pdf.js/src/core/core_utils.js

/* Copyright 2019 Mozilla Foundation
 *
 * 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.
 */
/* eslint no-var: error */

import { assert, BaseException, warn } from '../shared/util';

function getLookupTableFactory(initializer) {
  let lookup;
  return function() {
    if (initializer) {
      lookup = Object.create(null);
      initializer(lookup);
      initializer = null;
    }
    return lookup;
  };
}

class MissingDataException extends BaseException {
  constructor(begin, end) {
    super(`Missing data [${begin}, ${end})`);
    this.begin = begin;
    this.end = end;
  }
}

class XRefEntryException extends BaseException { }

class XRefParseException extends BaseException { }

/**
 * Get the value of an inheritable property.
 *
 * If the PDF specification explicitly lists a property in a dictionary as
 * inheritable, then the value of the property may be present in the dictionary
 * itself or in one or more parents of the dictionary.
 *
 * If the key is not found in the tree, `undefined` is returned. Otherwise,
 * the value for the key is returned or, if `stopWhenFound` is `false`, a list
 * of values is returned. To avoid infinite loops, the traversal is stopped when
 * the loop limit is reached.
 *
 * @param {Dict} dict - Dictionary from where to start the traversal.
 * @param {string} key - The key of the property to find the value for.
 * @param {boolean} getArray - Whether or not the value should be fetched as an
 *   array. The default value is `false`.
 * @param {boolean} stopWhenFound - Whether or not to stop the traversal when
 *   the key is found. If set to `false`, we always walk up the entire parent
 *   chain, for example to be able to find `\Resources` placed on multiple
 *   levels of the tree. The default value is `true`.
 */
function getInheritableProperty({ dict, key, getArray = false,
                                  stopWhenFound = true, }) {
  const LOOP_LIMIT = 100;
  let loopCount = 0;
  let values;

  while (dict) {
    const value = getArray ? dict.getArray(key) : dict.get(key);
    if (value !== undefined) {
      if (stopWhenFound) {
        return value;
      }
      if (!values) {
        values = [];
      }
      values.push(value);
    }
    if (++loopCount > LOOP_LIMIT) {
      warn(`getInheritableProperty: maximum loop count exceeded for "${key}"`);
      break;
    }
    dict = dict.get('Parent');
  }
  return values;
}

const ROMAN_NUMBER_MAP = [
  '', 'C', 'CC', 'CCC', 'CD', 'D', 'DC', 'DCC', 'DCCC', 'CM',
  '', 'X', 'XX', 'XXX', 'XL', 'L', 'LX', 'LXX', 'LXXX', 'XC',
  '', 'I', 'II', 'III', 'IV', 'V', 'VI', 'VII', 'VIII', 'IX'
];

/**
 * Converts positive integers to (upper case) Roman numerals.
 * @param {number} number - The number that should be converted.
 * @param {boolean} lowerCase - Indicates if the result should be converted
 *   to lower case letters. The default value is `false`.
 * @returns {string} The resulting Roman number.
 */
function toRomanNumerals(number, lowerCase = false) {
  assert(Number.isInteger(number) && number > 0,
         'The number should be a positive integer.');
  let pos, romanBuf = [];
  // Thousands
  while (number >= 1000) {
    number -= 1000;
    romanBuf.push('M');
  }
  // Hundreds
  pos = (number / 100) | 0;
  number %= 100;
  romanBuf.push(ROMAN_NUMBER_MAP[pos]);
  // Tens
  pos = (number / 10) | 0;
  number %= 10;
  romanBuf.push(ROMAN_NUMBER_MAP[10 + pos]);
  // Ones
  romanBuf.push(ROMAN_NUMBER_MAP[20 + number]);

  const romanStr = romanBuf.join('');
  return (lowerCase ? romanStr.toLowerCase() : romanStr);
}

export {
  getLookupTableFactory,
  MissingDataException,
  XRefEntryException,
  XRefParseException,
  getInheritableProperty,
  toRomanNumerals,
};