From 73e52f6aea27270c78dd0dbc35437de28a42b84b Mon Sep 17 00:00:00 2001
From: John <j@soft.fish>
Date: Tue, 9 Jul 2024 01:41:32 -0500
Subject: [PATCH] banked: Break address translation into its own function

---
 src/memory/banked.rs | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/memory/banked.rs b/src/memory/banked.rs
index a29614b..8239433 100644
--- a/src/memory/banked.rs
+++ b/src/memory/banked.rs
@@ -91,6 +91,12 @@ impl<const BASE: usize, const LEN: usize, const BANKS: usize> UpperBanked<BASE,
     pub fn selected(&self) -> usize {
         self.selected
     }
+
+    /// Translates an address into a (bank, address) pair
+    pub fn translate(&self, addr: usize) -> Option<(usize, usize)> {
+        let addr = addr.checked_sub(BASE).filter(|v| *v < LEN * 2)?;
+        Some((addr / LEN, addr % LEN))
+    }
 }
 
 impl<const BASE: usize, const LEN: usize, const BANKS: usize> Default
@@ -107,8 +113,7 @@ impl<const BASE: usize, const LEN: usize, const BANKS: usize> BusIO
 {
     fn read(&self, addr: usize) -> Option<u8> {
         // Pray this gets optimized
-        let addr = addr.checked_sub(BASE).filter(|v| *v < LEN * 2)?;
-        let (bank, addr) = (addr / LEN, addr % LEN);
+        let (bank, addr) = self.translate(addr)?;
         match bank {
             0 => self.mem[0].read(addr),
             _ => self.mem[self.selected].read(addr),
@@ -117,8 +122,7 @@ impl<const BASE: usize, const LEN: usize, const BANKS: usize> BusIO
 
     fn write(&mut self, addr: usize, data: u8) -> Option<()> {
         // Pray this gets optimized
-        let addr = addr.checked_sub(BASE).filter(|v| *v < LEN * 2)?;
-        let (bank, addr) = (addr / LEN, addr % LEN);
+        let (bank, addr) = self.translate(addr)?;
         match bank {
             0 => self.mem[0].write(addr, data),
             _ => self.mem[self.selected].write(addr, data),