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pub(crate) mod all;
pub(crate) mod none;
pub use self::all::All;
pub use self::none::None;
pub trait Mask: Sized {
type Iter: Iterator<Item = usize>;
fn test(&self, index: usize) -> bool;
fn iter(&self) -> Self::Iter;
fn join<I>(&self, iter: I) -> Join<Self::Iter, I::IntoIter>
where
Self: Sized,
I: IntoIterator,
{
Join {
mask: self.iter(),
right: iter.into_iter(),
last: 0,
}
}
}
impl<M: ?Sized> Mask for &'_ M
where
M: Mask,
{
type Iter = M::Iter;
fn test(&self, index: usize) -> bool {
(**self).test(index)
}
fn iter(&self) -> Self::Iter {
(**self).iter()
}
}
pub struct Join<A, B> {
mask: A,
right: B,
last: usize,
}
impl<A, B> Iterator for Join<A, B>
where
A: Iterator<Item = usize>,
B: Iterator,
{
type Item = B::Item;
fn next(&mut self) -> Option<Self::Item> {
let index = self.mask.next()?;
let offset = index - self.last;
let buf = self.right.nth(offset)?;
self.last = index + 1;
Some(buf)
}
}