js UUID

/*!
Math.uuid.js (v1.4) http://www.broofa.com mailto:robert@broofa.com

Copyright (c) 2010 Robert Kieffer
Dual licensed under the MIT and GPL licenses.
*/

/*
* Generate a random uuid.
*
* USAGE: Math.uuid(length, radix)
*   length - the desired number of characters
*   radix  - the number of allowable values for each character.
*
* EXAMPLES:
*   // No arguments  - returns RFC4122, version 4 ID
*   >>> Math.uuid()
*   "92329D39-6F5C-4520-ABFC-AAB64544E172"
*
*   // One argument - returns ID of the specified length
*   >>> Math.uuid(15)     // 15 character ID (default base=62)
*   "VcydxgltxrVZSTV"
*
*   // Two arguments - returns ID of the specified length, and radix. (Radix must be <= 62)
*   >>> Math.uuid(8, 2)  // 8 character ID (base=2)
*   "01001010"
*   >>> Math.uuid(8, 10) // 8 character ID (base=10)
*   "47473046"
*   >>> Math.uuid(8, 16) // 8 character ID (base=16)
*   "098F4D35"
*/
(function() {
// Private array of chars to use
var CHARS = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.split('');

Math.uuid = function (len, radix) {
var chars = CHARS, uuid = [], i;
radix = radix || chars.length;

if (len) {
// Compact form
for (i = 0; i < len; i++) uuid[i] = chars[0 | Math.random()*radix];
} else {
// rfc4122, version 4 form
var r;

// rfc4122 requires these characters
uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
uuid[14] = '4';

// Fill in random data.  At i==19 set the high bits of clock sequence as
// per rfc4122, sec. 4.1.5
for (i = 0; i < 36; i++) {
if (!uuid[i]) {
r = 0 | Math.random()*16;
uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];
}
}
}

return uuid.join('');
};

// A more performant, but slightly bulkier, RFC4122v4 solution.  We boost performance
// by minimizing calls to random()
Math.uuidFast = function() {
var chars = CHARS, uuid = new Array(36), rnd=0, r;
for (var i = 0; i < 36; i++) {
if (i==8 || i==13 ||  i==18 || i==23) {
uuid[i] = '-';
} else if (i==14) {
uuid[i] = '4';
} else {
if (rnd <= 0x02) rnd = 0x2000000 + (Math.random()*0x1000000)|0;
r = rnd & 0xf;
rnd = rnd >> 4;
uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];
}
}
return uuid.join('');
};

// A more compact, but less performant, RFC4122v4 solution:
Math.uuidCompact = function() {
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);
return v.toString(16);
});
};
})();

//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
// 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;
};

//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));
};