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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 --luacheck: ignore 212/self |
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20 return { |
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21 _items = t; |
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22 size = size; |
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23 count = function (self) return items; end; |
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24 push = function (self, item) |
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25 if items >= size then |
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26 if allow_wrapping then |
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27 tail = (tail%size)+1; -- Advance to next oldest item |
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28 items = items - 1; |
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29 else |
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30 return nil, "queue full"; |
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31 end |
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32 end |
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33 t[head] = item; |
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34 items = items + 1; |
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35 head = (head%size)+1; |
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36 return true; |
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37 end; |
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38 pop = function (self) |
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39 if items == 0 then |
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40 return nil; |
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41 end |
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42 local item; |
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43 item, t[tail] = t[tail], 0; |
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44 tail = (tail%size)+1; |
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45 items = items - 1; |
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46 return item; |
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47 end; |
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48 peek = function (self) |
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49 if items == 0 then |
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50 return nil; |
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51 end |
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52 return t[tail]; |
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53 end; |
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54 replace = function (self, data) |
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55 if items == 0 then |
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56 return self:push(data); |
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57 end |
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58 t[tail] = data; |
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59 return true; |
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60 end; |
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61 items = function (self) |
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62 return function (_, pos) |
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63 if pos >= items then |
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64 return nil; |
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65 end |
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66 local read_pos = tail + pos; |
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67 if read_pos > self.size then |
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68 read_pos = (read_pos%size); |
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69 end |
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70 return pos+1, t[read_pos]; |
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71 end, self, 0; |
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72 end; |
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73 consume = function (self) |
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74 return self.pop, self; |
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75 end; |
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76 }; |
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77 end |
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78 |
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79 return { |
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80 new = new; |
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81 }; |
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82 |