From 4be3570c853d2619c6e0497170ca34ab367fddc8 Mon Sep 17 00:00:00 2001
From: Theron <tspiegl@gmail.com>
Date: Sat, 1 Feb 2020 14:49:30 -0600
Subject: [PATCH] remove mutability from mapper read funcs

---
 src/cartridge/cnrom.rs | 2 +-
 src/cartridge/mmc1.rs  | 2 +-
 src/cartridge/mmc3.rs  | 2 +-
 src/cartridge/mod.rs   | 2 +-
 src/cartridge/nrom.rs  | 2 +-
 src/cartridge/uxrom.rs | 2 +-
 src/cpu/mod.rs         | 2 +-
 src/ppu/memory.rs      | 2 +-
 8 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/cartridge/cnrom.rs b/src/cartridge/cnrom.rs
index 0f3a3c7..b63aefa 100644
--- a/src/cartridge/cnrom.rs
+++ b/src/cartridge/cnrom.rs
@@ -15,7 +15,7 @@ impl Cnrom {
 }
 
 impl Mapper for Cnrom {
-    fn read(&mut self, address: usize) -> u8 {
+    fn read(&self, address: usize) -> u8 {
         let pl = self.cart.prg_rom.len();
         let addr = address % 0x4000;
         match address {
diff --git a/src/cartridge/mmc1.rs b/src/cartridge/mmc1.rs
index 2d43361..71a7330 100644
--- a/src/cartridge/mmc1.rs
+++ b/src/cartridge/mmc1.rs
@@ -111,7 +111,7 @@ impl Mmc1 {
 }
 
 impl Mapper for Mmc1 {
-    fn read(&mut self, address: usize) -> u8 {
+    fn read(&self, address: usize) -> u8 {
         match address {
             0x0000..=0x1FFF => {
                 if self.cart.chr_rom_size == 0 {
diff --git a/src/cartridge/mmc3.rs b/src/cartridge/mmc3.rs
index 5f7f51e..d78bb5c 100644
--- a/src/cartridge/mmc3.rs
+++ b/src/cartridge/mmc3.rs
@@ -67,7 +67,7 @@ impl Mmc3 {
 }
 
 impl Mapper for Mmc3 {
-    fn read(&mut self, address: usize) -> u8 {
+    fn read(&self, address: usize) -> u8 {
         let val = match address {
             0x0000..=0x1FFF => { // reading from CHR-ROM
                 let offset_1k = address % 0x400;
diff --git a/src/cartridge/mod.rs b/src/cartridge/mod.rs
index 9020bff..74ec843 100644
--- a/src/cartridge/mod.rs
+++ b/src/cartridge/mod.rs
@@ -15,7 +15,7 @@ use std::rc::Rc;
 use std::io::Read;
 
 pub trait Mapper {
-    fn read(&mut self, address: usize) -> u8;
+    fn read(&self, address: usize) -> u8;
     fn write(&mut self, address: usize, value: u8);
     fn get_mirroring(&mut self) -> Mirror;
     fn load_battery_backed_ram(&mut self);
diff --git a/src/cartridge/nrom.rs b/src/cartridge/nrom.rs
index 5f11758..e85a3c5 100644
--- a/src/cartridge/nrom.rs
+++ b/src/cartridge/nrom.rs
@@ -15,7 +15,7 @@ impl Nrom {
 }
 
 impl Mapper for Nrom {
-    fn read(&mut self, address: usize) -> u8 {
+    fn read(&self, address: usize) -> u8 {
         let addr = address % 0x4000;
         match address {
             0x0000..=0x1FFF => {
diff --git a/src/cartridge/uxrom.rs b/src/cartridge/uxrom.rs
index e410a06..697319b 100644
--- a/src/cartridge/uxrom.rs
+++ b/src/cartridge/uxrom.rs
@@ -17,7 +17,7 @@ impl Uxrom {
 }
 
 impl Mapper for Uxrom {
-    fn read(&mut self, address: usize) -> u8 {
+    fn read(&self, address: usize) -> u8 {
         match address {
             0x0000..=0x1FFF => {
                 if self.cart.chr_rom_size > 0 {
diff --git a/src/cpu/mod.rs b/src/cpu/mod.rs
index 54ea0d4..06df672 100644
--- a/src/cpu/mod.rs
+++ b/src/cpu/mod.rs
@@ -189,7 +189,7 @@ impl Cpu {
             0x4016          => self.read_controller(),
             0x4000..=0x4017 => 0, // can't read from these APU registers
             0x4018..=0x401F => 0, // APU and I/O functionality that is normally disabled. See CPU Test Mode.
-            0x4020..=0xFFFF => self.mapper.borrow_mut().read(address),
+            0x4020..=0xFFFF => self.mapper.borrow().read(address),
             _ => panic!("invalid read from 0x{:02x}", address),
         };
         val
diff --git a/src/ppu/memory.rs b/src/ppu/memory.rs
index 343647f..176eefc 100644
--- a/src/ppu/memory.rs
+++ b/src/ppu/memory.rs
@@ -4,7 +4,7 @@ impl super::Ppu {
 
     pub fn read(&mut self, address: usize) -> u8 {
         match address {
-            0x0000..=0x1FFF => self.mapper.borrow_mut().read(address),
+            0x0000..=0x1FFF => self.mapper.borrow().read(address),
             0x2000..=0x3EFF => self.read_nametable(address),
             0x3F00..=0x3FFF => {
                 let a = address % 0x0020;