copied.rs - source
Description: Source of the Rust file `library/core/src/iter/adapters/copied.rs`.
Keywords: rust, rustlang, rust-lang

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    use crate::iter::adapters::{zip::try_get_unchecked, TrustedRandomAccess};
    use crate::iter::{FusedIterator, TrustedLen};
    use crate::ops::Try;

    /// An iterator that copies the elements of an underlying iterator.
    ///
    /// This `struct` is created by the [`copied`] method on [`Iterator`]. See its
    /// documentation for more.
    ///
    /// [`copied`]: Iterator::copied
    /// [`Iterator`]: trait.Iterator.html
    #[stable(feature = "iter_copied", since = "1.36.0")]
    #[must_use = "iterators are lazy and do nothing unless consumed"]
    #[derive(Clone, Debug)]
    pub struct Copied<I> {
        it: I,
    }

    impl<I> Copied<I> {
        pub(in crate::iter) fn new(it: I) -> Copied<I> {
            Copied { it }
        }
    }

    fn copy_fold<T: Copy, Acc>(mut f: impl FnMut(Acc, T) -> Acc) -> impl FnMut(Acc, &T) -> Acc {
        move |acc, &elt| f(acc, elt)
    }

    fn copy_try_fold<T: Copy, Acc, R>(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R {
        move |acc, &elt| f(acc, elt)
    }

    #[stable(feature = "iter_copied", since = "1.36.0")]
    impl<'a, I, T: 'a> Iterator for Copied<I>
    where
        I: Iterator<Item = &'a T>,
        T: Copy,
    {
        type Item = T;

        fn next(&mut self) -> Option<T> {
            self.it.next().copied()
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            self.it.size_hint()
        }

        fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
        where
            Self: Sized,
            F: FnMut(B, Self::Item) -> R,
            R: Try<Ok = B>,
        {
            self.it.try_fold(init, copy_try_fold(f))
        }

        fn fold<Acc, F>(self, init: Acc, f: F) -> Acc
        where
            F: FnMut(Acc, Self::Item) -> Acc,
        {
            self.it.fold(init, copy_fold(f))
        }

        fn nth(&mut self, n: usize) -> Option<T> {
            self.it.nth(n).copied()
        }

        fn last(self) -> Option<T> {
            self.it.last().copied()
        }

        fn count(self) -> usize {
            self.it.count()
        }

        unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T
        where
            Self: TrustedRandomAccess,
        {
            // SAFETY: the caller must uphold the contract for
            // `Iterator::__iterator_get_unchecked`.
            *unsafe { try_get_unchecked(&mut self.it, idx) }
        }
    }

    #[stable(feature = "iter_copied", since = "1.36.0")]
    impl<'a, I, T: 'a> DoubleEndedIterator for Copied<I>
    where
        I: DoubleEndedIterator<Item = &'a T>,
        T: Copy,
    {
        fn next_back(&mut self) -> Option<T> {
            self.it.next_back().copied()
        }

        fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
        where
            Self: Sized,
            F: FnMut(B, Self::Item) -> R,
            R: Try<Ok = B>,
        {
            self.it.try_rfold(init, copy_try_fold(f))
        }

        fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc
        where
            F: FnMut(Acc, Self::Item) -> Acc,
        {
            self.it.rfold(init, copy_fold(f))
        }
    }

    #[stable(feature = "iter_copied", since = "1.36.0")]
    impl<'a, I, T: 'a> ExactSizeIterator for Copied<I>
    where
        I: ExactSizeIterator<Item = &'a T>,
        T: Copy,
    {
        fn len(&self) -> usize {
            self.it.len()
        }

        fn is_empty(&self) -> bool {
            self.it.is_empty()
        }
    }

    #[stable(feature = "iter_copied", since = "1.36.0")]
    impl<'a, I, T: 'a> FusedIterator for Copied<I>
    where
        I: FusedIterator<Item = &'a T>,
        T: Copy,
    {
    }

    #[doc(hidden)]
    #[unstable(feature = "trusted_random_access", issue = "none")]
    unsafe impl<I> TrustedRandomAccess for Copied<I>
    where
        I: TrustedRandomAccess,
    {
        #[inline]
        fn may_have_side_effect() -> bool {
            I::may_have_side_effect()
        }
    }

    #[stable(feature = "iter_copied", since = "1.36.0")]
    unsafe impl<'a, I, T: 'a> TrustedLen for Copied<I>
    where
        I: TrustedLen<Item = &'a T>,
        T: Copy,
    {
    }