--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/serve/util/cache.lua Tue Sep 11 23:27:56 2018 +0100
@@ -0,0 +1,178 @@
+
+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;
+}