presence/ble/BleAdvertiser.java

/*
 * 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.cts.verifier.presence.ble;

import android.annotation.SuppressLint;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.le.AdvertiseCallback;
import android.bluetooth.le.AdvertiseData;
import android.bluetooth.le.AdvertiseSettings;
import android.bluetooth.le.AdvertisingSet;
import android.bluetooth.le.AdvertisingSetCallback;
import android.bluetooth.le.AdvertisingSetParameters;
import android.bluetooth.le.BluetoothLeAdvertiser;
import android.util.Log;

import com.google.common.base.Preconditions;

import java.util.Arrays;

/** Advertises BLE beacons. */
@SuppressLint("MissingPermission")
public class BleAdvertiser {
    private static final String TAG = BleAdvertiser.class.getName();

    private static final int AVAILABLE_BYTES = 31;
    private static final int PARCEL_UUID_BYTES = 16;
    private static final int OVERHEAD_BYTES = 2;

    private final BluetoothLeAdvertiser advertiser =
            BluetoothAdapter.getDefaultAdapter().getBluetoothLeAdvertiser();
    private boolean isAdvertising;
    private boolean mIsExtendedAdvertisement;

    private final AdvertiseSettings settings =
            new AdvertiseSettings.Builder()
                    .setAdvertiseMode(AdvertiseSettings.ADVERTISE_MODE_LOW_LATENCY)
                    // 1db per
                    // http://cs/android/packages/modules/Bluetooth/framework/java/android/bluetooth/le/BluetoothLeAdvertiser.java?l=156&rcl=53aad85c594243e9d8e2778ce582f5c7382ad19c
                    .setTxPowerLevel(AdvertiseSettings.ADVERTISE_TX_POWER_HIGH)
                    .setConnectable(false)
                    .build();

    private final AdvertiseCallback advertisingCallback =
            new AdvertiseCallback() {
                @Override
                public void onStartSuccess(AdvertiseSettings settingsInEffect) {
                    super.onStartSuccess(settingsInEffect);
                    Log.i(TAG, "Advertising onStartSuccess: " + settingsInEffect);
                }

                @Override
                public void onStartFailure(int errorCode) {
                    super.onStartFailure(errorCode);
                    Log.i(TAG, "Advertising onStartFailure: " + errorCode);
                }
            };

    private final AdvertisingSetCallback mAdvertisingSetCallback =
            new AdvertisingSetCallback() {
                @Override
                public void onAdvertisingSetStarted(AdvertisingSet advertisingSet, int txPower,
                        int status) {
                    super.onAdvertisingSetStarted(advertisingSet, txPower, status);
                    Log.i(TAG, "onAdvertisingSetStarted");
                    mIsExtendedAdvertisement = true;
                }

                @Override
                public void onAdvertisingSetStopped(AdvertisingSet advertisingSet) {
                    super.onAdvertisingSetStopped(advertisingSet);
                    Log.i(TAG, "onAdvertisingSetStopped");
                    mIsExtendedAdvertisement = false;
                }
            };

    public BleAdvertiser() {}

    public void startAdvertising(byte[] payload, boolean isExtendedAdvertisement, int txPower) {
        if (isAdvertising) {
            stopAdvertising();
        }

        int freeBytesForPayload = getFreeBytesForPayload();
        Preconditions.checkArgument(
                payload.length <= freeBytesForPayload,
                "provided payload is too large! Limit is %s bytes, provided=%s",
                freeBytesForPayload,
                payload.length);

        AdvertiseData data = new AdvertiseData.Builder()
                // UUID (16 bytes) + service data overhead (2 bytes) + service data +
                // device name
                // overhead (2 bytes) = 20 bytes + service data bytes
                // This leaves 10 bytes or fewer, depending on the service data, for the
                // device name
                // since we only have 31 bytes available in AdvertiseData. To prevent BLE
                // advertising
                // from failing, don't set the device name.
                .setIncludeDeviceName(false)
                .addServiceData(Const.PARCEL_UUID, payload)
                .build();
        if (isExtendedAdvertisement) {
            advertiser.startAdvertisingSet(buildAdvertisingSetParameters(txPower), data, /*scanResponse= */ null, /*periodicParameters= */ null, /*periodicData= */ null, mAdvertisingSetCallback);
        } else {
            advertiser.startAdvertising(settings, data, advertisingCallback);
        }

        Log.i(TAG, "startAdvertising: %s" + Arrays.toString(payload));

        isAdvertising = true;
    }

    public void stopAdvertising() {
        Log.i(TAG, "stopAdvertising");
        if (mIsExtendedAdvertisement) {
            advertiser.stopAdvertisingSet(mAdvertisingSetCallback);
        } else {
            advertiser.stopAdvertising(advertisingCallback);
        }
        isAdvertising = false;
    }

    public boolean isAdvertising() {
        return isAdvertising;
    }

    /** Returns the number of bytes available for a payload */
    private static int getFreeBytesForPayload() {
        int bytesForServiceData = OVERHEAD_BYTES + 1; // + 1 for txOffset
        return AVAILABLE_BYTES - PARCEL_UUID_BYTES - bytesForServiceData;
    }

    private static AdvertisingSetParameters buildAdvertisingSetParameters(int txPower) {
        return new AdvertisingSetParameters.Builder()
                .setConnectable(true)
                .setInterval(AdvertisingSetParameters.INTERVAL_LOW)
                .setTxPowerLevel(txPower)
                .setIncludeTxPower(true)
                .build();
    }
}