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    // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    use prelude::v1::*;

    use ffi::CStr;
    use io;
    use libc::{self, c_int, size_t};
    use net::{SocketAddr, Shutdown};
    use str;
    use sync::atomic::{AtomicBool, Ordering};
    use sys::fd::FileDesc;
    use sys_common::{AsInner, FromInner, IntoInner};
    use sys_common::net::{getsockopt, setsockopt};
    use time::Duration;

    pub use sys::{cvt, cvt_r};
    pub use libc as netc;

    pub type wrlen_t = size_t;

    pub struct Socket(FileDesc);

    pub fn init() {}

    pub fn cvt_gai(err: c_int) -> io::Result<()> {
        if err == 0 { return Ok(()) }

        let detail = unsafe {
            str::from_utf8(CStr::from_ptr(libc::gai_strerror(err)).to_bytes()).unwrap()
                .to_owned()
        };
        Err(io::Error::new(io::ErrorKind::Other,
                           &format!("failed to lookup address information: {}",
                                    detail)[..]))
    }

    impl Socket {
        pub fn new(addr: &SocketAddr, ty: c_int) -> io::Result<Socket> {
            let fam = match *addr {
                SocketAddr::V4(..) => libc::AF_INET,
                SocketAddr::V6(..) => libc::AF_INET6,
            };
            unsafe {
                let fd = try!(cvt(libc::socket(fam, ty, 0)));
                let fd = FileDesc::new(fd);
                fd.set_cloexec();
                Ok(Socket(fd))
            }
        }

        pub fn accept(&self, storage: *mut libc::sockaddr,
                      len: *mut libc::socklen_t) -> io::Result<Socket> {
            let fd = try!(cvt_r(|| unsafe {
                libc::accept(self.0.raw(), storage, len)
            }));
            let fd = FileDesc::new(fd);
            fd.set_cloexec();
            Ok(Socket(fd))
        }

        pub fn duplicate(&self) -> io::Result<Socket> {
            // We want to atomically duplicate this file descriptor and set the
            // CLOEXEC flag, and currently that's done via F_DUPFD_CLOEXEC. This
            // flag, however, isn't supported on older Linux kernels (earlier than
            // 2.6.24).
            //
            // To detect this and ensure that CLOEXEC is still set, we
            // follow a strategy similar to musl [1] where if passing
            // F_DUPFD_CLOEXEC causes `fcntl` to return EINVAL it means it's not
            // supported (the third parameter, 0, is always valid), so we stop
            // trying that. We also *still* call the `set_cloexec` method as
            // apparently some kernel at some point stopped setting CLOEXEC even
            // though it reported doing so on F_DUPFD_CLOEXEC.
            //
            // Also note that Android doesn't have F_DUPFD_CLOEXEC, but get it to
            // resolve so we at least compile this.
            //
            // [1]: http://comments.gmane.org/gmane.linux.lib.musl.general/2963
            #[cfg(target_os = "android")]
            use libc::F_DUPFD as F_DUPFD_CLOEXEC;
            #[cfg(not(target_os = "android"))]
            use libc::F_DUPFD_CLOEXEC;

            let make_socket = |fd| {
                let fd = FileDesc::new(fd);
                fd.set_cloexec();
                Socket(fd)
            };
            static TRY_CLOEXEC: AtomicBool = AtomicBool::new(true);
            let fd = self.0.raw();
            if !cfg!(target_os = "android") && TRY_CLOEXEC.load(Ordering::Relaxed) {
                match cvt(unsafe { libc::fcntl(fd, F_DUPFD_CLOEXEC, 0) }) {
                    Err(ref e) if e.raw_os_error() == Some(libc::EINVAL) => {
                        TRY_CLOEXEC.store(false, Ordering::Relaxed);
                    }
                    res => return res.map(make_socket),
                }
            }
            cvt(unsafe { libc::fcntl(fd, libc::F_DUPFD, 0) }).map(make_socket)
        }

        pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
            self.0.read(buf)
        }

        pub fn set_timeout(&self, dur: Option<Duration>, kind: libc::c_int) -> io::Result<()> {
            let timeout = match dur {
                Some(dur) => {
                    if dur.as_secs() == 0 && dur.subsec_nanos() == 0 {
                        return Err(io::Error::new(io::ErrorKind::InvalidInput,
                                                  "cannot set a 0 duration timeout"));
                    }

                    let secs = if dur.as_secs() > libc::time_t::max_value() as u64 {
                        libc::time_t::max_value()
                    } else {
                        dur.as_secs() as libc::time_t
                    };
                    let mut timeout = libc::timeval {
                        tv_sec: secs,
                        tv_usec: (dur.subsec_nanos() / 1000) as libc::suseconds_t,
                    };
                    if timeout.tv_sec == 0 && timeout.tv_usec == 0 {
                        timeout.tv_usec = 1;
                    }
                    timeout
                }
                None => {
                    libc::timeval {
                        tv_sec: 0,
                        tv_usec: 0,
                    }
                }
            };
            setsockopt(self, libc::SOL_SOCKET, kind, timeout)
        }

        pub fn timeout(&self, kind: libc::c_int) -> io::Result<Option<Duration>> {
            let raw: libc::timeval = try!(getsockopt(self, libc::SOL_SOCKET, kind));
            if raw.tv_sec == 0 && raw.tv_usec == 0 {
                Ok(None)
            } else {
                let sec = raw.tv_sec as u64;
                let nsec = (raw.tv_usec as u32) * 1000;
                Ok(Some(Duration::new(sec, nsec)))
            }
        }

        pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
            let how = match how {
                Shutdown::Write => libc::SHUT_WR,
                Shutdown::Read => libc::SHUT_RD,
                Shutdown::Both => libc::SHUT_RDWR,
            };
            try!(cvt(unsafe { libc::shutdown(self.0.raw(), how) }));
            Ok(())
        }
    }

    impl AsInner<c_int> for Socket {
        fn as_inner(&self) -> &c_int { self.0.as_inner() }
    }

    impl FromInner<c_int> for Socket {
        fn from_inner(fd: c_int) -> Socket { Socket(FileDesc::new(fd)) }
    }

    impl IntoInner<c_int> for Socket {
        fn into_inner(self) -> c_int { self.0.into_raw() }
    }

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