Vendor things

third-party/vendor/slotmap/README.md

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+# slotmap
+
+A Rust library providing three containers with persistent unique keys to access
+stored values, `SlotMap`, `HopSlotMap` and `DenseSlotMap`. Upon insertion a key
+is returned that can be used to later access or remove the values. Insertion,
+deletion and access all take O(1) time with low overhead. Great for storing
+collections of objects that need stable, safe references but have no clear
+ownership otherwise, such as game entities or graph nodes. Two secondary maps,
+`SecondaryMap` and `SparseSecondaryMap` are also provided that allow you to map
+further objects to the keys created by one of the slot maps. Please refer to
+[**the documentation**](https://docs.rs/slotmap) for more information.
+
+The minimum required stable Rust version for `slotmap` is 1.49. To start using
+`slotmap` add the following to your `Cargo.toml`:
+
+```toml
+[dependencies]
+slotmap = "1.0"
+```
+
+# Example
+
+A short example:
+
+```rust
+use slotmap::{SlotMap, SecondaryMap};
+
+let mut sm = SlotMap::new();
+let foo = sm.insert("foo");  // Key generated on insert.
+let bar = sm.insert("bar");
+assert_eq!(sm[foo], "foo");
+assert_eq!(sm[bar], "bar");
+
+sm.remove(bar);
+let reuse = sm.insert("reuse");  // Space from bar reused.
+assert_eq!(sm.contains_key(bar), false);  // After deletion a key stays invalid.
+
+let mut sec = SecondaryMap::new();
+sec.insert(foo, "noun");  // We provide the key for secondary maps.
+sec.insert(reuse, "verb");
+
+for (key, val) in sm {
+    println!("{} is a {}", val, sec[key]);
+}
+```
+
+# License
+
+`slotmap` is released under the Zlib license, a permissive license. It is
+OSI and FSF approved and GPL compatible.