Auto merge of #377 - aoprisan:master, r=posborne

Added lseek and seek64

I have added lseek and seek64 to unistd, the last one targeting Linux/Android only. I wasn't sure where to place the Whence enum, or if it's a nice of doing, I am quite fresh to Rust.

src/unistd.rs

@@ -214,6 +214,40 @@ pub fn write(fd: RawFd, buf: &[u8]) -> Result<usize> {
     Errno::result(res).map(|r| r as usize)
 }
 
+pub enum Whence {
+    SeekSet,
+    SeekCur,
+    SeekEnd,
+    SeekData,
+    SeekHole
+}
+
+impl Whence {
+    fn to_libc_type(&self) -> c_int {
+        match self {
+            &Whence::SeekSet => libc::SEEK_SET,
+            &Whence::SeekCur => libc::SEEK_CUR,
+            &Whence::SeekEnd => libc::SEEK_END,
+            &Whence::SeekData => 3,
+            &Whence::SeekHole => 4
+        }
+    }
+
+}
+
+pub fn lseek(fd: RawFd, offset: libc::off_t, whence: Whence) -> Result<libc::off_t> {
+    let res = unsafe { libc::lseek(fd, offset, whence.to_libc_type()) };
+
+    Errno::result(res).map(|r| r as libc::off_t)
+}
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn lseek64(fd: RawFd, offset: libc::off64_t, whence: Whence) -> Result<libc::off64_t> {
+    let res = unsafe { libc::lseek64(fd, offset, whence.to_libc_type()) };
+
+    Errno::result(res).map(|r| r as libc::off64_t)
+}
+
 pub fn pipe() -> Result<(RawFd, RawFd)> {
     unsafe {
         let mut fds: [c_int; 2] = mem::uninitialized();
@@ -292,7 +326,6 @@ pub fn unlink<P: ?Sized + NixPath>(path: &P) -> Result<()> {
             libc::unlink(cstr.as_ptr())
         }
     }));
-
     Errno::result(res).map(drop)
 }
 

test/test_unistd.rs

@@ -3,6 +3,13 @@ use nix::unistd::ForkResult::*;
 use nix::sys::wait::*;
 use std::ffi::CString;
 
+use std::io::{Write, Read};
+use tempfile::tempfile;
+use libc::off_t;
+use std::os::unix::prelude::*;
+
+
+
 #[test]
 fn test_fork_and_waitpid() {
     let pid = fork();
@@ -112,6 +119,38 @@ macro_rules! execve_test_factory(
     )
 );
 
+#[test]
+fn test_lseek() {
+    const CONTENTS: &'static [u8] = b"abcdef123456";
+    let mut tmp = tempfile().unwrap();
+    tmp.write(CONTENTS).unwrap();
+
+    let offset: off_t = 5;
+    lseek(tmp.as_raw_fd(), offset, Whence::SeekSet).unwrap();
+
+    let mut buf = String::new();
+     tmp.read_to_string(&mut buf).unwrap();
+     assert_eq!(b"f123456", buf.as_bytes());
+
+     close(tmp.as_raw_fd()).unwrap();
+}
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+#[test]
+fn test_lseek64() {
+    const CONTENTS: &'static [u8] = b"abcdef123456";
+    let mut tmp = tempfile().unwrap();
+    tmp.write(CONTENTS).unwrap();
+
+    lseek64(tmp.as_raw_fd(), 5, Whence::SeekSet).unwrap();
+
+    let mut buf = String::new();
+    tmp.read_to_string(&mut buf).unwrap();
+    assert_eq!(b"f123456", buf.as_bytes());
+
+    close(tmp.as_raw_fd()).unwrap();
+}
+
 execve_test_factory!(test_execve, execve, b"/bin/sh", b"/system/bin/sh");
 
 #[cfg(any(target_os = "linux", target_os = "android"))]