feat: add get_{ref, mut} to arrow_ipc::File{Reader, Writer}

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

arrow-ipc/src/reader.rs

@@ -1038,6 +1038,20 @@ impl<R: Read + Seek> FileReader<R> {
             ))),
         }
     }
+
+    /// Gets a reference to the underlying reader.
+    ///
+    /// It is inadvisable to directly read from the underlying reader.
+    pub fn get_ref(&self) -> &R {
+        self.reader.get_ref()
+    }
+
+    /// Gets a mutable reference to the underlying reader.
+    ///
+    /// It is inadvisable to directly read from the underlying reader.
+    pub fn get_mut(&self) -> &mut R {
+        self.reader.get_mut()
+    }
 }
 
 impl<R: Read + Seek> Iterator for FileReader<R> {

arrow-ipc/src/writer.rs

@@ -832,6 +832,18 @@ impl<W: Write> FileWriter<W> {
         Ok(())
     }
 
+    /// Gets a reference to the underlying writer.
+    pub fn get_ref(&self) -> &W {
+        self.writer.get_ref()
+    }
+
+    /// Gets a mutable reference to the underlying writer.
+    ///
+    /// It is inadvisable to directly write to the underlying writer.
+    pub fn get_mut(&self) -> &mut W {
+        self.writer.get_mut()
+    }
+
     /// Unwraps the BufWriter housed in FileWriter.writer, returning the underlying
     /// writer
     ///