From 1593e2b7df05da71162b9ad0e3f12d577aec3131 Mon Sep 17 00:00:00 2001 From: "main()" Date: Mon, 4 May 2020 15:53:02 +0200 Subject: [PATCH 1/2] Add remove_current_as_list to LinkedList's CursorMut The `remove_current` method only returns the inner `T` and deallocates the list node. This is unnecessary for move operations, where the element is going to be linked back into this (or even a different) `LinkedList`. The `remove_current_as_list` method avoids this by returning the unlinked list node as a new single-element `LinkedList` structure . --- src/liballoc/collections/linked_list.rs | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/src/liballoc/collections/linked_list.rs b/src/liballoc/collections/linked_list.rs index bfa4045787f5b..952e5317840a1 100644 --- a/src/liballoc/collections/linked_list.rs +++ b/src/liballoc/collections/linked_list.rs @@ -1496,6 +1496,31 @@ impl<'a, T> CursorMut<'a, T> { } } + /// Removes the current element from the `LinkedList` without deallocating the list node. + /// + /// The node that was removed is returned as a new `LinkedList` containing only this node. + /// The cursor is moved to point to the next element in the current `LinkedList`. + /// + /// If the cursor is currently pointing to the "ghost" non-element then no element + /// is removed and `None` is returned. + #[unstable(feature = "linked_list_cursors", issue = "58533")] + pub fn remove_current_as_list(&mut self) -> Option> { + let unlinked_node = self.current?; + unsafe { + self.current = unlinked_node.as_ref().next; + self.list.unlink_node(unlinked_node); + + unlinked_node.as_mut().prev = None; + unlinked_node.as_mut().next = None; + Some(LinkedList { + head: Some(unlinked_node), + tail: Some(unlinked_node), + len: 1, + marker: PhantomData, + }) + } + } + /// Inserts the elements from the given `LinkedList` after the current one. /// /// If the cursor is pointing at the "ghost" non-element then the new elements are From c5cdf7fe920c8cb3b60f5a6e257f6cdfb51102d3 Mon Sep 17 00:00:00 2001 From: "main()" Date: Mon, 4 May 2020 16:10:59 +0200 Subject: [PATCH 2/2] whoops --- src/liballoc/collections/linked_list.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/liballoc/collections/linked_list.rs b/src/liballoc/collections/linked_list.rs index 952e5317840a1..cc0f07b822741 100644 --- a/src/liballoc/collections/linked_list.rs +++ b/src/liballoc/collections/linked_list.rs @@ -1505,7 +1505,7 @@ impl<'a, T> CursorMut<'a, T> { /// is removed and `None` is returned. #[unstable(feature = "linked_list_cursors", issue = "58533")] pub fn remove_current_as_list(&mut self) -> Option> { - let unlinked_node = self.current?; + let mut unlinked_node = self.current?; unsafe { self.current = unlinked_node.as_ref().next; self.list.unlink_node(unlinked_node);