1 files changed, 110 insertions, 0 deletions
diff --git a/src/Instruction.h b/src/Instruction.h
new file mode 100644
index 0000000..c80d2ca
--- /dev/null
+++ b/src/Instruction.h
@@ -0,0 +1,110 @@
+#pragma once
+
+#include <string>
+#include <cstdint>
+
+#include "ExecutorCases.h"
+#include "Exceptions.h"
+
+namespace x86 {
+  enum Register : uint8_t {
+    EAX = 0,    ECX = 1,     EDX = 2,    EBX = 3,
+    ESP = 4,    EBP = 5,     ESI = 6,    EDI = 7,
+
+    SIB_DISP = 254,
+    SIB_NONE = 255,
+  };
+
+  enum class ModRMState : uint8_t
+  {
+    INVALID = 0,
+    LR = 1,
+    LR_DISP8 = 2,
+    LR_DISP32 = 3,
+    DISP32 = 4,
+    R = 5
+  };
+
+  struct ModRM {
+    ModRMState m_State;
+    x86::Register m_Reg;
+    uint8_t m_Rm;
+    bool m_SIB;
+  };
+
+  struct SIB {
+    uint8_t m_Scale;
+    x86::Register m_Index;
+    x86::Register m_Base;
+  };
+
+  constexpr ModRM ProcessMODRM(uint8_t modrm) {
+    uint8_t mod_mask = 0b11000000;
+    uint8_t reg_mask = 0b00111000;
+    uint8_t rm_mask = 0b00000111;
+  
+    uint8_t mod = modrm & mod_mask;
+    uint8_t reg = (modrm & reg_mask) >> 3;
+    uint8_t rm = modrm & rm_mask;
+
+    ModRMState state = ModRMState::INVALID;
+    bool SIB = false;
+  
+    switch(mod) {
+    case 0b00000000:
+      state = ModRMState::LR;
+      if(rm == 0b00000101)
+	state = ModRMState::DISP32;
+      else if(rm == 0b00000100)
+	SIB = true;
+      break;
+    case 0b01000000:
+      state = ModRMState::LR_DISP8;
+      if(rm == 0b00000100)
+	SIB = true;
+      break;
+    case 0b10000000:
+      state = ModRMState::LR_DISP32;
+      if(rm == 0b00000100)
+	SIB = true;
+      break;
+    case 0b11000000:
+      state = ModRMState::R;
+      break;
+    default:
+      throw CPUException("Mod R/M Unknown exception!");
+    }
+    
+    return {.m_State = state, .m_Reg = (x86::Register)reg, .m_Rm = rm, .m_SIB = SIB};  
+  }
+  
+  SIB ProcessSIB(uint8_t sib);
+
+  // Helpers
+  std::string Register2Str(x86::Register reg);
+}
+
+enum Opcode : uint8_t {
+  INVALID = 0,
+  NOP = 0x90,
+  HLT = 0xF4,
+  MOV_R32_IMM32 = 0xB8,
+  MOV_RM32_R32 = 0x89,
+  ADD_RM32_R32 = 0x01,
+  ADD_R32_RM32 = 0x03,
+};
+
+std::string Opcode2Str(Opcode op);
+
+struct Instruction{
+  ExecutorCase m_Func;
+  uint8_t m_Prefix;
+  Opcode m_Opcode;
+  size_t m_Length;
+  uint32_t m_Operand1;
+  uint32_t m_Operand2;
+  x86::ModRM m_ModRM;
+  x86::SIB m_SIB;
+  uint8_t m_Displacement[4];
+  uint8_t m_DisplacementSize;
+};