@giro3d/giro3d/core/Shared.js

A JS/WebGL framework for 3D geospatial data visualization

/*
 * Copyright (c) 2015-2018, IGN France.
 * Copyright (c) 2018-2026, Giro3D team.
 * SPDX-License-Identifier: MIT
 */

/**
 * Represents an object that can be shared among multiple instances (multiple ownership).
 */
export default class Shared {
  _disposed = false;
  constructor(_object, _owner, _refCount, _onDispose) {
    this._object = _object;
    this._owner = _owner;
    this._refCount = _refCount;
    this._onDispose = _onDispose;
  }

  /**
   * The underlying shared object.
   */
  get object() {
    this.checkDisposed();
    return this._object;
  }

  /**
   * Gets the original (first) owner of the shared object.
   */
  get owner() {
    this.checkDisposed();
    return this._owner;
  }

  /**
   * Creates a new shared object with the specified owner.
   * @param obj - The object to share.
   * @param owner - The owner of the object.
   * @param onDispose - The callback to apply when the ref count reaches zero.
   */
  static new(obj, owner, onDispose) {
    const result = new Shared(obj, owner, {
      count: 1
    }, onDispose);
    return result;
  }

  /**
   * Clones the reference to the shared object, incrementing the ref count.
   * Note: this does _not_ clone the shared object itself.
   */
  clone() {
    this.checkDisposed();
    this._refCount.count++;
    return new Shared(this._object, this.owner, this._refCount, this._onDispose);
  }
  checkDisposed() {
    if (this._refCount.count === 0) {
      throw new Error('cannot use disposed Shared object');
    }
  }

  /**
   * Decrement the ref count of this object. If the count becomes zero, the underlying object is also disposed.
   */
  dispose() {
    // Idempotence of dispose()
    if (this._disposed) {
      return;
    }
    this._refCount.count--;
    if (this._refCount.count === 0) {
      this._disposed = true;
      this._onDispose(this._object);
    }
  }
}