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// 引入需要的库
use std::{cell::UnsafeCell, collections::VecDeque, marker::PhantomData};
use crate::task::{Schedule, Task};
// 本地调度器
pub(crate) struct LocalScheduler;
// 两种调度策略
impl Schedule for LocalScheduler {
// 就绪队列
fn schedule(&self, task: Task<Self>) {
crate::runtime::CURRENT.with(|cx| cx.tasks.push(task));
}
// 就绪队列,立刻执行
fn yield_now(&self, task: Task<Self>) {
crate::runtime::CURRENT.with(|cx| cx.tasks.push_front(task));
}
}
// 任务队列
pub(crate) struct TaskQueue {
// Local queue. 就绪队列
queue: UnsafeCell<VecDeque<Task<LocalScheduler>>>,
// Make sure the type is `!Send` and `!Sync`.
_marker: PhantomData<*const ()>, // 非跨线程
}
impl Default for TaskQueue {
// 默认构造函数
fn default() -> Self {
Self::new()
}
}
impl TaskQueue {
// 创建就绪队列实例
pub(crate) fn new() -> Self {
const DEFAULT_TASK_QUEUE_SIZE: usize = 4096; // 默认4096
Self::new_with_capacity(DEFAULT_TASK_QUEUE_SIZE)
}
// 创建指定容量的就绪队列实例
pub(crate) fn new_with_capacity(capacity: usize) -> Self {
Self {
queue: UnsafeCell::new(VecDeque::with_capacity(capacity)), // 指定容量
_marker: PhantomData, // 内存对齐?
}
}
// 获取就绪队列长度
pub(crate) fn len(&self) -> usize {
unsafe { (*self.queue.get()).len() }
}
// 判断就绪队列是否为空
pub(crate) fn is_empty(&self) -> bool {
self.len() == 0
}
// 将任务加入就绪队列尾部
pub(crate) fn push(&self, runnable: Task<LocalScheduler>) {
unsafe {
(*self.queue.get()).push_back(runnable);
}
}
// 将任务加入就绪队列头部, 约等于立刻执行
pub(crate) fn push_front(&self, runnable: Task<LocalScheduler>) {
unsafe {
(*self.queue.get()).push_front(runnable);
}
}
// 从就绪队列头部弹出任务
pub(crate) fn pop(&self) -> Option<Task<LocalScheduler>> {
unsafe { (*self.queue.get()).pop_front() }
}
}
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