prosody
d636815d81c3
util/cache.lua

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util/cache.lua @ 6933:d636815d81c3

util.cache: Ordered key->value data structure, with size limit (same as pubsub)
author Matthew Wild <mwild1@gmail.com>
date Tue, 24 Nov 2015 10:44:41 +0000
child 6943:0a31ec3193f0
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 assert(size > 0, "cache size must be greater than zero");
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6 local data = {};
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7 return setmetatable({ data = data, count = 0, size = size, head = nil, tail = nil }, cache_mt);
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8 end
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9
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10 local function _remove(list, m)
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11 if m.prev then
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12 m.prev.next = m.next;
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13 end
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14 if m.next then
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15 m.next.prev = m.prev;
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16 end
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17 if list.tail == m then
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18 list.tail = m.prev;
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19 end
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20 if list.head == m then
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21 list.head = m.next;
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22 end
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23 list.count = list.count - 1;
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24 end
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25
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26 local function _insert(list, m)
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27 if list.head then
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28 list.head.prev = m;
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29 end
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30 m.prev, m.next = nil, list.head;
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31 list.head = m;
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32 if not list.tail then
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33 list.tail = m;
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34 end
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35 list.count = list.count + 1;
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36 end
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37
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38 function cache_methods:set(k, v)
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39 local m = self.data[k];
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40 if m then
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41 -- Key already exists
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42 if v ~= nil then
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43 -- Bump to head of list
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44 _remove(self, m);
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45 _insert(self, m);
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46 m.value = v;
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47 else
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48 -- Remove from list
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49 _remove(self, m);
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50 self.data[k] = nil;
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51 end
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52 return;
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53 end
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54 -- New key
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55 if v == nil then
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56 return;
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57 end
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58 -- Check whether we need to remove oldest k/v
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59 if self.count == self.size then
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60 self.data[self.tail.key] = nil;
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61 _remove(self, self.tail);
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62 end
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63
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64 m = { key = k, value = v, prev = nil, next = nil };
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65 self.data[k] = m;
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66 _insert(self, m);
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67 end
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68
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69 function cache_methods:get(k)
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70 local m = self.data[k];
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71 if m then
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72 return m.value;
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73 end
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74 return nil;
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75 end
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76
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77 function cache_methods:items()
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78 local m = self.head;
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79 return function ()
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80 if not m then
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81 return;
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82 end
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83 local k, v = m.key, m.value;
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84 m = m.next;
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85 return k, v;
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86 end
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87 end
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88
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89 return {
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90 new = new;
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91 }