Add MessageHeap a min-heap for Message objects (c840603f) · Commits · e / os / android_frameworks_base

core/java/android/os/Message.java

+5 −1

Original line number	Diff line number	Diff line
		@@ -146,7 +146,11 @@ public final class Message implements Parcelable {
		@VisibleForTesting(visibility = VisibleForTesting.Visibility.PACKAGE)
		public long when;

		/package/ long insertSeq;
		/** @hide */
		public long insertSeq;

		/** @hide */
		public int heapIndex;

		/package/ Bundle data;

core/java/android/os/MessageHeap.java

0 → 100644

+324 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2025 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 athasEqualMessages
		*
		* 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.os;

		import android.os.Message;

		import android.util.Log;

		import androidx.annotation.NonNull;
		import androidx.annotation.Nullable;

		import dalvik.annotation.optimization.NeverCompile;

		import java.util.Arrays;

		/**
		* A min-heap of Message objects. Used by MessageQueue.
		* @hide
		*/
		public final class MessageHeap {
		static final int INITIAL_SIZE = 16;
		static final boolean DEBUG = false;
		private static final String TAG = "MessageHeap";

		Message[] mHeap = new Message[INITIAL_SIZE];
		int mNumElements = 0;

		private static int parentNodeIdx(int i) {
		return (i - 1) >>> 1;
		}

		private @Nullable Message getParentNode(int i) {
		return mHeap[parentNodeIdx(i)];
		}

		private static int rightNodeIdx(int i) {
		return 2 * i + 2;
		}

		private @Nullable Message getRightNode(int i) {
		return mHeap[rightNodeIdx(i)];
		}

		private static int leftNodeIdx(int i) {
		return 2 * i + 1;
		}

		private @Nullable Message getLeftNode(int i) {
		return mHeap[leftNodeIdx(i)];
		}

		public int capacity() {
		return mHeap.length;
		}

		public int size() {
		return mNumElements;
		}

		public boolean isEmpty() {
		return mNumElements == 0;
		}

		@Nullable Message getMessageAt(int index) {
		return mHeap[index];
		}

		/*
		* Returns:
		* 0 if x==y.
		* A value less than 0 if x<y.
		* A value greater than 0 if x>y.
		*/
		private int compareMessagesByIdx(int x, int y) {
		return Message.compareMessages(mHeap[x], mHeap[y]);
		}

		private void swap(int x, int y) {
		Message tmp = mHeap[x];
		mHeap[x] = mHeap[y];
		mHeap[y] = tmp;
		}

		private void siftDown(int i) {
		int smallest = i;
		int right, left;

		while (true) {
		right = rightNodeIdx(i);
		left = leftNodeIdx(i);

		if (right < mNumElements && compareMessagesByIdx(right, smallest) < 0) {
		smallest = right;
		}

		if (left < mNumElements && compareMessagesByIdx(left, smallest) < 0) {
		smallest = left;
		}

		if (smallest != i) {
		swap(i, smallest);
		i = smallest;
		continue;
		}
		break;
		}
		}

		private boolean siftUp(int i) {
		boolean swapped = false;
		/*
		* We never pass null to compareMessages here, mHeap[i] is known to be occupied as is
		* its parent node
		*/
		while (i != 0 && Message.compareMessages(mHeap[i], getParentNode(i)) < 0) {
		int p = parentNodeIdx(i);

		swap(i, p);
		swapped = true;
		i = p;
		}

		return swapped;
		}

		private void maybeGrow() {
		if (mNumElements == mHeap.length) {
		/*
		* Grow by 1.5x. We shrink by a factor of two below to avoid pinging between
		* grow/shrink.
		*/
		int newSize = mHeap.length + (mHeap.length >>> 1);
		Message[] newHeap;
		if (DEBUG) {
		Log.d(TAG, "maybeGrow mNumElements " + mNumElements + " mHeap.length "
		+ mHeap.length + " newSize " + newSize);
		}

		newHeap = Arrays.copyOf(mHeap, newSize);
		mHeap = newHeap;
		}
		}

		public void add(@NonNull Message m) {
		maybeGrow();

		int i = mNumElements++;
		m.heapIndex = i;
		mHeap[i] = m;

		siftUp(i);
		}

		public void maybeShrink() {
		int nextShrinkSize = mHeap.length;
		final int minElem = Math.max(mNumElements, INITIAL_SIZE);
		int newSize = INITIAL_SIZE;
		while (nextShrinkSize > minElem) {
		newSize = nextShrinkSize;
		nextShrinkSize = nextShrinkSize >>> 1;
		}
		if (DEBUG) {
		Log.d(TAG, "maybeShrink chosen new size " + newSize + " mNumElements "
		+ mNumElements + " mHeap.length " + mHeap.length);
		}

		if (newSize >= INITIAL_SIZE
		&& mNumElements <= newSize) {
		Message[] newHeap;

		newHeap = Arrays.copyOf(mHeap, newSize);
		mHeap = newHeap;

