From b3ca33a8147ed5bd9112a9f0bf4961789cf896de Mon Sep 17 00:00:00 2001
From: Fabien Freling <public@ffreling.com>
Date: Mon, 23 Mar 2015 17:34:22 +0100
Subject: [PATCH] Automatically increment PC register.

---
 src/cpu.ml | 36 ++++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/src/cpu.ml b/src/cpu.ml
index 861e2e2..294a767 100644
--- a/src/cpu.ml
+++ b/src/cpu.ml
@@ -95,44 +95,56 @@ let cmp_A cpu n =
 
 (** http://imrannazar.com/GameBoy-Z80-Opcode-Map *)
 let run cpu (mem: Memory.map) =
-  let n = Memory.get mem (cpu.reg.pc + 1) |> int_of_char in
+  let opcode = Memory.get mem cpu.reg.pc in
+  inc_pc cpu 1;
+  let n = Memory.get mem cpu.reg.pc |> int_of_char in
 (*  let nn = Memory.get mem (cpu.reg.pc + 2) in *)
 (*  Hexa.print_slice cartridge.full_rom cpu.reg.pc (cpu.reg.pc + 7); *)
-  match Memory.get mem cpu.reg.pc with
+  match opcode with
   | '\x00' -> printf "  NOP\n";
-              inc_pc cpu 1; inc_cycles cpu 4
+              inc_cycles cpu 4
 
   | '\x03' -> printf "  INC \tBC\n";
               inc_BC cpu;
-              inc_pc cpu 1; inc_cycles cpu 8
+              inc_cycles cpu 8
+
+  | '\x20' -> printf "  JR\t NZ, 0x%02X\n" n;
+              if cpu.flag.z = false then
+              begin
+                inc_pc cpu n; inc_cycles cpu 12
+              end else
+              begin
+                inc_pc cpu 1; inc_cycles cpu 8
+              end
 
   | '\x3E' -> printf "  LD \tA, 0x%02X\n" n;
               cpu.reg.a <- char_of_int(n);
-              inc_pc cpu 2; inc_cycles cpu 8
+              inc_pc cpu 1; inc_cycles cpu 8
 
   | '\xAF' -> printf "  XOR \tA, A\n";
               let int_A = int_of_char cpu.reg.a in
               cpu.reg.a <- char_of_int @@ int_A lxor int_A;
-              inc_pc cpu 1; inc_cycles cpu 4
+              inc_cycles cpu 4
 
-  | '\xC3' -> let addr = read_2B mem (cpu.reg.pc + 1) in
+  | '\xC3' -> let addr = read_2B mem cpu.reg.pc in
               printf "  JP \t0x%04X\n" addr;
               cpu.reg.pc <- addr; inc_cycles cpu 16
 
   | '\xE0' -> printf "  LDH \t(0xFF%02X), A\n" n;
               Memory.set mem (0xFF00 + n) cpu.reg.a;
-              inc_pc cpu 2; inc_cycles cpu 12
+              inc_pc cpu 1; inc_cycles cpu 12
 
   | '\xF0' -> printf "  LDH \tA, (0xFF%02X)\n" n;
               cpu.reg.a <- Memory.get mem (0xFF00 + n);
-              inc_pc cpu 2; inc_cycles cpu 12
+              inc_pc cpu 1; inc_cycles cpu 12
 
   | '\xF3' -> printf "  DI\n";
               (* fixme *)
-              inc_pc cpu 1; inc_cycles cpu 4
+              inc_cycles cpu 4
 
   | '\xFE' -> printf "  CP\t0x%02X\n" n;
               cmp_A cpu n;
-              inc_pc cpu 2; inc_cycles cpu 8
+              inc_pc cpu 1; inc_cycles cpu 8
 
-  | _ as x -> eprintf "opcode %02X\n" (int_of_char x); failwith "Unimplemented opcode."
+  | _ as x -> eprintf "opcode %02X\n" (int_of_char x);
+              failwith "Unimplemented opcode."