From 81f79dc7a55cce306a88643940c2d6da74c07e37 Mon Sep 17 00:00:00 2001
From: Erin <erin@erindesu.cz>
Date: Tue, 11 Jul 2023 10:29:23 +0200
Subject: [PATCH] Implement timer

---
 hbvm/src/main.rs   |  2 +-
 hbvm/src/vm/mod.rs | 26 ++++++++++++++++++++++----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/hbvm/src/main.rs b/hbvm/src/main.rs
index 255384e..5f9b27f 100644
--- a/hbvm/src/main.rs
+++ b/hbvm/src/main.rs
@@ -18,7 +18,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         return Ok(());
     } else {
         unsafe {
-            let mut vm = Vm::new_unchecked(&prog, TestTrapHandler);
+            let mut vm = Vm::<_, 0>::new_unchecked(&prog, TestTrapHandler);
             vm.memory.insert_test_page();
             println!("Program interrupt: {:?}", vm.run());
             println!("{:?}", vm.registers);
diff --git a/hbvm/src/vm/mod.rs b/hbvm/src/vm/mod.rs
index 0f6fa2f..6528161 100644
--- a/hbvm/src/vm/mod.rs
+++ b/hbvm/src/vm/mod.rs
@@ -79,7 +79,7 @@ macro_rules! cond_jump {
 }
 
 /// HoleyBytes Virtual Machine
-pub struct Vm<'a, T> {
+pub struct Vm<'a, T, const TIMER_QUOTIENT: usize> {
     /// Holds 256 registers
     ///
     /// Writing to register 0 is considered undefined behaviour
@@ -97,9 +97,12 @@ pub struct Vm<'a, T> {
 
     /// Program
     program: &'a [u8],
+
+    /// Program timer
+    timer: usize,
 }
 
-impl<'a, T: HandleTrap> Vm<'a, T> {
+impl<'a, T: HandleTrap, const TIMER_QUOTIENT: usize> Vm<'a, T, TIMER_QUOTIENT> {
     /// Create a new VM with program and trap handler
     ///
     /// # Safety
@@ -111,6 +114,7 @@ impl<'a, T: HandleTrap> Vm<'a, T> {
             traph,
             pc: 0,
             program,
+            timer: 0,
         }
     }
 
@@ -123,12 +127,19 @@ impl<'a, T: HandleTrap> Vm<'a, T> {
     /// Execute program
     ///
     /// Program can return [`VmRunError`] if a trap handling failed
-    pub fn run(&mut self) -> Result<(), VmRunError> {
+    pub fn run(&mut self) -> Result<VmRunOk, VmRunError> {
         use hbbytecode::opcode::*;
         loop {
             // Fetch instruction
             let Some(&opcode) = self.program.get(self.pc)
-                else { return Ok(()) };
+                else { return Ok(VmRunOk::End) };
+
+            if TIMER_QUOTIENT != 0 {
+                self.timer += 1;
+                if self.timer % TIMER_QUOTIENT == 0 {
+                    return Ok(VmRunOk::Timer);
+                }
+            }
 
             // Big match
             unsafe {
@@ -350,3 +361,10 @@ pub enum VmRunError {
     /// Unhandled store access exception
     StoreAccessEx(u64),
 }
+
+/// Virtual machine halt ok
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum VmRunOk {
+    End,
+    Timer,
+}