Crate rc_dlist_deque

rc-dlist-deque - Doubly-linked list based on std::Rc

This crate provides a doubly-linked list implementation for circumstances where Rc is suitable for managing the individual nodes.

How to use this crate

See the module-level documentation

When not to use this crate

Many programmers new to Rust look for a linked list when another data structure is better. Consider Vec and VecDeque. A doubly-linked list is good if:

• You need to retain and store, long-term, a reference to the middle of your list, and you need quick access to the corresponding item, and

• You need to be able to quickly add or remove items in the middle of your list, based on such references; or your references into the middle of the list must remain valid even as you add or remove other items elsewhere in the middle, and

• Your lists might be long.

In other circumstances, which is most circumstances, you probably wanted Vec or VecDeque instead. They have much lower overhead and are simpler to work with.

In particular:

• If you don't need to add/remove items in the middle, then a Vec or VecDeque works well. You can use array indices as your references.

• If you want a VecDeque with stable indices, this can be achieved by maintaining a signed counter of elements pushed/popped at the start.

• If you don't need to retain long-term references to the middle of the list, then you can use a vector. Adding or removing items in the middle does mean copying to shuffle items up or down, but if you aren't keeping a reference to the modification location you will have to walk along to find the right place anyway.

Note that there are a number of deque-ish alternatives to std::VecDeque which are not doubly linked lists and do not aim to support modification in the middle of the list, at least some of which seem like they might be useful. Search crates.io for deque, and also consider blist.

Other doubly-linked list libraries

If you do need a doubly-linked list, but do not need your items to be on more than one list at once, consider dlv-list-rs instead. It has a much simpler ownership model and will be faster too.

If you want each item to be able to be on more than one list at once (perhaps even selecting the linked list link within each node dynamically at runtime), then this crate rc-dlist-deque may be what you want.

Survey of available Rust doubly linked lists, compared to VecDeque

Crate or module	Ref to element (aka Index or Cursor)				Other misuse possible, and consequences	List owns (T is element type)	Cost of editing in middle		Memory locality	Element can be on multiple lists	API complete­ness	Send/​Sync	Safety	Comments
	Type	After altering list at front/​back	After altering list in middle	After removing ref'd element			Given ref to elem	Without ref to elem
Choose one of these approaches
std VecDeque	usize	wrong element if alteration at start	wrong element	wrong element	Rich API can invalidate indices	T	O(n)	O(n)	sequential	-	++	Yes	Good	Use if you don't need persistent cursors
std VecDeque with front counter	isize	valid	wrong element	wrong element		T	O(n)	O(n)	sequential	-	DIY	Yes	Good	Consider if you need to modify only at ends
rc-dlist-deque	Pointer​<L,S>	valid	valid	valid	Specify wrong list for alteration: debug_assert, "tangling"	Rc<T>	O(1)	O(n)	scattered to heap	Yes	+	-	Safe	Consider if you need each element on multiple lists
dlv-list-rs	Index​<T>	valid	valid	gives None ([] panics)	Specify wrong list for access or alteration: Maybe detected by luck, giving None, otherwise wrong element	T	O(1)	O(n)	random order in vector	-	+	Yes	Safe (exc.​IterMut)	Otherwise, use this
indexlist	Index​<T>					T	O(1)	O(n)		-	--	Yes	Safe	No IterMut
Use VecDeque instead of any of the following
intrusive_​collections linked_​list	Cursor​[Mut]	Mutation not possible while any other cursor exists (prevented by lifetimes). This almost entirely defeats the point of using a doubly linked list.				Various	O(1)	O(n)	scattered to heap	Yes	+	Yes	uses unsafe	If this API is enough for you, use VecDeque instead
ixlist	Cursor					T	O(1)	O(n)	random order in vector	-		Yes	Safe (exc.​IterMut)
linked-list	Cursor					T	O(1)	O(n)	scattered to heap	-		Yes	uses unsafe
std LinkedList	Not supported. This defeats the point of using a doubly linked list.					T		O(n)	scattered to heap	-		Yes
doubly						T		O(n)	scattered to heap	-		Yes	uses unsafe

Not considered here because single-ended, or special purpose): index_queue, c_linked_list, linked_list_allocator, linked-tail-list, static-linkedlist.

Not considered here because no Rustdocs, does not build with modern Rust: dynalist.

It can be hard to implement IterMut without using unsafe, so no criticism is intended for those crates that use unsafe for this.

Last updated May 2019.

Modules

dlist

See the crate-level documentatio for a discussion of whether to use this crate.

Macros

DlistDefineStaticSelector	DlistDefineStaticSelector!( SELTYPE, NODE [ MEMBS ]);
DlistImplSelector	DlistImplSelector!( [ +( TYPEPARAMS )] SELTYPE, NODE, SELVAR [ MEMBS ]);