////////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   ExtensionContract.sg
//

// This is the base contract to be used, and overridden by, every
// system extension loaded as a child process.

using Microsoft.Singularity.Directory;

namespace Microsoft.Singularity.Extending
{
    public contract ExtensionContract : ServiceContract
    {
        in message Shutdown();     // Shutdown the extension gracefully.
        out message AckShutdown();
        out message NakShutdown();

        out message Success();

        override state Start: one {
            Success! -> Ready;
        }

        state Ready: one
        {
            Shutdown? -> (AckShutdown! or NakShutdown!) -> Ready;
            // AckShutdown should really go to done.
        }
    }
}