From a6b4a97ebee1a3da459e23dac36c1805048ee414 Mon Sep 17 00:00:00 2001
From: s3lph <account-gitlab-ideynizv@kernelpanic.lol>
Date: Mon, 7 Feb 2022 10:35:04 +0100
Subject: [PATCH] Add SIGINT handler to emulator to trigger an NMI

---
 src/emu6502.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/emu6502.c b/src/emu6502.c
index a831984..0cc2e27 100644
--- a/src/emu6502.c
+++ b/src/emu6502.c
@@ -2,6 +2,7 @@
 #include <stdio.h>
 #include <stdint.h>
 #include <stdlib.h>
+#include <signal.h>
 #include <unistd.h>
 #include <malloc.h>
 #include <string.h>
@@ -12,6 +13,7 @@
 extern uint32_t instructions;
 extern void reset6502(void);
 extern void step6502(void);
+extern void nmi6502(void);
 
 uint8_t *ram, *screen, *f000;
 
@@ -56,6 +58,10 @@ void write6502(uint16_t address, uint8_t value) {
       ram[address] = value;
     }
   } else if (address >= 0x8000 && address <= 0x8fff) {
+    // Replace non-printable characters with dot
+    if (value < 32 || value > 126) {
+      value = '.';
+    }
     printf("%08x: WRITE %04x <- %02x, SCREEN(%d,%d)\n", instructions, address, value, (address&0x03ff)%40, (address&0x03ff)/40);
     screen[address & 0x03ff] = value;
   } else {
@@ -63,6 +69,11 @@ void write6502(uint16_t address, uint8_t value) {
   }
 }
 
+// Trigger a NMI on SIGINT
+void intv(int foo) {
+  nmi6502();
+}
+
 int main() {
   ram = (uint8_t*) malloc(RAMSIZE);
   screen = (uint8_t*) malloc(0x400);
@@ -71,6 +82,7 @@ int main() {
   f000 = mmap(0, 0x1000, PROT_READ, MAP_PRIVATE, ffd, 0);
 
   reset6502();
+  signal(SIGINT, intv);
   while (1) {
     usleep(1);
     step6502();