experimentation: benchmarking and alternate impl's

- Do some basic benchmarking with std::time
- Try writing bus writer based on iterator
  - Fail, because that requires mutable iterator
  - Begin rewriting bus based on simpler design instead.
    - Simpler design uses a unified memory model,
      which grows based on the maximum addresses expected in it
    - Still uses the "infallible" Read/Write traits from previous
      implementation. :( Alas, it's much faster during operation,
      even if it takes longer to instantiate.
    - Reassessed the syntax for bus macro
  - Made CPU tick generic over bus::Read and bus::Write traits

Cargo.lock

@@ -7,6 +7,7 @@ name = "chumpulator"
 version = "0.1.0"
 dependencies = [
  "owo-colors",
+ "rhexdump",
  "serde",
  "thiserror",
 ]
@@ -36,19 +37,25 @@ dependencies = [
 ]
 
 [[package]]
-name = "serde"
-version = "1.0.153"
+name = "rhexdump"
+version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3a382c72b4ba118526e187430bb4963cd6d55051ebf13d9b25574d379cc98d20"
+checksum = "c5e9af64574935e39f24d1c0313a997c8b880ca0e087c888bc6af8af31579847"
+
+[[package]]
+name = "serde"
+version = "1.0.154"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8cdd151213925e7f1ab45a9bbfb129316bd00799784b174b7cc7bcd16961c49e"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.153"
+version = "1.0.154"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ef476a5790f0f6decbc66726b6e5d63680ed518283e64c7df415989d880954f"
+checksum = "4fc80d722935453bcafdc2c9a73cd6fac4dc1938f0346035d84bf99fa9e33217"
 dependencies = [
  "proc-macro2",
  "quote",

Cargo.toml

@@ -7,5 +7,6 @@ edition = "2021"
 
 [dependencies]
 owo-colors = "^3"
+rhexdump = "0.1.1"
 serde = { version = "^1.0", features = ["derive"] }
 thiserror = "1.0.39"

src/bus.rs

@@ -1,11 +1,15 @@
 //! The Bus connects the CPU to Memory
 mod bus_device;
+mod iterator;
 
 use crate::dump::{BinDumpable, Dumpable};
 use bus_device::BusDevice;
+use iterator::BusIterator;
 use std::{
+    collections::HashMap,
     fmt::{Debug, Display, Formatter, Result},
     ops::Range,
+    slice::SliceIndex,
 };
 
 /// Creates a new bus, instantiating BusConnectable devices
@@ -27,6 +31,127 @@ macro_rules! bus {
     };
 }
 
