Reworking devices to set up for a simple buff device

src/device.rs

@@ -1,19 +1,39 @@
+pub mod buff;
 pub mod console;
 pub mod null;
 pub mod system;
 
 use crate::vm::Uxn;
 
+#[derive(Debug, PartialEq)]
+pub enum DeviceError {
+    AddressOverflow,
+    PortTypeError(u8, String),
+}
+
 pub trait Device: std::fmt::Debug {
     /**
      * Callbacks used by UXN to do input from a "device".
      */
-    fn dei1(&mut self, vm: &mut Uxn, port: u8) -> u8;
+    fn dei1(&mut self, vm: &mut Uxn, port: u8) -> Result<u8, DeviceError>;
-    fn dei2(&mut self, vm: &mut Uxn, port: u8) -> u16;
+
+    fn dei2(&mut self, vm: &mut Uxn, port: u8) -> Result<u16, DeviceError> {
+        return Ok(((self.dei1(vm, port)? as u16) << 8) + self.dei1(vm, port + 1)? as u16);
+    }
 
     /**
      * Callback used by UXN to do output through a "device".
      */
-    fn deo1(&mut self, vm: &mut Uxn, port: u8, val: u8);
+    fn deo1(&mut self, vm: &mut Uxn, port: u8, val: u8) -> Result<(), DeviceError>;
-    fn deo2(&mut self, vm: &mut Uxn, port: u8, val: u16);
+
+    fn deo2(&mut self, vm: &mut Uxn, port: u8, val: u16) -> Result<(), DeviceError> {
+        let slot = port & 0xF;
+        if slot < 0xF {
+            return Err(DeviceError::AddressOverflow);
+        }
+        let [high, low] = val.to_be_bytes();
+        self.deo1(vm, slot, high)?;
+        self.deo1(vm, slot + 1, low)?;
+        Ok(())
+    }
 }

src/device/buff.rs

@@ -0,0 +1,36 @@
+use crate::device::Device;
+use crate::device::DeviceError;
+use crate::vm::Uxn;
+
+/**
+ * The null device does nothing when reading or writing.
+ */
+#[derive(Debug)]
+pub struct BuffDevice {
+    buffer: [u8; 16],
+}
+
+impl BuffDevice {
+    pub fn new() -> BuffDevice {
+        BuffDevice { buffer: [0; 16] }
+    }
+}
+
+impl Device for BuffDevice {
+    fn dei1(&mut self, _vm: &mut Uxn, port: u8) -> Result<u8, DeviceError> {
+        let slot = (port & 0xF) as usize;
+        Ok(self.buffer[slot])
+    }
+    fn dei2(&mut self, _vm: &mut Uxn, port: u8) -> Result<u16, DeviceError> {
+        let slot = (port & 0xF) as usize;
+        Ok(0)
+    }
+    fn deo1(&mut self, _vm: &mut Uxn, port: u8, val: u8) -> Result<(), DeviceError> {
+        let slot = (port & 0xF) as usize;
+        Ok(())
+    }
+    fn deo2(&mut self, _vm: &mut Uxn, port: u8, val: u16) -> Result<(), DeviceError> {
+        let slot = (port & 0xF) as usize;
+        Ok(())
+    }
+}

src/device/console.rs

@@ -1,4 +1,4 @@
-use crate::device::Device;
+use crate::device::{Device, DeviceError};
 use crate::vm::Uxn;
 
 /**
@@ -40,21 +40,33 @@ impl Device for ConsoleDevice {
      * If inidx < inbuffer.size, we want to return the next character out of the
      * inbuffer.
      */
-    fn dei1(&mut self, vm: &mut Uxn, port: u8) -> u8 {
+    fn dei1(&mut self, vm: &mut Uxn, port: u8) -> Result<u8, DeviceError> {
         let slot = port & 0xF;
         match slot {
-            0x2 => 0,
+            0x2 => Ok(0),
-            _ => 0,
+            _ => Ok(0),
         }
     }
+
     // DEI2 is not supported on the terminal device
-    fn dei2(&mut self, vm: &mut Uxn, port: u8) -> u16 {
+    fn dei2(&mut self, vm: &mut Uxn, port: u8) -> Result<u16, DeviceError> {
-        0
+        Err(DeviceError::PortTypeError(
+            port,
+            "double reads from the console are not supported".into(),
+        ))
     }
 
