Expose CloseGuard as a public API (0c472adb) · Commits · e / os / android_frameworks_base

api/current.txt

+7 −0

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		@@ -48244,6 +48244,13 @@ package android.util {
		ctor public Base64OutputStream(java.io.OutputStream, int);
		}

		public final class CloseGuard {
		ctor public CloseGuard();
		method public void close();
		method public void open(@NonNull String);
		method public void warnIfOpen();
		}

		@Deprecated public final class Config {
		field @Deprecated public static final boolean DEBUG = false;
		field @Deprecated public static final boolean LOGD = true;

core/java/android/util/CloseGuard.java

0 → 100644

+138 −0

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		/*
		* 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();
		* ...;
		* }
		*
		* 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();
		* ...;
		* 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();
		}
		}

core/tests/coretests/Android.bp

+1 −0

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		@@ -24,6 +24,7 @@ android_test {
		],
		static_libs: [
		"frameworks-base-testutils",
		"core-test-rules", // for libcore.dalvik.system.CloseGuardSupport
		"core-tests-support",
		"android-common",
		"frameworks-core-util-lib",

core/tests/coretests/src/android/util/CloseGuardTest.java

0 → 100644

+98 −0

Original line number	Diff line number	Diff line
		/*
		* 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 libcore.dalvik.system.CloseGuardSupport;

		import org.junit.Rule;
		import org.junit.Test;
		import org.junit.rules.TestRule;

		/** Unit tests for {@link android.util.CloseGuard} */
		public class CloseGuardTest {

		@Rule
		public final TestRule rule = CloseGuardSupport.getRule();

		@Test
		public void testEnabled_NotOpen() throws Throwable {
		ResourceOwner owner = new ResourceOwner();
		assertUnreleasedResources(owner, 0);
		}

		@Test
		public void testEnabled_OpenNotClosed() throws Throwable {
		ResourceOwner owner = new ResourceOwner();
		owner.open();
		assertUnreleasedResources(owner, 1);
		}

		@Test
		public void testEnabled_OpenThenClosed() throws Throwable {
		ResourceOwner owner = new ResourceOwner();
		owner.open();
		owner.close();
		assertUnreleasedResources(owner, 0);
		}

		@Test(expected = NullPointerException.class)
		public void testOpen_withNullMethodName_throwsNPE() throws Throwable {
		CloseGuard closeGuard = new CloseGuard();
		closeGuard.open(null);
		}

		private void assertUnreleasedResources(ResourceOwner owner, int expectedCount)
		throws Throwable {
		try {
		CloseGuardSupport.getFinalizerChecker().accept(owner, expectedCount);
		} finally {
		// Close the resource so that CloseGuard does not generate a warning for real when it
		// is actually finalized.
		owner.close();
		}
		}

		/**
		* A test user of {@link CloseGuard}.
		*/
		private static class ResourceOwner {

		private final CloseGuard mCloseGuard;

		ResourceOwner() {
		mCloseGuard = new CloseGuard();
		}

		public void open() {
		mCloseGuard.open("close");
		}

		public void close() {
		mCloseGuard.close();
		}

		/**
		* Make finalize public so that it can be tested directly without relying on garbage
		* collection to trigger it.
		*/
		@Override
		public void finalize() throws Throwable {
		mCloseGuard.warnIfOpen();
		super.finalize();
		}
		}
		}