example first version of an interrupt handler implemented with closures

agb/examples/just_build.rs

@@ -6,6 +6,9 @@ fn panic_handler(_info: &core::panic::PanicInfo) -> ! {
     loop {}
 }
 
+#[no_mangle]
+pub extern "C" fn __RUST_INTERRUPT_HANDLER(_: u16) {}
+
 // implementation of tonc's "My first GBA demo"
 // https://coranac.com/tonc/text/first.htm
 

agb/interrupt_simple.s

@@ -14,5 +14,22 @@ InterruptHandlerSimple:
     orr r1, r1, r0 @ or with enabled and requested interrupts
     strh r1, [r2] @ acknowlege bios requests
 
+    mrs r2, cpsr
+    orr r2, r2, #0xD
+    msr cpsr_c, r2
+
+
+    ldr r1, =__RUST_INTERRUPT_HANDLER
+    push {lr}
+    adr lr, .IReturn
+    bx r1
+.IReturn:
+    pop {lr}
+
+    mrs r2, cpsr
+    bic r2, r2, #0xD
+    orr r2, r2, #0x92
+    msr cpsr_c, r2
+
     bx lr @ return to bios
 .pool

agb/src/interrupt.rs

@@ -1,3 +1,9 @@
+use core::{
+    cell::Cell,
+    marker::{PhantomData, PhantomPinned},
+    pin::Pin,
+};
+
 use crate::memory_mapped::MemoryMapped;
 
 #[allow(dead_code)]
@@ -55,3 +61,155 @@ pub fn enable_interrupts() {
 pub(crate) fn disable_interrupts() {
     INTERRUPTS_ENABLED.set(0);
 }
+
+pub struct InterruptRoot {
+    next: Cell<*const InterruptClosure>,
+}
+
+impl InterruptRoot {
+    const fn new() -> Self {
+        InterruptRoot {
+            next: Cell::new(core::ptr::null()),
+        }
+    }
+}
+
+static mut INTERRUPT_TABLE: Interrupts = Interrupts {
+    vblank: InterruptRoot::new(),
+    hblank: InterruptRoot::new(),
+};
+
+#[no_mangle]
+pub extern "C" fn __RUST_INTERRUPT_HANDLER(interrupt: u16) {
+    if interrupt & 1 != 0 {
+        unsafe { INTERRUPT_TABLE.vblank.trigger_interrupts() };
+    };
+}
+
+struct Interrupts {
+    vblank: InterruptRoot,
+    hblank: InterruptRoot,
+}
+
+pub struct InterruptClosureBounded<'a> {
+    c: InterruptClosure,
+    _phantom: PhantomData<&'a ()>,
+    _unpin: PhantomPinned,
+}
+
+pub struct InterruptClosure {
+    closure: *mut (dyn FnMut()),
+    next: Cell<*const InterruptClosure>,
+    root: *const InterruptRoot,
+}
+
+impl InterruptRoot {
+    fn trigger_interrupts(&self) {
+        let mut count = 0;
+        let mut c = self.next.get();
+        while !c.is_null() {
+            count += 1;
+            let closure_ptr = unsafe { &*c }.closure;
+            let closure_ref = unsafe { &mut *closure_ptr };
+            closure_ref();
+            c = unsafe { &*c }.next.get();
+        }
+    }
+}
+
+impl Drop for InterruptClosure {
+    fn drop(&mut self) {
+        let mut c = unsafe { &*self.root }.next.get();
+        let own_pointer = self as *const _;
+        if c == own_pointer {
+            unsafe { &*self.root }.next.set(self.next.get());
+            return;
+        }
+        loop {
+            let p = unsafe { &*c }.next.get();
+            if p == own_pointer {
+                unsafe { &*c }.next.set(self.next.get());
+                return;
+            }
+            c = p;
+        }
+    }
+}
+
+fn get_interrupt_handle_root<'a>(
+    f: &'a mut dyn FnMut(),
+    root: &InterruptRoot,
+) -> InterruptClosureBounded<'a> {
+    InterruptClosureBounded {
+        c: InterruptClosure {
+            closure: unsafe { core::mem::transmute(f as *mut _) },
+            next: Cell::new(core::ptr::null()),
+            root: root as *const _,
+        },
+        _phantom: PhantomData,
+        _unpin: PhantomPinned,
+    }
+}
+
+pub fn get_interrupt_handle<'a>(
+    f: &'a mut dyn FnMut(),
+    interrupt: Interrupt,
+) -> InterruptClosureBounded<'a> {
+    let root = match interrupt {
+        Interrupt::VBlank => unsafe { &INTERRUPT_TABLE.vblank },
+        _ => unimplemented!(
+            "sorry, I haven't yet added this interrupt. Please request it if you need it"
+        ),
+    };
+
+    get_interrupt_handle_root(f, root)
+}
+
+pub fn add_interrupt<'a>(interrupt: Pin<&'a InterruptClosureBounded<'a>>) {
+    let root = unsafe { &*interrupt.c.root };
+    let mut c = root.next.get();
+    if c.is_null() {
+        root.next.set((&interrupt.c) as *const _);
+        return;
+    }
+    loop {
+        let p = unsafe { &*c }.next.get();
+        if p.is_null() {
+            unsafe { &*c }.next.set((&interrupt.c) as *const _);
+            return;
+        }
+
+        c = p;
+    }
+}
+
+#[test_case]
+fn test_vblank_interrupt_handler(gba: &mut crate::Gba) {
+    {
+        let mut counter = 0;
+        let mut counter_2 = 0;
+
+        let mut vblank_interrupt = || counter += 1;
+        let mut vblank_interrupt_2 = || counter_2 += 1;
+
+        let interrupt_closure = get_interrupt_handle(&mut vblank_interrupt, Interrupt::VBlank);
+        let interrupt_closure = unsafe { Pin::new_unchecked(&interrupt_closure) };
+        add_interrupt(interrupt_closure);
+
+        let interrupt_closure_2 = get_interrupt_handle(&mut vblank_interrupt_2, Interrupt::VBlank);
+        let interrupt_closure_2 = unsafe { Pin::new_unchecked(&interrupt_closure_2) };
+        add_interrupt(interrupt_closure_2);
+
+        let vblank = gba.display.vblank.get();
+
+        while counter < 100 || counter_2 < 100 {
+            vblank.wait_for_VBlank();
+        }
+    }
+
+    assert_eq!(
+        unsafe { INTERRUPT_TABLE.vblank.next.get() },
+        core::ptr::null(),
+        "expected the interrupt table for vblank to be empty"
+    );
+}