从 u8 切片创建读取特征对象

Question

我正在尝试从 u8 切片创建一个 Read 特征对象，以在 murmur3 板条箱中使用，就像这样

fn main() {
    let mut arr: [u8; 4] = [1, 2, 3, 4];
    let mut slice: &mut [u8] = &mut arr;
    let mut read: &mut std::io::Read = &mut slice;
}

但我明白了

<anon>:4:42: 4:53 error: the trait `std::io::Read` is not implemented for the type `[u8]` [E0277]
<anon>:4     let mut read : & mut std::io::Read = & mut slice;
                                                  ^~~~~~~~~~~
<anon>:4:42: 4:53 help: see the detailed explanation for E0277
<anon>:4:42: 4:53 help: the following implementations were found:
<anon>:4:42: 4:53 help:   <&'a [u8] as std::io::Read>
<anon>:4:42: 4:53 note: required for the cast to the object type `std::io::Read`
error: aborting due to previous error

这段代码有什么问题？

Answer 1

正如错误消息告诉您的，&[u8] 有一个 Read impl。没有理由为 &mut[u8] 使用 Read impl，因此您可以删除代码中的一些 mut：

// no need for `mut arr`, because `Read` does not modify memory
let arr: [u8; 4] = [1, 2, 3, 4];
// `slice` needs to be `mut`, because `Read` will
// actually make the slice smaller with every step
let mut slice: &[u8] = &arr;
let mut read: &mut std::io::Read = &mut slice;