| /* |
| * Copyright (C) 2014 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.net; |
| |
| import android.annotation.SystemApi; |
| import android.os.Parcel; |
| import android.os.Parcelable; |
| |
| import java.util.Arrays; |
| import java.util.Objects; |
| |
| /** |
| * A curve defining the network score over a range of RSSI values. |
| * |
| * <p>For each RSSI bucket, the score may be any byte. Scores have no absolute meaning and are only |
| * considered relative to other scores assigned by the same scorer. Networks with no score are |
| * treated equivalently to a network with score {@link Byte#MIN_VALUE}, and will not be used. |
| * |
| * <p>For example, consider a curve starting at -110 dBm with a bucket width of 10 and the |
| * following buckets: {@code [-20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120]}. |
| * This represents a linear curve between -110 dBm and 30 dBm. It scores progressively higher at |
| * stronger signal strengths. |
| * |
| * <p>A network can be assigned a fixed score independent of RSSI by setting |
| * {@link #rssiBuckets} to a one-byte array whose element is the fixed score. {@link #start} |
| * should be set to the lowest RSSI value at which this fixed score should apply, and |
| * {@link #bucketWidth} should be set such that {@code start + bucketWidth} is equal to the |
| * highest RSSI value at which this fixed score should apply. |
| * |
| * <p>Note that RSSI values below -110 dBm or above 30 dBm are unlikely to cause any difference |
| * in connectivity behavior from those endpoints. That is, the connectivity framework will treat |
| * a network with a -120 dBm signal exactly as it would treat one with a -110 dBm signal. |
| * Therefore, graphs which specify scores outside this range may be truncated to this range by |
| * the system. |
| * |
| * @see ScoredNetwork |
| * @hide |
| */ |
| @SystemApi |
| public class RssiCurve implements Parcelable { |
| private static final int DEFAULT_ACTIVE_NETWORK_RSSI_BOOST = 25; |
| |
| /** The starting dBm of the curve. */ |
| public final int start; |
| |
| /** The width of each RSSI bucket, in dBm. */ |
| public final int bucketWidth; |
| |
| /** The score for each RSSI bucket. */ |
| public final byte[] rssiBuckets; |
| |
| /** |
| * The RSSI boost to give this network when active, in dBm. |
| * |
| * <p>When the system is connected to this network, it will pretend that the network has this |
| * much higher of an RSSI. This is to avoid switching networks when another network has only a |
| * slightly higher score. |
| */ |
| public final int activeNetworkRssiBoost; |
| |
| /** |
| * Construct a new {@link RssiCurve}. |
| * |
| * @param start the starting dBm of the curve. |
| * @param bucketWidth the width of each RSSI bucket, in dBm. |
| * @param rssiBuckets the score for each RSSI bucket. |
| */ |
| public RssiCurve(int start, int bucketWidth, byte[] rssiBuckets) { |
| this(start, bucketWidth, rssiBuckets, DEFAULT_ACTIVE_NETWORK_RSSI_BOOST); |
| } |
| |
| /** |
| * Construct a new {@link RssiCurve}. |
| * |
| * @param start the starting dBm of the curve. |
| * @param bucketWidth the width of each RSSI bucket, in dBm. |
| * @param rssiBuckets the score for each RSSI bucket. |
| * @param activeNetworkRssiBoost the RSSI boost to apply when this network is active, in dBm. |
| */ |
| public RssiCurve(int start, int bucketWidth, byte[] rssiBuckets, int activeNetworkRssiBoost) { |
| this.start = start; |
| this.bucketWidth = bucketWidth; |
| if (rssiBuckets == null || rssiBuckets.length == 0) { |
| throw new IllegalArgumentException("rssiBuckets must be at least one element large."); |
| } |
| this.rssiBuckets = rssiBuckets; |
