Merge "Add DataElementHeader"
diff --git a/nearby/service/java/com/android/server/nearby/presence/DataElementHeader.java b/nearby/service/java/com/android/server/nearby/presence/DataElementHeader.java
new file mode 100644
index 0000000..ae4a728
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/presence/DataElementHeader.java
@@ -0,0 +1,266 @@
+/*
+ * Copyright (C) 2022 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 com.android.server.nearby.presence;
+
+import android.annotation.Nullable;
+import android.nearby.BroadcastRequest;
+import android.nearby.DataElement;
+
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.util.Preconditions;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+
+import javax.annotation.Nonnull;
+
+/**
+ * Represents a data element header in Nearby Presence.
+ * Each header has 3 parts: tag, length and style.
+ * Tag: 1 bit (MSB at each byte). 1 for extending, which means there will be more bytes after
+ * the current one for the header.
+ * Length: The total length of a Data Element field. Length is up to 127 and is limited within
+ * the entire first byte in the header. (7 bits, MSB is the tag).
+ * Type: Represents {@link DataElement.DataType}. There is no limit for the type number.
+ *
+ * @hide
+ */
+public class DataElementHeader {
+ // Each Data reserved MSB for tag.
+ static final int TAG_BITMASK = 0b10000000;
+ static final int TAG_OFFSET = 7;
+
+ // If the header is only 1 byte, it has the format: 0b0LLLTTTT. (L for length, T for type.)
+ static final int SINGLE_AVAILABLE_LENGTH_BIT = 3;
+ static final int SINGLE_AVAILABLE_TYPE_BIT = 4;
+ static final int SINGLE_LENGTH_BITMASK = 0b01110000;
+ static final int SINGLE_LENGTH_OFFSET = SINGLE_AVAILABLE_TYPE_BIT;
+ static final int SINGLE_TYPE_BITMASK = 0b00001111;
+
+ // If there are multiple data element headers.
+ // First byte is always the length.
+ static final int MULTIPLE_LENGTH_BYTE = 1;
+ // Each byte reserves MSB for tag.
+ static final int MULTIPLE_BITMASK = 0b01111111;
+
+ @BroadcastRequest.BroadcastVersion
+ private final int mVersion;
+ @DataElement.DataType
+ private final int mDataType;
+ private final int mDataLength;
+
+ DataElementHeader(@BroadcastRequest.BroadcastVersion int version,
+ @DataElement.DataType int dataType, int dataLength) {
+ Preconditions.checkArgument(version == BroadcastRequest.PRESENCE_VERSION_V1,
+ "DataElementHeader is only supported in V1.");
+ Preconditions.checkArgument(dataLength >= 0, "Length should not be negative.");
+ Preconditions.checkArgument(dataLength < (1 << TAG_OFFSET),
+ "Data element should be equal or shorter than 128.");
+
+ this.mVersion = version;
+ this.mDataType = dataType;
+ this.mDataLength = dataLength;
+ }
+
+ /**
+ * The total type of the data element.
+ */
+ @DataElement.DataType
+ public int getDataType() {
+ return mDataType;
+ }
+
+ /**
+ * The total length of a Data Element field.
+ */
+ public int getDataLength() {
+ return mDataLength;
+ }
+
+ /** Serialize a {@link DataElementHeader} object into bytes. */
+ public byte[] toBytes() {
+ Preconditions.checkState(mVersion == BroadcastRequest.PRESENCE_VERSION_V1,
+ "DataElementHeader is only supported in V1.");
+ // Only 1 byte needed for the header
+ if (mDataType < (1 << SINGLE_AVAILABLE_TYPE_BIT)
+ && mDataLength < (1 << SINGLE_AVAILABLE_LENGTH_BIT)) {
+ return new byte[]{createSingleByteHeader(mDataType, mDataLength)};
+ }
+
+ return createMultipleBytesHeader(mDataType, mDataLength);
+ }
+
+ /** Creates a {@link DataElementHeader} object from bytes. */
+ @Nullable
+ public static DataElementHeader fromBytes(@BroadcastRequest.BroadcastVersion int version,
+ @Nonnull byte[] bytes) {
+ Objects.requireNonNull(bytes, "Data parsed in for DataElement should not be null.");
+
+ if (bytes.length == 0) {
+ return null;
+ }
+
+ if (bytes.length == 1) {
+ if (isExtending(bytes[0])) {
+ throw new IllegalArgumentException("The header is not complete.");
+ }
+ return new DataElementHeader(BroadcastRequest.PRESENCE_VERSION_V1,
+ getTypeSingleByte(bytes[0]), getLengthSingleByte(bytes[0]));
+ }
+
+ // The first byte should be length and there should be at least 1 more byte following to
+ // represent type.
