/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.server.wifi;
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import android.annotation.NonNull;
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import android.net.wifi.ScanResult;
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import android.net.wifi.WifiConfiguration;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.HashMap;
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/**
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* Maps BSSIDs to their individual ScanDetails for a given WifiConfiguration.
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*/
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public class ScanDetailCache {
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private static final String TAG = "ScanDetailCache";
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private static final boolean DBG = false;
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private final WifiConfiguration mConfig;
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private final int mMaxSize;
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private final int mTrimSize;
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private final HashMap<String, ScanDetail> mMap;
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/**
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* Scan Detail cache associated with each configured network.
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*
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* The cache size is trimmed down to |trimSize| once it crosses the provided |maxSize|.
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* Since this operation is relatively expensive, ensure that |maxSize| and |trimSize| are not
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* too close to each other. |trimSize| should always be <= |maxSize|.
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*
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* @param config WifiConfiguration object corresponding to the network.
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* @param maxSize Max size desired for the cache.
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* @param trimSize Size to trim the cache down to once it reaches |maxSize|.
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*/
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ScanDetailCache(WifiConfiguration config, int maxSize, int trimSize) {
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mConfig = config;
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mMaxSize = maxSize;
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mTrimSize = trimSize;
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mMap = new HashMap(16, 0.75f);
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}
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void put(ScanDetail scanDetail) {
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// First check if we have reached |maxSize|. if yes, trim it down to |trimSize|.
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if (mMap.size() >= mMaxSize) {
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trim();
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}
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mMap.put(scanDetail.getBSSIDString(), scanDetail);
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}
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/**
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* Get ScanResult object corresponding to the provided BSSID.
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*
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* @param bssid provided BSSID
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* @return {@code null} if no match ScanResult is found.
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*/
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public ScanResult getScanResult(String bssid) {
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ScanDetail scanDetail = getScanDetail(bssid);
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return scanDetail == null ? null : scanDetail.getScanResult();
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}
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/**
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* Get ScanDetail object corresponding to the provided BSSID.
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*
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* @param bssid provided BSSID
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* @return {@code null} if no match ScanDetail is found.
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*/
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public ScanDetail getScanDetail(@NonNull String bssid) {
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return mMap.get(bssid);
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}
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void remove(@NonNull String bssid) {
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mMap.remove(bssid);
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}
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int size() {
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return mMap.size();
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}
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boolean isEmpty() {
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return size() == 0;
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}
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Collection<String> keySet() {
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return mMap.keySet();
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}
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Collection<ScanDetail> values() {
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return mMap.values();
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}
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/**
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* Method to reduce the cache to |mTrimSize| size by removing the oldest entries.
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* TODO: Investigate if this method can be further optimized.
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*/
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private void trim() {
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int currentSize = mMap.size();
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if (currentSize < mTrimSize) {
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return; // Nothing to trim
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}
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ArrayList<ScanDetail> list = new ArrayList<ScanDetail>(mMap.values());
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if (list.size() != 0) {
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// Sort by descending timestamp
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Collections.sort(list, new Comparator() {
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public int compare(Object o1, Object o2) {
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ScanDetail a = (ScanDetail) o1;
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ScanDetail b = (ScanDetail) o2;
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if (a.getSeen() > b.getSeen()) {
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return 1;
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}
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if (a.getSeen() < b.getSeen()) {
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return -1;
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}
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return a.getBSSIDString().compareTo(b.getBSSIDString());
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}
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});
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}
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for (int i = 0; i < currentSize - mTrimSize; i++) {
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// Remove oldest results from scan cache
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ScanDetail result = list.get(i);
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mMap.remove(result.getBSSIDString());
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}
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}
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/* @hide */
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private ArrayList<ScanDetail> sort() {
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ArrayList<ScanDetail> list = new ArrayList<ScanDetail>(mMap.values());
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if (list.size() != 0) {
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Collections.sort(list, new Comparator() {
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public int compare(Object o1, Object o2) {
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ScanResult a = ((ScanDetail) o1).getScanResult();
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ScanResult b = ((ScanDetail) o2).getScanResult();
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if (a.seen > b.seen) {
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return -1;
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}
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if (a.seen < b.seen) {
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return 1;
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}
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if (a.level > b.level) {
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return -1;
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}
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if (a.level < b.level) {
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return 1;
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}
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return a.BSSID.compareTo(b.BSSID);
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}
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});
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}
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return list;
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}
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@Override
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public String toString() {
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StringBuilder sbuf = new StringBuilder();
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sbuf.append("Scan Cache: ").append('\n');
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ArrayList<ScanDetail> list = sort();
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long now_ms = System.currentTimeMillis();
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if (list.size() > 0) {
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for (ScanDetail scanDetail : list) {
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ScanResult result = scanDetail.getScanResult();
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long milli = now_ms - scanDetail.getSeen();
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long ageSec = 0;
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long ageMin = 0;
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long ageHour = 0;
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long ageMilli = 0;
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long ageDay = 0;
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if (now_ms > scanDetail.getSeen() && scanDetail.getSeen() > 0) {
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ageMilli = milli % 1000;
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ageSec = (milli / 1000) % 60;
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ageMin = (milli / (60 * 1000)) % 60;
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ageHour = (milli / (60 * 60 * 1000)) % 24;
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ageDay = (milli / (24 * 60 * 60 * 1000));
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}
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sbuf.append("{").append(result.BSSID).append(",").append(result.frequency);
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sbuf.append(",").append(String.format("%3d", result.level));
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if (ageSec > 0 || ageMilli > 0) {
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sbuf.append(String.format(",%4d.%02d.%02d.%02d.%03dms", ageDay,
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ageHour, ageMin, ageSec, ageMilli));
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}
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sbuf.append("} ");
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}
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sbuf.append('\n');
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}
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return sbuf.toString();
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}
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}
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