util.cache: Small update to prefix private fields with an underscore, add a :count...

diff --git a/util/cache.lua b/util/cache.lua
index 32670751f8be5133186a770f4daa12248b63341f..72b74351a37733e2374abb6b0a5b602043ff3f71 100644 (file)
--- a/util/cache.lua
+++ b/util/cache.lua
@@ -1,13 +1,3 @@
-local cache_methods = {};
-local cache_mt = { __index = cache_methods };
-
-local function new(size)
-       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 }, cache_mt);
-end
 
 local function _remove(list, m)
        if m.prev then
@@ -16,29 +6,32 @@ local function _remove(list, m)
        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
@@ -49,27 +42,33 @@ function cache_methods:set(k, v)
                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 = self._on_evict;
+               if on_evict then
+                       on_evict(tail.key, tail.value);
+               end
+               _remove(self, tail);
+               self._data[tail.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
@@ -77,7 +76,7 @@ function cache_methods:get(k)
 end
 
 function cache_methods:items()
-       local m = self.head;
+       local m = self._head;
        return function ()
                if not m then
                        return;
@@ -88,6 +87,18 @@ function cache_methods:items()
        end
 end
 
+function cache_methods:count()
+       return self._count;
+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;
 }