Initial commit

emulator.h

@@ -0,0 +1,67 @@
+#pragma once
+#include <cstdint>
+#include <vector>
+#include <array>
+#include "instruction.h"
+
+#define MEMORY_SIZE 0x00040000 // 256 kibibytes, or 262144
+#define PROGRAM_ROM_START 0x00001000
+#define GENERAL_PURPOSE_START 0x00010000
+
+#define PC_REG_OFFSET 7
+#define IHP_REG_OFFSET 8
+#define SP_REG_OFFSET 9
+#define FLAGS_REG_OFFSET 10
+
+#define PC registers[PC_REG_OFFSET]
+#define IHP registers[PC_REG_OFFSET]
+#define SP registers[PC_REG_OFFSET]
+#define FLAGS registers[PC_REG_OFFSET]
+
+#define FLAGS_CARRY (1 << 0)
+#define FLAGS_ZERO (1 << 1)
+#define FLAGS_NEGATIVE (1 << 2)
+
+/*
+ * All-purpose memory used by the emulator
+ * 4kb for call stack (0x00000000 -> 0x00000FFF)
+ * 65kb for program ROM (0x00001000 -> 0x0000FFFF)
+ * Rest for general purpose (0x00010000 -> MEMORY_SIZE)
+ */
+struct Memory {
+    size_t instructions = 0;
+    size_t calls = 0;
+
+    uint8_t memory[MEMORY_SIZE]{};
+
+    void addInstruction(const Instruction& inst);
+    void addCall(const uint16_t address);
+
+    uint8_t* operator[](const size_t& offset);
+
+    Memory() = default;
+    Memory(const std::vector<Instruction>& instructions) {
+        for (const auto& instruction : instructions) {
+           addInstruction(instruction.asBytecodeInstruction());
+        }
+    }
+};
+
+using Program = std::vector<Instruction>;
+
+class Emulator {
+    private:
+        std::array<uint16_t, 11> registers = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+
+        Memory memory = {};
+
+        bool halted = false;
+
+        Instruction fetchNextInst();
+        void updateFlags(int32_t opResult);
+
+    public:
+        void start();
+        Emulator() = delete;
+        Emulator(const Memory& memory) : memory(std::move(memory)) {}
+};