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    use libc::{self, SI_LOAD_SHIFT};
    use std::{cmp, mem};
    use std::time::Duration;

    use Result;
    use errno::Errno;

    /// System info structure returned by `sysinfo`.
    #[derive(Copy, Clone)]
    #[allow(missing_debug_implementations)] // libc::sysinfo doesn't impl Debug
    pub struct SysInfo(libc::sysinfo);

    impl SysInfo {
        /// Returns the load average tuple.
        ///
        /// The returned values represent the load average over time intervals of
        /// 1, 5, and 15 minutes, respectively.
        pub fn load_average(&self) -> (f64, f64, f64) {
            (
                self.0.loads[0] as f64 / (1 << SI_LOAD_SHIFT) as f64,
                self.0.loads[1] as f64 / (1 << SI_LOAD_SHIFT) as f64,
                self.0.loads[2] as f64 / (1 << SI_LOAD_SHIFT) as f64,
            )
        }

        /// Returns the time since system boot.
        pub fn uptime(&self) -> Duration {
            // Truncate negative values to 0
            Duration::from_secs(cmp::max(self.0.uptime, 0) as u64)
        }

        /// Current number of processes.
        pub fn process_count(&self) -> u16 {
            self.0.procs
        }

        /// Returns the amount of swap memory in Bytes.
        pub fn swap_total(&self) -> u64 {
            self.scale_mem(self.0.totalswap)
        }

        /// Returns the amount of unused swap memory in Bytes.
        pub fn swap_free(&self) -> u64 {
            self.scale_mem(self.0.freeswap)
        }

        /// Returns the total amount of installed RAM in Bytes.
        pub fn ram_total(&self) -> u64 {
            self.scale_mem(self.0.totalram)
        }

        /// Returns the amount of completely unused RAM in Bytes.
        ///
        /// "Unused" in this context means that the RAM in neither actively used by
        /// programs, nor by the operating system as disk cache or buffer. It is
        /// "wasted" RAM since it currently serves no purpose.
        pub fn ram_unused(&self) -> u64 {
            self.scale_mem(self.0.freeram)
        }

        fn scale_mem(&self, units: libc::c_ulong) -> u64 {
            units as u64 * self.0.mem_unit as u64
        }
    }

    /// Returns system information.
    ///
    /// [See `sysinfo(2)`](http://man7.org/linux/man-pages/man2/sysinfo.2.html).
    pub fn sysinfo() -> Result<SysInfo> {
        let mut info: libc::sysinfo = unsafe { mem::uninitialized() };
        let res = unsafe { libc::sysinfo(&mut info) };
        Errno::result(res).map(|_| SysInfo(info))
    }

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