First draft of StatsEvent.java (ffca2a35) · Commits · e / os / android_frameworks_base

core/java/android/util/StatsEvent.java

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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 static java.nio.charset.StandardCharsets.UTF_8;

		import android.annotation.NonNull;
		import android.annotation.Nullable;

		import com.android.internal.annotations.GuardedBy;

		/**
		* StatsEvent builds and stores the buffer sent over the statsd socket.
		* This class defines and encapsulates the socket protocol.
		* @hide
		**/
		public final class StatsEvent implements AutoCloseable {
		private static final int POS_NUM_ELEMENTS = 1;
		private static final int POS_TIMESTAMP = POS_NUM_ELEMENTS + 1;

		private static final int LOGGER_ENTRY_MAX_PAYLOAD = 4068;

		// Max payload size is 4 KB less 4 bytes which are reserved for statsEventTag.
		// See android_util_StatsLog.cpp.
		private static final int MAX_EVENT_PAYLOAD = LOGGER_ENTRY_MAX_PAYLOAD - 4;

		private static final byte INT_TYPE = 0;
		private static final byte LONG_TYPE = 1;
		private static final byte STRING_TYPE = 2;
		private static final byte LIST_TYPE = 3;
		private static final byte FLOAT_TYPE = 4;

		private static final int INT_TYPE_SIZE = 5;
		private static final int FLOAT_TYPE_SIZE = 5;
		private static final int LONG_TYPE_SIZE = 9;

		private static final int STRING_TYPE_OVERHEAD = 5;
		private static final int LIST_TYPE_OVERHEAD = 2;

		public static final int SUCCESS = 0;
		public static final int ERROR_BUFFER_LIMIT_EXCEEDED = -1;
		public static final int ERROR_NO_TIMESTAMP = -2;
		public static final int ERROR_TIMESTAMP_ALREADY_WRITTEN = -3;
		public static final int ERROR_NO_ATOM_ID = -4;
		public static final int ERROR_ATOM_ID_ALREADY_WRITTEN = -5;
		public static final int ERROR_UID_TAG_COUNT_MISMATCH = -6;

		private static Object sLock = new Object();

		@GuardedBy("sLock")
		private static StatsEvent sPool;

		private final byte[] mBuffer = new byte[MAX_EVENT_PAYLOAD];
		private int mPos;
		private int mNumElements;
		private int mAtomId;

		private StatsEvent() {
		// Write LIST_TYPE to buffer
		mBuffer[0] = LIST_TYPE;
		reset();
		}

		private void reset() {
		// Reset state.
		mPos = POS_TIMESTAMP;
		mNumElements = 0;
		mAtomId = 0;
		}

		/**
		* Returns a StatsEvent object from the pool.
		**/
		@NonNull
		public static StatsEvent obtain() {
		final StatsEvent statsEvent;
		synchronized (sLock) {
		statsEvent = null == sPool ? new StatsEvent() : sPool;
		sPool = null;
		}
		statsEvent.reset();
		return statsEvent;
		}

		@Override
		public void close() {
		synchronized (sLock) {
		if (null == sPool) {
		sPool = this;
		}
		}
		}

		/**
		* Writes the event timestamp to the buffer.
		**/
		public int writeTimestampNs(final long timestampNs) {
		if (hasTimestamp()) {
		return ERROR_TIMESTAMP_ALREADY_WRITTEN;
		}
		return writeLong(timestampNs);
		}

		private boolean hasTimestamp() {
		return mPos > POS_TIMESTAMP;
		}

		private boolean hasAtomId() {
		return mAtomId != 0;
		}

		/**
		* Writes the atom id to the buffer.
		**/
		public int writeAtomId(final int atomId) {
		if (!hasTimestamp()) {
		return ERROR_NO_TIMESTAMP;
		} else if (hasAtomId()) {
		return ERROR_ATOM_ID_ALREADY_WRITTEN;
		}

		final int writeResult = writeInt(atomId);
		if (SUCCESS == writeResult) {
		mAtomId = atomId;
		}
		return writeResult;
		}

		/**
		* Appends the given int to the StatsEvent buffer.
		**/
		public int writeInt(final int value) {
		if (!hasTimestamp()) {
		return ERROR_NO_TIMESTAMP;
		} else if (!hasAtomId()) {
		return ERROR_NO_ATOM_ID;
		} else if (mPos + INT_TYPE_SIZE > MAX_EVENT_PAYLOAD) {
		return ERROR_BUFFER_LIMIT_EXCEEDED;
		}

		mBuffer[mPos] = INT_TYPE;
		copyInt(mBuffer, mPos + 1, value);
		mPos += INT_TYPE_SIZE;
		mNumElements++;
		return SUCCESS;
		}

		/**
		* Appends the given long to the StatsEvent buffer.
		**/
		public int writeLong(final long value) {
		if (!hasTimestamp()) {
		return ERROR_NO_TIMESTAMP;
		} else if (!hasAtomId()) {
		return ERROR_NO_ATOM_ID;
		} else if (mPos + LONG_TYPE_SIZE > MAX_EVENT_PAYLOAD) {
		return ERROR_BUFFER_LIMIT_EXCEEDED;
		}

		mBuffer[mPos] = LONG_TYPE;
		copyLong(mBuffer, mPos + 1, value);
		mPos += LONG_TYPE_SIZE;
		mNumElements++;
		return SUCCESS;
		}

