How to generate Lua Code from State Diagrams

Lua is a powerful, efficient, lightweight, embeddable scripting language (http://www.lua.org/). To generate Lua code call the code generator with the command line flag -l lua .

The generator generates one Lua module which implements the complete state machine. Take this simple state machine as example.

For a simple state machine with 4 states and 2 events the generated module looks like this:

function testcase:new()
        local new_inst = {}
        setmetatable( new_inst, testcase)
 
        -- machine states
        new_inst.states = {
                S1="S1",
                S11="S11",
                S12="S12",
                S3="S3",
                __UNKNOWN_STATE__="__UNKNOWN_STATE__"
        }
 
        -- machine events
        new_inst.events = {
                evB="evB",
                evA="evA",
                TESTCASE_NO_MSG="TESTCASE_NO_MSG"
        }
 
        -- Set state vars to default states
        new_inst.stateVar = new_inst.states.S1
        new_inst.stateVarS1 = new_inst.states.S11 -- set init state of S1 
 
        new_inst.init=false
        return new_inst
end
 
function testcase:processEvent(Event)
...
return evConsumed;
end
 
return testcase

The statemachine can be used as follows:

testcase = require "testcase"
 
local testcase1 = testcase:new()
Event = {event = testcase1.events.TESTCASE_NO_MSG, condition=false};
testcase1:processEvent(Event)
 
Event.event=testcase1.events.evA;
testcase1:processEvent(Event)

The following state machine features are supported:

• States and sub-states
• Deep – and flat hierarchy
• Entry, Exit and Action code of states
• Regions are supported and implemented as sub-functions called from the main state machine handler
• Choice pseudo-states

The complete example is available in the examples/microwave_handbook_lua folder.

Any feedback is highly welcome!