From f2df347e56bac25adb680084e85f21d8d929dea7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Thalheim?= <joerg@thalheim.io>
Date: Wed, 8 Mar 2017 00:11:36 +0100
Subject: [PATCH] add support for `openat`

---
 CHANGELOG.md       |  1 +
 src/fcntl.rs       |  9 +++++++++
 test/test_fcntl.rs | 28 ++++++++++++++++++++++++++--
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9bcef57a70..982b3b7fe9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased]
 
 <!--### Added-->
+- Added `openat` in `::nix::fcntl`
 
 ### Changed
 - Marked `sys::mman::{ mmap, munmap, madvise, munlock, msync }` as unsafe.
diff --git a/src/fcntl.rs b/src/fcntl.rs
index e224d3b107..c9a3486fa4 100644
--- a/src/fcntl.rs
+++ b/src/fcntl.rs
@@ -26,6 +26,15 @@ pub fn open<P: ?Sized + NixPath>(path: &P, oflag: OFlag, mode: Mode) -> Result<R
     Errno::result(fd)
 }
 
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn openat<P: ?Sized + NixPath>(dirfd: RawFd, path: &P, oflag: OFlag, mode: Mode) -> Result<RawFd> {
+    let fd = try!(path.with_nix_path(|cstr| {
+        unsafe { libc::openat(dirfd, cstr.as_ptr(), oflag.bits(), mode.bits()) }
+    }));
+
+    Errno::result(fd)
+}
+
 pub enum FcntlArg<'a> {
     F_DUPFD(RawFd),
     F_DUPFD_CLOEXEC(RawFd),
diff --git a/test/test_fcntl.rs b/test/test_fcntl.rs
index ca2e89a338..a90d4b0048 100644
--- a/test/test_fcntl.rs
+++ b/test/test_fcntl.rs
@@ -5,11 +5,35 @@ mod linux_android {
 
     use libc::loff_t;
 
-    use nix::fcntl::{SpliceFFlags, splice, tee, vmsplice};
+    use nix::fcntl::{SpliceFFlags, splice, tee, vmsplice, openat, open, O_PATH, O_RDONLY};
+    use nix::sys::stat::Mode;
     use nix::sys::uio::IoVec;
     use nix::unistd::{close, pipe, read, write};
 
-    use tempfile::tempfile;
+    use tempfile::{tempfile, NamedTempFile};
+
+    #[test]
+    fn test_openat() {
+        const CONTENTS: &'static [u8] = b"abcd";
+        let mut tmp = NamedTempFile::new().unwrap();
+        tmp.write(CONTENTS).unwrap();
+
+        let dirfd = open(tmp.path().parent().unwrap(),
+                         O_PATH,
+                         Mode::empty()).unwrap();
+        let fd = openat(dirfd,
+                        tmp.path().file_name().unwrap(),
+                        O_RDONLY,
+                        Mode::empty()).unwrap();
+
+        let mut buf = [0u8; 1024];
+        assert_eq!(4, read(fd, &mut buf).unwrap());
+        assert_eq!(CONTENTS, &buf[0..4]);
+
+        close(fd).unwrap();
+        close(dirfd).unwrap();
+    }
+
 
     #[test]
     fn test_splice() {