| use crate::iter::{adapters::SourceIter, FusedIterator, InPlaceIterable}; |
| use crate::mem::{ManuallyDrop, MaybeUninit}; |
| use crate::ops::{ControlFlow, Try}; |
| use crate::{array, fmt}; |
| |
| /// An iterator that uses `f` to both filter and map elements from `iter`. |
| /// |
| /// This `struct` is created by the [`filter_map`] method on [`Iterator`]. See its |
| /// documentation for more. |
| /// |
| /// [`filter_map`]: Iterator::filter_map |
| /// [`Iterator`]: trait.Iterator.html |
| #[must_use = "iterators are lazy and do nothing unless consumed"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[derive(Clone)] |
| pub struct FilterMap<I, F> { |
| iter: I, |
| f: F, |
| } |
| impl<I, F> FilterMap<I, F> { |
| pub(in crate::iter) fn new(iter: I, f: F) -> FilterMap<I, F> { |
| FilterMap { iter, f } |
| } |
| } |
| |
| #[stable(feature = "core_impl_debug", since = "1.9.0")] |
| impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("FilterMap").field("iter", &self.iter).finish() |
| } |
| } |
| |
| fn filter_map_fold<T, B, Acc>( |
| mut f: impl FnMut(T) -> Option<B>, |
| mut fold: impl FnMut(Acc, B) -> Acc, |
| ) -> impl FnMut(Acc, T) -> Acc { |
| move |acc, item| match f(item) { |
| Some(x) => fold(acc, x), |
| None => acc, |
| } |
| } |
| |
| fn filter_map_try_fold<'a, T, B, Acc, R: Try<Output = Acc>>( |
| f: &'a mut impl FnMut(T) -> Option<B>, |
| mut fold: impl FnMut(Acc, B) -> R + 'a, |
| ) -> impl FnMut(Acc, T) -> R + 'a { |
| move |acc, item| match f(item) { |
| Some(x) => fold(acc, x), |
| None => try { acc }, |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<B, I: Iterator, F> Iterator for FilterMap<I, F> |
| where |
| F: FnMut(I::Item) -> Option<B>, |
| { |
| type Item = B; |
| |
| #[inline] |
| fn next(&mut self) -> Option<B> { |
| self.iter.find_map(&mut self.f) |
| } |
| |
| #[inline] |
| fn next_chunk<const N: usize>( |
| &mut self, |
| ) -> Result<[Self::Item; N], array::IntoIter<Self::Item, N>> { |
| let mut array: [MaybeUninit<Self::Item>; N] = MaybeUninit::uninit_array(); |
| |
| struct Guard<'a, T> { |
| array: &'a mut [MaybeUninit<T>], |
| initialized: usize, |
| } |
| |
| impl<T> Drop for Guard<'_, T> { |
| #[inline] |
| fn drop(&mut self) { |
| if const { crate::mem::needs_drop::<T>() } { |
| // SAFETY: self.initialized is always <= N, which also is the length of the array. |
| unsafe { |
| core::ptr::drop_in_place(MaybeUninit::slice_assume_init_mut( |
| self.array.get_unchecked_mut(..self.initialized), |
| )); |
| } |
| } |
| } |
| } |
| |
| let mut guard = Guard { array: &mut array, initialized: 0 }; |
| |
| let result = self.iter.try_for_each(|element| { |
| let idx = guard.initialized; |
| let val = (self.f)(element); |
| guard.initialized = idx + val.is_some() as usize; |
| |
| // SAFETY: Loop conditions ensure the index is in bounds. |
| |
| unsafe { |
| let opt_payload_at = core::intrinsics::option_payload_ptr(&val); |
| let dst = guard.array.as_mut_ptr().add(idx); |
| crate::ptr::copy_nonoverlapping(opt_payload_at.cast(), dst, 1); |
| crate::mem::forget(val); |
| }; |
| |
| if guard.initialized < N { ControlFlow::Continue(()) } else { ControlFlow::Break(()) } |
| }); |
| |
| let guard = ManuallyDrop::new(guard); |
| |
| match result { |
| ControlFlow::Break(()) => { |
| // SAFETY: The loop above is only explicitly broken when the array has been fully initialized |
| Ok(unsafe { MaybeUninit::array_assume_init(array) }) |
| } |
| ControlFlow::Continue(()) => { |
| let initialized = guard.initialized; |
| // SAFETY: The range is in bounds since the loop breaks when reaching N elements. |
| Err(unsafe { array::IntoIter::new_unchecked(array, 0..initialized) }) |
| } |
| } |
| } |
| |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| let (_, upper) = self.iter.size_hint(); |
| (0, upper) // can't know a lower bound, due to the predicate |
| } |
| |
| #[inline] |
| fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R |
| where |
| Self: Sized, |
| Fold: FnMut(Acc, Self::Item) -> R, |
| R: Try<Output = Acc>, |
| { |
| self.iter.try_fold(init, filter_map_try_fold(&mut self.f, fold)) |
| } |
| |
| #[inline] |
| fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc |
| where |
| Fold: FnMut(Acc, Self::Item) -> Acc, |
| { |
| self.iter.fold(init, filter_map_fold(self.f, fold)) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F> |
| where |
| F: FnMut(I::Item) -> Option<B>, |
| { |
| #[inline] |
| fn next_back(&mut self) -> Option<B> { |
| #[inline] |
| fn find<T, B>( |
| f: &mut impl FnMut(T) -> Option<B>, |
| ) -> impl FnMut((), T) -> ControlFlow<B> + '_ { |
| move |(), x| match f(x) { |
| Some(x) => ControlFlow::Break(x), |
| None => ControlFlow::Continue(()), |
| } |
| } |
| |
| self.iter.try_rfold((), find(&mut self.f)).break_value() |
| } |
| |
| #[inline] |
| fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R |
| where |
| Self: Sized, |
| Fold: FnMut(Acc, Self::Item) -> R, |
| R: Try<Output = Acc>, |
| { |
| self.iter.try_rfold(init, filter_map_try_fold(&mut self.f, fold)) |
| } |
| |
| #[inline] |
| fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc |
| where |
| Fold: FnMut(Acc, Self::Item) -> Acc, |
| { |
| self.iter.rfold(init, filter_map_fold(self.f, fold)) |
| } |
| } |
| |
| #[stable(feature = "fused", since = "1.26.0")] |
| impl<B, I: FusedIterator, F> FusedIterator for FilterMap<I, F> where F: FnMut(I::Item) -> Option<B> {} |
| |
| #[unstable(issue = "none", feature = "inplace_iteration")] |
| unsafe impl<I, F> SourceIter for FilterMap<I, F> |
| where |
| I: SourceIter, |
| { |
| type Source = I::Source; |
| |
| #[inline] |
| unsafe fn as_inner(&mut self) -> &mut I::Source { |
| // SAFETY: unsafe function forwarding to unsafe function with the same requirements |
| unsafe { SourceIter::as_inner(&mut self.iter) } |
| } |
| } |
| |
| #[unstable(issue = "none", feature = "inplace_iteration")] |
| unsafe impl<B, I: InPlaceIterable, F> InPlaceIterable for FilterMap<I, F> where |
| F: FnMut(I::Item) -> Option<B> |
| { |
| } |