| /* |
| * Copyright (C) 2011 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package libcore.io; |
| |
| import java.util.Objects; |
| |
| /** @hide */ |
| @libcore.api.CorePlatformApi |
| @libcore.api.IntraCoreApi |
| public final class Libcore { |
| private Libcore() { } |
| |
| /** |
| * Direct access to syscalls. Code should strongly prefer using {@link #os} |
| * unless it has a strong reason to bypass the helpful checks/guards that it |
| * provides. |
| */ |
| public static final Os rawOs = new Linux(); |
| |
| /** |
| * Access to syscalls with helpful checks/guards. |
| * For read access only; the only supported way to update this field is via |
| * {@link #compareAndSetOs}. |
| */ |
| @libcore.api.IntraCoreApi |
| public static volatile Os os = new BlockGuardOs(rawOs); |
| |
| public static Os getOs() { |
| return os; |
| } |
| |
| /** |
| * Updates {@link #os} if {@code os == expect}. The update is atomic with |
| * respect to other invocations of this method. |
| */ |
| public static boolean compareAndSetOs(Os expect, Os update) { |
| Objects.requireNonNull(update); |
| if (os != expect) { |
| return false; |
| } |
| synchronized (Libcore.class) { |
| boolean result = (os == expect); |
| if (result) { |
| os = update; |
| } |
| return result; |
| } |
| } |
| } |