Equivalent of inet_ntop in Rust

Question

Is there a readily available way to convert ip addresses (both v4 and v6) from binary to text form in Rust (an equivalent to inet_ntop)?

Examples:

• "3701A8C0" converts to "55.1.168.192",
• "20010db8000000000000000000000001" converts to "2001:db8::1".

Answer 1

inet_ntop takes as input a struct in_addr* or a struct in6_addr*. The direct equivalent of those structs in Rust are Ipv4Addr and Ipv6Addr, both of which implement the Display trait and can therefore be formatted easily to text or printed:

let addr = Ipv4Addr::from (0x3701A8C0);
assert_eq!(format!("{}", addr), String::from ("55.1.168.192"));
println!("{}", addr);

Answer 2

AFAIK, there is not a direct conversion, but you can do that with from_str_radix, and then with the conversion of an ip from a numeric type:

use std::{
    error::Error,
    io,
    net::{IpAddr, Ipv4Addr, Ipv6Addr},
    str::FromStr,
};

fn convert(s: &str) -> io::Result<IpAddr> {
    if let Ok(u) = u32::from_str_radix(s, 16) {
        Ok(Ipv4Addr::from(u).into())
    } else if let Ok(u) = u128::from_str_radix(s, 16) {
        Ok(Ipv6Addr::from(u).into())
    } else {
        Err(io::Error::new(io::ErrorKind::InvalidData, "Invalid input"))
    }
}

fn main() -> Result<(), Box<dyn Error>> {
    let ip = convert("3701A8C0")?;
    assert_eq!(ip, IpAddr::from_str("55.1.168.192")?);

    let ip = convert("20010db8000000000000000000000001")?;
    assert_eq!(ip, IpAddr::from_str("2001:db8::1")?);

    Ok(())
}

If you already know that it is, for example, and IPV4, this is a one-liner:

use std::{
    error::Error,
    net::{IpAddr, Ipv4Addr},
    str::FromStr,
};

fn main() -> Result<(), Box<dyn Error>> {
    let ip = u32::from_str_radix("3701A8C0", 16).map(Ipv4Addr::from)?;
    assert_eq!(ip, IpAddr::from_str("55.1.168.192")?);

    Ok(())
}