source: libcfa/src/concurrency/future.hfa@ becb85b9

//
// Cforall Version 1.0.0 Copyright (C) 2020 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// io/types.hfa --
//
// Author           : Thierry Delisle & Peiran Hong
// Created On       : Wed Jan 06 17:33:18 2021
// Last Modified By :
// Last Modified On :
// Update Count     :
//

#pragma once

#include "bits/locks.hfa"
#include "monitor.hfa"

forall( T ) {
        struct future {
                inline future_t;
                T result;
        };

        static inline {
                // Reset future back to original state
                void reset(future(T) & this) { reset( (future_t&)this ); }

                // check if the future is available
                bool available( future(T) & this ) { return available( (future_t&)this ); }

                // Mark the future as abandoned, meaning it will be deleted by the server
                // This doesn't work beause of the potential need for a destructor
                void abandon( future(T) & this );

                // Fulfil the future, returns whether or not someone was unblocked
                thread$ * fulfil( future(T) & this, T result ) {
                        this.result = result;
                        return fulfil( (future_t&)this );
                }

                // Wait for the future to be fulfilled
                // Also return whether the thread had to block or not
                [T, bool] wait( future(T) & this ) {
                        bool r = wait( (future_t&)this );
                        return [this.result, r];
                }

                // Wait for the future to be fulfilled
                T wait( future(T) & this ) {
                        [T, bool] tt;
                        tt = wait(this);
                        return tt.0;
                }
        }
}

forall( T ) {
        monitor multi_future {
                inline future_t;
                condition blocked;
                bool has_first;
                T result;
        };

        static inline {
                void ?{}(multi_future(T) & this) {
                        this.has_first = false;
                }

                bool $first( multi_future(T) & mutex this ) {
                        if (this.has_first) {
                                wait( this.blocked );
                                return false;
                        }

                        this.has_first = true;
                        return true;
                }

                void $first_done( multi_future(T) & mutex this ) {
                        this.has_first = false;
                        signal_all( this.blocked );
                }

                // Reset future back to original state
                void reset(multi_future(T) & mutex this) {
                        if( this.has_first != false) abort("Attempting to reset a multi_future with at least one blocked threads");
                        if( !is_empty(this.blocked) ) abort("Attempting to reset a multi_future with multiple blocked threads");
                        reset( (future_t&)this );
                }

                // Fulfil the future, returns whether or not someone was unblocked
                bool fulfil( multi_future(T) & this, T result ) {
                        this.result = result;
                        return fulfil( (future_t&)this ) != 0p;
                }

                // Wait for the future to be fulfilled
                // Also return whether the thread had to block or not
                [T, bool] wait( multi_future(T) & this ) {
                        bool sw = $first( this );
                        bool w = !sw;
                        if ( sw ) {
                                w = wait( (future_t&)this );
                                $first_done( this );
                        }

                        return [this.result, w];
                }

                // Wait for the future to be fulfilled
                T wait( multi_future(T) & this ) {
                        return wait(this).0;
                }
        }
}