prosody
0a31ec3193f0
util/cache.lua

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util/cache.lua @ 6943:0a31ec3193f0

util.cache: Make sure cache size is specified as an integer
author Kim Alvefur <zash@zash.se>
date Wed, 25 Nov 2015 20:49:41 +0100
parent 6933:d636815d81c3
child 6945:d779c55058c6
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
6933
d636815d81c3 util.cache: Ordered key->value data structure, with size limit (same as pubsub)
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1 local cache_methods = {};
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2 local cache_mt = { __index = cache_methods };
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3
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4 local function new(size)
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5 size = assert(tonumber(size), "cache size must be a number");
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6 size = math.floor(size);
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7 assert(size > 0, "cache size must be greater than zero");
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8 local data = {};
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9 return setmetatable({ data = data, count = 0, size = size, head = nil, tail = nil }, cache_mt);
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10 end
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11
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12 local function _remove(list, m)
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13 if m.prev then
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14 m.prev.next = m.next;
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15 end
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16 if m.next then
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17 m.next.prev = m.prev;
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18 end
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19 if list.tail == m then
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20 list.tail = m.prev;
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21 end
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22 if list.head == m then
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23 list.head = m.next;
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24 end
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25 list.count = list.count - 1;
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26 end
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27
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28 local function _insert(list, m)
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29 if list.head then
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30 list.head.prev = m;
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31 end
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32 m.prev, m.next = nil, list.head;
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33 list.head = m;
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34 if not list.tail then
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35 list.tail = m;
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36 end
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37 list.count = list.count + 1;
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38 end
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39
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40 function cache_methods:set(k, v)
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41 local m = self.data[k];
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42 if m then
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43 -- Key already exists
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44 if v ~= nil then
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45 -- Bump to head of list
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46 _remove(self, m);
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47 _insert(self, m);
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48 m.value = v;
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49 else
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50 -- Remove from list
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51 _remove(self, m);
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52 self.data[k] = nil;
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53 end
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54 return;
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55 end
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56 -- New key
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57 if v == nil then
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58 return;
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59 end
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60 -- Check whether we need to remove oldest k/v
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61 if self.count == self.size then
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62 self.data[self.tail.key] = nil;
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63 _remove(self, self.tail);
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64 end
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65
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66 m = { key = k, value = v, prev = nil, next = nil };
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67 self.data[k] = m;
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68 _insert(self, m);
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69 end
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70
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71 function cache_methods:get(k)
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72 local m = self.data[k];
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73 if m then
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74 return m.value;
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75 end
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76 return nil;
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77 end
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78
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79 function cache_methods:items()
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80 local m = self.head;
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81 return function ()
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82 if not m then
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83 return;
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84 end
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85 local k, v = m.key, m.value;
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86 m = m.next;
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87 return k, v;
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88 end
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89 end
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90
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91 return {
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92 new = new;
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93 }