rust - 为什么重新借用 &mut[u8] 使其大小在编译时未知？

Question

我正在创建一个可变的 [u8]缓冲是这样的:

let buffer: &mut [u8] = &mut [0u8; 34];

并在这里使用:

repr.emit(&mut *buffer, &caps.checksum);

并在这里重新借用:

assert_eq!(processor!(iface).process_ip_payload(&mut ip, &mut socket_set, Instant::from_millis(0), &mut *buffer), Ok(Some(expected_repr)));

我得到:

the size for values of type [u8] cannot be known at compilation time

doesn't have a size known at compile-time

为 ...,&mut *buffer)重新借用(最后一个，在断言时)。

原始缓冲区的大小在编译时是已知的。为什么再借使大小未知？

如果需要，这里是签名:

    pub fn emit<T: AsRef<[u8]> + AsMut<[u8]>>(
        &self,
        buffer: T,
        _checksum_caps: &ChecksumCapabilities,
    )
    fn process_ip_payload<'frame, T: AsRef<[u8]>>(
        &mut self,
        ip: &mut ip::Processor,
        sockets: &mut SocketSet,
        timestamp: Instant,
        frame: &'frame T,
    ) -> Result<Option<ip::Packet<'frame>>>

Answer 1

不要取消引用 buffer当您将其作为参数传入时:

assert_eq!(processor!(iface).process_ip_payload(
    &mut ip, &mut socket_set, Instant::from_millis(0), &mut buffer),
    Ok(Some(expected_repr)));

( &mut buffer 而不是 &mut *buffer )。