is_valid_ipv4_addr

lib.rs

#![crate_type = "staticlib"]
#![feature(test)]
extern crate test;

extern crate libc;

use std::slice;

fn is_valid_ipv4_addr<'a>(addr: &'a [u8]) -> bool {
    let mut maybe_octet: Option<u8> = None;
    let mut dots: u8 = 0;

    for c in addr {
        match c {
            46 => {
                if maybe_octet.is_none() {
                    // ip address cannot start with a '.'
                    return false;
                }
                dots = dots + 1;
                maybe_octet = None;
            }
            c => {
                if *c < 48 as u8 || *c > 57 {
                    return false;
                }
                match maybe_octet {
                    None => {
                        maybe_octet = Some(*c - 48);
                    }
                    Some(octet) => {
                        if *c == 48 && octet == 0 {
                            // Leading 0 is not allowed
                            return false;
                        }
                        if let Some(times_ten) = octet.checked_mul(10) {
                            if let Some(plus_c) = times_ten.checked_add(*c - 48) {
                                maybe_octet = Some(plus_c)
                            } else {
                                // Addition overflowed
                                return false;
                            }
                        } else {
                            // Multiplication overflowed
                            return false;
                        }
                    }
                }
            }
        }
    }
    dots == 3 && maybe_octet.is_some()
}

#[no_mangle]
#[allow(non_snake_case)]
pub extern "C" fn rust_net_is_valid_ipv4_addr<'a>(addr: &'a u8, addrLen: i32) -> bool {
    let address = unsafe { slice::from_raw_parts(addr, addrLen as usize) };
    is_valid_ipv4_addr(address)
}

#[cfg(test)]
mod tests {
    use is_valid_ipv4_addr;
    use test::{black_box, Bencher};

    #[test]
    fn test_with_localhost() {
        let ip: Vec<char> = vec!['1', '2', '7', '.', '0', '.', '0', '.', '1'];
        assert!(is_valid_ipv4_addr(&ip));
    }

    #[test]
    fn test_with_zeroes() {
        let ip: Vec<char> = vec!['0', '.', '0', '.', '0', '.', '0'];
        assert!(is_valid_ipv4_addr(&ip));
    }

    #[test]
    fn test_with_max() {
        let ip: Vec<char> = vec![
            '2', '5', '5', '.', '2', '5', '5', '.', '2', '5', '5', '.', '2', '5', '5',
        ];
        assert!(is_valid_ipv4_addr(&ip));
    }

    #[test]
    fn test_with_too_high_ip() {
        let ip: Vec<char> = vec![
            '2', '5', '6', '.', '2', '5', '5', '.', '2', '5', '5', '.', '2', '5', '5',
        ];
        assert!(!is_valid_ipv4_addr(&ip));
    }

    #[test]
    fn test_with_ip_starting_with_a_dot() {
        let ip: Vec<char> = vec![
            '.', '2', '5', '6', '.', '2', '5', '5', '.', '2', '5', '5', '.', '2', '5', '5',
        ];
        assert!(!is_valid_ipv4_addr(&ip));
    }

    #[test]
    fn test_with_ip_starting_with_4_digits() {
        let ip: Vec<char> = vec![
            '1', '1', '1', '1', '.', '2', '5', '5', '.', '2', '5', '5', '.', '2', '5', '5',
        ];
        assert!(!is_valid_ipv4_addr(&ip));
    }

    #[test]
    fn test_with_too_long_ip() {
        let ip: Vec<char> = vec![
            '2', '5', '5', '.', '2', '5', '5', '.', '2', '5', '5', '.', '2', '5', '5', '.', '2',
            '5', '5',
        ];
        assert!(!is_valid_ipv4_addr(&ip));
    }

    #[bench]
    fn bench_is_valid_ipv4_address(bench: &mut Bencher) {
        let ip: Vec<char> = vec![
            '1', '9', '2', '.', '1', '6', '8', '.', '1', '0', '1', '.', '1', '1', '7',
        ];
        bench.iter(|| black_box(is_valid_ipv4_addr(&ip)));
    }
}

if *c < '0' || *c > '9' {
     return false;
}

might read somewhat clearer as

if !c.is_digit() {
     return false;
}

(see https://doc.rust-lang.org/beta/std/primitive.char.html#method.is_digit)