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import { BitArray } from "./bit-array.ts";import { getLSBIndex } from "./utilities.ts";
/** * Implements a fast algorithm to manage availability of objects in an object pool using a BitArray. * * @example * // create a pool of 1600 indexes * const pool = Pool.create(100 * 16); * * // get the next available index and make it unavailable * pool.get(); * //=> 0 * pool.get(); * //=> 1 * * // set index available * pool.free(0); * pool.get(); * //=> 0 * * pool.get(); * //=> 2 */export class Pool extends BitArray {  nextAvailable = 0;
  /**   * Creates a Pool of the specified size.   *   * @param size the size of the pool   * @return a new Pool   */  static create<T extends typeof BitArray>(    this: T,    size: number,  ): InstanceType<T> {    const pool = new this(this.getLength(size));    pool.fill(4294967295);    return pool as InstanceType<T>;  }
  /**   * Makes a given index available.   *   * @param index index to be freed   */  free(index: number): void {    const { bucket, position } = this.getBitPosition(index);    this[bucket] |= 1 << position;    this.nextAvailable = bucket;  }
  /**   * Gets the next available index in the pool.   *   * @return the next available index   */  get(): number {    const { nextAvailable } = this;    if (!~nextAvailable) return -1;    const record = this[nextAvailable];    const index = getLSBIndex(record);    this[nextAvailable] &= ~(1 << index);
    // record is full, find next empty    if (this[nextAvailable] === 0) {      this.nextAvailable = -1;      for (let i = 0; i < this.length; i++) {        if (this[i] !== 0) {          this.nextAvailable = i;          break;        }      }    }
    return (nextAvailable << 5) + index;  }}