[][src]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.



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



DlistDefineStaticSelector!( SELTYPE, NODE [ MEMBS ]);


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