prosody
2e75b94e3a1e
util/queue.lua

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util/queue.lua @ 6756:2e75b94e3a1e

mod_storage_sql2: Add prosodyctl command to upgrade tables from the command-line
author Matthew Wild <mwild1@gmail.com>
date Tue, 07 Jul 2015 17:41:09 +0100
parent 6731:d4a6c9ee4bc5
child 6911:56c9bc4ba247
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343ca80ceb36 util.queue: Small fast FIFO/ringbuffer/queue library
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1 -- Prosody IM
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2 -- Copyright (C) 2008-2015 Matthew Wild
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3 -- Copyright (C) 2008-2015 Waqas Hussain
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4 --
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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
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9 -- Small ringbuffer library (i.e. an efficient FIFO queue with a size limit)
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10 -- (because unbounded dynamically-growing queues are a bad thing...)
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11
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12 local have_utable, utable = pcall(require, "util.table"); -- For pre-allocation of table
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13
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14 local function new(size, allow_wrapping)
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15 -- Head is next insert, tail is next read
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16 local head, tail = 1, 1;
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17 local items = 0; -- Number of stored items
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18 local t = have_utable and utable.create(size, 0) or {}; -- Table to hold items
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19
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20 return {
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21 size = size;
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22 count = function (self) return items; end;
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23 push = function (self, item)
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24 if items >= size then
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25 if allow_wrapping then
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26 tail = (tail%size)+1; -- Advance to next oldest item
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27 items = items - 1;
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28 else
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29 return nil, "queue full";
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30 end
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31 end
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32 t[head] = item;
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33 items = items + 1;
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34 head = (head%size)+1;
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35 return true;
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36 end;
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37 pop = function (self)
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38 if items == 0 then
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39 return nil;
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40 end
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41 local item;
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42 item, t[tail] = t[tail], 0;
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43 tail = (tail%size)+1;
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44 items = items - 1;
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45 return item;
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46 end;
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47 peek = function (self)
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48 if items == 0 then
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49 return nil;
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50 end
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51 return t[tail];
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52 end;
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53 };
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54 end
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55
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56 return {
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57 new = new;
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58 };
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59