     /**
      * Callback used by UXN to do output through a "device".
      */
-    fn deo1(&mut self, vm: &mut Uxn, port: u8, val: u8) {}
+    fn deo1(&mut self, vm: &mut Uxn, port: u8, val: u8) -> Result<(), DeviceError> {
-    fn deo2(&mut self, vm: &mut Uxn, port: u8, val: u16) {}
+        Ok(())
+    }
+
+    fn deo2(&mut self, vm: &mut Uxn, port: u8, val: u16) -> Result<(), DeviceError> {
+        Err(DeviceError::PortTypeError(
+            port,
+            "double writes to the console are not supported".into(),
+        ))
+    }
 }

src/device/null.rs

@@ -1,4 +1,4 @@
-use crate::device::Device;
+use crate::device::{Device, DeviceError};
 use crate::vm::Uxn;
 
 /**
@@ -14,12 +14,17 @@ impl NullDevice {
 }
 
 impl Device for NullDevice {
-    fn dei1(&mut self, _vm: &mut Uxn, _port: u8) -> u8 {
+    fn dei1(&mut self, _vm: &mut Uxn, _port: u8) -> Result<u8, DeviceError> {
-        0
+        Ok(0)
     }
-    fn dei2(&mut self, _vm: &mut Uxn, _port: u8) -> u16 {
+    fn dei2(&mut self, _vm: &mut Uxn, _port: u8) -> Result<u16, DeviceError> {
-        0
+        Ok(0)
+    }
+
+    fn deo1(&mut self, _vm: &mut Uxn, _port: u8, _val: u8) -> Result<(), DeviceError> {
+        Ok(())
+    }
+    fn deo2(&mut self, _vm: &mut Uxn, _port: u8, _val: u16) -> Result<(), DeviceError> {
+        Ok(())
     }
-    fn deo1(&mut self, _vm: &mut Uxn, _port: u8, _val: u8) {}
-    fn deo2(&mut self, _vm: &mut Uxn, _port: u8, _val: u16) {}
 }

src/device/system.rs

@@ -1,4 +1,4 @@
-use crate::device::Device;
+use crate::device::{Device, DeviceError};
 use crate::vm::Uxn;
 
 /**
@@ -6,48 +6,112 @@ use crate::vm::Uxn;
  */
 #[derive(Debug)]
 pub struct SystemDevice {
-    buffer: [u8; 0xF],
+    vector: u16, // 0x0
+    red: u16,    // 0x8
+    green: u16,  // 0xA
+    blue: u16,   // 0xC
+    debug: u8,   // 0xE
+    state: u8,   // 0xF
 }
 
 impl SystemDevice {
     pub fn new() -> SystemDevice {
-        SystemDevice { buffer: [0; 0xF] }
+        SystemDevice {
+            vector: 0,
+            red: 0,
+            blue: 0,
+            green: 0,
+            debug: 0,
+            state: 0,
+        }
     }
 }
 
 impl Device for SystemDevice {
-    fn dei1(&mut self, vm: &mut Uxn, port: u8) -> u8 {
+    fn dei1(&mut self, vm: &mut Uxn, port: u8) -> Result<u8, DeviceError> {
         let slot = port & 0xF;
-        match slot {
+        Ok(match slot {
+            // High and low words of the vector
+            0x0 => (self.vector >> 8) as u8,
+            0x1 => (self.vector & 0xFF) as u8,
+            // The stack ports (somewhat nonstandard)
             0x2 => vm.wst.borrow().idx(),
             0x3 => vm.rst.borrow().idx(),
-            x => self.buffer[x as usize],
+
+            // Red
+            0x8 => (self.red >> 8) as u8,
+            0x9 => (self.red & 0xFF) as u8,
+
+            // Green
+            0xa => (self.green >> 8) as u8,
+            0xb => (self.green & 0xFF) as u8,
+
+            // Blue
+            0xc => (self.blue >> 8) as u8,
+            0xd => (self.blue & 0xFF) as u8,
+
+            // The state ports
+            0xe => self.debug,
+            0xf => self.state,
+            _ => unreachable!(),
+        })
     }
-    }
+
-    fn dei2(&mut self, vm: &mut Uxn, port: u8) -> u16 {
+    fn deo1(&mut self, vm: &mut Uxn, port: u8, val: u8) -> Result<(), DeviceError> {
-        return ((self.dei1(vm, port) as u16) << 8) + self.dei1(vm, port + 1) as u16;
-    }
-    fn deo1(&mut self, vm: &mut Uxn, port: u8, val: u8) {
         let slot = port & 0xF;
         match slot {
+            // High and low words of the vector
+            0x0 => {
+                self.vector = self.vector & 0xFF | ((val as u16) << 8);
+            }
+            0x1 => {
+                self.vector = self.vector & 0xFF00 | (val as u16);
+            }
+
             // Note: This VM does not support mutating the stack pointers.
-            // This operation is not well defined upstream
+            // It probably should, but it doesn't.
-            0x2 => panic!("Invoked unsupported mutation of the data stack pointer"),
+            0x2 => {
-            0x3 => panic!("Invoked unsupported mutation of the return stack pointer"),
+                return Err(DeviceError::PortTypeError(
-            x => self.buffer[x as usize] = val,
+                    port,
+                    "Invoked unsupported mutation of the data stack pointer".into(),
+                ))
             }
+            0x3 => {
+                return Err(DeviceError::PortTypeError(
+                    port,
+                    "Invoked unsupported mutation of the return stack pointer".into(),
+                ))
             }
-    fn deo2(&mut self, vm: &mut Uxn, port: u8, val: u16) {
+
-        let slot = port & 0xF;
+            // Red
-        assert!(slot < 0xF, "Double-write beyond the end of the device");
+            0x8 => {
-        match slot {
+                self.red = self.red & 0xFF | ((val as u16) << 8);
-            0x2 => panic!("The data stack is single-width, panic on spurious double-write"),
-            0x3 => panic!("The return stack is single-width, panic on spurious double-write"),
-            x => {
-                let [high, low] = val.to_be_bytes();
-                self.deo1(vm, x, high);
-                self.deo1(vm, x + 1, low)
             }
+            0x9 => {
+                self.red = self.red & 0xFF00 | (val as u16);
             }
+
+            // Green
+            0xa => {
+                self.green = self.green & 0xFF | ((val as u16) << 8);
+            }
+            0xb => {
+                self.green = self.green & 0xFF00 | (val as u16);
+            }
+
+            // Blue
+            0xc => {
+                self.blue = self.blue & 0xFF | ((val as u16) << 8);
+            }
+            0xd => {
+                self.blue = self.blue & 0xFF00 | (val as u16);
+            }
+
+            // The state ports
+            0xe => self.debug = val,
+            0xf => self.state = val,
+            _ => unreachable!(),
+        }
+        Ok(())
     }
 }

