fcntl: adding macOs F_RDADVISE flag

changelog/2480.added.md

@@ -0,0 +1 @@
+Add fcntl constant `F_RDADVISE` for Apple target

src/fcntl.rs

@@ -2,6 +2,8 @@
 use crate::errno::Errno;
 #[cfg(all(target_os = "freebsd", target_arch = "x86_64"))]
 use core::slice;
+#[cfg(apple_targets)]
+use libc::off_t;
 use libc::{c_int, c_uint, size_t, ssize_t};
 #[cfg(any(
     target_os = "netbsd",
@@ -797,6 +799,9 @@ pub enum FcntlArg<'a> {
     /// Return the full path without firmlinks of the fd.
     #[cfg(apple_targets)]
     F_GETPATH_NOFIRMLINK(&'a mut PathBuf),
+    /// Issue an advisory read async with no copy to user
+    #[cfg(apple_targets)]
+    F_RDADVISE(off_t, c_int),
     // TODO: Rest of flags
 }
 
@@ -905,6 +910,14 @@ pub fn fcntl<Fd: std::os::fd::AsFd>(fd: Fd, arg: FcntlArg) -> Result<c_int> {
                 *path = PathBuf::from(OsString::from(optr.to_str().unwrap()));
                 return Ok(ok_res)
             },
+            #[cfg(apple_targets)]
+            F_RDADVISE(offset, count) => {
+                let rad = libc::radvisory {
+                   ra_offset: offset,
+                   ra_count: count,
+                };
+                libc::fcntl(fd, libc::F_RDADVISE, &rad)
+            }
         }
     };