react-native-macos/Libraries/Renderer/src/renderers/shared/fiber/ReactFiberStack.js

A framework for building native macOS apps using React

/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ReactFiberStack
 * @flow
 */

'use strict';

import type {Fiber} from 'ReactFiber';

export type StackCursor<T> = {
  current: T,
};

const warning = require('fbjs/lib/warning');

const valueStack: Array<any> = [];

if (__DEV__) {
  var fiberStack: Array<Fiber | null> = [];
}

let index = -1;

exports.createCursor = function<T>(defaultValue: T): StackCursor<T> {
  return {
    current: defaultValue,
  };
};

exports.isEmpty = function(): boolean {
  return index === -1;
};

exports.pop = function<T>(cursor: StackCursor<T>, fiber: Fiber): void {
  if (index < 0) {
    if (__DEV__) {
      warning(false, 'Unexpected pop.');
    }
    return;
  }

  if (__DEV__) {
    if (fiber !== fiberStack[index]) {
      warning(false, 'Unexpected Fiber popped.');
    }
  }

  cursor.current = valueStack[index];

  valueStack[index] = null;

  if (__DEV__) {
    fiberStack[index] = null;
  }

  index--;
};

exports.push = function<T>(
  cursor: StackCursor<T>,
  value: T,
  fiber: Fiber,
): void {
  index++;

  valueStack[index] = cursor.current;

  if (__DEV__) {
    fiberStack[index] = fiber;
  }

  cursor.current = value;
};

exports.reset = function(): void {
  while (index > -1) {
    valueStack[index] = null;

    if (__DEV__) {
      fiberStack[index] = null;
    }

    index--;
  }
};