devela 0.28.0

A development substrate of coherence.
Documentation 
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// devela::sys::mem::view::slice::iter
//
//! Defines [`SliceIter`], [`SliceIterMut`].
//

use crate::{
    IteratorLending, IteratorLendingDoubleEnded, IteratorLendingExactSize, IteratorLendingPeek,
};

#[doc = crate::_tags!(iterator lifetime)]
/// A lending iterator over a shared slice.
#[doc = crate::_doc_meta!{
    location("sys/mem/view"),
    #[cfg(target_pointer_width = "32")]
    test_size_of(__: SliceIter<'_, char> = 16|128; niche Option),
    #[cfg(target_pointer_width = "64")]
    test_size_of(__: SliceIter<'_, char> = 32|256; niche Option),
}]
///
/// Yields elements by reference in index order. Produces `&T` without copying.
#[derive(Debug)]
pub struct SliceIter<'s, T> {
    slice: &'s [T],
    front: usize,
    back: usize,
}
impl<'s, T> SliceIter<'s, T> {
    /// Creates an iterator over the given shared slice starting at index `0`.
    pub fn new(slice: &'s [T]) -> Self {
        let len = slice.len();
        Self { slice, front: 0, back: len }
    }
}
impl<'s, T> IteratorLending for SliceIter<'s, T> {
    type Item<'a>
        = &'a T
    where
        Self: 'a;

    fn next<'a>(&'a mut self) -> Option<Self::Item<'a>> {
        if self.front >= self.back {
            None
        } else {
            let i = self.front;
            self.front += 1;
            Some(&self.slice[i])
        }
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.back - self.front;
        (len, Some(len))
    }
}
impl<'s, T> IteratorLendingExactSize for SliceIter<'s, T> {}
impl<'s, T> IteratorLendingDoubleEnded for SliceIter<'s, T> {
    fn next_back<'a>(&'a mut self) -> Option<Self::Item<'a>> {
        if self.front >= self.back {
            None
        } else {
            self.back -= 1;
            Some(&self.slice[self.back])
        }
    }
}
impl<'s, T> IteratorLendingPeek for SliceIter<'s, T> {
    fn peek<'a>(&'a mut self) -> Option<Self::Item<'a>> {
        if self.front >= self.back { None } else { Some(&self.slice[self.front]) }
    }
}

//

#[doc = crate::_tags!(iterator lifetime)]
/// A lending iterator over an exclusive slice.
#[doc = crate::_doc_meta!{
    location("sys/mem/view"),
    #[cfg(target_pointer_width = "32")]
    test_size_of(__: SliceIterMut<'_, char> = 16|128),
    #[cfg(target_pointer_width = "64")]
    test_size_of(__: SliceIterMut<'_, char> = 32|256),
}]
///
/// Yields `&mut T` references in index order.
///
/// The returned reference is tied to the temporary mutable borrow of the iterator
/// taken by `next`, matching the [`IteratorLending`] contract.
///
/// # Examples
/// ```
/// # use devela::{IteratorLending, SliceIterMut};
/// let mut array = [0, 1, 2, 3];
/// let mut it = SliceIterMut::new(&mut array);
/// while let Some(x) = it.next() {
///     *x += 1;
/// }
/// assert_eq![array.as_slice(), &[1, 2, 3, 4]];
/// ```
#[derive(Debug)]
pub struct SliceIterMut<'s, T> {
    slice: &'s mut [T],
    front: usize,
    back: usize,
}
impl<'s, T> SliceIterMut<'s, T> {
    /// Creates an iterator over the given exclusive slice starting at index `0`.
    pub fn new(slice: &'s mut [T]) -> Self {
        let len = slice.len();
        Self { slice, front: 0, back: len }
    }
}
impl<'s, T> IteratorLending for SliceIterMut<'s, T> {
    type Item<'a>
        = &'a mut T
    where
        Self: 'a;

    fn next<'a>(&'a mut self) -> Option<Self::Item<'a>> {
        if self.front >= self.back {
            None
        } else {
            let i = self.front;
            self.front += 1;
            Some(&mut self.slice[i])
        }
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.back - self.front;
        (len, Some(len))
    }
}
impl<'s, T> IteratorLendingExactSize for SliceIterMut<'s, T> {}
impl<'s, T> IteratorLendingDoubleEnded for SliceIterMut<'s, T> {
    fn next_back<'a>(&'a mut self) -> Option<Self::Item<'a>> {
        if self.front >= self.back {
            None
        } else {
            self.back -= 1;
            Some(&mut self.slice[self.back])
        }
    }
}