-local cache_methods = {};
-local cache_mt = { __index = cache_methods };
-
-local function new(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 }, cache_mt);
-end
local function _remove(list, m)
if m.prev then
if m.next then
m.next.prev = m.prev;
end
- if list.tail == m then
- list.tail = m.prev;
+ if list._tail == m then
+ list._tail = m.prev;
end
- if list.head == m then
- list.head = m.next;
+ if list._head == m then
+ list._head = m.next;
end
- list.count = list.count - 1;
+ list._count = list._count - 1;
end
local function _insert(list, m)
- if list.head then
- list.head.prev = 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;
+ m.prev, m.next = nil, list._head;
+ list._head = m;
+ if not list._tail then
+ list._tail = m;
end
- list.count = list.count + 1;
+ 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];
+ local m = self._data[k];
if m then
-- Key already exists
if v ~= nil then
else
-- Remove from list
_remove(self, m);
- self.data[k] = nil;
+ self._data[k] = nil;
end
- return;
+ return true;
end
-- New key
if v == nil then
- return;
+ return true;
end
-- Check whether we need to remove oldest k/v
- if self.count == self.size then
- self.data[self.tail.key] = nil;
- _remove(self, self.tail);
+ 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;
+ self._data[k] = m;
_insert(self, m);
+ return true;
end
function cache_methods:get(k)
- local m = self.data[k];
+ local m = self._data[k];
if m then
return m.value;
end
end
function cache_methods:items()
- local m = self.head;
+ local m = self._head;
return function ()
if not m then
return;
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:table()
+ 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
+
+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;
}