arrays - 当 Vec 没有时，为什么 [u8] 可以作为 UdpSocket 的缓冲区？

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Reading from TcpStream results in empty buffer

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UdpSocket.recv_from fails with “end of file” but I can see the incoming package in Wireshark

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去年关闭。




我在网上找到了很多例子，其中 Vec<u8> 用作 UdpSocket.recv() 的缓冲区(例如 1 、 2 、 3 )。

然而，这似乎对我不起作用。以下代码的输出是:

[SEND] Wrote 4 bytes to the network: [1, 0, 0, 0]
[RECV] received 0 bytes: []
[SEND] Wrote 4 bytes to the network: [2, 0, 0, 0]
[RECV] received 0 bytes: []

这是代码:

use std::net::{SocketAddr, UdpSocket};
use std::{thread, time};

fn receiver(socket: UdpSocket, _remote: SocketAddr) {
    // This works:
    //   let mut buffer: [u8; 32] = [0; 32];
    // These don't:
    //   let mut buffer: Vec<u8> = Vec::with_capacity(32);
    let mut buffer: Vec<u8> = Vec::new();
    loop {
        match socket.recv(&mut buffer) {
            Ok(bytes) => {
                println!("[RECV] received {} bytes: {:?}", bytes, buffer);
            }
            Err(error) => {
                unimplemented!("Handle me: {:?}", error);
            }
        }
    }
}

fn sender(socket: UdpSocket, remote: SocketAddr) {
    thread::sleep(time::Duration::from_secs(3));

    let a = bincode::serialize(&1).unwrap();
    let b = bincode::serialize(&2).unwrap();

    match socket.send_to(&a, remote) {
        Ok(bytes) => {
            println!("[SEND] Wrote {} bytes to the network: {:?}", bytes, a);
        }
        Err(error) => {
            println!("{:?}", error);
        }
    }

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

    match socket.send_to(&b, remote) {
        Ok(bytes) => {
            println!("[SEND] Wrote {} bytes to the network: {:?}", bytes, b);
        }
        Err(error) => {
            println!("{:?}", error);
        }
    }
}

fn main() {
    use std::net::{IpAddr, Ipv4Addr};

    let send_addr = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 3333);
    let recv_addr = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 4444);

    let send_sock = UdpSocket::bind(send_addr).unwrap();
    let recv_sock = UdpSocket::bind(recv_addr).unwrap();

    let send_handle = thread::spawn(move || sender(send_sock, recv_addr));
    let recv_handle = thread::spawn(move || receiver(recv_sock, send_addr));

    let _ = send_handle.join();
    let _ = recv_handle.join();
}

当我使用 [u8; 32] 作为缓冲区时，它完美地工作:

[SEND] Wrote 4 bytes to the network: [1, 0, 0, 0]
[RECV] received 4 bytes: [1, 0, 0, 0, 0, 0, 0, 0, ...]
[SEND] Wrote 4 bytes to the network: [2, 0, 0, 0]
[RECV] received 4 bytes: [2, 0, 0, 0, 0, 0, 0, 0, ...]

这是 Rust 中的错误吗？我正在使用 1.41。

最佳答案

Vec::new 和 Vec::with_capacity 返回一个包含 0 个元素的 Vec，因此从它们借用 &mut buffer 将产生一个包含 0 个元素的切片。

recv 的参数必须有足够的容量来容纳字节，但由于 &mut buffer 是一个超过 0 字节的切片，因此该切片中没有足够的空间，因此多余的字节将被丢弃。

您可能希望在将 buffer.resize(32, 0) 传递给 recv 以反射(reflect)您使用数组 ( [u8; 32] ) 显示的情况之前。