Function makeLRUCacheMap

ses.cjs:1256–1365

(keysBudget)

 * @returns {WeakMap<K,V>}
 */
const        makeLRUCacheMap=  (keysBudget)=>{
  if( !isSafeInteger(keysBudget)||  keysBudget<  0) {
    throw TypeError('keysBudget must be a safe non-negative integer number');
   }
  /** @typedef {DoublyLinkedCell<WeakMap<K, V> | undefined>} LRUCacheCell */
  /** @type {WeakMap<K, LRUCacheCell>} */
  const keyToCell=  new WeakMap();
  let size=  0; // `size` must remain <= `keysBudget`
  // As a sigil, `head` uniquely is not in the `keyToCell` map.
  /** @type {LRUCacheCell} */
  const head=  makeSelfCell(undefined);

  const touchCell=  (key)=>{
    const cell=  keyToCell.get(key);
    if( cell===  undefined||  cell.data===  undefined) {
      // Either the key was GCed, or the cell was condemned.
      return undefined;
     }
    // Becomes most recently used
    spliceOut(cell);
    spliceAfter(head, cell);
    return cell;
   };

  /**
   * @param {K} key
   */
  const has=  (key)=>touchCell(key)!==  undefined;
  freeze(has);

  /**
   * @param {K} key
   */
  // UNTIL https://github.com/endojs/endo/issues/1514
  // Prefer: const get = key => touchCell(key)?.data?.get(key);
  const get=  (key)=>{
    const cell=  touchCell(key);
    return cell&&  cell.data&&  cell.data.get(key);
   };
  freeze(get);

  /**
   * @param {K} key
   * @param {V} value
   */
  const set=  (key, value)=>  {
    if( keysBudget<  1) {
      // eslint-disable-next-line no-use-before-define
      return lruCacheMap; // Implements WeakMap.set
     }

    let cell=  touchCell(key);
    if( cell===  undefined) {
      cell=  makeSelfCell(undefined);
      spliceAfter(head, cell); // start most recently used
     }
    if( !cell.data) {
      // Either a fresh cell or a reused condemned cell.