rust - 如何更改此函数的返回类型？

Question

我正在浏览 matasano crypto challenges使用 rust，使用 rust-crypto 实现 AES。我有这个功能来进行基本的 ECB 模式加密(基本上是从 rust-crypto repository's example 中逐字记录的):

pub fn aes_enc_ecb_128(key: &[u8], data: &[u8]) 
                       -> Result<Vec<u8>, symmetriccipher::SymmetricCipherError> {
    let mut encryptor = aes::ecb_encryptor(
            aes::KeySize::KeySize128,
            key,
            blockmodes::NoPadding);
    let mut final_result = Vec::<u8>::new();
    let mut read_buffer = buffer::RefReadBuffer::new(data);
    let mut buffer = [0; 4096];
    let mut write_buffer = buffer::RefWriteBuffer::new(&mut buffer);

    loop {
        let result = encryptor.encrypt(&mut read_buffer,
                                       &mut write_buffer,
                                       true);

        final_result.extend(write_buffer
                            .take_read_buffer()
                            .take_remaining().iter().map(|&i| i));
        match result {
            Ok(BufferResult::BufferUnderflow) => break,
            Ok(_) => {},
            Err(e) => return Err(e)
        }
    }

    Ok(final_result)
}

以上版本编译没有问题，并按预期工作。但是，为了使其适合我的其余错误处理方案，我想将返回类型更改为 Result<Vec<u8>,&'static str> .这是应用了该更改的函数:

pub fn aes_enc_ecb_128(key: &[u8], data: &[u8]) 
                       -> Result<Vec<u8>, &'static str> {
    let mut encryptor = aes::ecb_encryptor(
            aes::KeySize::KeySize128,
            key,
            blockmodes::NoPadding);
    let mut final_result = Vec::<u8>::new();
    let mut read_buffer = buffer::RefReadBuffer::new(data);
    let mut buffer = [0; 4096];
    let mut write_buffer = buffer::RefWriteBuffer::new(&mut buffer);

    loop {
        let result = encryptor.encrypt(&mut read_buffer,
                                       &mut write_buffer,
                                       true);

        final_result.extend(write_buffer
                            .take_read_buffer()
                            .take_remaining().iter().map(|&i| i));
        match result {
            Ok(BufferResult::BufferUnderflow) => break,
            Ok(_) => {},
            Err(_) => return Err("Encryption failed")
        }
    }

    Ok(final_result)
}

当我尝试编译此版本时，出现以下错误(为清楚起见删除了路径):

error: source trait is private
         let result = encryptor.encrypt(&mut read_buffer,
                                        &mut write_buffer,
                                        true);
error: source trait is private
let r = decryptor.decrypt(&mut read_buffer, &mut write_buffer, true);
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

我能够更改此类型的唯一方法是将原始函数包装在这样的转换函数中:

pub fn converted_enc(key: &[u8], data: &[u8]) 
                       -> Result<Vec<u8>, &'static str> {
   match aes_enc_ecb_128(key,data) {
       Ok(v) => Ok(v),
       Err(_) => Err("Encryption failed")
   } 
}

为了让返回值适合我的 API 的其余部分，我应该做什么而不是上面的操作，为什么更直接的方法失败了？

我正在使用以下版本的 rust/cargo:

rustc 1.2.0-nightly (0cc99f9cc 2015-05-17) (built 2015-05-18)
cargo 0.2.0-nightly (ac61996 2015-05-17) (built 2015-05-17)

Answer 1

我认为您遇到了编译器的错误。你的代码应该编译

您可以使用 crypto::symmetriccipher::Encryptor; 作为解决方法:

pub fn aes_enc_ecb_128(key: &[u8], data: &[u8]) 
                       -> Result<Vec<u8>, &'static str> {
    use crypto::symmetriccipher::Encryptor;
    let mut encryptor = aes::ecb_encryptor(
            aes::KeySize::KeySize128,
            key,
            blockmodes::NoPadding);
    let mut final_result = Vec::<u8>::new();
    let mut read_buffer = buffer::RefReadBuffer::new(data);
    let mut buffer = [0; 4096];
    let mut write_buffer = buffer::RefWriteBuffer::new(&mut buffer);

    loop {
        let result = encryptor.encrypt(&mut read_buffer,
                                       &mut write_buffer,
                                       true);

        final_result.extend(write_buffer
                            .take_read_buffer()
                            .take_remaining().iter().map(|&i| i));
        match result {
            Ok(BufferResult::BufferUnderflow) => break,
            Ok(_) => {},
            Err(_) => return Err("Encryption failed")
        }
    }

    Ok(final_result)
}