+#[macro_export]
+macro_rules! newbus {
+    ($($name:literal $(:)? [$range:expr] $(= $data:expr)?) ,* $(,)?) => {
+        $crate::bus::NewBus::new()
+        $(
+            .add_region($name, $range)
+            $(
+                .load_region($name, $data)
+            )?
+        )*
+    };
+}
+
+/// Store memory in a series of named regions with ranges
+#[derive(Debug, Default)]
+pub struct NewBus {
+    memory: Vec<u8>,
+    region: HashMap<&'static str, Range<usize>>,
+}
+
+impl NewBus {
+    /// Construct a new bus
+    pub fn new() -> Self {
+        NewBus::default()
+    }
+    /// Gets the length of the bus' backing memory
+    pub fn len(&self) -> usize {
+        self.memory.len()
+    }
+    /// Returns true if the backing memory contains no elements
+    pub fn is_empty(&self) -> bool {
+        self.memory.is_empty()
+    }
+    /// Grows the NewBus backing memory to at least size bytes, but does not truncate
+    pub fn with_size(&mut self, size: usize){
+        if self.len() < size {
+            self.memory.resize(size, 0);
+        }
+    }
+    pub fn add_region(mut self, name: &'static str, range: Range<usize>) -> Self {
+        self.with_size(range.end);
+        self.region.insert(name, range);
+        self
+    }
+    pub fn load_region(mut self, name: &str, data: &[u8]) -> Self {
+        use std::io::Write;
+        if let Some(mut region) = self.get_region_mut(name) {
+            dbg!(region.write(data)).ok(); // TODO: THIS SUCKS
+        }
+        self
+    }
+    /// Gets a slice of bus memory
+    pub fn get<I>(&self, index: I) -> Option<&<I as SliceIndex<[u8]>>::Output>
+    where
+        I: SliceIndex<[u8]>,
+    {
+        self.memory.get(index)
+    }
+    /// Gets a mutable slice of bus memory
+    pub fn get_mut<I>(&mut self, index: I) -> Option<&mut <I as SliceIndex<[u8]>>::Output>
+    where
+        I: SliceIndex<[u8]>,
+    {
+        self.memory.get_mut(index)
+    }
+    /// Gets a slice of a named region of memory
+    pub fn get_region(&self, name: &str) -> Option<&[u8]> {
+        self.get(self.region.get(name)?.clone())
+    }
+    /// Gets a mutable slice to a named region of memory
+    pub fn get_region_mut(&mut self, name: &str) -> Option<&mut [u8]> {
+        self.get_mut(self.region.get(name)?.clone())
+    }
+}
+
+impl Read<u8> for NewBus {
+    fn read(&self, addr: impl Into<usize>) -> u8 {
+        *self.memory.get(addr.into()).unwrap_or(&0xc5)
+    }
+}
+
+impl Read<u16> for NewBus {
+    fn read(&self, addr: impl Into<usize>) -> u16 {
+        let addr: usize = addr.into();
+        if let Some(bytes) = self.memory.get(addr..addr + 2) {
+            u16::from_be_bytes(bytes.try_into().expect("asked for 2 bytes, got != 2 bytes"))
+        } else {
+            0xc5c5
+        }
+        //u16::from_le_bytes(self.memory.get([addr;2]))
+    }
+}
+
+impl Write<u8> for NewBus {
+    fn write(&mut self, addr: impl Into<usize>, data: u8) {
+        let addr: usize = addr.into();
+        if let Some(byte) = self.get_mut(addr) {
+            *byte = data;
+        }
+    }
+}
+
+impl Write<u16> for NewBus {
+    fn write(&mut self, addr: impl Into<usize>, data: u16) {
+        let addr: usize = addr.into();
+        if let Some(slice) = self.get_mut(addr..addr + 2) {
+            slice.swap_with_slice(data.to_be_bytes().as_mut())
+        }
+    }
+}
+
+impl Display for NewBus {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        use rhexdump::Rhexdump;
+        let mut rhx = Rhexdump::default();
+        rhx.set_bytes_per_group(2).expect("2 <= MAX_BYTES_PER_GROUP (8)");
+        rhx.display_duplicate_lines(false);
+        write!(f, "{}", rhx.hexdump(&self.memory))
+    }
+}
+
 /// BusConnectable objects can be connected to a bus with `Bus::connect()`
 ///
 /// The bus performs address translation, so your object will receive
@@ -34,19 +159,20 @@ macro_rules! bus {
 pub trait BusConnectible: Debug + Display {
     fn read_at(&self, addr: u16) -> Option<u8>;
     fn write_to(&mut self, addr: u16, data: u8);
+    fn get_mut(&mut self, addr: u16) -> Option<&mut u8>;
 }
 
 // Traits Read and Write are here purely to make implementing other things more bearable
 /// Do whatever `Read` means to you
 pub trait Read<T> {
     /// Read a T from address `addr`
-    fn read(&self, addr: u16) -> T;
+    fn read(&self, addr: impl Into<usize>) -> T;
 }
 
 /// Write "some data" to the Bus
 pub trait Write<T> {
     /// Write a T to address `addr`
-    fn write(&mut self, addr: u16, data: T);
+    fn write(&mut self, addr: impl Into<usize>, data: T);
 }
 
