functionfoundry/fn/oct2dec.js

Pure function JavaScript library

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = oct2dec;

var _error = require('./error');

var _error2 = _interopRequireDefault(_error);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

// OCT2DEC converts a octal value into a decimal value.
function oct2dec(octalNumber) {
  // Credits: Based on implementation found in https://gist.github.com/ghalimi/4525876#file-oct2dec-js
  // Return error.when number passed in is not octal or has more than 10 digits
  if (!/^[0-7]{1,10}$/.test(octalNumber)) return _error2.default.num;

  // Convert octal number to decimal number
  var nonNegativeDecimalNumber = parseInt(octalNumber, 8);

  // Returns the corresponding decimal number
  // Two's Complement Decimal Range: -(2^N-1) to (2^N-1 - 1) where N=30 (N = number of bits) and ^ means raised to the power of
  // 2^N-1 = 2^(30 - 1) = 2^29 = 536870912
  // 2^N-1 - 1 = 536870912 - 1 = 536870911
  // 2^N = 2^30 = 1073741824
  // Two's Complement Decimal Range: [-536870912,536870911]
  // Largest octal number allowed: 7777777777 which in decimal is 1073741823 = 2^N - 1
  // Case 1: Negative Range
  //  if nonNegativeDecimalNumber >= 2^N-1, then return (nonNegativeNumber - 2^N)
  //  Smallest Number: 2^N-1 - 2^N = 2^N-1 - 2*2^N-1 = 2^N-1 * (1 - 2) = 2^N-1 * (-1) = -2^N-1
  //  Largest Number: (2^N - 1) - (2^N) = (2^N - 2^N) - 1 = -1
  //  Range: [-2^N-1, -1] = [-536870912, -1]
  //
  // Smallest octal number allowed: 0 which in decimal is 0
  // Case 2: Non-Negative Range
  //   Range: [0, 2^N-1 - 1] = [0, 536870911]

  return nonNegativeDecimalNumber >= 536870912 ? nonNegativeDecimalNumber - 1073741824 : nonNegativeDecimalNumber;
} // Copyright 2015 JC Fisher

module.exports = exports['default'];