		if (DEBUG) {
		Log.d(TAG, "maybeShrink SHRUNK mNumElements " + mNumElements + " mHeap.length "
		+ mHeap.length + " newSize " + newSize);
		}
		}
		}

		public @Nullable Message poll() {
		if (mNumElements > 0) {
		Message ret = mHeap[0];
		mNumElements--;

		mHeap[0] = mHeap[mNumElements];
		mHeap[mNumElements] = null;

		siftDown(0);

		maybeShrink();
		return ret;
		}
		return null;
		}

		public @Nullable Message peek() {
		return mNumElements > 0 ? mHeap[0] : null;
		}

		public void remove(int i) throws IllegalArgumentException {
		if (i >= mNumElements \|\| mNumElements == 0 \|\| i < 0) {
		throw new IllegalArgumentException("Index " + i + " out of bounds: "
		+ mNumElements);
		} else if (i == (mNumElements - 1)) {
		mHeap[i] = null;
		mNumElements--;
		} else {
		mNumElements--;
		mHeap[i] = mHeap[mNumElements];
		mHeap[mNumElements] = null;
		if (!siftUp(i)) {
		siftDown(i);
		}
		}
		/* Don't shink here, let the caller do this once it has removed all matching items. */
		}

		public void removeMessage(@NonNull Message m) throws IllegalArgumentException {
		remove(m.heapIndex);
		}

		public void removeAll() {
		mHeap = new Message[INITIAL_SIZE];
		mNumElements = 0;
		}

		@Override
		public String toString() {
		StringBuilder b = new StringBuilder();
		b.append("MessageHeap size: ");
		b.append(mNumElements);
		b.append(" mHeap.length ");
		b.append(mHeap.length);
		for (int i = 0; i < mNumElements; i++) {
		b.append(" [");
		b.append(i);
		b.append("]\t");
		b.append(mHeap[i].when);
		b.append(" seq: ");
		b.append(mHeap[i].insertSeq);
		b.append(" async: ");
		b.append(mHeap[i].isAsynchronous());
		}
		return b.toString();
		}

		@NeverCompile
		private boolean verify(int root) {
		int right = rightNodeIdx(root);
		int left = leftNodeIdx(root);

		if (left >= mNumElements && right >= mNumElements) {
		return true;
		}

		if (left < mNumElements && compareMessagesByIdx(left, root) < 0) {
		Log.e(TAG, "Verify failure: root idx/when: " + root + "/" + mHeap[root].when
		+ " left node idx/when: " + left + "/" + mHeap[left].when);
		return false;
		}

		if (right < mNumElements && compareMessagesByIdx(right, root) < 0) {
		Log.e(TAG, "Verify failure: root idx/when: " + root + "/" + mHeap[root].when
		+ " right node idx/when: " + right + "/" + mHeap[right].when);
		return false;
		}

		if (!verify(right) \|\| !verify(left)) {
		return false;
		}

		int localHeapCount = 0;
		for (int i = 0; i < mHeap.length; i++) {
		if (mHeap[i] != null) {
		localHeapCount++;
		}
		}

		if (mNumElements != localHeapCount) {
		Log.e(TAG, "Verify failure mNumLElements is " + mNumElements +
		" but I counted " + localHeapCount + " heap elements");
		return false;
		}
		return true;
		}

		@NeverCompile
		private boolean checkDanglingReferences(String where) {
		/* First, let's make sure we didn't leave any dangling references */
		for (int i = mNumElements; i < mHeap.length; i++) {
		if (mHeap[i] != null) {
		Log.e(TAG, "[" + where
		+ "] Verify failure: dangling reference found at index "
		+ i + ": " + mHeap[i] + " Async " + mHeap[i].isAsynchronous()
		+ " mNumElements " + mNumElements + " mHeap.length " + mHeap.length);
		return false;
		}
		}
		return true;
		}

		@NeverCompile
		public boolean verify() {
		if (!checkDanglingReferences("MessageHeap")) {
		return false;
		}
		return verify(0);
		}
		}

core/java/android/os/OWNERS

+1 −0

Original line number	Diff line number	Diff line
		@@ -131,6 +131,7 @@ per-file TestLooperManager.java = file:/MESSAGE_QUEUE_OWNERS
		per-file Handler.java = file:/MESSAGE_QUEUE_OWNERS
		per-file HandlerThread.java = file:/MESSAGE_QUEUE_OWNERS
		per-file HandlerExecutor.java = file:/MESSAGE_QUEUE_OWNERS
		per-file MessageHeap.java = file:/MESSAGE_QUEUE_OWNERS

		# Stats
		per-file IStatsBootstrapAtomService.aidl = file:/services/core/java/com/android/server/stats/OWNERS

core/tests/coretests/src/android/os/MessageHeapTest.java

0 → 100644

+198 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2025 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 athasEqualMessages
		*
		* 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.os;

		import static org.junit.Assert.assertTrue;
		import static org.junit.Assert.fail;

		import android.os.Message;
		import android.os.MessageHeap;

		import android.util.Log;

		import androidx.test.runner.AndroidJUnit4;

		import java.util.concurrent.atomic.AtomicLong;
		import java.util.Random;

		import org.junit.Test;
		import org.junit.runner.RunWith;

