#32 new threaded PLC code

scada-common/mqueue.lua

@@ -0,0 +1,59 @@
+--
+-- Message Queue
+--
+
+TYPE = {
+    COMMAND = 0,
+    DATA = 1,
+    PACKET = 2
+}
+
+function new()
+    local queue = {}
+
+    local length = function ()
+        return #queue
+    end
+
+    local empty = function ()
+        return #queue == 0
+    end
+
+    local ready = function ()
+        return #queue > 0
+    end
+    
+    local _push = function (qtype, message)
+        table.insert(queue, { qtype = qtype, message = message })
+    end
+    
+    local push_command = function (message)
+        _push(TYPE.COMMAND, message)
+    end
+
+    local push_data = function (message)
+        _push(TYPE.DATA, message)
+    end
+
+    local push_packet = function (message)
+        _push(TYPE.PACKET, message)
+    end
+
+    local pop = function ()
+        if #queue > 0 then
+            return table.remove(queue)
+        else 
+            return nil
+        end
+    end
+
+    return {
+        length = length,
+        empty = empty,
+        ready = ready,
+        push_packet = push_packet,
+        push_data = push_data,
+        push_command = push_command,
+        pop = pop
+    }
+end