message: Don't reset read/write every time we check if we can read or write
diff: @@ -64,6 +64,9 @@ impl FILE {
  }
  */
  + if let Some(_) = self.read {
  + return true;
  + }
  if let Some(_) = self.write {
  self.write(&[]);
  }
  @@ -93,6 +96,9 @@ impl FILE {
  return false;
  }
  // Buffer repositioning
  + if let Some(_) = self.write {
  + return true;
  + }
  self.read = None;
  self.write = Some((self.unget, self.unget, self.buf.len() - 1));
  return true;
  