From b95ab33ec9129a899555f068e2ffd9f0927da7df Mon Sep 17 00:00:00 2001
From: Alex Janka <alex@alexjanka.com>
Date: Fri, 24 Feb 2023 10:50:59 +1100
Subject: [PATCH] cpu gets interrupts from struct rather than accessing memory
 directly

---
 src/processor/memory.rs            |  9 ++----
 src/processor/memory/interrupts.rs | 21 +++++++++++++
 src/processor/mod.rs               | 50 +++++++-----------------------
 3 files changed, 36 insertions(+), 44 deletions(-)

diff --git a/src/processor/memory.rs b/src/processor/memory.rs
index 12a992d..7a50f81 100644
--- a/src/processor/memory.rs
+++ b/src/processor/memory.rs
@@ -1,14 +1,11 @@
+use self::mmio::{Apu, Gpu, Joypad, Serial, Timer};
 pub use self::rom::Rom;
-use self::{
-    interrupts::Interrupt,
-    mmio::{Apu, Gpu, Joypad, Serial, Timer},
-};
 use crate::{processor::SplitRegister, verbose_println, Cpu};
 use gilrs::Gilrs;
 use minifb::{Key, Window};
 
 mod interrupts;
-pub use interrupts::Interrupts;
+pub use interrupts::{Interrupt, Interrupts};
 pub mod mmio;
 pub(crate) mod rom;
 
@@ -21,7 +18,7 @@ pub struct Memory {
     ram: [u8; 8192],
     switchable_ram: [u8; 8192],
     cpu_ram: [u8; 128],
-    interrupts: Interrupts,
+    pub(super) interrupts: Interrupts,
     pub(super) ime: bool,
     pub(super) ime_scheduled: u8,
     dma_addr: u8,
diff --git a/src/processor/memory/interrupts.rs b/src/processor/memory/interrupts.rs
index f69dc07..90b0540 100644
--- a/src/processor/memory/interrupts.rs
+++ b/src/processor/memory/interrupts.rs
@@ -74,4 +74,25 @@ impl Interrupts {
             Interrupt::Joypad => self.flag_register.joypad = status,
         }
     }
+
+    pub fn get_next_interrupt(&mut self) -> Option<Interrupt> {
+        if self.enable_register.vblank && self.flag_register.vblank {
+            self.flag_register.vblank = false;
+            Some(Interrupt::Vblank)
+        } else if self.enable_register.lcd_stat && self.flag_register.lcd_stat {
+            self.flag_register.lcd_stat = false;
+            Some(Interrupt::LcdStat)
+        } else if self.enable_register.timer && self.flag_register.timer {
+            self.flag_register.timer = false;
+            Some(Interrupt::Timer)
+        } else if self.enable_register.serial && self.flag_register.serial {
+            self.flag_register.serial = false;
+            Some(Interrupt::Serial)
+        } else if self.enable_register.joypad && self.flag_register.joypad {
+            self.flag_register.joypad = false;
+            Some(Interrupt::Joypad)
+        } else {
+            None
+        }
+    }
 }
diff --git a/src/processor/mod.rs b/src/processor/mod.rs
index 55cda48..7010177 100644
--- a/src/processor/mod.rs
+++ b/src/processor/mod.rs
@@ -1,11 +1,7 @@
-use std::time::Instant;
-
-use self::memory::Memory;
-use crate::{
-    util::{clear_bit, get_bit},
-    verbose_println,
-};
+use self::memory::{Interrupt, Memory};
+use crate::verbose_println;
 use gilrs::Gilrs;
+use std::time::Instant;
 
 mod instructions;
 pub mod memory;
@@ -88,37 +84,15 @@ impl Cpu {
 
     fn handle_interrupts(&mut self) -> u8 {
         if self.memory.ime || self.halted {
-            let req_and_enabled = self.memory.get(0xFF0F) & self.memory.get(0xFFFF);
-            // all interrupts should last 5 cycles?
-            if get_bit(req_and_enabled, 0) {
-                // vblank
-                self.service_interrupt(0x40);
-                self.memory
-                    .set(0xFF0F, clear_bit(self.memory.get(0xFF0F), 0));
-                5
-            } else if get_bit(req_and_enabled, 1) {
-                // lcd stat
-                self.service_interrupt(0x48);
-                self.memory
-                    .set(0xFF0F, clear_bit(self.memory.get(0xFF0F), 1));
-                5
-            } else if get_bit(req_and_enabled, 2) {
-                // timer
-                self.service_interrupt(0x50);
-                self.memory
-                    .set(0xFF0F, clear_bit(self.memory.get(0xFF0F), 2));
-                5
-            } else if get_bit(req_and_enabled, 3) {
-                // serial
-                self.service_interrupt(0x58);
-                self.memory
-                    .set(0xFF0F, clear_bit(self.memory.get(0xFF0F), 3));
-                5
-            } else if get_bit(req_and_enabled, 4) {
-                // joypad
-                self.service_interrupt(0x60);
-                self.memory
-                    .set(0xFF0F, clear_bit(self.memory.get(0xFF0F), 4));
+            if let Some(interrupt) = self.memory.interrupts.get_next_interrupt() {
+                let interrupt_addr = match interrupt {
+                    Interrupt::Vblank => 0x40,
+                    Interrupt::LcdStat => 0x48,
+                    Interrupt::Timer => 0x50,
+                    Interrupt::Serial => 0x58,
+                    Interrupt::Joypad => 0x60,
+                };
+                self.service_interrupt(interrupt_addr);
                 5
             } else {
                 0