From 188717e22867351177cbf25129fb7cc773dcaf2b Mon Sep 17 00:00:00 2001
From: transistor <trans@jabberwocky.ca>
Date: Sat, 25 Dec 2021 16:30:07 -0800
Subject: [PATCH] Added option to ignore reads/writes to unmapped bus areas

---
 src/machines/genesis.rs |  8 +++++---
 src/memory.rs           | 24 ++++++++++++++++++++++--
 src/system.rs           |  4 ++++
 todo.txt                |  7 ++++---
 4 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/src/machines/genesis.rs b/src/machines/genesis.rs
index 496e2bf..5b5fe96 100644
--- a/src/machines/genesis.rs
+++ b/src/machines/genesis.rs
@@ -6,7 +6,7 @@ use crate::error::Error;
 use crate::system::System;
 use crate::signals::{Signal};
 use crate::memory::{MemoryBlock, Bus, BusPort};
-use crate::devices::{wrap_transmutable, Address, Addressable};
+use crate::devices::{wrap_transmutable, Address, Addressable, Debuggable};
 
 use crate::cpus::m68k::{M68k, M68kType};
 use crate::cpus::z80::{Z80, Z80Type};
@@ -68,13 +68,15 @@ pub fn build_genesis<H: Host>(host: &mut H, options: SegaGenesisOptions) -> Resu
     let coproc_register = wrap_transmutable(CoprocessorBankRegister::new(bank_register.clone()));
     let coproc_area = wrap_transmutable(CoprocessorBankArea::new(bank_register, system.bus.clone()));
 
-    let coproc_bus = Rc::new(RefCell::new(Bus::new()));
+    let mut coproc_bus = Rc::new(RefCell::new(Bus::new()));
+    coproc_bus.borrow_mut().set_ignore_unmapped(true);
     coproc_bus.borrow_mut().insert(0x0000, coproc_ram.clone());
     coproc_bus.borrow_mut().insert(0x4000, coproc_ym_sound.clone());
     coproc_bus.borrow_mut().insert(0x6000, coproc_register.clone());
     coproc_bus.borrow_mut().insert(0x7f11, coproc_sn_sound.clone());
     coproc_bus.borrow_mut().insert(0x8000, coproc_area);
-    let coproc = Z80::new(Z80Type::Z80, 3_579_545, BusPort::new(0, 16, 8, coproc_bus.clone()));
+    let mut coproc = Z80::new(Z80Type::Z80, 3_579_545, BusPort::new(0, 16, 8, coproc_bus.clone()));
+    coproc.set_debugging(true);
     let mut reset = coproc.reset.clone();
     let mut bus_request = coproc.bus_request.clone();
     reset.set(true);
diff --git a/src/memory.rs b/src/memory.rs
index 1539838..8dc35e7 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -118,16 +118,22 @@ pub struct Block {
 }
 
 pub struct Bus {
+    ignore_unmapped: bool,
     blocks: Vec<Block>,
 }
 
 impl Bus {
     pub fn new() -> Bus {
         Bus {
+            ignore_unmapped: false,
             blocks: vec!(),
         }
     }
 
+    pub fn set_ignore_unmapped(&mut self, ignore_unmapped: bool) {
+        self.ignore_unmapped = ignore_unmapped;
+    }
+
     pub fn clear_all_bus_devices(&mut self) {
         self.blocks.clear();
     }
@@ -180,13 +186,27 @@ impl Addressable for Bus {
     }
 
     fn read(&mut self, addr: Address, data: &mut [u8]) -> Result<(), Error> {
-        let (dev, relative_addr) = self.get_device_at(addr, data.len())?;
+        let (dev, relative_addr) = match self.get_device_at(addr, data.len()) {
+            Ok(result) => result,
+            Err(err) if self.ignore_unmapped => {
+                info!("{:?}", err);
+                return Ok(())
+            },
+            Err(err) => return Err(err),
+        };
         let result = dev.borrow_mut().as_addressable().unwrap().read(relative_addr, data);
         result
     }
 
     fn write(&mut self, addr: Address, data: &[u8]) -> Result<(), Error> {
-        let (dev, relative_addr) = self.get_device_at(addr, data.len())?;
+        let (dev, relative_addr) = match self.get_device_at(addr, data.len()) {
+            Ok(result) => result,
+            Err(err) if self.ignore_unmapped => {
+                info!("{:?}", err);
+                return Ok(())
+            },
+            Err(err) => return Err(err),
+        };
         let result = dev.borrow_mut().as_addressable().unwrap().write(relative_addr, data);
         result
     }
diff --git a/src/system.rs b/src/system.rs
index 798d0a2..d144583 100644
--- a/src/system.rs
+++ b/src/system.rs
@@ -50,6 +50,10 @@ impl System {
         self.interrupt_controller.borrow_mut()
     }
 
+    pub fn get_device(&self, name: &str) -> Result<TransmutableBox, Error> {
+        self.devices.get(name).cloned().ok_or_else(|| Error::new(&format!("system: no device named {}", name)))
+    }
+
     pub fn add_device(&mut self, name: &str, device: TransmutableBox) -> Result<(), Error> {
         self.try_queue_device(device.clone());
         self.devices.insert(name.to_string(), device);
diff --git a/todo.txt b/todo.txt
index b1534e8..6c6c2aa 100644
--- a/todo.txt
+++ b/todo.txt
@@ -1,12 +1,13 @@
 
+* there is an issue with Mortal Kombat 2 where it will crash randomly at the start of a fight.  The code is actually swapping
+  stacks a bunch of times, and at some point, the stack is corrupted or something and it `rts`s to the wrong address...
 
-* for the line based hscroll, you need to add that extra cell cycle...
 * there is still some kind of hscroll glitch, and it seems to entirely be caused by the horizontal scroll offset value.  I could be calculating or adding/moding
   it incorrectly somewhere somehow, or the data in the hscroll table could be incorrect due to the cpu impl
+
+
 * go through the testcases and make sure they are decoded correctly
 
-
-
 * should you rename devices.rs traits.rs?
 * add command line arguments to speed up or slow down either the frame rate limiter or the simulated time per frame