mchains/fixed_size/fibonacci/main.cpp

/*
 * Usage of select() with send_case() for calculation of Fibonacci numbers.
 */
 
#include <so_5_extra/mchains/fixed_size.hpp>
 
#include <so_5/all.hpp>
 
#include <chrono>
 
using namespace std;
using namespace std::chrono_literals;
using namespace so_5;
 
struct quit {};
 
void fibonacci( mchain_t values_ch, mchain_t quit_ch )
{
    int x = 0, y = 1;
    mchain_select_result_t r;
    do
    {
        r = select(
            from_all().handle_n(1),
            // Sends a new message of type 'int' with value 'x' inside
            // when values_ch is ready for a new outgoing message.
            send_case( values_ch, message_holder_t<int>::make(x),
                    [&x, &y] { // This block of code will be called after the send().
                        auto old_x = x;
                        x = y; y = old_x + y;
                    } ),
            // Receive a 'quit' message from quit_ch if it is here.
            receive_case( quit_ch, [](quit){} ) );
    }
    // Continue the loop while we send something and receive nothing.
    while( r.was_sent() && !r.was_handled() );
}
 
int main()
{
    wrapped_env_t sobj;
 
    thread fibonacci_thr;
    auto thr_joiner = auto_join( fibonacci_thr );
 
    // The chain for Fibonacci number will have limited capacity.
    auto values_ch = extra::mchains::fixed_size::create_mchain<2>(
            sobj.environment(),
            1s, // Wait no more than 1s on overflow.
            mchain_props::overflow_reaction_t::abort_app );
 
    // The chain for `quit` signal should contant no more than one message.
    auto quit_ch = extra::mchains::fixed_size::create_mchain<1>(
            sobj.environment(),
            mchain_props::overflow_reaction_t::drop_newest );
 
    auto ch_closer = auto_close_drop_content( values_ch, quit_ch );
 
    fibonacci_thr = thread{ fibonacci, values_ch, quit_ch };
 
    // Read the first 10 numbers from values_ch.
    receive( from( values_ch ).handle_n( 10 ),
            // And show every number to the standard output.
            []( int v ) { cout << v << endl; } );
 
    send< quit >( quit_ch );
}