Resolve a host for v4 or v6 in Swift

resolve.swift

#if os(OSX)
import Cocoa
#else
import Foundation
#endif

/**
 resolves a host names ip address for the specified family
 - parameters:
    - name: the host name to resolve
    - family: AF_INET for V4 and AF_INET6 for V6
 - returns: a string representation of the host name's IPv4 or IPv6 address, nil on error
*/
func resolve(host name: String,
             for family: Int32) -> String? {
    
    guard let cname = name.cString(using: .ascii) else { return nil }
    var res: UnsafeMutablePointer<addrinfo>?
    let status = getaddrinfo(cname, nil, nil, &res)
    defer {
        freeaddrinfo(res)
    }
    guard status == 0 else { return nil }
    for res in sequence(first: res?.pointee.ai_next, next: { $0?.pointee.ai_next }) {
        guard let addr = res?.pointee.ai_addr else { continue }
        if addr.pointee.sa_family == family {
            var buf = [CChar](repeating: 0, count: Int(NI_MAXHOST))
            let status = getnameinfo(
                addr,
                socklen_t(addr.pointee.sa_len),
                &buf,
                socklen_t(buf.count),
                nil,
                socklen_t(0),
                NI_NUMERICHOST
            )
            if status == 0 { return String(cString: buf) }
        }
    }
    return nil
}

// ------------------ these are just for examples. ------------------

func getAddresses(of host: String) {
    if let ipv6 = resolve(host: host, for: AF_INET6) {
        print("IPv6 of \(host) = \(ipv6)")
    } else {
        print("error getting \(host) IPv6")
    }
    if let ipv4 = resolve(host: host, for: AF_INET) {
        print("IPv4 of \(host) = \(ipv4)")
    } else {
        print("error getting \(host) IPv4")
    }
}

getAddresses(of: "www.spectrum.com")