scheduler done

src/kernel/mod.rs

@@ -1,3 +1,3 @@
 mod process;
-mod thread;
+pub mod thread;
 mod scheduler;

src/kernel/scheduler.rs

@@ -1,10 +1,11 @@
 use crate::utility::list::List;
 use crate::kernel::thread::Thread;
+use crate::utility::system::{g_current_thread, g_thread_to_be_destroyed};
 use std::rc::Rc;
 
 
 struct Scheduler<> {
-    ready_list: List<Rc<Thread>>
+    ready_list: List<Thread>
 }
 
 impl Scheduler {
@@ -24,9 +25,48 @@ impl Scheduler {
     /// 
     /// ## Pamameter
     /// 
-    /// **thread**: Thread is the thread to be put on the read list
-    pub fn ready_to_run(&mut self, thread: Rc<Thread>) {
+    /// **thread** is the thread to be put on the read list
+    pub fn ready_to_run(&mut self, thread: Thread) {
         self.ready_list.push_back(thread);
     }
     
+    /// Return the next thread to be scheduled onto the CPU.
+    /// If there are no ready threads, return Option::None
+    /// 
+    /// Thread is removed from the ready list.
+    /// 
+    /// **return** Thread thread to be scheduled
+    pub fn find_next_to_run(&mut self) -> Option<Thread> {
+        self.ready_list.pop_back()
+    }
+
+    /// Dispatch the CPU to next_thread. Save the state of the old thread 
+    /// and load the state of the new thread.
+    /// 
+    /// We assume the state of the previously running thread has already been changed from running to blocked or ready.
+    /// 
+    /// Global variable g_current_thread become next_thread
+    /// 
+    /// ## Parameter
+    /// 
+    /// **next_thread** thread to dispatch to the CPU
+    pub fn switch_to(&self, next_thread: Thread) {
+        let old_thread = Box::clone(&g_current_thread).unwrap();
+
+        g_current_thread.check_overflow();
+
+        g_current_thread = Box::new(Option::Some(next_thread));
+
+        old_thread.save_processor_state();
+        old_thread.save_simulator_state();
+
+        if(old_thread != g_current_thread) {
+            next_thread.restore_processor_state();
+            next_thread.restore_simulator_state();
+        }
+
+        if(g_thread_to_be_destroyed.is_some()) {
+            drop(g_thread_to_be_destroyed.take());
+        }
+    }
 }

src/utility/system.rs

@@ -1,3 +1,8 @@
+use crate::kernel::thread::Thread;
+
+
+pub static g_current_thread: Box<Option<Thread>> = Box::new(Option::None);
+pub static g_thread_to_be_destroyed: Box<Option<Thread>> = Box::new(Option::None);
 
 pub enum ObjectType {
     SEMAPHORE_TYPE,