rust - How to read a specific number of bytes from a stream?

Question

I have a struct with a BufStream<T> where T: Read+Write. The BufStream can be a TcpStream and I'd like to read n bytes from it. Not a fixed amount of bytes in a predefined buffer, but I have a string/stream which indicates the number of bytes to read next.

Is there a nice way to do that?

Answer 1

Since Rust 1.6, Read::read_exact can be used to do this. If bytes_to_read is the number of bytes you need to read, possibly determined at runtime, and reader is the stream to read from:

let mut buf = vec![0u8; bytes_to_read];
reader.read_exact(&mut buf)?;

The part that wasn't clear to me from the read_exact documentation was that the target buffer can be a dynamically-allocated Vec.

Thanks to the Rust Gitter community for pointing me to this solution.