From b4c81fa3f993f42e11dbbd54c7087f2c5f212c9a Mon Sep 17 00:00:00 2001
From: Fabien Freling <public@ffreling.com>
Date: Tue, 1 Mar 2016 23:15:56 +0100
Subject: [PATCH] Add CPU.handle_interrupts

---
 src/cpu.ml       | 33 +++++++++++++++++++++------------
 src/interrupt.ml | 28 +++++++++++++++++++++++++++-
 src/oboy.ml      |  2 ++
 3 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/src/cpu.ml b/src/cpu.ml
index b51ee60..e305de3 100644
--- a/src/cpu.ml
+++ b/src/cpu.ml
@@ -306,7 +306,7 @@ let run cpu (mem: Memory.map) =
 
   | '\xFB' -> let inst = sprintf "EI" in
               (* enable interrupts *)
-              Interrupt.ime := true;
+              Interrupt.gIME := true;
               inst, 4
 
   |  x -> eprintf "opcode 0x%02X\n" (int_of_char x);
@@ -323,7 +323,7 @@ let run cpu (mem: Memory.map) =
  *  Interrupt handlers
  *
  ************************************************)
-let handle_interrupt cpu mem flag =
+let handle_interrupt cpu mmap flag =
   let int_vector = match flag with
   | Interrupt.V_Blank  -> 0x40
   | Interrupt.LCD_Stat -> 0x48
@@ -331,25 +331,34 @@ let handle_interrupt cpu mem flag =
   | Interrupt.Serial   -> 0x58
   | Interrupt.Joypad   -> 0x60 in
 
-  (* TODO: reset IF flag *)
-  Interrupt.ime := false;
+  Interrupt.reset_IF_flag flag mmap;
+  Interrupt.gIME := false;
 
-  push_pc_stack cpu mem;
-  cpu.reg.pc <- int_vector
+  push_pc_stack cpu mmap;
+  cpu.reg.pc <- int_vector;
 
-  (* TODO: run cpu until RETI is called *)
+  (* run cpu until RETI is called *)
+  let last_inst = ref "" in
+  while !last_inst <> "RETI" do
+    let inst, cycles = run cpu mmap in
+    last_inst := inst
+  done;
+
+  Interrupt.gIME := true
 
 
 
-let handle_interrupts cpu mem ie if_ =
-  if not !Interrupt.ime then 
+let handle_interrupts cpu mmap =
+  if not !Interrupt.gIME then
     () (* Interrupt Master Enable flag set to false, nothing to do *)
-  else (
+  else begin
     (* N.B.: flags are precomputed once but an interrupt could be requested
        during that time *)
+    let ie = Interrupt.get_IE mmap in 
+    let if_ = Interrupt.get_IF mmap in 
     let interrupts = ie land if_ in
     let flags = Interrupt.get_flags interrupts in
     match flags with
     | [] -> () (* No interrupt *)
-    | _ -> List.iter (fun x -> handle_interrupt cpu mem x) flags
-  )
+    | _ -> List.iter (fun x -> handle_interrupt cpu mmap x) flags
+  end
diff --git a/src/interrupt.ml b/src/interrupt.ml
index 3e28847..94f5b69 100644
--- a/src/interrupt.ml
+++ b/src/interrupt.ml
@@ -6,7 +6,11 @@
  * LICENSE file at the top level directory of this source tree.
  *)
 
-let ime = ref false;;
+(** Interrupt Master Enable flag *)
+let gIME = ref false
+
+let ie_addr = 0xFFFF
+let if_addr = 0xFFF0
 
 type t =
   | V_Blank
@@ -15,6 +19,14 @@ type t =
   | Serial
   | Joypad
 
+
+let get_flag_mask = function
+  | V_Blank  -> 0b00000001
+  | LCD_Stat -> 0b00000010
+  | Timer    -> 0b00000100
+  | Serial   -> 0b00001000
+  | Joypad   -> 0b00010000
+
 (** Return the list of interrupt flags sorted by priority. *)
 let get_flags byte =
 
@@ -38,3 +50,17 @@ let get_flags byte =
     | _ -> List.rev accu in
 
   get_flag byte 0 []
+
+
+(** Interrupt Enable *)
+let get_IE mem = Memory.get mem ie_addr |> int_of_char
+
+(** Interrupt Flag *)
+let get_IF mem = Memory.get mem if_addr |> int_of_char
+
+let reset_IF_flag flag mem =
+  let if_reg = get_IF mem in
+  let flag_mask = get_flag_mask flag in
+  let new_if_reg = if_reg land (lnot flag_mask) |> char_of_int in
+  Memory.set mem if_addr new_if_reg
+
diff --git a/src/oboy.ml b/src/oboy.ml
index f333dbd..0d44ee3 100644
--- a/src/oboy.ml
+++ b/src/oboy.ml
@@ -21,6 +21,8 @@ let rec run (cpu: Cpu.t) (mem: Memory.t) (screen: Screen.t) =
       let inst, cycles = Cpu.run cpu mem.map in
       printf "[Instruction] %s\n" inst;
 
+      Cpu.handle_interrupts cpu mem.map;
+
       Memory.update_timers mem cycles;
 
       run_for cpu mem (cycles_remaining - cycles)