Add test for AsyncFd::to_file_descriptor

tests/async_fd/fixed.rs

@@ -2,7 +2,7 @@
 
 use a10::fs::OpenOptions;
 
-use crate::util::{test_queue, Waker, LOREM_IPSUM_5};
+use crate::util::{require_kernel, test_queue, Waker, LOREM_IPSUM_5};
 
 #[test]
 fn to_direct_descriptor() {
@@ -38,3 +38,54 @@ fn to_direct_descriptor() {
         "read content is different"
     );
 }
+
+#[test]
+fn to_file_descriptor() {
+    require_kernel!(6, 8);
+
+    let sq = test_queue();
+    let waker = Waker::new();
+
+    // TODO: use open with direct descriptor?
+    let open_file = OpenOptions::new().open(sq, LOREM_IPSUM_5.path.into());
+    let regular_fd = waker.block_on(open_file).unwrap();
+    let direct_fd = waker.block_on(regular_fd.to_direct_descriptor()).unwrap();
+    let regular_fd2 = waker.block_on(direct_fd.to_file_descriptor()).unwrap();
+
+    let mut buf = Vec::with_capacity(LOREM_IPSUM_5.content.len() + 1);
+
+    // Regular fd.
+    let read = regular_fd.read_at(buf, 0);
+    buf = waker.block_on(read).unwrap();
+    if buf.is_empty() {
+        panic!("read zero bytes");
+    }
+    assert!(
+        buf == &LOREM_IPSUM_5.content[..buf.len()],
+        "read content is different"
+    );
+
+    // Direct descriptor.
+    buf.clear();
+    let read = direct_fd.read_at(buf, 0);
+    buf = waker.block_on(read).unwrap();
+    if buf.is_empty() {
+        panic!("read zero bytes");
+    }
+    assert!(
+        buf == &LOREM_IPSUM_5.content[..buf.len()],
+        "read content is different"
+    );
+
+    // Regular fd (created from the direct descriptor).
+    buf.clear();
+    let read = regular_fd2.read_at(buf, 0);
+    buf = waker.block_on(read).unwrap();
+    if buf.is_empty() {
+        panic!("read zero bytes");
+    }
+    assert!(
+        buf == &LOREM_IPSUM_5.content[..buf.len()],
+        "read content is different"
+    );
+}