prosody
c3011ab945b8
util/random.lua

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util/random.lua @ 6421:c3011ab945b8

util.random: Ensure at least 4 bytes of previous random state is used when generating new randomness
author Kim Alvefur <zash@zash.se>
date Thu, 18 Sep 2014 10:21:38 +0200
parent 6420:0c070e30a7db
child 7050:ae044691de0f
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bd812a7713ad util.random: Generic util lib for generating strings of random bytes
Matthew Wild <mwild1@gmail.com>
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1 -- Prosody IM
bd812a7713ad util.random: Generic util lib for generating strings of random bytes
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2 -- Copyright (C) 2008-2014 Matthew Wild
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3 -- Copyright (C) 2008-2014 Waqas Hussain
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4 --
bd812a7713ad util.random: Generic util lib for generating strings of random bytes
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5 -- This project is MIT/X11 licensed. Please see the
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6 -- COPYING file in the source package for more information.
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7 --
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8
bd812a7713ad util.random: Generic util lib for generating strings of random bytes
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9 local tostring = tostring;
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10 local os_time = os.time;
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11 local os_clock = os.clock;
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12 local ceil = math.ceil;
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13 local H = require "util.hashes".sha512;
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14
bd812a7713ad util.random: Generic util lib for generating strings of random bytes
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15 local last_uniq_time = 0;
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16 local function uniq_time()
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17 local new_uniq_time = os_time();
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18 if last_uniq_time >= new_uniq_time then new_uniq_time = last_uniq_time + 1; end
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19 last_uniq_time = new_uniq_time;
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20 return new_uniq_time;
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21 end
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22
bd812a7713ad util.random: Generic util lib for generating strings of random bytes
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23 local function new_random(x)
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24 return H(x..os_clock()..tostring({}));
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25 end
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26
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27 local buffer = new_random(uniq_time());
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28
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29 local function seed(x)
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30 buffer = new_random(buffer..x);
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31 end
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32
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33 local function bytes(n)
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34 if #buffer < n+4 then seed(uniq_time()); end
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35 local r = buffer:sub(1, n);
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36 buffer = buffer:sub(n+1);
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37 return r;
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38 end
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39
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40 return {
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41 seed = seed;
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42 bytes = bytes;
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43 };