		@RunWith(AndroidJUnit4.class)
		public final class MessageHeapTest {
		private static final String TAG = "MessageHeapTest";

		private final AtomicLong mNextInsertSeq = new AtomicLong(1);
		private final AtomicLong mNextFrontInsertSeq = new AtomicLong(-1);

		private final Random mRand = new Random(8675309);

		private void insertMessage(MessageHeap heap, long when) {
		long seq = when != 0 ? mNextInsertSeq.incrementAndGet()
		: mNextFrontInsertSeq.decrementAndGet();

		Message m = new Message();
		m.when = when;
		m.insertSeq = seq;
		heap.add(m);
		}

		private static boolean popAndVerifyUntilEmpty(MessageHeap heap) {
		Message last = null;
		Message m;

		while (!heap.isEmpty()) {
		m = heap.poll();
		if (last != null && m.when < last.when) {
		Log.e(TAG, "popAndVerifyUntilEmpty: heap property broken last: " + last.when
		+ " popped: " + m.when);
		return false;
		}
		last = m;
		}
		return true;
		}

		private static boolean verify(MessageHeap heap) {
		if (!heap.verify()) {
		return false;
		}

		if (!popAndVerifyUntilEmpty(heap)) {
		return false;
		}
		return true;
		}

		private long getPositiveRandLong() {
		try {
		return Math.absExact(mRand.nextLong());
		} catch (ArithmeticException e) {
		return 0;
		}
		}

		private MessageHeap fillWithRandomValues(int numValues) {
		MessageHeap heap = new MessageHeap();
		for (int i = 0; i < numValues; i++) {
		insertMessage(heap, getPositiveRandLong());
		}
		return heap;
		}

		@Test
		public void fillSequentially() {
		MessageHeap heap = new MessageHeap();
		for (int i = 0; i < 4_000; i++) {
		insertMessage(heap, i);
		}
		assertTrue(verify(heap));
		}

		@Test
		public void reverseOrderTest() {
		MessageHeap heap = new MessageHeap();
		for (int i = 99; i >= 90; i--) {
		insertMessage(heap, i);
		}
		assertTrue(verify(heap));
		}

		@Test
		public void zerosTest() {
		MessageHeap heap = new MessageHeap();
		for (int i = 0; i < 10; i++) {
		insertMessage(heap, 0);
		}
		assertTrue(verify(heap));
		}

		@Test
		public void randomValuesTest() {
		final int numValues = 4_000;
		MessageHeap heap = new MessageHeap();
		for (int i = 0; i < numValues; i++) {
		insertMessage(heap, getPositiveRandLong());
		}
		assertTrue(verify(heap));
		}

		@Test
		public void fillWithRandomValuesAndZeros() {
		final int numValues = 4_000;
		MessageHeap heap = fillWithRandomValues(numValues);
		for (int i = 0; i < numValues; i++) {
		long when = getPositiveRandLong();
		if ((when % 4) == 0) {
		when = 0;
		}
		insertMessage(heap, when);
		}
		assertTrue(verify(heap));
		}

		@Test
		public void randomRemoveTest() {
		MessageHeap heap = fillWithRandomValues(4_000);
		for (int i = 0; i < heap.size(); i++) {
		if (mRand.nextBoolean()) {
		heap.remove(i);
		}
		}
		heap.maybeShrink();
		assertTrue(verify(heap));
		}

		@Test
		public void growTest() {
		MessageHeap heap = fillWithRandomValues(4_000);
		assertTrue(verify(heap));
		}

		@Test
		public void shrinkSlightly() {
		MessageHeap heap = fillWithRandomValues(4_000);
		for (int i = 0; i < 1_000; i++) {
		heap.remove(i);
		}
		heap.maybeShrink();
		assertTrue(verify(heap));
		}

		@Test
		public void shrinkCompletely() {
		MessageHeap heap = fillWithRandomValues(4_000);
		heap.removeAll();
		assertTrue(verify(heap));
		}

		@Test
		public void removeBoundsTest() {
		MessageHeap heap = new MessageHeap();
		for (int i = 0; i < 10; i++) {
		insertMessage(heap, 0);
		}
		try {
		heap.remove(heap.size());
		heap.remove(-1);
		fail("Expected IllegalArgumentException for out of bounds test");
		} catch (IllegalArgumentException e) {

		}
		assertTrue(verify(heap));
		}
		}

core/tests/coretests/src/android/os/OWNERS

+1 −0

Original line number	Diff line number	Diff line
		@@ -21,6 +21,7 @@ per-file RemoteCallbackListTest.java = shayba@google.com

		# MessageQueue
		per-file MessageQueueTest.java = file:/MESSAGE_QUEUE_OWNERS
		per-file MessageHeapTest.java = file:/MESSAGE_QUEUE_OWNERS

		# Perfetto SDK
		per-file PerfettoTrace*Test.java = zezeozue@google.com, ktimofeev@google.com