From a8dac6e8051fb8f918f45431c4192148f99e1399 Mon Sep 17 00:00:00 2001
From: Sam M W <you@example.com>
Date: Mon, 3 Apr 2023 06:15:07 +0100
Subject: [PATCH] extract memory functionality into a trait

---
 README.md                  |  1 +
 examples/euclidean_algo.rs |  1 +
 examples/mos6502.rs        |  1 +
 src/cpu.rs                 |  1 +
 src/instruction.rs         |  1 +
 src/memory.rs              | 19 ++++++++++++++++---
 6 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 7f7303c..bcd6c4d 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,7 @@ Source: [Wikipedia](https://en.wikipedia.org/wiki/MOS_Technology_6502)
 ## How to use this library
 
 ```rust
+use mos6502::memory::Bus;
 use mos6502::cpu;
 
 fn main() {
diff --git a/examples/euclidean_algo.rs b/examples/euclidean_algo.rs
index 0177362..446f5d2 100644
--- a/examples/euclidean_algo.rs
+++ b/examples/euclidean_algo.rs
@@ -1,6 +1,7 @@
 extern crate mos6502;
 
 use mos6502::cpu;
+use mos6502::memory::Bus;
 
 fn main() {
     println!("Enter two numbers (< 128) to know their GCD:");
diff --git a/examples/mos6502.rs b/examples/mos6502.rs
index c71080c..26fa717 100644
--- a/examples/mos6502.rs
+++ b/examples/mos6502.rs
@@ -29,6 +29,7 @@ extern crate mos6502;
 
 #[cfg(not(test))]
 use mos6502::cpu;
+use mos6502::memory::Bus;
 
 #[cfg(not(test))]
 fn main() {
diff --git a/src/cpu.rs b/src/cpu.rs
index 6de3598..43d05be 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -26,6 +26,7 @@
 // POSSIBILITY OF SUCH DAMAGE.
 
 use crate::instruction::{self, DecodedInstr, Instruction, OpInput};
+use crate::memory::Bus;
 use crate::memory::Memory;
 use crate::registers::{Registers, StackPointer, Status, StatusArgs};
 
diff --git a/src/instruction.rs b/src/instruction.rs
index b755d05..a2e6508 100644
--- a/src/instruction.rs
+++ b/src/instruction.rs
@@ -26,6 +26,7 @@
 // POSSIBILITY OF SUCH DAMAGE.
 
 use crate::cpu::CPU;
+use crate::memory::Bus;
 use crate::memory::Memory;
 
 // Abbreviations
diff --git a/src/memory.rs b/src/memory.rs
index c4f9535..7194de7 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -58,26 +58,39 @@ impl Default for Memory {
     }
 }
 
+pub trait Bus {
+    fn get_byte(&self, address: u16) -> u8;
+    fn set_byte(&mut self, address: u16, value: u8) -> u8;
+
+    fn set_bytes(&mut self, start: u16, values: &[u8]) {
+        for i in 0..values.len() as u16 {
+            self.set_byte(start + i, values[i as usize]);
+        }
+    }
+}
+
 impl Memory {
     pub fn new() -> Memory {
         Memory {
             bytes: [0; MEMORY_SIZE],
         }
     }
+}
 
-    pub fn get_byte(&self, address: u16) -> u8 {
+impl Bus for Memory {
+    fn get_byte(&self, address: u16) -> u8 {
         self.bytes[address as usize]
     }
 
     // Sets the byte at the given address to the given value and returns the
     // previous value at the address.
-    pub fn set_byte(&mut self, address: u16, value: u8) -> u8 {
+    fn set_byte(&mut self, address: u16, value: u8) -> u8 {
         let old_value = self.get_byte(address);
         self.bytes[address as usize] = value;
         old_value
     }
 
-    pub fn set_bytes(&mut self, start: u16, values: &[u8]) {
+    fn set_bytes(&mut self, start: u16, values: &[u8]) {
         let start = start as usize;
 
         // This panics if the range is invalid