		/**
		* Appends the given float to the StatsEvent buffer.
		**/
		public int writeFloat(final float value) {
		if (!hasTimestamp()) {
		return ERROR_NO_TIMESTAMP;
		} else if (!hasAtomId()) {
		return ERROR_NO_ATOM_ID;
		} else if (mPos + FLOAT_TYPE_SIZE > MAX_EVENT_PAYLOAD) {
		return ERROR_BUFFER_LIMIT_EXCEEDED;
		}

		mBuffer[mPos] = FLOAT_TYPE;
		copyInt(mBuffer, mPos + 1, Float.floatToIntBits(value));
		mPos += FLOAT_TYPE_SIZE;
		mNumElements++;
		return SUCCESS;
		}

		/**
		* Appends the given boolean to the StatsEvent buffer.
		**/
		public int writeBoolean(final boolean value) {
		return writeInt(value ? 1 : 0);
		}

		/**
		* Appends the given byte array to the StatsEvent buffer.
		**/
		public int writeByteArray(@NonNull final byte[] value) {
		if (!hasTimestamp()) {
		return ERROR_NO_TIMESTAMP;
		} else if (!hasAtomId()) {
		return ERROR_NO_ATOM_ID;
		} else if (mPos + STRING_TYPE_OVERHEAD + value.length > MAX_EVENT_PAYLOAD) {
		return ERROR_BUFFER_LIMIT_EXCEEDED;
		}

		mBuffer[mPos] = STRING_TYPE;
		copyInt(mBuffer, mPos + 1, value.length);
		System.arraycopy(value, 0, mBuffer, mPos + STRING_TYPE_OVERHEAD, value.length);
		mPos += STRING_TYPE_OVERHEAD + value.length;
		mNumElements++;
		return SUCCESS;
		}

		/**
		* Appends the given String to the StatsEvent buffer.
		**/
		public int writeString(@NonNull final String value) {
		final byte[] valueBytes = stringToBytes(value);
		return writeByteArray(valueBytes);
		}

		/**
		* Appends the AttributionNode specified as array of uids and array of tags.
		**/
		public int writeAttributionNode(@NonNull final int[] uids, @NonNull final String[] tags) {
		if (!hasTimestamp()) {
		return ERROR_NO_TIMESTAMP;
		} else if (!hasAtomId()) {
		return ERROR_NO_ATOM_ID;
		} else if (mPos + LIST_TYPE_OVERHEAD > MAX_EVENT_PAYLOAD) {
		return ERROR_BUFFER_LIMIT_EXCEEDED;
		}

		final int numTags = tags.length;
		final int numUids = uids.length;
		if (numTags != numUids) {
		return ERROR_UID_TAG_COUNT_MISMATCH;
		}

		int pos = mPos;
		mBuffer[pos] = LIST_TYPE;
		mBuffer[pos + 1] = (byte) numTags;
		pos += LIST_TYPE_OVERHEAD;
		for (int i = 0; i < numTags; i++) {
		final byte[] tagBytes = stringToBytes(tags[i]);

		if (pos + LIST_TYPE_OVERHEAD + INT_TYPE_SIZE
		+ STRING_TYPE_OVERHEAD + tagBytes.length > MAX_EVENT_PAYLOAD) {
		return ERROR_BUFFER_LIMIT_EXCEEDED;
		}

		mBuffer[pos] = LIST_TYPE;
		mBuffer[pos + 1] = 2;
		pos += LIST_TYPE_OVERHEAD;
		mBuffer[pos] = INT_TYPE;
		copyInt(mBuffer, pos + 1, uids[i]);
		pos += INT_TYPE_SIZE;
		mBuffer[pos] = STRING_TYPE;
		copyInt(mBuffer, pos + 1, tagBytes.length);
		System.arraycopy(tagBytes, 0, mBuffer, pos + STRING_TYPE_OVERHEAD, tagBytes.length);
		pos += STRING_TYPE_OVERHEAD + tagBytes.length;
		}
		mPos = pos;
		mNumElements++;
		return SUCCESS;
		}

		/**
		* Returns the byte array containing data in the statsd socket format.
		* @hide
		**/
		@NonNull
		public byte[] getBuffer() {
		// Encode number of elements in the buffer.
		mBuffer[POS_NUM_ELEMENTS] = (byte) mNumElements;
		return mBuffer;
		}

		/**
		* Returns number of bytes used by the buffer.
		* @hide
		**/
		public int size() {
		return mPos;
		}

		/**
		* Getter for atom id.
		* @hide
		**/
		public int getAtomId() {
		return mAtomId;
		}

		@NonNull
		private static byte[] stringToBytes(@Nullable final String value) {
		return (null == value ? "" : value).getBytes(UTF_8);
		}

		// Helper methods for copying primitives
		private static void copyInt(@NonNull byte[] buff, int pos, int value) {
		buff[pos] = (byte) (value);
		buff[pos + 1] = (byte) (value >> 8);
		buff[pos + 2] = (byte) (value >> 16);
		buff[pos + 3] = (byte) (value >> 24);
		}

		private static void copyLong(@NonNull byte[] buff, int pos, long value) {
		buff[pos] = (byte) (value);
		buff[pos + 1] = (byte) (value >> 8);
		buff[pos + 2] = (byte) (value >> 16);
		buff[pos + 3] = (byte) (value >> 24);
		buff[pos + 4] = (byte) (value >> 32);
		buff[pos + 5] = (byte) (value >> 40);
		buff[pos + 6] = (byte) (value >> 48);
		buff[pos + 7] = (byte) (value >> 56);
		}
		}