src/vm.rs

@@ -15,6 +15,7 @@ use crate::stack::*;
 pub enum UxnError {
     StackError(StackError),
     MemoryError(MemoryError),
+    DeviceError(DeviceError),
     ExecutionLimit(u16),
     Break,
     ArithmeticOverflow,
@@ -34,6 +35,12 @@ impl From<MemoryError> for UxnError {
     }
 }
 
+impl From<DeviceError> for UxnError {
+    fn from(e: DeviceError) -> UxnError {
+        UxnError::DeviceError(e)
+    }
+}
+
 #[derive(Debug)]
 pub struct Uxn {
     pub memory: Rc<RefCell<TrivialMemory>>,
@@ -83,27 +90,27 @@ impl Uxn {
     }
 
     pub fn is_halted(&mut self) -> bool {
-        self.dei1(0x0f) != 0
+        self.dei1(0x0f).unwrap() != 0
     }
 
     fn device(&self, port: u8) -> Rc<RefCell<dyn Device>> {
         Rc::clone(&self.devices[(port & 0xF0 >> 4) as usize])
     }
 
-    pub fn dei1(&mut self, port: u8) -> u8 {
+    pub fn dei1(&mut self, port: u8) -> Result<u8, DeviceError> {
         self.device(port).borrow_mut().dei1(self, port)
     }
 
-    pub fn dei2(&mut self, port: u8) -> u16 {
+    pub fn dei2(&mut self, port: u8) -> Result<u16, DeviceError> {
         self.device(port).borrow_mut().dei2(self, port)
     }
 
-    pub fn deo1(&mut self, port: u8, val: u8) {
+    pub fn deo1(&mut self, port: u8, val: u8) -> Result<(), DeviceError> {
-        self.device(port).borrow_mut().deo1(self, port, val);
+        self.device(port).borrow_mut().deo1(self, port, val)
     }
 
-    pub fn deo2(&mut self, port: u8, val: u16) {
+    pub fn deo2(&mut self, port: u8, val: u16) -> Result<(), DeviceError> {
-        self.device(port).borrow_mut().deo2(self, port, val);
+        self.device(port).borrow_mut().deo2(self, port, val)
     }
 
     pub fn sta1(&mut self, address: u16, val: u8) -> Result<(), MemoryError> {
@@ -359,13 +366,13 @@ impl Uxn {
                         // DEI port8 -- a8
                         let mut wst = wst.borrow_mut();
                         let port = wst.pop1()?;
-                        wst.push1(self.dei1(port))?;
+                        wst.push1(self.dei1(port)?)?;
                     }
                     (_, _, 1, Icode::DEI) => {
                         // DEI2 port8 -- a16
                         let mut wst = wst.borrow_mut();
                         let port = wst.pop1()?;
-                        wst.push2(self.dei2(port))?;
+                        wst.push2(self.dei2(port)?)?;
                     }
                     (_, _, 0, Icode::DEO) => {
                         // DEO1 a8 port8 --