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Dima
Asked:2024-03-04 02:27:57 +0800 CST2024-03-04 02:27:57 +0800 CST

Rust：如何在线程之间传递哈希图？

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刚刚开始使用 Rust 中的线程。我无法在两个线程之间传递哈希表。如何正确地做到这一点以及我的错误在哪里？任务是在一个线程中收集哈希表并在另一个线程中打印它。

use std::thread;
use std::time::Duration;
use std::fs;
use std::io::{stdin, Read};
use std::collections::HashMap;


fn main() {
    
    let mut hello = String::from("Hello, ");
    let mut influx_data:HashMap<String, i32> = HashMap::new();

//second thread
    thread::spawn(move || {
        let mut character = [0];
        hello = String::from("sasasas ");
        while let Ok(_) = stdin().read(&mut character) {
            
if character[0] == b'\n' {
        influx_data.entry(hello).and_modify(|count| *count += 1).or_insert(1);  
            println!("counter_bss cnt=7\n");
            }
        }

            thread::sleep(Duration::from_secs(1));
    });

//main thread    
    loop {
        let data = "Some data!";
        fs::write("/tmp/foo", data).expect("Unable to write file");

        for (key, value) in &influx_data {
        println!("{} {}", key, value);
        }

        thread::sleep(Duration::from_secs(10));
   }

}

错误

   |
23 |                 influx_data.entry(hello).and_modify(|count| *count += 1).or_insert(1);  
   |                                   ^^^^^ value moved here, in previous iteration of loop
rust

1 个回答

  1. Best Answer

    首先，你的问题不在于地图，而在于钥匙hello。Rust 担心该符号\n可能会出现多次，并且entry会在第一次出现后丢弃密钥。你需要打电话entry(hello.clone())

    接下来，您有一个 HashMap 对象，但写入器和读取器位于不同的线程上。他们的寿命不同，彼此之间没有投资。所以你不能只创建一个链接并将其传递给spawn函数，你会得到一个错误

    `influx_data` does not live long enough
borrowed value does not live long enough

    您需要创建一个共享容器。特别是对于多线程访问，RustMutex具有Arc. 这些容器的组合允许从不同线程共享访问对象

    let data_owner = Arc::new(Mutex::new(influx_data));
let data_for_thread = data_owner.clone();

    容器data_owner存储您的地图main，容器data_for_thread 将移至封闭处。要访问映射，您需要捕获互斥锁：

    data_for_thread.lock().unwrap().entry(...)
...
for (key, value) in data_owner.lock().unwrap().iter() {...}

    use std::collections::HashMap;
use std::fs;
use std::io::{stdin, Read};
use std::sync::{Arc, Mutex};
use std::thread;
use std::time::Duration;

fn main() {
    let mut hello = String::from("Hello, ");
    let influx_data: HashMap<String, i32> = HashMap::new();
    let data_owner = Arc::new(Mutex::new(influx_data));
    let data_for_thread = data_owner.clone();

    //second thread
    thread::spawn(move || {
        let mut character = [0];
        hello = String::from("sasasas ");
        while let Ok(_) = stdin().read(&mut character) {
            if character[0] == b'\n' {
                data_for_thread
                    .lock()
                    .unwrap()
                    .entry(hello.clone())
                    .and_modify(|count| *count += 1)
                    .or_insert(1);
                println!("counter_bss cnt=7\n");
            }
        }

        thread::sleep(Duration::from_secs(1));
    });

    //main thread
    loop {
        let data = "Some data!";
        fs::write("/tmp/foo", data).expect("Unable to write file");

        for (key, value) in data_owner.lock().unwrap().iter() {
            println!("{} {}", key, value);
        }

        thread::sleep(Duration::from_secs(10));
    }
}

    日志如下所示：

    1
counter_bss cnt=7

2
counter_bss cnt=7

3
counter_bss cnt=7

sasasas  3
4
counter_bss cnt=7

sasasas  4
5
counter_bss cnt=7

sasasas  5

    作品

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