js uuid 算法 转

/*

uuid.js - Version 0.3
JavaScript Class to create a UUID like identifier

Copyright (C) 2006-2008, Erik Giberti (AF-Design), All rights reserved.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.

This program 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 General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place, Suite 330, Boston, MA 02111-1307 USA

The latest version of this file can be downloaded from
http://www.af-design.com/resources/javascript_uuid.php

HISTORY:
6/5/06     - Initial Release
5/22/08 - Updated code to run faster, removed randrange(min,max) in favor of
          a simpler rand(max) function. Reduced overhead by using getTime()
          method of date class (suggestion by James Hall).
9/5/08    - Fixed a bug with rand(max) and additional efficiencies pointed out
      by Robert Kieffer http://broofa.com/

KNOWN ISSUES:
- Still no way to get MAC address in JavaScript
- Research into other versions of UUID show promising possibilities
  (more research needed)
- Documentation needs improvement

*/

// On creation of a UUID object, set it's initial value
function UUID(){
    this.id = this.createUUID();
}

// When asked what this Object is, lie and return it's value
UUID.prototype.valueOf = function(){ return this.id; }
UUID.prototype.toString = function(){ return this.id; }

//
// INSTANCE SPECIFIC METHODS
//

UUID.prototype.createUUID = function(){
    //
    // Loose interpretation of the specification DCE 1.1: Remote Procedure Call
    // described at http://www.opengroup.org/onlinepubs/009629399/apdxa.htm#tagtcjh_37
    // since JavaScript doesn't allow access to internal systems, the last 48 bits
    // of the node section is made up using a series of random numbers (6 octets long).
    // 
    var dg = new Date(1582, 10, 15, 0, 0, 0, 0);
    var dc = new Date();
    var t = dc.getTime() - dg.getTime();
    var tl = UUID.getIntegerBits(t,0,31);
    var tm = UUID.getIntegerBits(t,32,47);
    var thv = UUID.getIntegerBits(t,48,59) + '1'; // version 1, security version is 2
    var csar = UUID.getIntegerBits(UUID.rand(4095),0,7);
    var csl = UUID.getIntegerBits(UUID.rand(4095),0,7);

    // since detection of anything about the machine/browser is far to buggy,
    // include some more random numbers here
    // if NIC or an IP can be obtained reliably, that should be put in
    // here instead.
    var n = UUID.getIntegerBits(UUID.rand(8191),0,7) +
            UUID.getIntegerBits(UUID.rand(8191),8,15) +
            UUID.getIntegerBits(UUID.rand(8191),0,7) +
            UUID.getIntegerBits(UUID.rand(8191),8,15) +
            UUID.getIntegerBits(UUID.rand(8191),0,15); // this last number is two octets long
    return tl + tm  + thv  + csar + csl + n;
}


//
// GENERAL METHODS (Not instance specific)
//


// Pull out only certain bits from a very large integer, used to get the time
// code information for the first part of a UUID. Will return zero's if there
// aren't enough bits to shift where it needs to.
UUID.getIntegerBits = function(val,start,end){
    var base16 = UUID.returnBase(val,16);
    var quadArray = new Array();
    var quadString = '';
    var i = 0;
    for(i=0;i<base16.length;i++){
        quadArray.push(base16.substring(i,i+1));   
    }
    for(i=Math.floor(start/4);i<=Math.floor(end/4);i++){
        if(!quadArray[i] || quadArray[i] == '') quadString += '0';
        else quadString += quadArray[i];
    }
    return quadString;
}

// Replaced from the original function to leverage the built in methods in
// JavaScript. Thanks to Robert Kieffer for pointing this one out
UUID.returnBase = function(number, base){
    return (number).toString(base).toUpperCase();
}

// pick a random number within a range of numbers
// int b rand(int a); where 0 <= b <= a
UUID.rand = function(max){
    return Math.floor(Math.random() * (max + 1));
}

// end of UUID class file
/*
for(var i = 0; i < 10; i++){
    document.write(new UUID().id);
    document.write("<br/>");
}
*/