1 files changed, 126 insertions, 0 deletions
diff --git a/third_party/rust/nix/src/features.rs b/third_party/rust/nix/src/features.rs
new file mode 100644
index 0000000000..39d17604e1
--- /dev/null
+++ b/third_party/rust/nix/src/features.rs
@@ -0,0 +1,126 @@
+//! Feature tests for OS functionality
+pub use self::os::*;
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+mod os {
+    use crate::sys::utsname::uname;
+    use crate::Result;
+    use std::os::unix::ffi::OsStrExt;
+
+    // Features:
+    // * atomic cloexec on socket: 2.6.27
+    // * pipe2: 2.6.27
+    // * accept4: 2.6.28
+
+    static VERS_UNKNOWN: usize = 1;
+    static VERS_2_6_18: usize = 2;
+    static VERS_2_6_27: usize = 3;
+    static VERS_2_6_28: usize = 4;
+    static VERS_3: usize = 5;
+
+    #[inline]
+    fn digit(dst: &mut usize, b: u8) {
+        *dst *= 10;
+        *dst += (b - b'0') as usize;
+    }
+
+    fn parse_kernel_version() -> Result<usize> {
+        let u = uname()?;
+
+        let mut curr: usize = 0;
+        let mut major: usize = 0;
+        let mut minor: usize = 0;
+        let mut patch: usize = 0;
+
+        for &b in u.release().as_bytes() {
+            if curr >= 3 {
+                break;
+            }
+
+            match b {
+                b'.' | b'-' => {
+                    curr += 1;
+                }
+                b'0'..=b'9' => match curr {
+                    0 => digit(&mut major, b),
+                    1 => digit(&mut minor, b),
+                    _ => digit(&mut patch, b),
+                },
+                _ => break,
+            }
+        }
+
+        Ok(if major >= 3 {
+            VERS_3
+        } else if major >= 2 {
+            if minor >= 7 {
+                VERS_UNKNOWN
+            } else if minor >= 6 {
+                if patch >= 28 {
+                    VERS_2_6_28
+                } else if patch >= 27 {
+                    VERS_2_6_27
+                } else {
+                    VERS_2_6_18
+                }
+            } else {
+                VERS_UNKNOWN
+            }
+        } else {
+            VERS_UNKNOWN
+        })
+    }
+
+    fn kernel_version() -> Result<usize> {
+        static mut KERNEL_VERS: usize = 0;
+
+        unsafe {
+            if KERNEL_VERS == 0 {
+                KERNEL_VERS = parse_kernel_version()?;
+            }
+
+            Ok(KERNEL_VERS)
+        }
+    }
+
+    /// Check if the OS supports atomic close-on-exec for sockets
+    pub fn socket_atomic_cloexec() -> bool {
+        kernel_version()
+            .map(|version| version >= VERS_2_6_27)
+            .unwrap_or(false)
+    }
+
+    #[test]
+    pub fn test_parsing_kernel_version() {
+        assert!(kernel_version().unwrap() > 0);
+    }
+}
+
+#[cfg(any(
+        target_os = "dragonfly",    // Since ???
+        target_os = "freebsd",      // Since 10.0
+        target_os = "illumos",      // Since ???
+        target_os = "netbsd",       // Since 6.0
+        target_os = "openbsd",      // Since 5.7
+        target_os = "redox",        // Since 1-july-2020
+))]
+mod os {
+    /// Check if the OS supports atomic close-on-exec for sockets
+    pub const fn socket_atomic_cloexec() -> bool {
+        true
+    }
+}
+
+#[cfg(any(
+    target_os = "macos",
+    target_os = "ios",
+    target_os = "fuchsia",
+    target_os = "haiku",
+    target_os = "solaris"
+))]
+mod os {
+    /// Check if the OS supports atomic close-on-exec for sockets
+    pub const fn socket_atomic_cloexec() -> bool {
+        false
+    }
+}