*: implement ExactSizeIterator where possible

src/codec/packet/mod.rs

@@ -191,4 +191,12 @@ impl<'a> Iterator for SideDataIter<'a> {
 			}
 		}
 	}
+
+	fn size_hint(&self) -> (usize, Option<usize>) {
+		unsafe {
+			((*self.ptr).side_data_elems as usize, Some((*self.ptr).side_data_elems as usize))
+		}
+	}
 }
+
+impl<'a> ExactSizeIterator for SideDataIter<'a> { }

src/codec/subtitle/mod.rs

@@ -118,8 +118,16 @@ impl<'a> Iterator for RectIter<'a> {
 			}
 		}
 	}
+
+	fn size_hint(&self) -> (usize, Option<usize>) {
+		unsafe {
+			((*self.ptr).num_rects as usize, Some((*self.ptr).num_rects as usize))
+		}
+	}
 }
 
+impl<'a> ExactSizeIterator for RectIter<'a> { }
+
 pub enum Rect<'a> {
 	None,
 	Bitmap(Bitmap<'a>),