add the ability to add after instruction hooks

.rubocop.yml

@@ -0,0 +1,2 @@
+inherit_gem:
+  rubocop-shopify: rubocop.yml

ext/ruby6502/fake6502.h

@@ -4,6 +4,7 @@
 void reset6502();
 void step6502();
 void exec6502(uint32_t tickcount);
+void hookexternal(void *funcptr);
 
 uint16_t getPC();
 uint8_t getSP();

ext/ruby6502/ruby6502.c

@@ -3,6 +3,7 @@
 #include "fake6502.h"
 
 static VALUE mRuby6502;
+uint8_t has_hooks = 0;
 
 static VALUE program_counter(VALUE self)
 {
@@ -73,6 +74,33 @@ void write6502(uint16_t address, uint8_t value)
   rb_ary_store(memArray, address, rbValue);
 }
 
+static VALUE set_hooks(VALUE self)
+{
+  has_hooks = 1;
+  return Qtrue;
+}
+
+static VALUE unset_hooks(VALUE self)
+{
+  has_hooks = 0;
+  return Qtrue;
+}
+
+static VALUE get_has_hooks(VALUE self)
+{
+  if (has_hooks) {
+    return Qtrue;
+  } else {
+    return Qfalse;
+  }
+}
+
+void execute_hooks() {
+  if (has_hooks) {
+    rb_funcall(mRuby6502, rb_intern("execute_hooks"), 0);
+  }
+}
+
 void Init_ruby6502()
 {
   mRuby6502 = rb_define_module("Ruby6502");
@@ -83,7 +111,14 @@ void Init_ruby6502()
   rb_define_singleton_method(mRuby6502, "_y_register", y_register, 0);
   rb_define_singleton_method(mRuby6502, "_status_flags", status_flags, 0);
   rb_define_singleton_method(mRuby6502, "instruction_count", instruction_count, 0);
+
+  rb_define_singleton_method(mRuby6502, "set_hooks", set_hooks, 0);
+  rb_define_singleton_method(mRuby6502, "unset_hooks", unset_hooks, 0);
+  rb_define_singleton_method(mRuby6502, "hooks?", get_has_hooks, 0);
+
   rb_define_singleton_method(mRuby6502, "reset", reset, 0);
   rb_define_singleton_method(mRuby6502, "step", step, 0);
   rb_define_singleton_method(mRuby6502, "exec", exec, 1);
+
+  hookexternal(execute_hooks);
 }

lib/ruby6502.rb

@@ -4,6 +4,7 @@
 
 module Ruby6502
   MEMORY = [0] * 256 * 256
+  HOOKS = []
 
   def self.load(bytearray, location: 0)
     byte_size = bytearray.size
@@ -18,11 +19,18 @@ def self.load(bytearray, location: 0)
   end
 
   def self.read(location:, bytes:)
-    if location >= MEMORY.size
-      raise "#{format("%04x", location)} is outside bounds"
-    end
+    raise "#{format("%04x", location)} is outside bounds" if location >= MEMORY.size
+
+    MEMORY[location...location + bytes]
+  end
+
+  def self.execute_hooks
+    HOOKS.each(&:call)
+  end
 
-    return MEMORY[location ... location + bytes]
+  def self.register_hook(&hook)
+    set_hooks unless hooks?
+    HOOKS << hook
   end
 
   def self.program_counter

ruby6502.gemspec

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require File.expand_path("../lib/ruby6502/version", __FILE__)
+require File.expand_path("lib/ruby6502/version", __dir__)
 
 Ruby6502::GEMSPEC = Gem::Specification.new do |s|
   s.name        = "ruby6502"