 /// The Bus connects bus readers with bus writers.
@@ -71,28 +197,39 @@ impl Bus {
         self.devices.push(BusDevice::new(name, range, device));
         self
     }
-    pub fn get_region_by_name(&self, name: &str) -> Option<Range<u16>> {
-        for item in &self.devices {
-            if item.name == name {
-                return Some(item.range.clone());
-            }
-        }
-        None
+    pub fn get_region_by_name(&mut self, name: &str) -> Option<&mut BusDevice> {
+        self.devices.iter_mut().find(|item| item.name == name)
     }
 }
 
 /// lmao
 impl BusConnectible for Bus {
     fn read_at(&self, addr: u16) -> Option<u8> {
-        Some(self.read(addr))
+        let mut result: u8 = 0;
+        for item in &self.devices {
+            result |= item.read_at(addr).unwrap_or(0)
+        }
+        Some(result)
     }
     fn write_to(&mut self, addr: u16, data: u8) {
-        self.write(addr, data)
+        for item in &mut self.devices {
+            item.write_to(addr, data)
+        }
+    }
+
+    fn get_mut(&mut self, addr: u16) -> Option<&mut u8> {
+        for item in &mut self.devices {
+            if let Some(mutable) = item.get_mut(addr) {
+                return Some(mutable);
+            }
+        }
+        None
     }
 }
 
 impl Read<u8> for Bus {
-    fn read(&self, addr: u16) -> u8 {
+    fn read(&self, addr: impl Into<usize>)  -> u8 {
+        let addr = addr.into() as u16;
         let mut result: u8 = 0;
         for item in &self.devices {
             result |= item.read_at(addr).unwrap_or(0)
@@ -102,18 +239,18 @@ impl Read<u8> for Bus {
 }
 
 impl Read<u16> for Bus {
-    fn read(&self, addr: u16) -> u16 {
+    fn read(&self, addr: impl Into<usize>) -> u16 {
+        let addr = addr.into() as u16;
         let mut result = 0;
-        for item in &self.devices {
-            result |= (item.read_at(addr).unwrap_or(0) as u16) << 8;
-            result |= item.read_at(addr.wrapping_add(1)).unwrap_or(0) as u16;
-        }
+        result |= (self.read_at(addr).unwrap_or(0) as u16) << 8;
+        result |= self.read_at(addr.wrapping_add(1)).unwrap_or(0) as u16;
         result
     }
 }
 
 impl Write<u8> for Bus {
-    fn write(&mut self, addr: u16, data: u8) {
+    fn write(&mut self, addr: impl Into<usize>, data: u8) {
+        let addr = addr.into() as u16;
         for item in &mut self.devices {
             item.write_to(addr, data)
         }
@@ -121,10 +258,18 @@ impl Write<u8> for Bus {
 }
 
 impl Write<u16> for Bus {
-    fn write(&mut self, addr: u16, data: u16) {
-        for item in &mut self.devices {
-            item.write_to(addr, (data >> 8) as u8);
-            item.write_to(addr.wrapping_add(1), data as u8);
+    fn write(&mut self, addr: impl Into<usize>, data: u16) {
+        let addr = addr.into() as u16;
+        self.write_to(addr, (data >> 8) as u8);
+        self.write_to(addr.wrapping_add(1), data as u8);
+    }
+}
+
+impl Write<u32> for Bus {
+    fn write(&mut self, addr: impl Into<usize>, data: u32) {
+        let addr = addr.into() as u16;
+        for i in 0..4 {
+            self.write_to(addr.wrapping_add(i), (data >> (3 - i * 8)) as u8);
         }
     }
 }
@@ -140,8 +285,11 @@ impl Display for Bus {
 
