ace2_common.js

'use strict';

/**
 * This code is mostly from the old Etherpad. Please help us to comment this code.
 * This helps other people to understand this code better and helps them to improve it.
 * TL;DR COMMENTS ON THIS FILE ARE HIGHLY APPRECIATED
 */

/**
 * Copyright 2009 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const isNodeText = (node) => (node.nodeType === 3);

const getAssoc = (obj, name) => obj[`_magicdom_${name}`];

const setAssoc = (obj, name, value) => {
  // note that in IE designMode, properties of a node can get
  // copied to new nodes that are spawned during editing; also,
  // properties representable in HTML text can survive copy-and-paste
  obj[`_magicdom_${name}`] = value;
};

// "func" is a function over 0..(numItems-1) that is monotonically
// "increasing" with index (false, then true).  Finds the boundary
// between false and true, a number between 0 and numItems inclusive.


const binarySearch = (numItems, func) => {
  if (numItems < 1) return 0;
  if (func(0)) return 0;
  if (!func(numItems - 1)) return numItems;
  let low = 0; // func(low) is always false
  let high = numItems - 1; // func(high) is always true
  while ((high - low) > 1) {
    const x = Math.floor((low + high) / 2); // x != low, x != high
    if (func(x)) high = x;
    else low = x;
  }
  return high;
};

const binarySearchInfinite = (expectedLength, func) => {
  let i = 0;
  while (!func(i)) i += expectedLength;
  return binarySearch(i, func);
};

const noop = () => {};

exports.isNodeText = isNodeText;
exports.getAssoc = getAssoc;
exports.setAssoc = setAssoc;
exports.binarySearch = binarySearch;
exports.binarySearchInfinite = binarySearchInfinite;
exports.noop = noop;