Annotate

util/cache.lua @ 6997:0ab228bc21c6

util.datamanager: Handle potential issues from fallocate
author Kim Alvefur <zash@zash.se>
date Fri, 11 Dec 2015 20:24:36 +0100
parent 6945:d779c55058c6
child 7016:e0a0af42b09f
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1
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2 local function _remove(list, m)
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3 if m.prev then
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4 m.prev.next = m.next;
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5 end
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6 if m.next then
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7 m.next.prev = m.prev;
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8 end
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9 if list._tail == m then
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10 list._tail = m.prev;
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11 end
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12 if list._head == m then
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13 list._head = m.next;
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14 end
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15 list._count = list._count - 1;
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16 end
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17
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18 local function _insert(list, m)
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19 if list._head then
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20 list._head.prev = m;
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21 end
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22 m.prev, m.next = nil, list._head;
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23 list._head = m;
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24 if not list._tail then
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25 list._tail = m;
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26 end
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27 list._count = list._count + 1;
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28 end
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29
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30 local cache_methods = {};
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31 local cache_mt = { __index = cache_methods };
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32
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33 function cache_methods:set(k, v)
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34 local m = self._data[k];
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35 if m then
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36 -- Key already exists
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37 if v ~= nil then
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38 -- Bump to head of list
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39 _remove(self, m);
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40 _insert(self, m);
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41 m.value = v;
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42 else
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43 -- Remove from list
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44 _remove(self, m);
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45 self._data[k] = nil;
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46 end
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47 return true;
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48 end
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49 -- New key
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50 if v == nil then
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51 return true;
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52 end
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53 -- Check whether we need to remove oldest k/v
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54 if self._count == self.size then
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55 local tail = self._tail;
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56 local on_evict = self._on_evict;
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57 if on_evict then
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58 on_evict(tail.key, tail.value);
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59 end
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60 _remove(self, tail);
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61 self._data[tail.key] = nil;
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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 return true;
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68 end
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69
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70 function cache_methods:get(k)
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71 local m = self._data[k];
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72 if m then
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73 return m.value;
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74 end
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75 return nil;
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76 end
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77
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78 function cache_methods:items()
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79 local m = self._head;
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80 return function ()
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81 if not m then
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82 return;
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83 end
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84 local k, v = m.key, m.value;
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85 m = m.next;
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86 return k, v;
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87 end
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88 end
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89
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90 function cache_methods:count()
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91 return self._count;
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92 end
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93
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94 local function new(size, on_evict)
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95 size = assert(tonumber(size), "cache size must be a number");
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96 size = math.floor(size);
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97 assert(size > 0, "cache size must be greater than zero");
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98 local data = {};
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99 return setmetatable({ _data = data, _count = 0, size = size, _head = nil, _tail = nil, _on_evict = on_evict }, cache_mt);
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100 end
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101
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102 return {
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103 new = new;
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104 }