From d77c884c4e0826e80a3eda01a129a2792ae509f5 Mon Sep 17 00:00:00 2001
From: Determinant <ted.sybil@gmail.com>
Date: Thu, 4 Jan 2018 15:40:18 +0800
Subject: remove RefCell in memory/mapper to improve performance

---
 src/bin.rs    |  3 +--
 src/mapper.rs | 24 ++++++++++++++++++++++++
 src/memory.rs | 24 ++++++++++++------------
 3 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/src/bin.rs b/src/bin.rs
index 7d94c7b..839b630 100644
--- a/src/bin.rs
+++ b/src/bin.rs
@@ -3,7 +3,6 @@ extern crate core;
 use std::fs::File;
 use std::sync::{Mutex, Condvar};
 use std::io::Read;
-use std::cell::RefCell;
 use std::intrinsics::transmute;
 use std::process::exit;
 
@@ -423,7 +422,7 @@ fn main() {
         _ => panic!("unsupported mapper {}", mapper_id)
     };
 
-    let mapper = RefCell::new(&mut (*m) as &mut mapper::Mapper);
+    let mapper = mapper::RefMapper::new(&mut (*m) as &mut mapper::Mapper);
     let mut cpu = CPU::new(CPUMemory::new(&mapper, Some(&p1ctl), None));
     let mut ppu = PPU::new(PPUMemory::new(&mapper), &mut (*win));
     let mut apu = APU::new(&mut spkr);
diff --git a/src/mapper.rs b/src/mapper.rs
index cf946a2..446d5b9 100644
--- a/src/mapper.rs
+++ b/src/mapper.rs
@@ -1,5 +1,6 @@
 #![allow(dead_code)]
 extern crate core;
+use core::cell::UnsafeCell;
 use memory::{VMem, CPUBus};
 use cartridge::{Cartridge, BankType, MirrorType};
 
@@ -8,6 +9,29 @@ pub trait Mapper : VMem {
     fn tick(&mut self, _bus: &CPUBus) {}
 }
 
+pub struct RefMapper<'a> {
+    mapper: UnsafeCell<&'a mut Mapper>
+}
+
+impl<'a> RefMapper<'a> {
+    pub fn new(mapper: &'a mut Mapper) -> Self {
+        RefMapper { mapper: UnsafeCell::new(mapper) }
+    }
+
+    #[inline(always)]
+    pub fn get_mut(&self) -> &'a mut Mapper {
+        unsafe { *self.mapper.get() }
+    }
+}
+
+impl<'a> core::ops::Deref for RefMapper<'a> {
+    type Target = &'a mut Mapper;
+    #[inline(always)]
+    fn deref(&self) -> &&'a mut Mapper {
+        unsafe { &*self.mapper.get() }
+    }
+}
+
 pub struct Mapper1<'a, C> where C: Cartridge {
     cart: C,
     prg_banks: [&'a [u8]; 2],
diff --git a/src/memory.rs b/src/memory.rs
index 985070f..765aeb5 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -3,7 +3,7 @@ use ppu::PPU;
 use apu::{APU, Sampler};
 use mos6502::{CPU, CPU_FREQ};
 use cartridge::MirrorType;
-use mapper::Mapper;
+use mapper::RefMapper;
 use controller::Controller;
 use core::cell::{RefCell, Cell};
 use core::ptr::null_mut;
@@ -89,14 +89,14 @@ impl<'a> CPUBus<'a> {
 pub struct CPUMemory<'a> {
     sram: [u8; 2048],
     pub bus: CPUBus<'a>,
-    mapper: &'a RefCell<&'a mut Mapper>,
+    mapper: &'a RefMapper<'a>,
     ctl1: Option<&'a Controller>,
     ctl2: Option<&'a Controller>
 }
 
 impl<'a> CPUMemory<'a> {
     pub fn new(
-               mapper: &'a RefCell<&'a mut Mapper>,
+               mapper: &'a RefMapper<'a>,
                ctl1: Option<&'a Controller>,
                ctl2: Option<&'a Controller>) -> Self {
         CPUMemory{sram: [0; 2048],
@@ -137,7 +137,7 @@ impl<'a> CPUMemory<'a> {
         } else if addr < 0x6000 {
             0
         } else {
-            self.mapper.borrow().read(addr)
+            self.mapper.read(addr)
         }
     }
 
@@ -200,7 +200,7 @@ impl<'a> CPUMemory<'a> {
             }
         } else if addr < 0x6000 {
         } else {
-            self.mapper.borrow_mut().write(addr, data)
+            self.mapper.get_mut().write(addr, data)
         }
     }
 }
@@ -220,11 +220,11 @@ impl<'a> VMem for CPUMemory<'a> {
 pub struct PPUMemory<'a> {
     nametable: [u8; 0x800],
     palette: [u8; 0x20],
-    mapper: &'a RefCell<&'a mut Mapper>,
+    mapper: &'a RefMapper<'a>
 }
 
 impl<'a> PPUMemory<'a> {
-    pub fn new(mapper: &'a RefCell<&'a mut Mapper>) -> Self {
+    pub fn new(mapper: &'a RefMapper<'a>) -> Self {
         PPUMemory{
             nametable: [0; 0x800],
             palette: [0; 0x20],
@@ -257,7 +257,7 @@ fn get_mirror_palette(addr: u16) -> u16 {
 impl<'a> PPUMemory<'a> {
     #[inline(always)]
     pub fn read_nametable(&self, addr: u16) -> u8 {
-        let mt = self.mapper.borrow().get_cart().get_mirror_type();
+        let mt = self.mapper.get_cart().get_mirror_type();
         self.nametable[(get_mirror_addr(mt, addr) & 0x7ff) as usize]
     }
 
@@ -268,7 +268,7 @@ impl<'a> PPUMemory<'a> {
 
     #[inline(always)]
     pub fn write_nametable(&mut self, addr: u16, data: u8) {
-        let mt = self.mapper.borrow().get_cart().get_mirror_type();
+        let mt = self.mapper.get_cart().get_mirror_type();
         self.nametable[(get_mirror_addr(mt, addr) & 0x7ff) as usize] = data
     }
 
@@ -279,17 +279,17 @@ impl<'a> PPUMemory<'a> {
 
     #[inline(always)]
     pub fn read_mapper(&self, addr: u16) -> u8 {
-        self.mapper.borrow().read(addr)
+        self.mapper.read(addr)
     }
 
     #[inline(always)]
     fn write_mapper(&self, addr: u16, data: u8) {
-        self.mapper.borrow_mut().write(addr, data)
+        self.mapper.get_mut().write(addr, data)
     }
 
     #[inline(always)]
     pub fn tick(&self, bus: &CPUBus) {
-        self.mapper.borrow_mut().tick(bus)
+        self.mapper.get_mut().tick(bus)
     }
 }
 
-- 
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