| /* |
| * Copyright (C) 2019 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 android.util; |
| |
| import android.annotation.NonNull; |
| |
| /** |
| * CloseGuard is a mechanism for flagging implicit finalizer cleanup of |
| * resources that should have been cleaned up by explicit close |
| * methods (aka "explicit termination methods" in Effective Java). |
| * <p> |
| * A simple example: <pre> {@code |
| * class Foo { |
| * |
| * private final CloseGuard guard = CloseGuard.get(); |
| * |
| * ... |
| * |
| * public Foo() { |
| * ...; |
| * guard.open("cleanup"); |
| * } |
| * |
| * public void cleanup() { |
| * guard.close(); |
| * ...; |
| * if (Build.VERSION.SDK_INT >= 28) { |
| * Reference.reachabilityFence(this); |
| * } |
| * // For full correctness in the absence of a close() call, other methods may also need |
| * // reachabilityFence() calls. |
| * } |
| * |
| * protected void finalize() throws Throwable { |
| * try { |
| * // Note that guard could be null if the constructor threw. |
| * if (guard != null) { |
| * guard.warnIfOpen(); |
| * } |
| * cleanup(); |
| * } finally { |
| * super.finalize(); |
| * } |
| * } |
| * } |
| * }</pre> |
| * |
| * In usage where the resource to be explicitly cleaned up is |
| * allocated after object construction, CloseGuard protection can |
| * be deferred. For example: <pre> {@code |
| * class Bar { |
| * |
| * private final CloseGuard guard = CloseGuard.get(); |
| * |
| * ... |
| * |
| * public Bar() { |
| * ...; |
| * } |
| * |
| * public void connect() { |
| * ...; |
| * guard.open("cleanup"); |
| * } |
| * |
| * public void cleanup() { |
| * guard.close(); |
| * ...; |
| * if (Build.VERSION.SDK_INT >= 28) { |
| * Reference.reachabilityFence(this); |
| * } |
| * // For full correctness in the absence of a close() call, other methods may also need |
| * // reachabilityFence() calls. |
| * } |
| * |
| * protected void finalize() throws Throwable { |
| * try { |
| * // Note that guard could be null if the constructor threw. |
| * if (guard != null) { |
| * guard.warnIfOpen(); |
| * } |
| * cleanup(); |
| * } finally { |
| * super.finalize(); |
| * } |
| * } |
| * } |
| * }</pre> |
| * |
| * When used in a constructor, calls to {@code open} should occur at |
| * the end of the constructor since an exception that would cause |
| * abrupt termination of the constructor will mean that the user will |
| * not have a reference to the object to cleanup explicitly. When used |
| * in a method, the call to {@code open} should occur just after |
| * resource acquisition. |
| */ |
| public final class CloseGuard { |
| private final dalvik.system.CloseGuard mImpl; |
| |
| /** |
| * Constructs a new CloseGuard instance. |
| * {@link #open(String)} can be used to set up the instance to warn on failure to close. |
| */ |
| public CloseGuard() { |
| mImpl = dalvik.system.CloseGuard.get(); |
| } |
| |
| /** |
| * Initializes the instance with a warning that the caller should have explicitly called the |
| * {@code closeMethodName} method instead of relying on finalization. |
| * |
| * @param closeMethodName non-null name of explicit termination method. Printed by warnIfOpen. |
| * @throws NullPointerException if closeMethodName is null. |
| */ |
| public void open(@NonNull String closeMethodName) { |
| mImpl.open(closeMethodName); |
| } |
| |
| /** Marks this CloseGuard instance as closed to avoid warnings on finalization. */ |
| public void close() { |
| mImpl.close(); |
| } |
| |
| /** |
| * Logs a warning if the caller did not properly cleanup by calling an explicit close method |
| * before finalization. |
| */ |
| public void warnIfOpen() { |
| mImpl.warnIfOpen(); |
| } |
| } |