+ // The last header byte's MSB should be 0.
+ if (!isExtending(bytes[0]) || isExtending(bytes[bytes.length - 1])) {
+ throw new IllegalArgumentException("The header format is wrong.");
+ }
+
+ return new DataElementHeader(version,
+ getTypeMultipleBytes(Arrays.copyOfRange(bytes, 1, bytes.length)),
+ getHeaderValue(bytes[0]));
+ }
+
+ /** Creates a header based on type and length.
+ * This is used when the type is <= 16 and length is <= 7. */
+ static byte createSingleByteHeader(int type, int length) {
+ return (byte) (convertTag(/* extend= */ false)
+ | convertLengthSingleByte(length)
+ | convertTypeSingleByte(type));
+ }
+
+ /** Creates a header based on type and length.
+ * This is used when the type is > 16 or length is > 7. */
+ static byte[] createMultipleBytesHeader(int type, int length) {
+ List<Byte> typeIntList = convertTypeMultipleBytes(type);
+ byte[] res = new byte[typeIntList.size() + MULTIPLE_LENGTH_BYTE];
+ int index = 0;
+ res[index++] = convertLengthMultipleBytes(length);
+
+ for (int typeInt : typeIntList) {
+ res[index++] = (byte) typeInt;
+ }
+ return res;
+ }
+
+ /** Constructs a Data Element header with length indicated in byte format.
+ * The most significant bit is the tag, 2- 4 bits are the length, 5 - 8 bits are the type.
+ */
+ @VisibleForTesting
+ static int convertLengthSingleByte(int length) {
+ Preconditions.checkArgument(length >= 0, "Length should not be negative.");
+ Preconditions.checkArgument(length < (1 << SINGLE_AVAILABLE_LENGTH_BIT),
+ "In single Data Element header, length should be shorter than 8.");
+ return (length << SINGLE_LENGTH_OFFSET) & SINGLE_LENGTH_BITMASK;
+ }
+
+ /** Constructs a Data Element header with type indicated in byte format.
+ * The most significant bit is the tag, 2- 4 bits are the length, 5 - 8 bits are the type.
+ */
+ @VisibleForTesting
+ static int convertTypeSingleByte(int type) {
+ Preconditions.checkArgument(type >= 0, "Type should not be negative.");
+ Preconditions.checkArgument(type < (1 << SINGLE_AVAILABLE_TYPE_BIT),
+ "In single Data Element header, type should be smaller than 16.");
+
+ return type & SINGLE_TYPE_BITMASK;
+ }
+
+ /**
+ * Gets the length of Data Element from the header. (When there is only 1 byte of header)
+ */
+ static int getLengthSingleByte(byte header) {
+ Preconditions.checkArgument(!isExtending(header),
+ "Cannot apply this method for the extending header.");
+ return (header & SINGLE_LENGTH_BITMASK) >> SINGLE_LENGTH_OFFSET;
+ }
+
+ /**
+ * Gets the type of Data Element from the header. (When there is only 1 byte of header)
+ */
+ static int getTypeSingleByte(byte header) {
+ Preconditions.checkArgument(!isExtending(header),
+ "Cannot apply this method for the extending header.");
+ return header & SINGLE_TYPE_BITMASK;
+ }
+
+ /** Creates a DE(data element) header based on length.
+ * This is used when header is more than 1 byte. The first byte is always the length.
+ */
+ static byte convertLengthMultipleBytes(int length) {
+ Preconditions.checkArgument(length < (1 << TAG_OFFSET),
+ "Data element should be equal or shorter than 128.");
+ return (byte) (convertTag(/* extend= */ true) | (length & MULTIPLE_BITMASK));
+ }
+
+ /** Creates a DE(data element) header based on type.
+ * This is used when header is more than 1 byte. The first byte is always the length.
+ */
+ @VisibleForTesting
+ static List<Byte> convertTypeMultipleBytes(int type) {
+ List<Byte> typeBytes = new ArrayList<>();
+ while (type > 0) {
+ byte current = (byte) (type & MULTIPLE_BITMASK);
+ type = type >> TAG_OFFSET;
+ typeBytes.add(current);
+ }
+
+ Collections.reverse(typeBytes);
+ int size = typeBytes.size();
+ // The last byte's MSB should be 0.
+ for (int i = 0; i < size - 1; i++) {
+ typeBytes.set(i, (byte) (convertTag(/* extend= */ true) | typeBytes.get(i)));
+ }
+ return typeBytes;
+ }
+
+ /** Creates a DE(data element) header based on type.
+ * This is used when header is more than 1 byte. The first byte is always the length.
+ * Uses Integer when doing bit operation to avoid error.
