nosqldb-oraclejs/lib/hex2dec.js

Oracle NoSQL Database JS Driver

/*-
 *
 *  This file is part of Oracle NoSQL Database
 *  Copyright (C) 2014, 2018 Oracle and/or its affiliates.  All rights reserved.
 *
 * If you have received this file as part of Oracle NoSQL Database the
 * following applies to the work as a whole:
 *
 *   Oracle NoSQL Database server software is free software: you can
 *   redistribute it and/or modify it under the terms of the GNU Affero
 *   General Public License as published by the Free Software Foundation,
 *   version 3.
 *
 *   Oracle NoSQL Database is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *   Affero General Public License for more details.
 *
 * If you have received this file as part of Oracle NoSQL Database Client or
 * distributed separately the following applies:
 *
 *   Oracle NoSQL Database client software is free software: you can
 *   redistribute it and/or modify it under the terms of the Apache License
 *   as published by the Apache Software Foundation, version 2.0.
 *
 * You should have received a copy of the GNU Affero General Public License
 * and/or the Apache License in the LICENSE file along with Oracle NoSQL
 * Database client or server distribution.  If not, see
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 * or
 * <http://www.apache.org/licenses/LICENSE-2.0>.
 *
 * An active Oracle commercial licensing agreement for this product supersedes
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'use strict';

// Adds two arrays for the given base (10 or 16), returning the result.
// This turns out to be the only 'primitive' operation we need.
function add(x, y, base) {
  var z = [];
  var n = Math.max(x.length, y.length);
  var carry = 0;
  var i = 0;
  while (i < n || carry) {
    var xi = i < x.length ? x[i] : 0;
    var yi = i < y.length ? y[i] : 0;
    var zi = carry + xi + yi;
    z.push(zi % base);
    carry = Math.floor(zi / base);
    i++;
  }
  return z;
}

// Returns a*x, where x is an array of decimal digits and a is an ordinary
// JavaScript number. Base is the number base of the array x.
function multiplyByNumber(num, x, base) {
  if (num < 0) return null;
  if (num == 0) return [];

  var result = [];
  var power = x;
  while (true) {
    if (num & 1) result = add(result, power, base);
    num = num >> 1;
    if (num === 0) break;
    power = add(power, power, base);
  }

  return result;
}

function parseToDigitsArray(str, base) {
  var digits = str.split('');
  var ary = [];
  for (var i = digits.length - 1; i >= 0; i--) {
    var n = parseInt(digits[i], base);
    if (isNaN(n)) return null;
    ary.push(n);
  }
  return ary;
}

function convertBase(str, fromBase, toBase) {
  var digits = parseToDigitsArray(str, fromBase);
  if (digits === null) return null;

  var outArray = [];
  var power = [1];
  for (var i = 0; i < digits.length; i++) {
    // invariant: at this point, fromBase^i = power
    if (digits[i]) outArray =
      add(outArray, multiplyByNumber(digits[i], power, toBase), toBase);
    power = multiplyByNumber(fromBase, power, toBase);
  }

  var out = '';
  for (var i = outArray.length - 1; i >= 0; i--)
    out += outArray[i].toString(toBase);
  return out;
}
exports.convertBase = convertBase;

exports.decToHex = function (decStr) {
  var hex = convertBase(decStr, 10, 16);
  return hex ? '0x' + hex : null;
};

exports.hexToDec = function (hexStr) {
  if (hexStr.substring(0, 2) === '0x') hexStr = hexStr.substring(2);
  hexStr = hexStr.toLowerCase();
  return convertBase(hexStr, 16, 10);
};