Initial code

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];
+  }
+}