format/stream: avoid unsoundness splitting Stream into StreamMut

src/format/stream/stream_mut.rs

@@ -0,0 +1,41 @@
+use std::ops::Deref;
+
+use ffi::*;
+use ::Rational;
+use super::Stream;
+
+#[derive(Eq, PartialEq)]
+pub struct StreamMut<'a> {
+	ptr: *mut AVStream,
+	imm: Stream<'a>,
+}
+
+impl<'a> StreamMut<'a> {
+	pub unsafe fn wrap(ptr: *mut AVStream) -> Self {
+		StreamMut { ptr: ptr, imm: Stream::wrap(ptr) }
+	}
+
+	pub unsafe fn as_ptr(&self) -> *const AVStream {
+		self.ptr as *const _
+	}
+
+	pub unsafe fn as_mut_ptr(&mut self) -> *mut AVStream {
+		self.ptr
+	}
+}
+
+impl<'a> StreamMut<'a> {
+	pub fn set_frame_rate(&mut self, value: Rational) {
+		unsafe {
+			av_stream_set_r_frame_rate(self.as_mut_ptr(), value.into());
+		}
+	}
+}
+
+impl<'a> Deref for StreamMut<'a> {
+	type Target = Stream<'a>;
+
+	fn deref(&self) -> &Self::Target {
+		&self.imm
+	}
+}