util/uuid.lua

-- Prosody IM

-- Copyright (C) 2008-2010 Matthew Wild

-- Copyright (C) 2008-2010 Waqas Hussain

-- 

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

local m_random = math.random;

local tostring = tostring;

local os_time = os.time;

local os_clock = os.clock;

local sha1 = require "util.hashes".sha1;

module "uuid"

local last_uniq_time = 0;

local function uniq_time()

	local new_uniq_time = os_time();

	if last_uniq_time >= new_uniq_time then new_uniq_time = last_uniq_time + 1; end

	last_uniq_time = new_uniq_time;

	return new_uniq_time;

end

local function new_random(x)

	return sha1(x..os_clock()..tostring({}), true);

end

local buffer = new_random(uniq_time());

local function _seed(x)

	buffer = new_random(buffer..x);

end

local function get_nibbles(n)

	if #buffer < n then _seed(uniq_time()); end

	local r = buffer:sub(0, n);

	buffer = buffer:sub(n+1);

	return r;

end

local function get_twobits()

	return ("%x"):format(get_nibbles(1):byte() % 4 + 8);

end

function generate()

	-- generate RFC 4122 complaint UUIDs (version 4 - random)

	return get_nibbles(8).."-"..get_nibbles(4).."-4"..get_nibbles(3).."-"..(get_twobits())..get_nibbles(3).."-"..get_nibbles(12);

end

seed = _seed;

return _M;