 impl Dumpable for Bus {
     fn dump(&self, range: Range<usize>) {
-        for index in range {
-            let byte: u8 = self.read(index as u16);
+        for (index, byte) in self
+            .into_iter()
+            .range(range.start as u16..range.end as u16) // this causes a truncation
+            .enumerate()
+        {
             crate::dump::as_hexdump(index, byte);
         }
     }
@@ -155,3 +303,13 @@ impl BinDumpable for Bus {
         }
     }
 }
+
+impl<'a> IntoIterator for &'a Bus {
+    type Item = u8;
+
+    type IntoIter = iterator::BusIterator<'a>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        BusIterator::new(0..u16::MAX, self)
+    }
+}

src/bus/bus_device.rs

@@ -42,6 +42,9 @@ impl BusConnectible for BusDevice {
             self.device.write_to(addr, data);
         }
     }
+    fn get_mut(&mut self, addr: u16) -> Option<&mut u8> {
+        return self.device.get_mut(addr);
+    }
 }
 
 impl Display for BusDevice {

src/bus/iterator.rs

@@ -0,0 +1,52 @@
+//! Iterators for working with Busses
+
+use super::{Bus, Read};
+use std::ops::Range;
+
+pub trait IterMut<'a> {
+    type Item;
+    fn next(&'a mut self) -> Option<&'a mut Self::Item>;
+}
+
+pub trait IntoIterMut<'a> {
+    type Item;
+
+    type IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter;
+}
+
+#[derive(Debug)]
+pub struct BusIterator<'a> {
+    range: Range<u16>,
+    addr: u16,
+    bus: &'a Bus,
+}
+
+impl<'a> BusIterator<'a> {
+    /// Creates a new BusIterator with a specified range
+    pub fn new(range: Range<u16>, bus: &'a Bus) -> BusIterator<'a> {
+        BusIterator {
+            addr: range.start,
+            range,
+            bus,
+        }
+    }
+    pub fn range(mut self, range: Range<u16>) -> Self {
+        self.range = range;
+        self
+    }
+}
+
+impl<'a> Iterator for BusIterator<'a> {
+    type Item = u8;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut res = None;
+        if self.range.contains(&self.addr) {
+            res = Some(self.bus.read(self.addr));
+            self.addr += 1;
+        }
+        res
+    }
+}

src/cpu.rs

@@ -3,7 +3,7 @@
 pub mod disassemble;
 
 use self::disassemble::Disassemble;
-use crate::bus::{Bus, Read, Write};
+use crate::bus::{Read, Write};
 use owo_colors::OwoColorize;
 
 type Reg = usize;
@@ -116,7 +116,10 @@ impl CPU {
         }
     }
 
-    pub fn tick(&mut self, bus: &mut Bus) {
+    pub fn tick<B>(&mut self, bus: &mut B)
+    where
+        B: Read<u8> + Write<u8> + Read<u16> + Write<u16>
+    {
         std::print!("{:3} {:03x}: ", self.cycle.bright_black(), self.pc);
         // fetch opcode
         let opcode: u16 = bus.read(self.pc);
@@ -205,7 +208,7 @@ impl CPU {
             // Cxbb: Stores a random number + the provided byte into vX
             0xc => self.rand(x, b),
             // Dxyn: Draws n-byte sprite to the screen at coordinates (vX, vY)
-            0xd => self.draw(x, y, n),
+            0xd => self.draw(x, y, n, bus),
 
