx +// Set delay timer value = Vx +void Chip8::OP_Fx15() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + delayTimer = registers[Vx]; +} + +// Fx18: LD ST, Vx +// Set sound timer value = Vx +void Chip8::OP_Fx18() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + soundTimer = registers[Vx]; +} + +// Fx1E: ADD I, Vx +// Set I += Vx +void Chip8::OP_Fx1E() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + index += registers[Vx]; +} + +// Fx29: LD F, Vx +// Set I = location of sprite for digit Vx +void Chip8::OP_Fx29() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + uint8_t digit = registers[Vx]; + + index = FONTSET_START_ADDRESS + (5 * digit); +} + +// Fx33: LD B, Vx +// Store BCD representation of Vx in memory locations I, I+1, and I+2 +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; +} + +// Fx55: LD [I], Vx +// Store registers V0 through Vx in memory starting at location I +void Chip8::OP_Fx55() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + + for (uint8_t i = 0; i <= Vx; ++i) { + memory[index + i] = registers[i]; + } +} + +// Fx65: LD Vx, [I] +// Read registers V0 through Vx in memory starting at location I +void Chip8::OP_Fx65() { + uint8_t Vx = (opcode & 0x0F00u) >> 8u; + + for (uint8_t i = 0; i <= Vx; ++i) { + registers[i] = memory[index + i]; + } +} |