+ */
+ @VisibleForTesting
+ static int getTypeMultipleBytes(byte[] typeByteArray) {
+ int type = 0;
+ int size = typeByteArray.length;
+ for (int i = 0; i < size; i++) {
+ type = (type << TAG_OFFSET) | getHeaderValue(typeByteArray[i]);
+ }
+ return type;
+ }
+
+ /** Gets the integer value of the 7 bits in the header. (The MSB is tag) */
+ @VisibleForTesting
+ static int getHeaderValue(byte header) {
+ return (header & MULTIPLE_BITMASK);
+ }
+
+ /** Sets the MSB of the header byte. If this is the last byte of headers, MSB is 0.
+ * If there are at least header following, the MSB is 1.
+ */
+ @VisibleForTesting
+ static byte convertTag(boolean extend) {
+ return (byte) (extend ? 0b10000000 : 0b00000000);
+ }
+
+ /** Returns {@code true} if there are at least 1 byte of header after the current one. */
+ @VisibleForTesting
+ static boolean isExtending(byte header) {
+ return (header & TAG_BITMASK) != 0;
+ }
+}
diff --git a/nearby/tests/unit/src/com/android/server/nearby/presence/DataElementHeaderTest.java b/nearby/tests/unit/src/com/android/server/nearby/presence/DataElementHeaderTest.java
new file mode 100644
index 0000000..e186709
--- /dev/null
+++ b/nearby/tests/unit/src/com/android/server/nearby/presence/DataElementHeaderTest.java
@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 2022 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 com.android.server.nearby.presence;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.junit.Assert.assertThrows;
+
+import android.nearby.BroadcastRequest;
+
+import org.junit.Test;
+
+import java.util.List;
+
+/**
+ * Unit test for {@link DataElementHeader}.
+ */
+public class DataElementHeaderTest {
+
+ private static final int VERSION = BroadcastRequest.PRESENCE_VERSION_V1;
+
+ @Test
+ public void test_illegalLength() {
+ assertThrows(IllegalArgumentException.class,
+ () -> new DataElementHeader(VERSION, 12, 128));
+ }
+
+ @Test
+ public void test_singeByteConversion() {
+ DataElementHeader header = new DataElementHeader(VERSION, 12, 3);
+ byte[] bytes = header.toBytes();
+ assertThat(bytes).isEqualTo(new byte[]{(byte) 0b00111100});
+
+ DataElementHeader afterConversionHeader = DataElementHeader.fromBytes(VERSION, bytes);
+ assertThat(afterConversionHeader.getDataLength()).isEqualTo(3);
+ assertThat(afterConversionHeader.getDataType()).isEqualTo(12);
+ }
+
+ @Test
+ public void test_multipleBytesConversion() {
+ DataElementHeader header = new DataElementHeader(VERSION, 6, 100);
+ DataElementHeader afterConversionHeader =
+ DataElementHeader.fromBytes(VERSION, header.toBytes());
+ assertThat(afterConversionHeader.getDataLength()).isEqualTo(100);
+ assertThat(afterConversionHeader.getDataType()).isEqualTo(6);
+ }
+
+ @Test
+ public void test_fromBytes() {
+ // Single byte case.
+ byte[] singleByte = new byte[]{(byte) 0b01011101};
+ DataElementHeader singeByteHeader = DataElementHeader.fromBytes(VERSION, singleByte);
+ assertThat(singeByteHeader.getDataLength()).isEqualTo(5);
+ assertThat(singeByteHeader.getDataType()).isEqualTo(13);
+
+ // Two bytes case.
+ byte[] twoBytes = new byte[]{(byte) 0b11011101, (byte) 0b01011101};
+ DataElementHeader twoBytesHeader = DataElementHeader.fromBytes(VERSION, twoBytes);
+ assertThat(twoBytesHeader.getDataLength()).isEqualTo(93);
+ assertThat(twoBytesHeader.getDataType()).isEqualTo(93);
+
+ // Three bytes case.
+ byte[] threeBytes = new byte[]{(byte) 0b11011101, (byte) 0b11111111, (byte) 0b01011101};
+ DataElementHeader threeBytesHeader = DataElementHeader.fromBytes(VERSION, threeBytes);
+ assertThat(threeBytesHeader.getDataLength()).isEqualTo(93);
+ assertThat(threeBytesHeader.getDataType()).isEqualTo(16349);
+
+ // Four bytes case.