             // # Skips instruction on value of keypress
             // |opcode| effect                             |
@@ -231,12 +234,12 @@ impl CPU {
             // | fX55 | DMA Stor from I to registers 0..X  |
             // | fX65 | DMA Load from I to registers 0..X  |
             0xf => match b {
-                0x07 => self.get_delay_timer(x, bus),
-                0x0A => self.wait_for_key(x, bus),
-                0x15 => self.load_delay_timer(x, bus),
-                0x18 => self.load_sound_timer(x, bus),
-                0x1E => self.add_to_indirect(x, bus),
-                0x29 => self.load_sprite_x(x, bus),
+                0x07 => self.get_delay_timer(x),
+                0x0A => self.wait_for_key(x),
+                0x15 => self.load_delay_timer(x),
+                0x18 => self.load_sound_timer(x),
+                0x1E => self.add_to_indirect(x),
+                0x29 => self.load_sprite_x(x),
                 0x33 => self.bcd_convert_i(x, bus),
                 0x55 => self.dma_store(x, bus),
                 0x65 => self.dma_load(x, bus),
@@ -290,7 +293,7 @@ impl CPU {
     }
     /// 00e0: Clears the screen memory to 0
     #[inline]
-    fn clear_screen(&mut self, bus: &mut Bus) {
+    fn clear_screen(&mut self, bus: &mut impl Write<u8>) {
         for addr in self.screen..self.screen + 0x100 {
             bus.write(addr, 0u8);
         }
@@ -299,7 +302,7 @@ impl CPU {
     }
     /// 00ee: Returns from subroutine
     #[inline]
-    fn ret(&mut self, bus: &mut Bus) {
+    fn ret(&mut self, bus: &impl Read<u16>) {
         self.sp = self.sp.wrapping_add(2);
         self.pc = bus.read(self.sp);
     }
@@ -310,7 +313,7 @@ impl CPU {
     }
     /// 2aaa: Pushes pc onto the stack, then jumps to a
     #[inline]
-    fn call(&mut self, a: Adr, bus: &mut Bus) {
+    fn call(&mut self, a: Adr, bus: &mut impl Write<u16>) {
         bus.write(self.sp, self.pc);
         self.sp = self.sp.wrapping_sub(2);
         self.pc = a;
@@ -427,12 +430,23 @@ impl CPU {
     }
     /// Dxyn: Draws n-byte sprite to the screen at coordinates (vX, vY)
     #[inline]
-    fn draw(&mut self, x: Reg, y: Reg, n: Nib) {
-        // TODO: Screen
-        todo!("{}", format_args!("draw\t#{n:x}, v{x:x}, v{y:x}").red());
+    fn draw<I>(&mut self, x: Reg, y: Reg, n: Nib, bus: &mut I)
+    where
+        I: Read<u8> + Read<u16>
+    {
+        println!("{}", format_args!("draw\t#{n:x}, v{x:x}, v{y:x}").red());
+        self.v[0xf] = 0;
         // TODO: Repeat for all N
-        // TODO: Calculate the lower bound address based on the X,Y position on the screen
-        // TODO: Read a u16 from the bus containing the two bytes which might need to be updated
+        for byte in 0..n as u16 {
+            // TODO: Calculate the lower bound address based on the X,Y position on the screen
+            let lower_bound = ((y as u16 + byte) * 8) + x as u16 / 8;
+            // TODO: Read a byte of sprite data into a u16, and shift it x % 8 bits
+            let sprite_line: u8 = bus.read(self.i);
+            // TODO: Read a u16 from the bus containing the two bytes which might need to be updated
+            let screen_word: u16 = bus.read(self.screen + lower_bound);
+            // TODO: Update the screen word by XORing the sprite byte
+            todo!("{sprite_line}, {screen_word}")
+        }
     }
     /// Ex9E: Skip next instruction if key == #X
     #[inline]
@@ -457,12 +471,12 @@ impl CPU {
     /// vX = DT
     /// ```
     #[inline]
-    fn get_delay_timer(&mut self, x: Reg, _bus: &mut Bus) {
+    fn get_delay_timer(&mut self, x: Reg) {
         self.v[x] = self.delay;
     }
     /// Fx0A: Wait for key, then vX = K
     #[inline]
-    fn wait_for_key(&mut self, x: Reg, _bus: &mut Bus) {
+    fn wait_for_key(&mut self, x: Reg) {
         // TODO: I/O
 
