# mod.rs - source
Source of the Rust file `src/task/mod.rs`.
Keywords: rust, rustlang, rust-lang

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    mod context;
    mod switch;
    #[allow(clippy::module_inception)]
    mod task;

    use crate::loader::{get_app_data, get_num_app};
    use crate::sync::UPSafeCell;
    use crate::trap::TrapContext;
    use alloc::vec::Vec;
    use lazy_static::*;
    use switch::__switch;
    use task::{TaskControlBlock, TaskStatus};

    pub use context::TaskContext;

    pub struct TaskManager {
        num_app: usize,
        inner: UPSafeCell<TaskManagerInner>,
    }

    struct TaskManagerInner {
        tasks: Vec<TaskControlBlock>,
        current_task: usize,
    }

    lazy_static! {
        pub static ref TASK_MANAGER: TaskManager = {
            println!("init TASK_MANAGER");
            let num_app = get_num_app();
            println!("num_app = {}", num_app);
            let mut tasks: Vec<TaskControlBlock> = Vec::new();
            for i in 0..num_app {
                tasks.push(TaskControlBlock::new(get_app_data(i), i));
            }
            TaskManager {
                num_app,
                inner: unsafe {
                    UPSafeCell::new(TaskManagerInner {
                        tasks,
                        current_task: 0,
                    })
                },
            }
        };
    }

    impl TaskManager {
        fn run_first_task(&self) -> ! {
            let mut inner = self.inner.exclusive_access();
            let next_task = &mut inner.tasks[0];
            next_task.task_status = TaskStatus::Running;
            let next_task_cx_ptr = &next_task.task_cx as *const TaskContext;
            drop(inner);
            let mut _unused = TaskContext::zero_init();
            // before this, we should drop local variables that must be dropped manually
            unsafe {
                __switch(&mut _unused as *mut _, next_task_cx_ptr);
            }
            panic!("unreachable in run_first_task!");
        }

        fn mark_current_suspended(&self) {
            let mut inner = self.inner.exclusive_access();
            let cur = inner.current_task;
            inner.tasks[cur].task_status = TaskStatus::Ready;
        }

        fn mark_current_exited(&self) {
            let mut inner = self.inner.exclusive_access();
            let cur = inner.current_task;
            inner.tasks[cur].task_status = TaskStatus::Exited;
        }

        fn find_next_task(&self) -> Option<usize> {
            let inner = self.inner.exclusive_access();
            let current = inner.current_task;
            (current + 1..current + self.num_app + 1)
                .map(|id| id % self.num_app)
                .find(|id| inner.tasks[*id].task_status == TaskStatus::Ready)
        }

        fn get_current_token(&self) -> usize {
            let inner = self.inner.exclusive_access();
            inner.tasks[inner.current_task].get_user_token()
        }

        fn get_current_trap_cx(&self) -> &'static mut TrapContext {
            let inner = self.inner.exclusive_access();
            inner.tasks[inner.current_task].get_trap_cx()
        }

        fn run_next_task(&self) {
            if let Some(next) = self.find_next_task() {
                let mut inner = self.inner.exclusive_access();
                let current = inner.current_task;
                inner.tasks[next].task_status = TaskStatus::Running;
                inner.current_task = next;
                let current_task_cx_ptr = &mut inner.tasks[current].task_cx as *mut TaskContext;
                let next_task_cx_ptr = &inner.tasks[next].task_cx as *const TaskContext;
                drop(inner);
                // before this, we should drop local variables that must be dropped manually
                unsafe {
                    __switch(current_task_cx_ptr, next_task_cx_ptr);
                }
                // go back to user mode
            } else {
                panic!("All applications completed!");
            }
        }
    }

    pub fn run_first_task() {
        TASK_MANAGER.run_first_task();
    }

    fn run_next_task() {
        TASK_MANAGER.run_next_task();
    }

    fn mark_current_suspended() {
        TASK_MANAGER.mark_current_suspended();
    }

    fn mark_current_exited() {
        TASK_MANAGER.mark_current_exited();
    }

    pub fn suspend_current_and_run_next() {
        mark_current_suspended();
        run_next_task();
    }

    pub fn exit_current_and_run_next() {
        mark_current_exited();
        run_next_task();
    }

    pub fn current_user_token() -> usize {
        TASK_MANAGER.get_current_token()
    }

    pub fn current_trap_cx() -> &'static mut TrapContext {
        TASK_MANAGER.get_current_trap_cx()
    }