--- M6502/M6502.xs	2007/08/03 09:18:08	108
+++ M6502/M6502.xs	2008/04/13 00:32:39	195
@@ -10,8 +10,20 @@
 M6502 *R = NULL;
 int debug = 0;
 
+// same as memory size
+#define CACHE_SIZE 0xffff
 byte opCache[CACHE_SIZE];
 
+#define CALLBACK_READ_SKIP	0x00
+#define CALLBACK_READ_ONCE	0x01
+#define CALLBACK_READ_ALWAYS	0x02
+#define CALLBACK_READ_MASK	0x0f
+#define CALLBACK_WRITE_SKIP	0x00
+#define CALLBACK_WRITE_ONCE	0x10
+#define CALLBACK_WRITE_ALWAYS	0x20
+#define CALLBACK_WRITE_MASK	0xf0
+byte perlCallBack[CACHE_SIZE];
+
 void update_C_R(void) {
 	R->A = SvIV( get_sv("M6502::A", FALSE) );
 	R->P = SvIV( get_sv("M6502::P", FALSE) );
@@ -71,7 +83,13 @@
 /** required if there is a #define FAST_RDOP.               **/
 /************************************ TO BE WRITTEN BY USER **/
 
-byte mem(word Addr) {
+byte mem(register word Addr) {
+
+	if ( perlCallBack[Addr] & CALLBACK_READ_MASK == CALLBACK_READ_SKIP )
+		return opCache[Addr];
+	if ( perlCallBack[Addr] & CALLBACK_READ_MASK == CALLBACK_READ_ONCE )
+		perlCallBack[Addr] = perlCallBack[Addr] & CALLBACK_WRITE_MASK | CALLBACK_READ_SKIP;
+
 	byte byte;
 	int count;
 	debugf(("mem(%04x)", Addr));
@@ -112,6 +130,9 @@
 void Wr6502(register word Addr,register byte Value) {
 	debugf(("Wr6502(%04x,%02x)", Addr, Value));
 	opCache[Addr] = Value;
+	if ( perlCallBack[Addr] & CALLBACK_WRITE_MASK == CALLBACK_WRITE_SKIP ) return;
+	if ( perlCallBack[Addr] & CALLBACK_WRITE_MASK == CALLBACK_WRITE_ONCE )
+		perlCallBack[Addr] = perlCallBack[Addr] & CALLBACK_READ_MASK | CALLBACK_WRITE_SKIP;
 	dSP;
 	ENTER;
 	SAVETMPS;
@@ -126,7 +147,6 @@
 
 byte Op6502(register word Addr) {
 	byte Op;
-	if ( opCache[Addr] ) return opCache[Addr];
 	Op = mem(Addr);
 	debugf(("Op6502(%04x,%02x) PC:%04x", Addr, Op, R->PC.W));
 	return Op;
@@ -174,7 +194,8 @@
 			PerlIO_stdoutf("can't alloc %d bytes for M6502", sizeof(M6502));
 			exit(1);
 		}
-		memset( opCache, 0, sizeof(opCache) );
+		memset( opCache, 0, CACHE_SIZE );
+		memset( perlCallBack, CALLBACK_READ_ALWAYS | CALLBACK_WRITE_ALWAYS, CACHE_SIZE );
 	}
 	Reset6502(R);
 	debugf(("Reset6502 over"));
@@ -205,6 +226,22 @@
 	return debug;
 }
 
+/* FIXME somehow check if Addr will fit in int on current platform */
+void set_read_callback(int Addr) {
+	perlCallBack[Addr] == perlCallBack[Addr] & CALLBACK_WRITE_MASK | CALLBACK_READ_ALWAYS;
+}
+
+void set_write_callback(int Addr) {
+	perlCallBack[Addr] == perlCallBack[Addr] & CALLBACK_READ_MASK | CALLBACK_WRITE_ALWAYS;
+}
+
+/* we fake here, since we will need to call perl at least once to get initial value... */
+int disable_all_callbacks(void) {
+	memset( perlCallBack, CALLBACK_READ_ONCE | CALLBACK_WRITE_ONCE, CACHE_SIZE );
+	return perlCallBack[0];
+}
+
+
 MODULE = M6502		PACKAGE = M6502
 
 PROTOTYPES: DISABLE
@@ -226,3 +263,13 @@
 
 int
 exec(int cycles)
+
+void
+set_read_callback(int Addr)
+
+void
+set_write_callback(int Addr)
+
+int
+disable_all_callbacks()
+