         std::println!("{}", format_args!("waitk\tv{x:x}").red());
@@ -472,7 +486,7 @@ impl CPU {
     /// DT = vX
     /// ```
     #[inline]
-    fn load_delay_timer(&mut self, x: Reg, _bus: &mut Bus) {
+    fn load_delay_timer(&mut self, x: Reg) {
         self.delay = self.v[x];
     }
     /// Fx18: Load vX into ST
@@ -480,7 +494,7 @@ impl CPU {
     /// ST = vX;
     /// ```
     #[inline]
-    fn load_sound_timer(&mut self, x: Reg, _bus: &mut Bus) {
+    fn load_sound_timer(&mut self, x: Reg) {
         self.sound = self.v[x];
     }
     /// Fx1e: Add vX to I,
@@ -488,7 +502,7 @@ impl CPU {
     /// I += vX;
     /// ```
     #[inline]
-    fn add_to_indirect(&mut self, x: Reg, _bus: &mut Bus) {
+    fn add_to_indirect(&mut self, x: Reg) {
         self.i += self.v[x] as u16;
     }
     /// Fx29: Load sprite for character x into I
@@ -496,19 +510,19 @@ impl CPU {
     /// I = sprite(X);
     /// ```
     #[inline]
-    fn load_sprite_x(&mut self, x: Reg, _bus: &mut Bus) {
+    fn load_sprite_x(&mut self, x: Reg) {
         self.i = self.font + (5 * x as Adr);
     }
     /// Fx33: BCD convert X into I`[0..3]`
     #[inline]
-    fn bcd_convert_i(&mut self, x: Reg, _bus: &mut Bus) {
+    fn bcd_convert_i(&mut self, x: Reg, _bus: &mut impl Write<u8>) {
         // TODO: I/O
 
         std::println!("{}", format_args!("bcd\t{x:x}, &I").red());
     }
     /// Fx55: DMA Stor from I to registers 0..X
     #[inline]
-    fn dma_store(&mut self, x: Reg, bus: &mut Bus) {
+    fn dma_store(&mut self, x: Reg, bus: &mut impl Write<u8>) {
         for reg in 0..=x {
             bus.write(self.i + reg as u16, self.v[reg]);
         }
@@ -516,7 +530,7 @@ impl CPU {
     }
     /// Fx65: DMA Load from I to registers 0..X
     #[inline]
-    fn dma_load(&mut self, x: Reg, bus: &mut Bus) {
+    fn dma_load(&mut self, x: Reg, bus: &mut impl Read<u8>) {
         for reg in 0..=x {
             self.v[reg] = bus.read(self.i + reg as u16);
         }

src/lib.rs

@@ -19,7 +19,8 @@ pub mod screen;
 pub mod prelude {
     use super::*;
     pub use crate::bus;
-    pub use bus::{Bus, BusConnectible};
+    pub use crate::newbus;
+    pub use bus::{Bus, BusConnectible, Read, Write};
     pub use cpu::{disassemble::Disassemble, CPU};
     pub use dump::{BinDumpable, Dumpable};
     pub use mem::Mem;

src/main.rs

@@ -1,7 +1,15 @@
 use chumpulator::{bus::Read, prelude::*};
 use std::fs::read;
+use std::time::{Duration, Instant};
+
+/// What I want:
+/// I want a data bus that stores as much memory as I need to implement a chip 8 emulator
+/// I want that data bus to hold named memory ranges and have a way to get a memory region
 
