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use std::collections::BTreeSet;
use std::convert::AsRef;
use elsa::FrozenIndexSet;
struct StringInterner {
set: FrozenIndexSet<String>,
}
impl StringInterner {
fn new() -> Self {
StringInterner {
set: FrozenIndexSet::new(),
}
}
fn get_or_intern<T>(&self, value: T) -> usize
where
T: AsRef<str>,
{
// TODO use Entry in case the standard Entry API gets improved
// (here to avoid premature allocation or double lookup)
self.set.insert_full(value.as_ref().to_string()).0
}
fn get<T>(&self, value: T) -> Option<usize>
where
T: AsRef<str>,
{
self.set.get_full(value.as_ref()).map(|(i, _r)| i)
}
fn resolve(&self, index: usize) -> Option<&str> {
self.set.get_index(index)
}
}
fn main() {
let interner = StringInterner::new();
let lonely = interner.get_or_intern("lonely");
let best_friend = interner.get_or_intern("best friend");
let threes_a_crowd = interner.get_or_intern("threes a crowd");
let rando = interner.get_or_intern("rando");
let _facebook = interner.get_or_intern("facebook");
let best_friend_2 = interner.get_or_intern("best friend");
let best_friend_3 = interner.get("best friend").unwrap();
let best_friend_ref = interner.resolve(best_friend).unwrap();
let mut set = BTreeSet::new();
set.insert(lonely);
set.insert(best_friend);
set.insert(threes_a_crowd);
set.insert(rando);
set.insert(best_friend_2);
assert_eq!(set.len(), 4);
assert_eq!(best_friend, best_friend_2);
assert_eq!(best_friend_2, best_friend_3);
assert_eq!(best_friend_ref, "best friend");
}
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