fcntl: Adding F_TRANSFEREXTENTS fcntl constant for macOs.

Author: devnexen

src/fcntl.rs

@@ -819,6 +819,12 @@ pub enum FcntlArg<'a> {
     /// is used as both IN/OUT as both its l2p_devoffset and
     /// l2p_contigbytes can be used for more specific queries.
     F_LOG2PHYS_EXT(&'a mut libc::log2phys),
+    /// Transfer any extra space in the file past the logical EOF
+    /// (as previously allocated via F_PREALLOCATE) to another file.
+    /// The other file is specified via a file descriptor as the lone extra argument.
+    /// Both descriptors must reference regular files in the same volume.
+    #[cfg(apple_targets)]
+    F_TRANSFEREXTENTS(RawFd),
     // TODO: Rest of flags
 }
 
@@ -952,6 +958,12 @@ pub fn fcntl<Fd: std::os::fd::AsFd>(fd: Fd, arg: FcntlArg) -> Result<c_int> {
             F_PREALLOCATE(st) => {
                 libc::fcntl(fd, libc::F_PREALLOCATE, st)
             },
+            #[cfg(apple_targets)]
+            F_TRANSFEREXTENTS(rawfd) => {
+                // FIXME: ongoing (PR)[https://github.com/rust-lang/libc/pull/3925/files]
+                const F_TRANSFEREXTENTS: c_int = 110;
+                libc::fcntl(fd, F_TRANSFEREXTENTS, rawfd)
+            },
         }
     };
 

test/test_fcntl.rs

@@ -792,3 +792,16 @@ fn test_f_log2phys() {
     assert_ne!(res, -1);
     assert_ne!({ info.l2p_devoffset }, 3);
 }
+
+#[cfg(apple_targets)]
+#[test]
+fn test_f_transferextents() {
+    use nix::fcntl::*;
+    use std::os::fd::AsRawFd;
+
+    let tmp1 = NamedTempFile::new().unwrap();
+    let tmp2 = NamedTempFile::new().unwrap();
+    let res = fcntl(&tmp1, FcntlArg::F_TRANSFEREXTENTS(tmp2.as_raw_fd()))
+        .expect("transferextents failed");
+    assert_ne!(res, -1);
+}