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    use std::fmt;
    use std::mem::{self, MaybeUninit};
    use std::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
    use std::ptr;

    #[cfg(any(unix, target_os = "redox"))]
    use libc::{
        in6_addr, in_addr, sa_family_t, sockaddr, sockaddr_in, sockaddr_in6, sockaddr_storage,
        socklen_t, AF_INET, AF_INET6,
    };
    #[cfg(windows)]
    use winapi::shared::in6addr::{in6_addr_u, IN6_ADDR as in6_addr};
    #[cfg(windows)]
    use winapi::shared::inaddr::{in_addr_S_un, IN_ADDR as in_addr};
    #[cfg(windows)]
    use winapi::shared::ws2def::{
        ADDRESS_FAMILY as sa_family_t, AF_INET, AF_INET6, SOCKADDR as sockaddr,
        SOCKADDR_IN as sockaddr_in, SOCKADDR_STORAGE as sockaddr_storage,
    };
    #[cfg(windows)]
    use winapi::shared::ws2ipdef::{SOCKADDR_IN6_LH_u, SOCKADDR_IN6_LH as sockaddr_in6};
    #[cfg(windows)]
    use winapi::um::ws2tcpip::socklen_t;

    /// The address of a socket.
    ///
    /// `SockAddr`s may be constructed directly to and from the standard library
    /// `SocketAddr`, `SocketAddrV4`, and `SocketAddrV6` types.
    pub struct SockAddr {
        storage: sockaddr_storage,
        len: socklen_t,
    }

    impl fmt::Debug for SockAddr {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            let mut builder = fmt.debug_struct("SockAddr");
            builder.field("family", &self.family());
            if let Some(addr) = self.as_inet() {
                builder.field("inet", &addr);
            } else if let Some(addr) = self.as_inet6() {
                builder.field("inet6", &addr);
            }
            builder.finish()
        }
    }

    impl SockAddr {
        /// Constructs a `SockAddr` from its raw components.
        pub unsafe fn from_raw_parts(addr: *const sockaddr, len: socklen_t) -> SockAddr {
            let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
            ptr::copy_nonoverlapping(
                addr as *const _ as *const u8,
                storage.as_mut_ptr() as *mut u8,
                len as usize,
            );

            SockAddr {
                // This is safe as we written the address to `storage` above.
                storage: storage.assume_init(),
                len,
            }
        }

        /// Constructs a `SockAddr` with the family `AF_UNIX` and the provided path.
        ///
        /// This function is only available on Unix when the `unix` feature is
        /// enabled.
        ///
        /// # Failure
        ///
        /// Returns an error if the path is longer than `SUN_LEN`.
        #[cfg(all(unix, feature = "unix"))]
        pub fn unix<P>(path: P) -> ::std::io::Result<SockAddr>
        where
            P: AsRef<::std::path::Path>,
        {
            use libc::{c_char, sockaddr_un, AF_UNIX};
            use std::cmp::Ordering;
            use std::io;
            use std::os::unix::ffi::OsStrExt;

            unsafe {
                let mut addr = mem::zeroed::<sockaddr_un>();
                addr.sun_family = AF_UNIX as sa_family_t;

                let bytes = path.as_ref().as_os_str().as_bytes();

                match (bytes.get(0), bytes.len().cmp(&addr.sun_path.len())) {
                    // Abstract paths don't need a null terminator
                    (Some(&0), Ordering::Greater) => {
                        return Err(io::Error::new(
                            io::ErrorKind::InvalidInput,
                            "path must be no longer than SUN_LEN",
                        ));
                    }
                    (Some(&0), _) => {}
                    (_, Ordering::Greater) | (_, Ordering::Equal) => {
                        return Err(io::Error::new(
                            io::ErrorKind::InvalidInput,
                            "path must be shorter than SUN_LEN",
                        ));
                    }
                    _ => {}
                }

                for (dst, src) in addr.sun_path.iter_mut().zip(bytes) {
                    *dst = *src as c_char;
                }
                // null byte for pathname is already there since we zeroed up front

                let base = &addr as *const _ as usize;
                let path = &addr.sun_path as *const _ as usize;
                let sun_path_offset = path - base;

                let mut len = sun_path_offset + bytes.len();
                match bytes.get(0) {
                    Some(&0) | None => {}
                    Some(_) => len += 1,
                }
                Ok(SockAddr::from_raw_parts(
                    &addr as *const _ as *const _,
                    len as socklen_t,
                ))
            }
        }

        /// Returns this address as a `SocketAddrV4` if it is in the `AF_INET`
        /// family.
        pub fn as_inet(&self) -> Option<SocketAddrV4> {
            match self.as_std() {
                Some(SocketAddr::V4(addr)) => Some(addr),
                _ => None,
            }
        }

        /// Returns this address as a `SocketAddrV6` if it is in the `AF_INET6`
        /// family.
        pub fn as_inet6(&self) -> Option<SocketAddrV6> {
            match self.as_std() {
                Some(SocketAddr::V6(addr)) => Some(addr),
                _ => None,
            }
        }

        /// Returns this address as a `SocketAddr` if it is in the `AF_INET`
        /// or `AF_INET6` family, otherwise returns `None`.
        pub fn as_std(&self) -> Option<SocketAddr> {
            if self.storage.ss_family == AF_INET as sa_family_t {
                // Safety: if the ss_family field is AF_INET then storage must be a sockaddr_in.
                let addr = unsafe { &*(&self.storage as *const _ as *const sockaddr_in) };

