1 files changed, 49 insertions, 0 deletions
diff --git a/server/src/vm/chain.lua b/server/src/vm/chain.lua
new file mode 100644
index 00000000..23b38a75
--- /dev/null
+++ b/server/src/vm/chain.lua
@@ -0,0 +1,49 @@
+local valueMgr = require 'vm.value'
+local sourceMgr = require 'vm.source'
+
+local mt = {}
+mt.__index = mt
+mt.type = 'chain'
+
+mt.min = 100
+mt.max = 100
+mt.count = 0
+
+function mt:clearCache()
+    if self.count <= self.max then
+        return
+    end
+    local n = 0
+    for uri, value in pairs(self.cache) do
+        local ok = value:eachInfo(function ()
+            return true
+        end)
+        if ok then
+            n = n + 1
+        else
+            self.cache[uri] = nil
+        end
+    end
+    self.count = n
+    self.max = self.count * 2
+    if self.max < self.min then
+        self.max = self.min
+    end
+end
+
+function mt:get(uri)
+    if not self.cache[uri] then
+        self.count = self.count + 1
+        self:clearCache()
+        self.cache[uri] = valueMgr.create('any', sourceMgr.dummy())
+        self.cache[uri]:markGlobal()
+        self.cache[uri].uri = uri
+    end
+    return self.cache[uri]
+end
+
+return function ()
+    return setmetatable({
+        cache = {},
+    }, mt)
+end