1 files changed, 114 insertions, 0 deletions
diff --git a/src/cpu.adb b/src/cpu.adb
new file mode 100644
index 0000000..809e039
--- /dev/null
+++ b/src/cpu.adb
@@ -0,0 +1,114 @@
+with Ada.Sequential_IO;
+with Ada.Text_IO;
+with Bit_Ops;
+
+package body CPU is
+   function Get_Opcode (Inst : in out Instance) return Opcode is
+      Op : aliased Opcode_Raw;
+      Op_Record : Opcode with Address => Op'Address;
+   begin
+      Op := Opcode_Raw (Inst.Memory (Inst.Program_Counter)) * 2 ** 8;
+      Op := Op + Opcode_Raw (Inst.Memory (Inst.Program_Counter + 1));
+      Inst.Program_Counter := Inst.Program_Counter + 2;
+      return Op_Record;
+   end Get_Opcode;
+
+   procedure Reg_Store (Inst : in out Instance; VX : Register_Index) is
+   begin
+      for I in 0 .. VX loop
+         Inst.Memory (Inst.Address_Register + Address (I)) :=
+            Inst.Registers (I);
+      end loop;
+   end Reg_Store;
+
+   procedure Reg_Load (Inst : in out Instance; VX : Register_Index) is
+   begin
+      for I in 0 .. VX loop
+         Inst.Registers (I) := Inst.Memory
+            (Inst.Address_Register + Address (I));
+      end loop;
+   end Reg_Load;
+
+   procedure Ret (Inst : in out Instance) is
+   begin
+      Jump (Inst, Inst.Stack.Last_Element);
+      Inst.Stack.Delete_Last;
+   end Ret;
+
+   procedure Call (Inst : in out Instance; A : Address) is
+   begin
+      Inst.Stack.Append (Inst.Program_Counter);
+      Jump (Inst, A);
+   end Call;
+
+   procedure Jump (Inst : in out Instance; A : Address) is
+   begin
+      Inst.Program_Counter := A;
+   end Jump;
+
+   procedure Skip (Inst : in out Instance) is
+   begin
+      Inst.Program_Counter := Inst.Program_Counter + 2;
+   end Skip;
+
+   procedure Math (Inst : in out Instance; VX, VY : Register_Index; N : Byte)
+   is begin
+      case N is
+         when 0 =>
+            Inst.Registers (VX) := Inst.Registers (VY);
+         when 1 =>
+            Inst.Registers (VX) := Bit_Ops.Bitwise_Or
+               (Inst.Registers (VX), Inst.Registers (VY));
+         when 2 =>
+            Inst.Registers (VX) := Bit_Ops.Bitwise_And
+               (Inst.Registers (VX), Inst.Registers (VY));
+         when 3 =>
+            Inst.Registers (VX) := Bit_Ops.Bitwise_Xor
+               (Inst.Registers (VX), Inst.Registers (VY));
+         when 4 =>
+            declare
+               X : constant Byte := Inst.Registers (VX);
+               Y : constant Byte := Inst.Registers (VY);
+            begin
+               Inst.Registers (VX) := X + Y;
+               Inst.Registers (15) :=
+                  (if Integer (X) + Integer (Y) > Integer (X + Y)
+                     then 1 else 0);
+            end;
+         when 5 =>
+            declare
+               X : constant Byte := Inst.Registers (VX);
+               Y : constant Byte := Inst.Registers (VY);
+            begin
+               Inst.Registers (VX) := X - Y;
+               Inst.Registers (15) := (if X >= Y then 1 else 0);
+            end;
+         when 6 =>
+            Inst.Registers (15) := Inst.Registers (VX) mod 2;
+            Inst.Registers (VX) := Inst.Registers (VX) / 2;
+         when 14 =>
+            Inst.Registers (15) := Inst.Registers (VX) / (2 ** 7);
+            Inst.Registers (VX) := Inst.Registers (VX) * 2;
+         when others => begin
+            Ada.Text_IO.Put_Line ("Uh oh!");
+            Ada.Text_IO.Put_Line (Byte'Image (N));
+         end;
+      end case;
+   end Math;
+
+   procedure Load_File (Inst : in out Instance; File_Name : String) is
+      package Byte_IO is new Ada.Sequential_IO (Byte);
+
+      I : Address := Start_Address;
+      File_Handle : Byte_IO.File_Type;
+   begin
+      Byte_IO.Open (File_Handle, Byte_IO.In_File, File_Name);
+
+      while not Byte_IO.End_Of_File (File_Handle) loop
+         Byte_IO.Read (File_Handle, Inst.Memory (I));
+         I := I + 1;
+      end loop;
+
+      Byte_IO.Close (File_Handle);
+   end Load_File;
+end CPU;