A state machine language DSL based on the syntax of Boost-SML.
The aim of this DSL is to facilitate the use of state machines, as they quite fast can become overly complicated to write and get an overview of.
The DSL is defined as follows:
statemachine!{
*SrcState1 + Event1 [ guard1 ] / action1 = DstState2, // * denotes starting state
SrcState2 + Event2 [ guard2 ] / action2 = DstState1,
// ...
}
Where guard
and action
are optional and can be left out. A guard
is a function which returns true
if the state transition should happen, and false
if the transition should not happen, while action
are functions that are run during the transition which are guaranteed to finish before entering the new state.
This implies that any state machine must be written as a list of transitions.
The state machine needs a context to be defined.
The StateMachineContext
is generated from the statemachine!
proc-macro and is what implements guards and actions, and data that is available in all states within the state machine and persists between state transitions:
statemachine!{
State1 + Event1 = State2,
// ...
}
pub struct Context;
impl StateMachineContext for Context {}
fn main() {
let mut sm = StateMachine::new(Context);
// ...
}
See example examples/context.rs
for a usage example.
Any stat may have some data associated with it (except the starting state), which means that this data is only exists while in this state.
pub struct MyStateData(pub u32);
statemachine!{
State1(MyStateData) + Event1 = State2,
// ...
}
See example examples/state_with_data.rs
for a usage example.
Data may be passed along with an event into the guard
and action
:
pub struct MyEventData(pub u32);
statemachine!{
State1 + Event1(MyEventData) [guard] = State2,
// ...
}
Event data may also have associated lifetimes which the statemachine!
macro will pick up and add the Events
structure. This means the following will also work:
pub struct MyEventData<'a>(pub &'a u32);
statemachine!{
State1 + Event1(MyEventData<'a>) [guard1] = State2,
State1 + Event2(&'a [u8]) [guard2] = State3,
// ...
}
See example examples/event_with_data.rs
for a usage example.
See example examples/guard_action_syntax.rs
for a usage-example.
Here are some examples of state machines converted from UML to the State Machine Language DSL. Runnable versions of each example is available in the examples
folder.
DSL implementation:
statemachine!{
*State1 + Event1 = State2,
State2 + Event2 = State3,
}
This example is available in ex1.rs
.
DSL implementation:
statemachine!{
*State1 + Event1 = State2,
State2 + Event2 = State3,
State3 + Event3 = State2,
}
This example is available in ex2.rs
.
DSL implementation:
statemachine!{
*State1 + Event1 [guard] / action = State2,
}
This example is available in ex3.rs
.
List of contributors in alphabetical order:
- Emil Fresk (@korken89)
Licensed under either of
-
Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
-
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.