 fn main() -> Result<(), std::io::Error> {
+    let mut now;
+    println!("Building Bus...");
+    let mut time = Instant::now();
     let mut bus = bus! {
         // Load the charset into ROM
         "charset" [0x0050..0x00a0] = Mem::new(0x50).load_charset(0).w(false),
@@ -12,20 +20,52 @@ fn main() -> Result<(), std::io::Error> {
         // Create some stack memory
         "stack"   [0xF000..0xF800] = Mem::new(0x800).r(true).w(true),
     };
-
-    println!("{bus}");
+    now = time.elapsed();
+    println!("Elapsed: {:?}\nBuilding NewBus...", now);
+    time = Instant::now();
+    let mut newbus = newbus! {
+        // Load the charset into ROM
+        "charset" [0x0050..0x00a0] = include_bytes!("mem/charset.bin"),
+        // Load the ROM file into RAM
+        "userram" [0x0200..0x0F00] = &read("chip-8/Fishie.ch8")?,
+        // Create a screen
+        "screen"  [0x0F00..0x1000],
+        // Create some stack memory
+        "stack"   [0x2000..0x2800],
+    };
+    now = time.elapsed();
+    println!("Elapsed: {:?}", now);
+    println!("{newbus}");
 
     let disassembler = Disassemble::default();
-    for addr in 0x200..0x290 {
-        if addr % 2 == 0 {
-            println!("{addr:03x}: {}", disassembler.instruction(bus.read(addr)));
+    if false {
+        for addr in 0x200..0x290 {
+            if addr % 2 == 0 {
+                println!(
+                    "{addr:03x}: {}",
+                    disassembler.instruction(bus.read(addr as usize))
+                );
+            }
         }
     }
 
     let mut cpu = CPU::new(0xf00, 0x50, 0x200, 0xf7fe, disassembler);
-    for _instruction in 0..100 {
+    let mut cpu2 = cpu.clone();
+    println!("Old Bus:");
+    for _instruction in 0..6 {
+        time = Instant::now();
         cpu.tick(&mut bus);
-        //bus.dump(0xF7e0..0xf800);
+        now = time.elapsed();
+        println!("         Elapsed: {:?}", now);
+        std::thread::sleep(Duration::from_micros(2000).saturating_sub(time.elapsed()));
+    }
+    println!("New Bus:");
+    for _instruction in 0..6 {
+        time = Instant::now();
+        cpu2.tick(&mut newbus);
+        now = time.elapsed();
+        println!("         Elapsed: {:?}", now);
+        std::thread::sleep(Duration::from_micros(2000).saturating_sub(time.elapsed()));
     }
     Ok(())
 }

src/mem.rs

@@ -144,4 +144,10 @@ impl BusConnectible for Mem {
                 *value = data
         }
     }
+    fn get_mut(&mut self, addr: u16) -> Option<&mut u8> {
+        if !self.attr.w {
+            return None;
+        }
+        self.mem.get_mut(addr as usize)
+    }
 }

src/screen.rs

@@ -1,5 +1,7 @@
 //! Stores and displays the Chip-8's screen memory
 
+#![allow(unused_imports)]
+
 use crate::{bus::BusConnectible, dump::Dumpable, mem::Mem};
 use std::{
     fmt::{Display, Formatter, Result},
@@ -8,39 +10,21 @@ use std::{
 
 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub struct Screen {
-    mem: Mem,
-    width: usize,
-    height: usize,
+    pub width: usize,
+    pub height: usize,
 }
 
 impl Screen {
     pub fn new(width: usize, height: usize) -> Screen {
+        Screen { width, height }
+    }
+}
+
+impl Default for Screen {
+    fn default() -> Self {
         Screen {
-            mem: Mem::new(width * height / 8),
-            width,
-            height,
+            width: 64,
+            height: 32,
         }
     }
 }
-
-impl BusConnectible for Screen {
-    fn read_at(&self, addr: u16) -> Option<u8> {
-        self.mem.read_at(addr)
-    }
-
-    fn write_to(&mut self, addr: u16, data: u8) {
-        self.mem.write_to(addr, data)
-    }
-}
-
-impl Dumpable for Screen {
-    fn dump(&self, range: Range<usize>) {
-        self.mem.dump(range)
-    }
-}
-
-impl Display for Screen {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        write!(f, "{}", self.mem.window(0..self.width * self.height / 8))
-    }
-}