如何将 futures_io::AsyncRead 转换为 rusoto::ByteStream？

Question

我正在尝试构建一个从 SFTP 服务器提取文件并将其上传到 S3 的服务。

对于 SFTP 部分，我使用 async-ssh2, which gives me a file handler implementing futures::AsyncRead. Since these SFTP files may be quite large, I am trying to turn this File handler into a ByteStream that I can upload using Rusoto. It looks like a ByteStream can be initialized with a futures::Stream。

我的计划是在 File 对象上实现 Stream（基于代码 here）以与 Rusoto 兼容（为后代复制下面的代码）：

use core::pin::Pin;
use core::task::{Context, Poll};
use futures::{ready, stream::Stream};

pub struct ByteStream<R>(R);

impl<R: tokio::io::AsyncRead + Unpin> Stream for ByteStream<R> {
    type Item = u8;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
        let mut buf = [0; 1];

        match ready!(Pin::new(&mut self.0).poll_read(cx, &mut buf)) {
            Ok(n) if n != 0 => Some(buf[0]).into(),
            _ => None.into(),
        }
    }
}

这样做是不是一个好方法？我看到了this question, but it seems to be using tokio::io::AsyncRead。使用 tokio 是执行此操作的规范方法吗？如果是这样，有没有办法将 futures_io::AsyncRead 转换为 tokio::io::AsyncRead？

Answer 1

这就是我进行转换的方式。我基于上面的代码，只是我使用了更大的缓冲区 (8 KB) 来减少网络调用的次数。

use bytes::Bytes;
use core::pin::Pin;
use core::task::{Context, Poll};
use futures::{ready, stream::Stream};
use futures_io::AsyncRead;
use rusoto_s3::StreamingBody;

const KB: usize = 1024;

struct ByteStream<R>(R);

impl<R: AsyncRead + Unpin> Stream for ByteStream<R> {
    type Item = Result<Bytes, std::io::Error>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
        let mut buf = vec![0_u8; 8 * KB];

        match ready!(Pin::new(&mut self.0).poll_read(cx, &mut buf[..])) {
            Ok(n) if n != 0 => Some(Ok(Bytes::from(buf))).into(),
            Ok(_) => None.into(),
            Err(e) => Some(Err(e)).into(),
        }
    }
}

允许我这样做：

fn to_streamingbody(body: async_ssh2::File) -> Option<StreamingBody> {
    let stream = ByteStream(body);
    Some(StreamingBody::new(stream))
}

（注意rusoto::StreamingBody和rusoto::ByteStream是别名）

如何将 futures_io::AsyncRead 转换为 rusoto::ByteStream？

How do I convert a futures_io::AsyncRead to rusoto::ByteStream?

rust

rusoto