Rust Buffered Iterator

bufferediterator.rs

extern crate std;

pub struct BufferedIterator<Iter: Iterator> {
	iter: Iter,
	buffer: Vec<Iter::Item>,
}

impl<Iter: Iterator> BufferedIterator<Iter> {
	pub fn new(iter: Iter) -> Self {
		BufferedIterator{
			iter: iter,
			buffer: Vec::new(),
		}
	}
	
	pub fn peek(&mut self) -> Option<&Iter::Item> {
		if self.buffer.is_empty() {
			if let Some(e) = self.iter.next() {
				self.buffer.push(e)
			}
		}
		
		self.buffer.last()
	}
	
	pub fn unget(&mut self, e: Iter::Item) {
		self.buffer.insert(0, e)
	}
}

impl<Iter: Iterator> Iterator for BufferedIterator<Iter> {
	type Item = Iter::Item;
	
	fn next(&mut self) -> Option<Self::Item> {
		self.buffer.pop().or_else(|| self.iter.next())
	}
}