1 /*
   2  * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 package jdk.vm.ci.options;
  24 
  25 import java.io.Serializable;
  26 import java.util.function.Supplier;
  27 
  28 import jdk.vm.ci.options.OptionValue.OverrideScope;
  29 
  30 /**
  31  * A cached value that needs to be recomputed when an option changes.
  32  */
  33 public class DerivedOptionValue<T> {
  34 
  35     public interface OptionSupplier<T> extends Supplier<T>, Serializable {
  36     }
  37 
  38     private final T initialValue;
  39     private final OptionSupplier<T> supplier;
  40 
  41     public DerivedOptionValue(OptionSupplier<T> supplier) {
  42         this.supplier = supplier;
  43         assert OptionValue.getOverrideScope() == null : "derived option value should be initialized outside any override scope";
  44         this.initialValue = createValue();
  45     }
  46 
  47     public T getValue() {
  48         OverrideScope overrideScope = OptionValue.getOverrideScope();
  49         if (overrideScope != null) {
  50             return overrideScope.getDerived(this);
  51         } else {
  52             return initialValue;
  53         }
  54     }
  55 
  56     T createValue() {
  57         return supplier.get();
  58     }
  59 }