                #[cfg(unix)]
                let ip = Ipv4Addr::from(addr.sin_addr.s_addr.to_ne_bytes());
                #[cfg(windows)]
                let ip = {
                    let ip_bytes = unsafe { addr.sin_addr.S_un.S_un_b() };
                    Ipv4Addr::from([ip_bytes.s_b1, ip_bytes.s_b2, ip_bytes.s_b3, ip_bytes.s_b4])
                };
                let port = u16::from_be(addr.sin_port);
                Some(SocketAddr::V4(SocketAddrV4::new(ip, port)))
            } else if self.storage.ss_family == AF_INET6 as sa_family_t {
                // Safety: if the ss_family field is AF_INET6 then storage must be a sockaddr_in6.
                let addr = unsafe { &*(&self.storage as *const _ as *const sockaddr_in6) };

                #[cfg(unix)]
                let ip = Ipv6Addr::from(addr.sin6_addr.s6_addr);
                #[cfg(windows)]
                let ip = Ipv6Addr::from(*unsafe { addr.sin6_addr.u.Byte() });
                let port = u16::from_be(addr.sin6_port);
                Some(SocketAddr::V6(SocketAddrV6::new(
                    ip,
                    port,
                    addr.sin6_flowinfo,
                    #[cfg(unix)]
                    addr.sin6_scope_id,
                    #[cfg(windows)]
                    unsafe {
                        *addr.u.sin6_scope_id()
                    },
                )))
            } else {
                None
            }
        }

        /// Returns this address's family.
        pub fn family(&self) -> sa_family_t {
            self.storage.ss_family
        }

        /// Returns the size of this address in bytes.
        pub fn len(&self) -> socklen_t {
            self.len
        }

        /// Returns a raw pointer to the address.
        pub fn as_ptr(&self) -> *const sockaddr {
            &self.storage as *const _ as *const _
        }
    }

    impl From<SocketAddrV4> for SockAddr {
        fn from(addr: SocketAddrV4) -> SockAddr {
            #[cfg(unix)]
            let sin_addr = in_addr {
                s_addr: u32::from_ne_bytes(addr.ip().octets()),
            };
            #[cfg(windows)]
            let sin_addr = unsafe {
                let mut s_un = mem::zeroed::<in_addr_S_un>();
                *s_un.S_addr_mut() = u32::from_ne_bytes(addr.ip().octets());
                in_addr { S_un: s_un }
            };

            let sockaddr_in = sockaddr_in {
                sin_family: AF_INET as sa_family_t,
                sin_port: addr.port().to_be(),
                sin_addr,
                sin_zero: Default::default(),
                #[cfg(any(
                    target_os = "dragonfly",
                    target_os = "freebsd",
                    target_os = "haiku",
                    target_os = "ios",
                    target_os = "macos",
                    target_os = "netbsd",
                    target_os = "openbsd"
                ))]
                sin_len: 0,
            };
            let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
            // Safety: A `sockaddr_in` is memory compatible with a `sockaddr_storage`
            unsafe { (storage.as_mut_ptr() as *mut sockaddr_in).write(sockaddr_in) };
            SockAddr {
                storage: unsafe { storage.assume_init() },
                len: mem::size_of::<sockaddr_in>() as socklen_t,
            }
        }
    }

    impl From<SocketAddrV6> for SockAddr {
        fn from(addr: SocketAddrV6) -> SockAddr {
            #[cfg(unix)]
            let sin6_addr = in6_addr {
                s6_addr: addr.ip().octets(),
            };
            #[cfg(windows)]
            let sin6_addr = unsafe {
                let mut u = mem::zeroed::<in6_addr_u>();
                *u.Byte_mut() = addr.ip().octets();
                in6_addr { u }
            };
            #[cfg(windows)]
            let u = unsafe {
                let mut u = mem::zeroed::<SOCKADDR_IN6_LH_u>();
                *u.sin6_scope_id_mut() = addr.scope_id();
                u
            };

            let sockaddr_in6 = sockaddr_in6 {
                sin6_family: AF_INET6 as sa_family_t,
                sin6_port: addr.port().to_be(),
                sin6_addr,
                sin6_flowinfo: addr.flowinfo(),
                #[cfg(unix)]
                sin6_scope_id: addr.scope_id(),
                #[cfg(windows)]
                u,
                #[cfg(any(
                    target_os = "dragonfly",
                    target_os = "freebsd",
                    target_os = "haiku",
                    target_os = "ios",
                    target_os = "macos",
                    target_os = "netbsd",
                    target_os = "openbsd"
                ))]
                sin6_len: 0,
                #[cfg(any(target_os = "solaris", target_os = "illumos"))]
                __sin6_src_id: 0,
            };
            let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
            // Safety: A `sockaddr_in6` is memory compatible with a `sockaddr_storage`
            unsafe { (storage.as_mut_ptr() as *mut sockaddr_in6).write(sockaddr_in6) };
            SockAddr {
                storage: unsafe { storage.assume_init() },
                len: mem::size_of::<sockaddr_in6>() as socklen_t,
            }
        }
    }

    impl From<SocketAddr> for SockAddr {
        fn from(addr: SocketAddr) -> SockAddr {
            match addr {
                SocketAddr::V4(addr) => addr.into(),
                SocketAddr::V6(addr) => addr.into(),
            }
        }
    }

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

        #[test]
        fn inet() {
            let raw = "127.0.0.1:80".parse::<SocketAddrV4>().unwrap();
            let addr = SockAddr::from(raw);
            assert!(addr.as_inet6().is_none());
            let addr = addr.as_inet().unwrap();
            assert_eq!(raw, addr);
        }

        #[test]
        fn inet6() {
            let raw = "[2001:db8::ff00:42:8329]:80"
                .parse::<SocketAddrV6>()
                .unwrap();
            let addr = SockAddr::from(raw);
            assert!(addr.as_inet().is_none());
            let addr = addr.as_inet6().unwrap();
            assert_eq!(raw, addr);
        }
    }