use super::Itertools;
use super::size_hint;
use super::misc::GenericRange;
#[derive(Copy, Clone)]
pub struct ISlice<I> {
start: usize,
end: usize,
iter: I,
}
impl<I> ISlice<I>
where I: Iterator
{
pub fn new<R: GenericRange>(iter: I, range: R) -> Self
{
ISlice {
start: range.start().unwrap_or(0),
end: range.end().unwrap_or(::std::usize::MAX),
iter: iter,
}
}
}
impl<I> Iterator for ISlice<I>
where I: Iterator
{
type Item = I::Item;
fn next(&mut self) -> Option<I::Item>
{
if self.start != 0 {
let st = self.start;
let n = self.iter.dropn(self.start);
self.start = 0;
self.end -= n;
if n != st {
return None
}
}
if self.end != 0 {
self.end -= 1;
self.iter.next()
} else {
None
}
}
fn size_hint(&self) -> (usize, Option<usize>)
{
let len = self.end - self.start;
size_hint::min(self.iter.size_hint(), (len, Some(len)))
}
}
impl<I> ExactSizeIterator for ISlice<I>
where I: ExactSizeIterator
{ }