SML (State Machine Language)
Your scalable C++14 one header only State Machine Library with no dependencies
Let's release a TCP connection!
Quick start
Download
[Boost::ext].SML requires only one file. Get the latest header here!
Include
#include <boost/sml.hpp>
namespace sml = boost::sml;
Dependencies
struct sender {
template<class TMsg>
constexpr void send(const TMsg& msg) { std::printf("send: %d\n", msg.id); }
};
Events
struct ack { bool valid{}; };
struct fin { int id{}; bool valid{}; };
struct release {};
struct timeout {};
Guards
constexpr auto is_valid = [](const auto& event) { return event.valid; };
Actions
constexpr auto send_fin = [](sender& s) { s.send(fin{0}); };
constexpr auto send_ack = [](const auto& event, sender& s) { s.send(event); };
State Machine
struct tcp_release {
auto operator()() const {
using namespace sml;
/**
* Initial state: *initial_state
* Transition DSL: src_state + event [ guard ] / action = dst_state
*/
return make_transition_table(
*"established"_s + event<release> / send_fin = "fin wait 1"_s,
"fin wait 1"_s + event<ack> [ is_valid ] = "fin wait 2"_s,
"fin wait 2"_s + event<fin> [ is_valid ] / send_ack = "timed wait"_s,
"timed wait"_s + event<timeout> = X
);
}
};
Usage
int main() {
using namespace sml;
sender s{};
sm<tcp_release> sm{s}; // pass dependencies via ctor
assert(sm.is("established"_s));
sm.process_event(release{}); // complexity O(1)
assert(sm.is("fin wait 1"_s));
sm.process_event(ack{true}); // prints 'send: 0'
assert(sm.is("fin wait 2"_s));
sm.process_event(fin{42, true}); // prints 'send: 42'
assert(sm.is("timed wait"_s));
sm.process_event(timeout{});
assert(sm.is(X)); // terminated
}
MSVC-2015 (Example)
- use
state<class state_name>
instead of"state_name"_s
- expliclty state a lambda's result type
auto action = [] -> void {}
Compile
- GCC/Clang
$CXX -std=c++14 -O2 -fno-exceptions -Wall -Wextra -Werror -pedantic tcp_release.cpp
- MSVC
cl /std:c++14 /Ox /W3 tcp_release.cpp
tcp_release.cpp | Clang-3.8 | GCC-6.3 | MSVC-2015 |
---|---|---|---|
Compilation Time | 0.102s | 0.118s | 0.296s |
Binary size (stripped) | 6.2kb | 6.2kb | 105kb |
ASM x86-64 - https://godbolt.org/z/y99L50 |
|
Run
send: 0
send: 42
Benchmark
Enum/Switch | Variant | [Boost::ext].SML - 1.1.0 | Boost-1.65.MSM-eUML | Boost-1.65.Statechart | |
---|---|---|---|---|---|
Compilation time | 0.132s | 15.321s | 0.582s | 1m15.935s | 5.671s |
Execution time | 679ms | 827ms | 622ms | 664ms | 2282ms |
Memory usage | 1b | 2b/8b | 1b | 120b | 224b |
Executable size | 15K | 187K | 34K | 611K | 211K |
Examples
Documentation
- Introduction
- Overview
- Features/Benchmarks
- Tutorial/Workshop
- UML vs SML
- User Guide
- Examples
- FAQ
- CHANGELOG
Disclaimer [Boost::ext].SML
is not an official Boost library.