1# slotmap 2 3A Rust library providing three containers with persistent unique keys to access 4stored values, `SlotMap`, `HopSlotMap` and `DenseSlotMap`. Upon insertion a key 5is returned that can be used to later access or remove the values. Insertion, 6deletion and access all take O(1) time with low overhead. Great for storing 7collections of objects that need stable, safe references but have no clear 8ownership otherwise, such as game entities or graph nodes. Two secondary maps, 9`SecondaryMap` and `SparseSecondaryMap` are also provided that allow you to map 10further objects to the keys created by one of the slot maps. Please refer to 11[**the documentation**](https://docs.rs/slotmap) for more information. 12 13The minimum required stable Rust version for `slotmap` is 1.49. To start using 14`slotmap` add the following to your `Cargo.toml`: 15 16```toml 17[dependencies] 18slotmap = "1.0" 19``` 20 21# Example 22 23A short example: 24 25```rust 26use slotmap::{SlotMap, SecondaryMap}; 27 28let mut sm = SlotMap::new(); 29let foo = sm.insert("foo"); // Key generated on insert. 30let bar = sm.insert("bar"); 31assert_eq!(sm[foo], "foo"); 32assert_eq!(sm[bar], "bar"); 33 34sm.remove(bar); 35let reuse = sm.insert("reuse"); // Space from bar reused. 36assert_eq!(sm.contains_key(bar), false); // After deletion a key stays invalid. 37 38let mut sec = SecondaryMap::new(); 39sec.insert(foo, "noun"); // We provide the key for secondary maps. 40sec.insert(reuse, "verb"); 41 42for (key, val) in sm { 43 println!("{} is a {}", val, sec[key]); 44} 45``` 46 47# License 48 49`slotmap` is released under the Zlib license, a permissive license. It is 50OSI and FSF approved and GPL compatible. 51