Move DropGuard into wait_until_rng_ready

Author: newpavlov

src/use_file.rs

@@ -134,6 +134,14 @@ fn get_rng_fd() -> Result<libc::c_int, Error> {
 // libsodium uses `libc::poll` similarly to this.
 #[cfg(any(target_os = "android", target_os = "linux"))]
 fn wait_until_rng_ready() -> Result<(), Error> {
+    struct DropGuard<F: FnMut()>(F);
+
+    impl<F: FnMut()> Drop for DropGuard<F> {
+        fn drop(&mut self) {
+            self.0()
+        }
+    }
+
     let fd = open_readonly(b"/dev/random\0")?;
     let mut pfd = libc::pollfd {
         fd,
@@ -158,11 +166,3 @@ fn wait_until_rng_ready() -> Result<(), Error> {
         }
     }
 }
-
-struct DropGuard<F: FnMut()>(F);
-
-impl<F: FnMut()> Drop for DropGuard<F> {
-    fn drop(&mut self) {
-        self.0()
-    }
-}