Implement a stack for emulation

src/display.rs

@@ -1,4 +1,3 @@
-
 /// Represents the display's width in pixels.
 const DISPLAY_WIDTH: usize = 64;
 
@@ -22,7 +21,7 @@ pub struct TerminalDisplay {
 impl TerminalDisplay {
     pub fn new() -> TerminalDisplay {
         TerminalDisplay {
-            display_data: [false; DISPLAY_WIDTH * DISPLAY_HEIGHT]
+            display_data: [false; DISPLAY_WIDTH * DISPLAY_HEIGHT],
         }
     }
 }

src/emulator.rs

@@ -1,9 +1,10 @@
+use crate::display::Display;
+use crate::stack::Stack;
 use anyhow::anyhow;
 use log::{debug, info};
 use std::fs::File;
 use std::io::Read;
-use std::path::{Path};
-use crate::display::{Display};
+use std::path::Path;
 
 const MEMORY_SIZE: usize = 4096;
 const NUMBER_OF_REGISTERS: usize = 16;
@@ -27,7 +28,10 @@ const FONT_SPRITES: [u8; 80] = [
 ];
 
 /// Emulator emulates the Chip8 CPU.
-pub struct Emulator<D> where D: Display {
+pub struct Emulator<D>
+where
+    D: Display,
+{
     /// Memory represents the emulator's memory.
     memory: [u8; MEMORY_SIZE],
     /// Registers holds the general purpose registers.
@@ -44,10 +48,14 @@ pub struct Emulator<D> where D: Display {
     /// The stack pointer register.
     stack_pointer: u8,
     /// The display_data holds all the data associated with the display
-    display: D
+    display: D,
+    stack: Stack<u16>,
 }
 
-impl <D> Emulator<D> where D: Display {
+impl<D> Emulator<D>
+where
+    D: Display,
+{
     /// Creates a new `Emulator` instance.
     ///
     pub fn new(display: D) -> Emulator<D> {
@@ -60,6 +68,7 @@ impl <D> Emulator<D> where D: Display {
             delay_timer: 0,
             sound_timer: 0,
             stack_pointer: 0,
+            stack: Stack::new(),
         };
 
         emulator.load_font_data();
@@ -113,7 +122,7 @@ impl <D> Emulator<D> where D: Display {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::display::{TerminalDisplay};
+    use crate::display::TerminalDisplay;
     use pretty_assertions::assert_eq;
 
     #[test]

src/main.rs

@@ -1,9 +1,10 @@
+use crate::display::TerminalDisplay;
 use crate::emulator::Emulator;
 use env_logger;
-use crate::display::TerminalDisplay;
 
-mod emulator;
 mod display;
+mod emulator;
+mod stack;
 
 fn main() -> Result<(), anyhow::Error> {
     env_logger::init();

src/stack.rs

@@ -0,0 +1,65 @@
+use std::fmt::Debug;
+
+/// Implements a simple stack based on a vector.
+#[derive(Debug)]
+pub struct Stack<T> {
+    storage: Vec<T>,
+}
+
+impl<T: Debug> Stack<T> {
+    pub fn new() -> Self {
+        Stack {
+            storage: Vec::new(),
+        }
+    }
+
+    /// Pushes an element on the top of the stack
+    pub fn push(&mut self, element: T) {
+        self.storage.push(element)
+    }
+
+    /// Returns the top element from the stack.
+    pub fn pop(&mut self) -> Option<T> {
+        self.storage.pop()
+    }
+
+    //
+    pub fn peek(&self) -> Option<&T> {
+        self.storage.last()
+    }
+
+    /// Size returns the size of the stack.
+    pub fn size(&self) -> usize {
+        self.storage.len()
+    }
+
+    /// Is Empty returns true if the stack is empty.
+    pub fn is_empty(&self) -> bool {
+        self.storage.len() == 0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn basic_operations() {
+        // Given
+        let mut stack = Stack::<u16>::new();
+
+        // Then
+        stack.push(15);
+
+        assert_eq!(1, stack.size());
+        assert_eq!(15u16, *stack.peek().unwrap());
+
+        let element = stack.pop();
+        assert_eq!(15u16, element.unwrap());
+        assert_eq!(0, stack.size());
+        assert_eq!(true, stack.is_empty());
+
+        let element = stack.pop();
+        assert_eq!(true, element.is_none())
+    }
+}