Add support for preadv and pwritev to sys/uio on Linux.

2 files changed, 101 insertions, 0 deletions

diff --git a/src/sys/uio.rs b/src/sys/uio.rs
index 43f0a23a..605ced4c 100644
--- a/src/sys/uio.rs
+++ b/src/sys/uio.rs
@@ -21,6 +21,18 @@ mod ffi {
         // doc: http://man7.org/linux/man-pages/man2/readv.2.html
         pub fn readv(fd: RawFd, iov: *const IoVec<&mut [u8]>, iovcnt: c_int) -> ssize_t;
 
+        // vectorized write at a specified offset
+        // doc: http://man7.org/linux/man-pages/man2/pwritev.2.html
+        #[cfg(any(target_os = "linux", target_os = "android"))]
+        pub fn pwritev(fd: RawFd, iov: *const IoVec<&[u8]>, iovcnt: c_int,
+                       offset: off_t) -> ssize_t;
+
+        // vectorized read at a specified offset
+        // doc: http://man7.org/linux/man-pages/man2/preadv.2.html
+        #[cfg(any(target_os = "linux", target_os = "android"))]
+        pub fn preadv(fd: RawFd, iov: *const IoVec<&mut [u8]>, iovcnt: c_int,
+                      offset: off_t) -> ssize_t;
+
         // write to a file at a specified offset
         // doc: http://man7.org/linux/man-pages/man2/pwrite.2.html
         pub fn pwrite(fd: RawFd, buf: *const c_void, nbyte: size_t,
@@ -52,6 +64,32 @@ pub fn readv(fd: RawFd, iov: &mut [IoVec<&mut [u8]>]) -> Result<usize> {
     return Ok(res as usize)
 }
 
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn pwritev(fd: RawFd, iov: &[IoVec<&[u8]>],
+               offset: off_t) -> Result<usize> {
+    let res = unsafe {
+        ffi::pwritev(fd, iov.as_ptr(), iov.len() as c_int, offset)
+    };
+    if res < 0 {
+        Err(Error::Sys(Errno::last()))
+    } else {
+        Ok(res as usize)
+    }
+}
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn preadv(fd: RawFd, iov: &mut [IoVec<&mut [u8]>],
+              offset: off_t) -> Result<usize> {
+    let res = unsafe {
+        ffi::preadv(fd, iov.as_ptr(), iov.len() as c_int, offset)
+    };
+    if res < 0 {
+        Err(Error::Sys(Errno::last()))
+    } else {
+        Ok(res as usize)
+    }
+}
+
 pub fn pwrite(fd: RawFd, buf: &[u8], offset: off_t) -> Result<usize> {
     let res = unsafe {
         ffi::pwrite(fd, buf.as_ptr() as *const c_void, buf.len() as size_t,
diff --git a/test/sys/test_uio.rs b/test/sys/test_uio.rs
index d3d6d413..b12f1bb6 100644
--- a/test/sys/test_uio.rs
+++ b/test/sys/test_uio.rs
@@ -128,3 +128,66 @@ fn test_pread() {
 
     remove_file(path).unwrap();
 }
+
+#[test]
+#[cfg(any(target_os = "linux", target_os = "android"))]
+fn test_pwritev() {
+    use std::io::Read;
+
+    let to_write: Vec<u8> = (0..128).collect();
+    let expected: Vec<u8> = [vec![0;100], to_write.clone()].concat();
+
+    let iovecs = [
+        IoVec::from_slice(&to_write[0..17]),
+        IoVec::from_slice(&to_write[17..64]),
+        IoVec::from_slice(&to_write[64..128]),
+    ];
+
+    // pwritev them into a temporary file
+    let path = "pwritev_test_file";
+    let mut file = OpenOptions::new().write(true).read(true).create(true)
+                                    .truncate(true).open(path).unwrap();
+
+    let written = pwritev(file.as_raw_fd(), &iovecs, 100).ok().unwrap();
+    assert_eq!(written, to_write.len());
+
+    // Read the data back and make sure it matches
+    let mut contents = Vec::new();
+    file.read_to_end(&mut contents).unwrap();
+    assert_eq!(contents, expected);
+
+    remove_file(path).unwrap();
+}
+
+#[test]
+#[cfg(any(target_os = "linux", target_os = "android"))]
+fn test_preadv() {
+    use std::io::Write;
+
+    let to_write: Vec<u8> = (0..200).collect();
+    let expected: Vec<u8> = (100..200).collect();
+
+    let path = "preadv_test_file";
+
+    let mut file = OpenOptions::new().read(true).write(true).create(true)
+                                    .truncate(true).open(path).unwrap();
+    file.write_all(&to_write).unwrap();
+
+    let mut buffers: Vec<Vec<u8>> = vec![
+        vec![0; 24],
+        vec![0; 1],
+        vec![0; 75],
+    ];
+
+    {
+        // Borrow the buffers into IoVecs and preadv into them
+        let mut iovecs: Vec<_> = buffers.iter_mut().map(
+            |buf| IoVec::from_mut_slice(&mut buf[..])).collect();
+        assert_eq!(Ok(100), preadv(file.as_raw_fd(), &mut iovecs, 100));
+    }
+
+    let all = buffers.concat();
+    assert_eq!(all, expected);
+
+    remove_file(path).unwrap();
+}