use std::cell::RefCell;
use std::collections::VecDeque;
use std::rc::Rc;
struct TeeBuffer<A, I>
{
backlog: VecDeque<A>,
iter: I,
owner: bool,
}
pub struct Tee<I> where
I: Iterator
{
rcbuffer: Rc<RefCell<TeeBuffer<I::Item, I>>>,
id: bool,
}
pub fn new<I>(iter: I) -> (Tee<I>, Tee<I>) where
I: Iterator
{
let buffer = TeeBuffer{backlog: VecDeque::new(), iter: iter, owner: false};
let t1 = Tee{rcbuffer: Rc::new(RefCell::new(buffer)), id: true};
let t2 = Tee{rcbuffer: t1.rcbuffer.clone(), id: false};
(t1, t2)
}
impl<I> Iterator for Tee<I> where
I: Iterator,
I::Item: Clone,
{
type Item = I::Item;
fn next(&mut self) -> Option<I::Item>
{
let mut buffer = self.rcbuffer.borrow_mut();
if buffer.owner == self.id {
match buffer.backlog.pop_front() {
None => {}
some_elt => return some_elt,
}
}
match buffer.iter.next() {
None => None,
Some(elt) => {
buffer.backlog.push_back(elt.clone());
buffer.owner = !self.id;
Some(elt)
}
}
}
fn size_hint(&self) -> (usize, Option<usize>)
{
let buffer = self.rcbuffer.borrow();
let (mut lower, mut upper) = buffer.iter.size_hint();
if buffer.owner == self.id {
let log_len = buffer.backlog.len();
lower = lower.saturating_add(log_len);
upper = upper.and_then(|x| x.checked_add(log_len));
}
(lower, upper)
}
}