From 443fb46beb5c1b428436d89fe439edd1a30ef37a Mon Sep 17 00:00:00 2001
From: Ben Kurtovic <ben.kurtovic@gmail.com>
Date: Thu, 26 Mar 2015 04:03:10 -0400
Subject: [PATCH] Add signal handling, plus basic instruction fetch logic.

---
 src/iomanager.c | 27 ++++++++++++++++++++++++++-
 src/z80.c       | 22 ++++++++++++++++++++--
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/src/iomanager.c b/src/iomanager.c
index 2fff5e3..806b950 100644
--- a/src/iomanager.c
+++ b/src/iomanager.c
@@ -1,11 +1,24 @@
 /* Copyright (C) 2014-2015 Ben Kurtovic <ben.kurtovic@gmail.com>
    Released under the terms of the MIT License. See LICENSE for details. */
 
+#include <signal.h>
+#include <stdbool.h>
 #include <unistd.h>
 
 #include "iomanager.h"
 #include "logging.h"
 
+static volatile bool caught_signal;
+
+/*
+    Signal handler for SIGINT.
+*/
+static void handle_sigint(int sig)
+{
+    (void) sig;  // We don't care
+    caught_signal = true;
+}
+
 /*
     Emulate a Game Gear. Handle I/O with the host computer.
 
@@ -13,11 +26,14 @@
 */
 void iomanager_emulate(GameGear *gg)
 {
+    caught_signal = false;
+    signal(SIGINT, handle_sigint);
+
     DEBUG("IOManager powering GameGear")
     gamegear_power(gg, true);
 
     // TODO: use SDL events
-    while (1) {
+    while (!caught_signal) {
         if (gamegear_simulate(gg)) {
             ERROR("caught exception: %s", gamegear_get_exception(gg))
 #ifdef DEBUG_MODE
@@ -28,6 +44,15 @@ void iomanager_emulate(GameGear *gg)
         usleep(1000 * 1000 / 60);
     }
 
+    if (caught_signal) {
+        WARN("caught signal, stopping...")
+#ifdef DEBUG_MODE
+        z80_dump_registers(&gg->cpu);
+#endif
+    }
+
     DEBUG("IOManager unpowering GameGear")
     gamegear_power(gg, false);
+
+    signal(SIGINT, SIG_DFL);
 }
diff --git a/src/z80.c b/src/z80.c
index ba55b39..f572548 100644
--- a/src/z80.c
+++ b/src/z80.c
@@ -86,6 +86,19 @@ static inline uint8_t get_interrupt_mode(Z80 *z80)
     return 2;
 }
 
+/* ------------------------------------------------------------------------- */
+
+static uint8_t z80_inst_nop(Z80 *z80) {
+    z80->regfile.pc++;
+    return 4;
+}
+
+static uint8_t (*instruction_lookup_table[256])(Z80*) = {
+    z80_inst_nop
+};
+
+/* ------------------------------------------------------------------------- */
+
 /*
     Emulate the given number of cycles of the Z80, or until an exception.
 
@@ -98,9 +111,14 @@ bool z80_do_cycles(Z80 *z80, double cycles)
     if (z80->except)
         return true;
 
-    z80->pending_cycles += cycles;
-    // TODO: fetch instruction...
+    cycles -= z80->pending_cycles;
+    while (cycles > 0) {
+        // uint8_t opcode = mmu_read_byte(&z80->mmu, z80->regfile.pc);
+        uint8_t opcode = 0x00;
+        cycles -= (*instruction_lookup_table[opcode])(z80) - 2;
+    }
 
+    z80->pending_cycles = -cycles;
     return false;
 }