| /* |
| * 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 com.android.wifitrackerlib; |
| |
| import android.net.wifi.ScanResult; |
| |
| import androidx.annotation.NonNull; |
| |
| import java.time.Clock; |
| import java.util.ArrayList; |
| import java.util.HashMap; |
| import java.util.List; |
| |
| /** |
| * Utility class to keep a running list of scan results merged by BSSID. |
| * |
| * Thread-safe. |
| */ |
| public class ScanResultUpdater { |
| private HashMap<String, ScanResult> mScanResultsByBssid = new HashMap<>(); |
| private final long mMaxScanAgeMillis; |
| private final Object mLock = new Object(); |
| private final Clock mClock; |
| |
| /** |
| * Creates a ScanResultUpdater with no max scan age. |
| * |
| * @param clock Elapsed real time Clock to compare with ScanResult timestamps. |
| */ |
| public ScanResultUpdater(Clock clock) { |
| this(clock, Long.MAX_VALUE); |
| } |
| |
| /** |
| * Creates a ScanResultUpdater with a max scan age in milliseconds. Scans older than this limit |
| * will be pruned upon update/retrieval to keep the size of the scan list down. |
| */ |
| public ScanResultUpdater(Clock clock, long maxScanAgeMillis) { |
| mMaxScanAgeMillis = maxScanAgeMillis; |
| mClock = clock; |
| } |
| |
| /** |
| * Updates scan result list and replaces older scans of the same BSSID. |
| */ |
| public void update(@NonNull List<ScanResult> newResults) { |
| synchronized (mLock) { |
| evictOldScans(); |
| |
| for (ScanResult result : newResults) { |
| ScanResult prevResult = mScanResultsByBssid.get(result.BSSID); |
| if (prevResult == null || (prevResult.timestamp < result.timestamp)) { |
| mScanResultsByBssid.put(result.BSSID, result); |
| } |
| } |
| } |
| } |
| |
| /** |
| * Returns all seen scan results merged by BSSID. |
| */ |
| @NonNull |
| public List<ScanResult> getScanResults() { |
| return getScanResults(mMaxScanAgeMillis); |
| } |
| |
| /** |
| * Returns all seen scan results merged by BSSID and newer than maxScanAgeMillis. |
| * maxScanAgeMillis must be less than or equal to the mMaxScanAgeMillis field if it was set. |
| */ |
| @NonNull |
| public List<ScanResult> getScanResults(long maxScanAgeMillis) throws IllegalArgumentException { |
| if (maxScanAgeMillis > mMaxScanAgeMillis) { |
| throw new IllegalArgumentException( |
| "maxScanAgeMillis argument cannot be greater than mMaxScanAgeMillis!"); |
| } |
| synchronized (mLock) { |
| List<ScanResult> ageFilteredResults = new ArrayList<>(); |
| for (ScanResult result : mScanResultsByBssid.values()) { |
| if (mClock.millis() - result.timestamp / 1000 <= maxScanAgeMillis) { |
| ageFilteredResults.add(result); |
| } |
| } |
| return ageFilteredResults; |
| } |
| } |
| |
| private void evictOldScans() { |
| synchronized (mLock) { |
| mScanResultsByBssid.entrySet().removeIf((entry) -> |
| mClock.millis() - entry.getValue().timestamp / 1000 > mMaxScanAgeMillis); |
| } |
| } |
| } |