+ byte[] fourBytes = new byte[]{
+ (byte) 0b11011101, (byte) 0b11111111, (byte) 0b11111111, (byte) 0b01011101};
+
+ DataElementHeader fourBytesHeader = DataElementHeader.fromBytes(VERSION, fourBytes);
+ assertThat(fourBytesHeader.getDataLength()).isEqualTo(93);
+ assertThat(fourBytesHeader.getDataType()).isEqualTo(2097117);
+ }
+
+ @Test
+ public void test_fromBytesIllegal_singleByte() {
+ assertThrows(IllegalArgumentException.class,
+ () -> DataElementHeader.fromBytes(VERSION, new byte[]{(byte) 0b11011101}));
+ }
+
+ @Test
+ public void test_fromBytesIllegal_twoBytes_wrongFirstByte() {
+ assertThrows(IllegalArgumentException.class,
+ () -> DataElementHeader.fromBytes(VERSION,
+ new byte[]{(byte) 0b01011101, (byte) 0b01011101}));
+ }
+
+ @Test
+ public void test_fromBytesIllegal_twoBytes_wrongLastByte() {
+ assertThrows(IllegalArgumentException.class,
+ () -> DataElementHeader.fromBytes(VERSION,
+ new byte[]{(byte) 0b11011101, (byte) 0b11011101}));
+ }
+
+ @Test
+ public void test_fromBytesIllegal_threeBytes() {
+ assertThrows(IllegalArgumentException.class,
+ () -> DataElementHeader.fromBytes(VERSION,
+ new byte[]{(byte) 0b11011101, (byte) 0b11011101, (byte) 0b11011101}));
+ }
+
+ @Test
+ public void test_multipleBytesConversion_largeNumber() {
+ DataElementHeader header = new DataElementHeader(VERSION, 22213546, 66);
+ DataElementHeader afterConversionHeader =
+ DataElementHeader.fromBytes(VERSION, header.toBytes());
+ assertThat(afterConversionHeader.getDataLength()).isEqualTo(66);
+ assertThat(afterConversionHeader.getDataType()).isEqualTo(22213546);
+ }
+
+ @Test
+ public void test_isExtending() {
+ assertThat(DataElementHeader.isExtending((byte) 0b10000100)).isTrue();
+ assertThat(DataElementHeader.isExtending((byte) 0b01110100)).isFalse();
+ assertThat(DataElementHeader.isExtending((byte) 0b00000000)).isFalse();
+ }
+
+ @Test
+ public void test_convertTag() {
+ assertThat(DataElementHeader.convertTag(true)).isEqualTo((byte) 128);
+ assertThat(DataElementHeader.convertTag(false)).isEqualTo(0);
+ }
+
+ @Test
+ public void test_getHeaderValue() {
+ assertThat(DataElementHeader.getHeaderValue((byte) 0b10000100)).isEqualTo(4);
+ assertThat(DataElementHeader.getHeaderValue((byte) 0b00000100)).isEqualTo(4);
+ assertThat(DataElementHeader.getHeaderValue((byte) 0b11010100)).isEqualTo(84);
+ assertThat(DataElementHeader.getHeaderValue((byte) 0b01010100)).isEqualTo(84);
+ }
+
+ @Test
+ public void test_convertTypeMultipleIntList() {
+ List<Byte> list = DataElementHeader.convertTypeMultipleBytes(128);
+ assertThat(list.size()).isEqualTo(2);
+ assertThat(list.get(0)).isEqualTo((byte) 0b10000001);
+ assertThat(list.get(1)).isEqualTo((byte) 0b00000000);
+
+ List<Byte> list2 = DataElementHeader.convertTypeMultipleBytes(10);
+ assertThat(list2.size()).isEqualTo(1);
+ assertThat(list2.get(0)).isEqualTo((byte) 0b00001010);
+
+ List<Byte> list3 = DataElementHeader.convertTypeMultipleBytes(5242398);
+ assertThat(list3.size()).isEqualTo(4);
+ assertThat(list3.get(0)).isEqualTo((byte) 0b10000010);
+ assertThat(list3.get(1)).isEqualTo((byte) 0b10111111);
+ assertThat(list3.get(2)).isEqualTo((byte) 0b11111100);
+ assertThat(list3.get(3)).isEqualTo((byte) 0b00011110);
+ }
+
+ @Test
+ public void test_getTypeMultipleBytes() {
+ byte[] inputBytes = new byte[]{(byte) 0b11011000, (byte) 0b10000000, (byte) 0b00001001};
+ // 0b101100000000000001001
+ assertThat(DataElementHeader.getTypeMultipleBytes(inputBytes)).isEqualTo(1441801);
+
+ byte[] inputBytes2 = new byte[]{(byte) 0b00010010};
+ assertThat(DataElementHeader.getTypeMultipleBytes(inputBytes2)).isEqualTo(18);
+
+ byte[] inputBytes3 = new byte[]{(byte) 0b10000001, (byte) 0b00000000};
+ assertThat(DataElementHeader.getTypeMultipleBytes(inputBytes3)).isEqualTo(128);
+ }
+}