Drain

src/drain.rs

@@ -0,0 +1,54 @@
+// Copyright (c) 2024 Yegor Bugayenko
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+use crate::Drain;
+use core::iter::FusedIterator;
+
+impl<'a, K, V> Drop for Drain<'a, K, V> {
+    fn drop(&mut self) {
+        for pair in &mut self.iter {
+            unsafe { pair.assume_init_drop() };
+        }
+    }
+}
+
+impl<'a, K: PartialEq, V> Iterator for Drain<'a, K, V> {
+    type Item = (K, V);
+
+    #[inline]
+    #[must_use]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next().map(|p| unsafe { p.assume_init_read() })
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.iter.len(), Some(self.iter.len()))
+    }
+}
+
+impl<'a, K: PartialEq, V> ExactSizeIterator for Drain<'a, K, V> {
+    #[inline]
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+}
+
+impl<'a, K: PartialEq, V> FusedIterator for Drain<'a, K, V> {}

src/lib.rs

@@ -54,6 +54,7 @@ mod clone;
 mod ctors;
 mod debug;
 mod display;
+mod drain;
 mod entry;
 mod eq;
 mod from;
@@ -66,7 +67,7 @@ mod serialization;
 mod set;
 mod values;
 
-pub use crate::set::{Set, SetIntoIter, SetIter};
+pub use crate::set::{Set, SetDrain, SetIntoIter, SetIter};
 use core::mem::MaybeUninit;
 
 /// A faster alternative of [`std::collections::HashMap`].
@@ -175,3 +176,10 @@ pub struct VacantEntry<'a, K: 'a + PartialEq, V: 'a, const N: usize> {
     key: K,
     table: &'a mut Map<K, V, N>,
 }
+
+/// A draining iterator over the entries of a `Map`.
+///
+/// This struct is created by the drain method on `Map`. See its documentation for more.
+pub struct Drain<'a, K: 'a, V: 'a> {
+    iter: core::slice::IterMut<'a, MaybeUninit<(K, V)>>,
+}

src/map.rs

@@ -18,7 +18,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-use crate::{Entry, Map, OccupiedEntry, VacantEntry};
+use crate::{Drain, Entry, Map, OccupiedEntry, VacantEntry};
 use core::borrow::Borrow;
 
 mod internal {
@@ -105,6 +105,17 @@ impl<K: PartialEq, V, const N: usize> Map<K, V, N> {
         self.len
     }
 
+    /// Clears the map, returning all key-value pairs as an iterator. Keeps the allocated memory for reuse.
+    ///
+    /// If the returned iterator is dropped before being fully consumed, it drops the remaining key-value pairs. The returned iterator keeps a mutable borrow on the map to optimize its implementation.
+    pub fn drain(&mut self) -> Drain<'_, K, V> {
+        let drain = Drain {
+            iter: self.pairs[0..self.len].iter_mut(),
+        };
+        self.len = 0;
+        drain
+    }
+
     /// Does the map contain this key?
     #[inline]
     #[must_use]

src/set/drain.rs

@@ -0,0 +1,46 @@
+// Copyright (c) 2024 Yegor Bugayenko
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+use crate::SetDrain;
+use core::iter::FusedIterator;
+
+impl<'a, K: PartialEq> Iterator for SetDrain<'a, K> {
+    type Item = K;
+
+    #[inline]
+    #[must_use]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next().map(|(k, ())| k)
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.iter.len(), Some(self.iter.len()))
+    }
+}
+
+impl<'a, K: PartialEq> ExactSizeIterator for SetDrain<'a, K> {
+    #[inline]
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+}
+
+impl<'a, K: PartialEq> FusedIterator for SetDrain<'a, K> {}

src/set/functions.rs

@@ -18,7 +18,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-use crate::Set;
+use crate::{Set, SetDrain};
 use core::borrow::Borrow;
 
 impl<T: PartialEq, const N: usize> Set<T, N> {
@@ -43,6 +43,15 @@ impl<T: PartialEq, const N: usize> Set<T, N> {
         self.map.len()
     }
 
+    /// Clears the set, returning all elements as an iterator. Keeps the allocated memory for reuse.
+    ///
+    /// If the returned iterator is dropped before being fully consumed, it drops the remaining elements. The returned iterator keeps a mutable borrow on the set to optimize its implementation.
+    pub fn drain(&mut self) -> SetDrain<'_, T> {
+        SetDrain {
+            iter: self.map.drain(),
+        }
+    }
+
     /// Does the set contain this key?
     #[inline]
     #[must_use]

src/set/mod.rs

@@ -2,6 +2,7 @@ mod clone;
 mod ctors;
 mod debug;
 mod display;
+mod drain;
 mod eq;
 mod from;
 mod functions;
@@ -54,3 +55,9 @@ pub struct SetIter<'a, T> {
 pub struct SetIntoIter<T: PartialEq, const N: usize> {
     iter: crate::IntoKeys<T, (), N>,
 }
+
+#[repr(transparent)]
+#[allow(clippy::module_name_repetitions)]
+pub struct SetDrain<'a, T: PartialEq> {
+    iter: crate::Drain<'a, T, ()>,
+}