Add a sysinfo wrapper

CHANGELOG.md

@@ -6,6 +6,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased]
 
 ### Added
+- Added a `sysinfo` wrapper.
+  ([#922](https://github.com/nix-rust/nix/pull/922))
 
 ### Changed
 

src/sys/mod.rs

@@ -70,6 +70,9 @@ pub mod statfs;
 
 pub mod statvfs;
 
+#[cfg(any(target_os = "android", target_os = "linux"))]
+pub mod sysinfo;
+
 pub mod termios;
 
 pub mod time;

src/sys/sysinfo.rs

@@ -0,0 +1,73 @@
+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))
+}

test/sys/mod.rs

@@ -16,6 +16,8 @@ mod test_signalfd;
 mod test_socket;
 mod test_sockopt;
 mod test_select;
+#[cfg(any(target_os = "android", target_os = "linux"))]
+mod test_sysinfo;
 mod test_termios;
 mod test_ioctl;
 mod test_wait;

test/sys/test_sysinfo.rs

@@ -0,0 +1,18 @@
+use nix::sys::sysinfo::*;
+
+#[test]
+fn sysinfo_works() {
+    let info = sysinfo().unwrap();
+
+    let (l1, l5, l15) = info.load_average();
+    assert!(l1 >= 0.0);
+    assert!(l5 >= 0.0);
+    assert!(l15 >= 0.0);
+
+    info.uptime();  // just test Duration construction
+
+    assert!(info.swap_free() <= info.swap_total(),
+            "more swap available than installed (free: {}, total: {})",
+            info.swap_free(),
+            info.swap_total());
+}