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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 {
let mut start = range.start().unwrap_or(0);
let end = range.end().unwrap_or(::std::usize::MAX);
if start > end {
start = end;
}
ISlice {
start: start,
end: end,
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;
let sh = self.iter.size_hint();
size_hint::min(size_hint::sub_scalar(sh, self.start), (len, Some(len)))
}
}
impl<I> ExactSizeIterator for ISlice<I>
where I: ExactSizeIterator
{}