/IronPython_Main/Languages/Ruby/Ruby/Runtime/ConstantStorage.cs

/* ****************************************************************************

 *

 * Copyright (c) Microsoft Corporation. 

 *

 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 

 * copy of the license can be found in the License.html file at the root of this distribution. If 

 * you cannot locate the  Apache License, Version 2.0, please send an email to 

 * ironruby@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 

 * by the terms of the Apache License, Version 2.0.

 *

 * You must not remove this notice, or any other, from this software.

 *

 *

 * ***************************************************************************/



using System;

using Microsoft.Scripting.Utils;

using IronRuby.Builtins;



namespace IronRuby.Runtime {

    internal struct ConstantStorage {

        internal static ConstantStorage Removed = new ConstantStorage(false);



        public readonly object Value;

        public readonly WeakReference WeakValue;



        internal bool IsRemoved {

            get { return Value == Removed.Value; }

        }



        internal ConstantStorage(object value) {

            Value = value;



            if (value == null) {

                // We use null as a missing constant sentinel and the real null is wrapped in a singleton WeakRef:

                WeakValue = ConstantSiteCache.WeakNull;

            } else {

                switch (Type.GetTypeCode(value.GetType())) {

                    case TypeCode.Object:

                        RubyModule module = value as RubyModule;

                        if (module != null) {

                            WeakValue = module.WeakSelf;

                        } else {

                            WeakValue = new WeakReference(value);

                        }

                        break;



                    case TypeCode.String:

                        WeakValue = new WeakReference(value);

                        break;



                    default:

                        WeakValue = null;

                        break;

                }

            }

        }



        internal ConstantStorage(object value, WeakReference weakValue) {

            Assert.NotNull(value, weakValue);

            Value = value;

            WeakValue = weakValue;

        }



        private ConstantStorage(bool dummy) {

            Value = new object();

            WeakValue = null;

        }

    }

}