异步编程

主要用于提高 I/O 密集型程序的并发性能，避免阻塞线程，从而提升整体执行效率。

异步编程机制通过非阻塞 I/O 提升 I/O 密集型应用的并发性能，适合构建高性能、高并发的网络服务等场景。

use std::fs;

#[tokio::main]
async fn main() {
    // 写入文件
    // fs::write("read.txt", "Hello").unwrap();

    // 读取文件
    // let result = fs::read_to_string("read.txt");
    // match result {
    //     Ok(content) => println!("File content: {}", content),
    //     Err(e) => println!("Failed to read file: {}", e),
    // }

    let result = tokio::fs::read_to_string("read.txt").await;
    match result {
        Ok(content) => println!("File content: {}", content),
        Err(e) => println!("Failed to read file: {}", e),
    }
}

#[tokio::main]
async fn main() {
    // say_hello().await;
    // say_goodbye().await;

    // 同时运行两个异步函数
    // tokio::join!(say_hello(), say_goodbye(),);

    // 同时运行两个异步函数，哪个先完成就执行哪个
    tokio::select! {
        result = say_name() => {
            println!("Name: {}", result);
        }
        _ = tokio::time::sleep(tokio::time::Duration::from_millis(500)) => {
            println!("Timeout");
        }
    }

    // let handle = tokio::spawn(async {
    //     println!("Je suis un thread");
    // });

    // handle.await.unwrap();
}

async fn say_hello() {
    tokio::time::sleep(std::time::Duration::from_secs(1)).await;
    println!("Hello, world!");
}

async fn say_goodbye() {
    tokio::time::sleep(std::time::Duration::from_secs(1)).await;
    println!("Goodbye, world!");
}

async fn say_name() -> &'static str {
    tokio::time::sleep(std::time::Duration::from_secs(1)).await;
    "John"
}