Auto merge of #552 - Mic92:fstatat, r=posborne

add support for openat, fstatat, readlink, readlinkat

2 files changed, 74 insertions, 2 deletions

diff --git a/src/fcntl.rs b/src/fcntl.rs
index e224d3b1..a295de3a 100644
--- a/src/fcntl.rs
+++ b/src/fcntl.rs
@@ -1,7 +1,9 @@
-use {Errno, Result, NixPath};
-use libc::{self, c_int, c_uint};
+use {Error, Errno, Result, NixPath};
+use libc::{self, c_int, c_uint, c_char, size_t, ssize_t};
 use sys::stat::Mode;
 use std::os::unix::io::RawFd;
+use std::ffi::OsStr;
+use std::os::unix::ffi::OsStrExt;
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
 use sys::uio::IoVec;  // For vmsplice
@@ -18,6 +20,25 @@ mod ffi {
     pub const F_GET_SEALS: c_int = 1034;
 }
 
+#[cfg(not(any(target_os = "ios", target_os = "macos")))]
+libc_bitflags!{
+    pub flags AtFlags: c_int {
+        AT_SYMLINK_NOFOLLOW,
+        #[cfg(any(target_os = "linux", target_os = "android"))]
+        AT_NO_AUTOMOUNT,
+        #[cfg(any(target_os = "linux", target_os = "android"))]
+        AT_EMPTY_PATH
+    }
+}
+
+#[cfg(any(target_os = "ios", target_os = "macos"))]
+bitflags!(
+    pub flags AtFlags: c_int {
+        // hack because bitflags require one entry
+        const EMPTY = 0x0
+    }
+);
+
 pub fn open<P: ?Sized + NixPath>(path: &P, oflag: OFlag, mode: Mode) -> Result<RawFd> {
     let fd = try!(path.with_nix_path(|cstr| {
         unsafe { libc::open(cstr.as_ptr(), oflag.bits(), mode.bits() as c_uint) }
@@ -26,6 +47,44 @@ pub fn open<P: ?Sized + NixPath>(path: &P, oflag: OFlag, mode: Mode) -> Result<R
     Errno::result(fd)
 }
 
+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() as c_uint) }
+    }));
+    Errno::result(fd)
+}
+
+fn wrap_readlink_result<'a>(buffer: &'a mut[u8], res: ssize_t) 
+  -> Result<&'a OsStr> {
+    match Errno::result(res) {
+        Err(err) => Err(err),
+        Ok(len) => {
+            if (len as usize) >= buffer.len() {
+                Err(Error::Sys(Errno::ENAMETOOLONG))
+            } else {
+                Ok(OsStr::from_bytes(&buffer[..(len as usize)]))
+            }
+        }
+    }
+}
+
+pub fn readlink<'a, P: ?Sized + NixPath>(path: &P, buffer: &'a mut [u8]) -> Result<&'a OsStr> {
+    let res = try!(path.with_nix_path(|cstr| {
+        unsafe { libc::readlink(cstr.as_ptr(), buffer.as_mut_ptr() as *mut c_char, buffer.len() as size_t) }
+    }));
+
+    wrap_readlink_result(buffer, res)
+}
+
+
+pub fn readlinkat<'a, P: ?Sized + NixPath>(dirfd: RawFd, path: &P, buffer: &'a mut [u8]) -> Result<&'a OsStr> {
+    let res = try!(path.with_nix_path(|cstr| {
+        unsafe { libc::readlinkat(dirfd, cstr.as_ptr(), buffer.as_mut_ptr() as *mut c_char, buffer.len() as size_t) }
+    }));
+
+    wrap_readlink_result(buffer, res)
+}
+
 pub enum FcntlArg<'a> {
     F_DUPFD(RawFd),
     F_DUPFD_CLOEXEC(RawFd),
diff --git a/src/sys/stat.rs b/src/sys/stat.rs
index 1ff35923..054aedc1 100644
--- a/src/sys/stat.rs
+++ b/src/sys/stat.rs
@@ -2,6 +2,7 @@ pub use libc::dev_t;
 pub use libc::stat as FileStat;
 
 use {Errno, Result, NixPath};
+use fcntl::AtFlags;
 use libc::{self, mode_t};
 use std::mem;
 use std::os::unix::io::RawFd;
@@ -121,3 +122,15 @@ pub fn fstat(fd: RawFd) -> Result<FileStat> {
 
     Ok(dst)
 }
+
+pub fn fstatat<P: ?Sized + NixPath>(dirfd: RawFd, pathname: &P, f: AtFlags) -> Result<FileStat> {
+    let mut dst = unsafe { mem::uninitialized() };
+    let res = try!(pathname.with_nix_path(|cstr| {
+        unsafe { libc::fstatat(dirfd, cstr.as_ptr(), &mut dst as *mut FileStat, f.bits() as libc::c_int) }
+    }));
+
+    try!(Errno::result(res));
+
+    Ok(dst)
+}
+