Coordinate Compression utility with Rust.

co_co.rs

use std::collections::BTreeMap;

#[derive(Debug)]
pub struct CoCo<K: Ord> {
    forward: BTreeMap<K, usize>,
    backward: Vec<K>,
}

impl<K: Ord> CoCo<K> {
    pub const fn new() -> Self {
        Self {
            forward: BTreeMap::new(),
            backward: vec![],
        }
    }

    pub fn forward(&mut self, key: K) -> usize
    where
        K: Clone,
    {
        if let Some(idx) = self.forward.get(&key) {
            *idx
        } else {
            let new_idx = self.backward.len();
            self.forward.insert(key.clone(), new_idx);
            self.backward.push(key);
            new_idx
        }
    }

    pub fn backward(&self, idx: usize) -> Option<&K> {
        self.backward.get(idx)
    }
}