format/context/input: add seek() method

src/util/mod.rs

@@ -10,6 +10,7 @@ pub mod chroma;
 pub mod time;
 pub mod channel_layout;
 pub mod option;
+pub mod range;
 
 use std::ffi::CStr;
 use std::str::from_utf8_unchecked;

src/util/range.rs

@@ -0,0 +1,35 @@
+use std::ops;
+
+pub trait Range<T> {
+	fn start(&self) -> Option<&T> {
+		None
+	}
+
+	fn end(&self) -> Option<&T> {
+		None
+	}
+}
+
+impl<T> Range<T> for ops::Range<T> {
+	fn start(&self) -> Option<&T> {
+		Some(&self.start)
+	}
+
+	fn end(&self) -> Option<&T> {
+		Some(&self.end)
+	}
+}
+
+impl<T> Range<T> for ops::RangeTo<T> {
+	fn end(&self) -> Option<&T> {
+		Some(&self.end)
+	}
+}
+
+impl<T> Range<T> for ops::RangeFrom<T> {
+	fn start(&self) -> Option<&T> {
+		Some(&self.start)
+	}
+}
+
+impl<T> Range<T> for ops::RangeFull { }