**
 * UUID.core.js: The minimal subset of the RFC-compliant UUID generator UUID.js.
 *
 * @fileOverview
 * @author  LiosK
 * @version core-1.0
 * @license The MIT License: Copyright (c) 2012 LiosK.
 */

/** @constructor */
function UUID() {}

/**
 * The simplest function to get an UUID string.
 * @returns {string} A version 4 UUID string.
 */
UUID.generate = function() {
  var rand = UUID._gri, hex = UUID._ha;
  return  hex(rand(32), 8)          // time_low
        + "-"
        + hex(rand(16), 4)          // time_mid
        + "-"
        + hex(0x4000 | rand(12), 4) // time_hi_and_version
        + "-"
        + hex(0x8000 | rand(14), 4) // clock_seq_hi_and_reserved clock_seq_low
        + "-"
        + hex(rand(48), 12);        // node
};

/**
 * Returns an unsigned x-bit random integer.
 * @param {int} x A positive integer ranging from 0 to 53, inclusive.
 * @returns {int} An unsigned x-bit random integer (0 <= f(x) < 2^x).
 */
UUID._gri = function(x) { // _getRandomInt
  if (x <   0) return NaN;
  if (x <= 30) return (0 | Math.random() * (1 <<      x));
  if (x <= 53) return (0 | Math.random() * (1 <<     30))
                    + (0 | Math.random() * (1 << x - 30)) * (1 << 30);
  return NaN;
};

/**
 * Converts an integer to a zero-filled hexadecimal string.
 * @param {int} num
 * @param {int} length
 * @returns {string}
 */
UUID._ha = function(num, length) {  // _hexAligner
  var str = num.toString(16), i = length - str.length, z = "0";
  for (; i > 0; i >>>= 1, z += z) { if (i & 1) { str = z + str; } }
  return str;
};