如何在Rust中使用sha256哈希输出进行sha256哈希

Question

我写了一些 Rust 代码，但存在生命周期问题。

let mut sha256 = Sha256::new();
sha256.input_str(input.as_slice());

for i in range(0i,16) {
    println!("i == {}, hash == {}", i, sha256.result_str());
    let bytes = sha256.result_bytes().as_slice();
    sha256.input(bytes);
}

错误是：

$ cargo build && ./target/hello_world asdfasdf
   Compiling hello_world v0.1.0 (file:///home/chris/hello_world)
src/hello_world.rs:41:21: 41:42 error: borrowed value does not live long enough
src/hello_world.rs:41         let bytes = sha256.result_bytes().as_slice();
                                          ^~~~~~~~~~~~~~~~~~~~~
src/hello_world.rs:39:27: 43:6 note: reference must be valid for the block at 39:26...
src/hello_world.rs:39     for i in range(0i,16) {
src/hello_world.rs:40         println!("i == {}, hash == {}", i, sha256.result_str());
src/hello_world.rs:41         let bytes = sha256.result_bytes().as_slice();
src/hello_world.rs:42         sha256.input(bytes);
src/hello_world.rs:43     }
src/hello_world.rs:41:9: 41:53 note: ...but borrowed value is only valid for the statement at 41:8; consider using a `let` binding to increase its lifetime
src/hello_world.rs:41         let bytes = sha256.result_bytes().as_slice();
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
error: aborting due to previous error
Could not compile `hello_world`.

To learn more, run the command again with --verbose.

我该如何修改这个内容，同时确保它能高效执行？

- fadedbee

---

https://crates.io/crates/sha2 - fadedbee

Answer 1

这是因为在那一行代码之后，result_bytes()的结果被丢弃了，而as_slice()获取了它的引用。借用检查器不允许这种情况发生。

如果要使其正常工作，应该这样编写：

let mut sha256 = Sha256::new();
sha256.input_str(input.as_slice());

for i in range(0i,16) {
    println!("i == {}, hash == {}", i, sha256.result_str());
    let bytes = sha256.result_bytes();
    sha256.reset();
    sha256.input(bytes.as_slice());
}

希望它有所帮助。

- snf