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    //! Query network interface addresses
    //!
    //! Uses the Linux and/or BSD specific function `getifaddrs` to query the list
    //! of interfaces and their associated addresses.

    use std::ffi;
    use std::iter::Iterator;
    use std::mem;
    use std::option::Option;

    use libc;

    use {Result, Errno};
    use sys::socket::SockAddr;
    use net::if_::*;

    /// Describes a single address for an interface as returned by `getifaddrs`.
    #[derive(Clone, Eq, Hash, PartialEq, Debug)]
    pub struct InterfaceAddress {
        /// Name of the network interface
        pub interface_name: String,
        /// Flags as from `SIOCGIFFLAGS` ioctl
        pub flags: InterfaceFlags,
        /// Network address of this interface
        pub address: Option<SockAddr>,
        /// Netmask of this interface
        pub netmask: Option<SockAddr>,
        /// Broadcast address of this interface, if applicable
        pub broadcast: Option<SockAddr>,
        /// Point-to-point destination address
        pub destination: Option<SockAddr>,
    }

    cfg_if! {
        if #[cfg(any(target_os = "emscripten", target_os = "fuchsia", target_os = "linux"))] {
            fn get_ifu_from_sockaddr(info: &libc::ifaddrs) -> *const libc::sockaddr {
                info.ifa_ifu
            }
        } else {
            fn get_ifu_from_sockaddr(info: &libc::ifaddrs) -> *const libc::sockaddr {
                info.ifa_dstaddr
            }
        }
    }

    impl InterfaceAddress {
        /// Create an `InterfaceAddress` from the libc struct.
        fn from_libc_ifaddrs(info: &libc::ifaddrs) -> InterfaceAddress {
            let ifname = unsafe { ffi::CStr::from_ptr(info.ifa_name) };
            let address = unsafe { SockAddr::from_libc_sockaddr(info.ifa_addr) };
            let netmask = unsafe { SockAddr::from_libc_sockaddr(info.ifa_netmask) };
            let mut addr = InterfaceAddress {
                interface_name: ifname.to_string_lossy().to_string(),
                flags: InterfaceFlags::from_bits_truncate(info.ifa_flags as i32),
                address: address,
                netmask: netmask,
                broadcast: None,
                destination: None,
            };

            let ifu = get_ifu_from_sockaddr(info);
            if addr.flags.contains(InterfaceFlags::IFF_POINTOPOINT) {
                addr.destination = unsafe { SockAddr::from_libc_sockaddr(ifu) };
            } else if addr.flags.contains(InterfaceFlags::IFF_BROADCAST) {
                addr.broadcast = unsafe { SockAddr::from_libc_sockaddr(ifu) };
            }

            addr
        }
    }

    /// Holds the results of `getifaddrs`.
    ///
    /// Use the function `getifaddrs` to create this Iterator. Note that the
    /// actual list of interfaces can be iterated once and will be freed as
    /// soon as the Iterator goes out of scope.
    #[derive(Debug, Eq, Hash, PartialEq)]
    pub struct InterfaceAddressIterator {
        base: *mut libc::ifaddrs,
        next: *mut libc::ifaddrs,
    }

    impl Drop for InterfaceAddressIterator {
        fn drop(&mut self) {
            unsafe { libc::freeifaddrs(self.base) };
        }
    }

    impl Iterator for InterfaceAddressIterator {
        type Item = InterfaceAddress;
        fn next(&mut self) -> Option<<Self as Iterator>::Item> {
            match unsafe { self.next.as_ref() } {
                Some(ifaddr) => {
                    self.next = ifaddr.ifa_next;
                    Some(InterfaceAddress::from_libc_ifaddrs(ifaddr))
                }
                None => None,
            }
        }
    }

    /// Get interface addresses using libc's `getifaddrs`
    ///
    /// Note that the underlying implementation differs between OSes. Only the
    /// most common address families are supported by the nix crate (due to
    /// lack of time and complexity of testing). The address family is encoded
    /// in the specific variant of `SockAddr` returned for the fields `address`,
    /// `netmask`, `broadcast`, and `destination`. For any entry not supported,
    /// the returned list will contain a `None` entry.
    ///
    /// # Example
    /// ```
    /// let addrs = nix::ifaddrs::getifaddrs().unwrap();
    /// for ifaddr in addrs {
    ///   match ifaddr.address {
    ///     Some(address) => {
    ///       println!("interface {} address {}",
    ///                ifaddr.interface_name, address);
    ///     },
    ///     None => {
    ///       println!("interface {} with unsupported address family",
    ///                ifaddr.interface_name);
    ///     }
    ///   }
    /// }
    /// ```
    pub fn getifaddrs() -> Result<InterfaceAddressIterator> {
        let mut addrs: *mut libc::ifaddrs = unsafe { mem::uninitialized() };
        Errno::result(unsafe { libc::getifaddrs(&mut addrs) }).map(|_| {
            InterfaceAddressIterator {
                base: addrs,
                next: addrs,
            }
        })
    }

    #[cfg(test)]
    mod tests {
        use super::*;

        // Only checks if `getifaddrs` can be invoked without panicking.
        #[test]
        fn test_getifaddrs() {
            let _ = getifaddrs();
        }
    }

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