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util/cache.lua @ 11110:67fb92e312f1 0.11
mod_websocket: Enforce stanza size limit and close stream
author | Matthew Wild <mwild1@gmail.com> |
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date | Thu, 17 Sep 2020 16:42:36 +0100 |
parent | 8398:3eff1b60269a |
child | 11198:c4c06fbb7d87 |
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local function _remove(list, m) if m.prev then m.prev.next = m.next; end if m.next then m.next.prev = m.prev; end if list._tail == m then list._tail = m.prev; end if list._head == m then list._head = m.next; end list._count = list._count - 1; end local function _insert(list, m) if list._head then list._head.prev = m; end m.prev, m.next = nil, list._head; list._head = m; if not list._tail then list._tail = m; end list._count = list._count + 1; end local cache_methods = {}; local cache_mt = { __index = cache_methods }; function cache_methods:set(k, v) local m = self._data[k]; if m then -- Key already exists if v ~= nil then -- Bump to head of list _remove(self, m); _insert(self, m); m.value = v; else -- Remove from list _remove(self, m); self._data[k] = nil; end return true; end -- New key if v == nil then return true; end -- Check whether we need to remove oldest k/v if self._count == self.size then local tail = self._tail; local on_evict, evicted_key, evicted_value = self._on_evict, tail.key, tail.value; if on_evict ~= nil and (on_evict == false or on_evict(evicted_key, evicted_value) == false) then -- Cache is full, and we're not allowed to evict return false; end _remove(self, tail); self._data[evicted_key] = nil; end m = { key = k, value = v, prev = nil, next = nil }; self._data[k] = m; _insert(self, m); return true; end function cache_methods:get(k) local m = self._data[k]; if m then return m.value; end return nil; end function cache_methods:items() local m = self._head; return function () if not m then return; end local k, v = m.key, m.value; m = m.next; return k, v; end end function cache_methods:values() local m = self._head; return function () if not m then return; end local v = m.value; m = m.next; return v; end end function cache_methods:count() return self._count; end function cache_methods:head() local head = self._head; if not head then return nil, nil; end return head.key, head.value; end function cache_methods:tail() local tail = self._tail; if not tail then return nil, nil; end return tail.key, tail.value; end function cache_methods:resize(new_size) new_size = assert(tonumber(new_size), "cache size must be a number"); new_size = math.floor(new_size); assert(new_size > 0, "cache size must be greater than zero"); local on_evict = self._on_evict; while self._count > new_size do local tail = self._tail; local evicted_key, evicted_value = tail.key, tail.value; if on_evict ~= nil and (on_evict == false or on_evict(evicted_key, evicted_value) == false) then -- Cache is full, and we're not allowed to evict return false; end _remove(self, tail); self._data[evicted_key] = nil; end self.size = new_size; return true; end function cache_methods:table() --luacheck: ignore 212/t if not self.proxy_table then self.proxy_table = setmetatable({}, { __index = function (t, k) return self:get(k); end; __newindex = function (t, k, v) if not self:set(k, v) then error("failed to insert key into cache - full"); end end; __pairs = function (t) return self:items(); end; __len = function (t) return self:count(); end; }); end return self.proxy_table; end function cache_methods:clear() self._data = {}; self._count = 0; self._head = nil; self._tail = nil; end local function new(size, on_evict) size = assert(tonumber(size), "cache size must be a number"); size = math.floor(size); assert(size > 0, "cache size must be greater than zero"); local data = {}; return setmetatable({ _data = data, _count = 0, size = size, _head = nil, _tail = nil, _on_evict = on_evict }, cache_mt); end return { new = new; }