Crate internment[][src]

A very easy to use library for interning strings or other data in rust. Interned data is very efficient to either hash or compare for equality (just a pointer comparison). Data is also automatically de-duplicated.

You have three options with the internment crate:

  1. Intern, which will never free your data. This means that an Intern is Copy, so you can make as many copies of the pointer as you may care to at no cost.

  2. LocalIntern, which will only free your data when the calling thread exits. This means that a LocalIntern is Copy, so you can make as many copies of the pointer as you may care to at no cost. However, you cannot share a LocalIntern with another thread. On the plus side, it is faster to create a LocalIntern than an Intern.

  3. ArcIntern, which reference-counts your data and frees it when there are no more references. ArcIntern will keep memory use down, but requires locking whenever a clone of your pointer is made, as well as when dropping the pointer.

In each case, accessing your data is a single pointer dereference, and the size of any internment data structure (Intern, LocalIntern, or ArcIntern) is a single pointer. In each case, you have a guarantee that a single data value (as defined by Eq and Hash) will correspond to a single pointer value. This means that we can use pointer comparison (and a pointer hash) in place of value comparisons, which is very fast.


use internment::Intern;
let x = Intern::new("hello");
let y = Intern::new("world");
assert_ne!(x, y);



A pointer to a reference-counted interned object.


A pointer to an interned object.


A pointer to a thread-local interned object.