saslauthd_yaml/common/src/io.rs

use std::io::{Error, Read, Write};

/// The saslauthd protocol transmits strings as
/// 16-bit unsigned network-byte-order lengths followed
/// by the string itself.
///
pub fn read_string(stream: &mut impl Read) -> Result<String, Error> {
    let mut length_buffer = [0u8, 0u8];

    stream.read_exact(&mut length_buffer)?;
    let length = u16::from_be_bytes(length_buffer);

    let mut string_buffer = vec![0u8; length as usize];

    stream.read_exact(&mut string_buffer)?;

    match String::from_utf8(string_buffer) {
        Ok(str) => Ok(str),
        Err(_err) => Err(Error::other("Invalid UTF-8 sent")),
    }
}

pub fn write_string(stream: &mut impl Write, s: &str) -> Result<(), Error> {
    let length = s.len();

    if length > 0xffff {
        return Err(Error::other("String too long to write"));
    }

    let length_buffer = [(length >> 8) as u8, (length & 0xff) as u8];

    stream.write_all(&length_buffer)?;
    stream.write_all(s.as_bytes())?;

    Ok(())
}