js-proxy/esm/heap.js

The one-stop shop solution for JS Proxies and FFI APIs

import { NUMBER } from 'proxy-target/types';

export const create = () => {
  const ids = new Map;
  const values = new Map;
  let uid = 0;
  return {
    /**
     * Clear all references retained in the current heap.
     */
    clear: () => {
      ids.clear();
      values.clear();
    },

    /**
     * Remove by id or value any previously stored reference.
     * @param {number | unknown} id the held value by id or the value itself.
     * @returns {boolean} `true` if the operation was successful, `false` otherwise.
     */
    drop: id => {
      const [a, b] = typeof id === NUMBER ? [values, ids] : [ids, values];
      const had = a.has(id);
      if (had) {
        b.delete(a.get(id));
        a.delete(id);
      }
      return had;
    },

    /**
     * Return the held value reference by its unique identifier.
     * @param {number} id the unique identifier for the value reference.
     * @returns {unknown} the related value / reference or undefined.
     */
    get: id => values.get(id),

    /**
     * Create once a unique number id for a generic value reference.
     * @param {unknown} value a reference used to create a unique identifier.
     * @returns {number} a unique identifier for that reference.
     */
    hold: value => {
      if (!ids.has(value)) {
        let id;
        // a bit apocalyptic scenario but if this thread runs forever
        // and the id does a whole int32 roundtrip we might have still
        // some reference dangling around
        while (/* c8 ignore next */ values.has(id = uid++));
        ids.set(value, id);
        values.set(id, value);
      }
      return ids.get(value);
    },
  };
};

// globally shared heap
const { clear, drop, get, hold } = create();
export { clear, drop, get, hold };