如何将字节向量流式传输到 BufWriter？

Posted 2023-02-19

【中文标题】如何将字节向量流式传输到 BufWriter？

【英文标题】：How to stream a vector of bytes to BufWriter?

【发布时间】：2022-01-20 17:34:38

【问题描述】：

我正在尝试使用 io::copy(&mut reader, &mut writer) 将字节流式传输到 tcp 服务器，但它给了我这个错误：the trait "std::io::Read" is not implemented for "Vec<integer>"。在这里，我有一个字节向量，这与我打开文件并将其转换为字节相同。我想将字节写入BufWriter。我做错了什么？

use std::io;
use std::net::TcpStream;
use std::io::BufWriter;

pub fn connect() 
    if let Ok(stream) = TcpStream::connect("localhost:8080") 
        println!("Connection established!");
        let mut reader = vec![
            137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0, 70, 0, 0, 0, 70,
        ];
        let mut writer = BufWriter::new(&stream);
        io::copy(&mut reader, &mut writer).expect("Failed to write to stream");
     else 
        println!("Couldn't connect to the server")
    

error[E0277]: the trait bound `Vec<integer>: std::io::Read` is not satisfied
  --> src/lib.rs:12:31
   |
12 |         io::copy(&mut reader, &mut writer).expect("Failed to write to stream");
   |         --------              ^^^^^^^^^^^ the trait `std::io::Read` is not implemented for `Vec<integer>`
   |         |
   |         required by a bound introduced by this call
   |
note: required by a bound in `std::io::copy`

【参考方案1】：

像这样使用.as_slice() 对我有用：

pub fn connect() 
    if let Ok(stream) = TcpStream::connect("localhost:8080") 
        println!("Connection established!");
        let reader = vec![
            137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0, 70, 0, 0, 0, 70,
        ];
        let mut writer = BufWriter::new(&stream);
        io::copy(&mut reader.as_slice(), &mut writer).expect("Failed to write to stream");
     else 
        println!("Couldn't connect to the server")
    

那是因为std::io::Read 支持切片。

【参考方案2】：

这里编译器有点麻烦，Vec 没有实现 Read 但&[u8] 实现了，在创建可变引用之前，您只需从 vec 获取一个 slice：

copy(&mut reader.as_slice(), &mut writer).expect("Failed to write to stream");

另见：

What is the difference between storing a Vec vs a Slice? What are the differences between Rust's `String` and `str`?

【讨论】：

好的，切片是什么？

现在服务器出现紧急情况：thread "main" panicked at "called "Result::unwrap()" on an "Err" value: Error kind: InvalidData, message: "stream did not contain valid UTF-8" "。是否可以将字节流式传输到 tcp 服务器？

@Nicke7117 您发送的另一个问题我无法真正帮助您

@Nicke7117 最好将您的服务器恐慌作为一个单独的问题询问。

@Nicke7117 “什么是切片？” → doc.rust-lang.org/reference/types/slice.html 和 doc.rust-lang.org/std/primitive.slice.html