| this.activeNetworkRssiBoost = activeNetworkRssiBoost; |
| } |
| |
| private RssiCurve(Parcel in) { |
| start = in.readInt(); |
| bucketWidth = in.readInt(); |
| int bucketCount = in.readInt(); |
| rssiBuckets = new byte[bucketCount]; |
| in.readByteArray(rssiBuckets); |
| activeNetworkRssiBoost = in.readInt(); |
| } |
| |
| @Override |
| public int describeContents() { |
| return 0; |
| } |
| |
| @Override |
| public void writeToParcel(Parcel out, int flags) { |
| out.writeInt(start); |
| out.writeInt(bucketWidth); |
| out.writeInt(rssiBuckets.length); |
| out.writeByteArray(rssiBuckets); |
| out.writeInt(activeNetworkRssiBoost); |
| } |
| |
| /** |
| * Lookup the score for a given RSSI value. |
| * |
| * @param rssi The RSSI to lookup. If the RSSI falls below the start of the curve, the score at |
| * the start of the curve will be returned. If it falls after the end of the curve, the |
| * score at the end of the curve will be returned. |
| * @return the score for the given RSSI. |
| */ |
| public byte lookupScore(int rssi) { |
| return lookupScore(rssi, false /* isActiveNetwork */); |
| } |
| |
| /** |
| * Lookup the score for a given RSSI value. |
| * |
| * @param rssi The RSSI to lookup. If the RSSI falls below the start of the curve, the score at |
| * the start of the curve will be returned. If it falls after the end of the curve, the |
| * score at the end of the curve will be returned. |
| * @param isActiveNetwork Whether this network is currently active. |
| * @return the score for the given RSSI. |
| */ |
| public byte lookupScore(int rssi, boolean isActiveNetwork) { |
| if (isActiveNetwork) { |
| rssi += activeNetworkRssiBoost; |
| } |
| |
| int index = (rssi - start) / bucketWidth; |
| |
| // Snap the index to the closest bucket if it falls outside the curve. |
| if (index < 0) { |
| index = 0; |
| } else if (index > rssiBuckets.length - 1) { |
| index = rssiBuckets.length - 1; |
| } |
| |
| return rssiBuckets[index]; |
| } |
| |
| /** |
| * Determine if two RSSI curves are defined in the same way. |
| * |
| * <p>Note that two curves can be equivalent but defined differently, e.g. if one bucket in one |
| * curve is split into two buckets in another. For the purpose of this method, these curves are |
| * not considered equal to each other. |
| */ |
| @Override |
| public boolean equals(Object o) { |
| if (this == o) return true; |
| if (o == null || getClass() != o.getClass()) return false; |
| |
| RssiCurve rssiCurve = (RssiCurve) o; |
| |
| return start == rssiCurve.start && |
| bucketWidth == rssiCurve.bucketWidth && |
| Arrays.equals(rssiBuckets, rssiCurve.rssiBuckets) && |
| activeNetworkRssiBoost == rssiCurve.activeNetworkRssiBoost; |
| } |
| |
| @Override |
| public int hashCode() { |
| return Objects.hash(start, bucketWidth, activeNetworkRssiBoost) ^ Arrays.hashCode(rssiBuckets); |
| } |
| |
| @Override |
| public String toString() { |
| StringBuilder sb = new StringBuilder(); |
| sb.append("RssiCurve[start=") |
| .append(start) |
| .append(",bucketWidth=") |
| .append(bucketWidth) |
| .append(",activeNetworkRssiBoost=") |
| .append(activeNetworkRssiBoost); |
| |
| sb.append(",buckets="); |
| for (int i = 0; i < rssiBuckets.length; i++) { |
| sb.append(rssiBuckets[i]); |
| if (i < rssiBuckets.length - 1) { |
| sb.append(","); |
| } |
| } |
| sb.append("]"); |
| |
| return sb.toString(); |
| } |
| |
| public static final Creator<RssiCurve> CREATOR = |
| new Creator<RssiCurve>() { |
| @Override |
| public RssiCurve createFromParcel(Parcel in) { |
| return new RssiCurve(in); |
| } |
| |
| @Override |
| public RssiCurve[] newArray(int size) { |
| return new RssiCurve[size]; |
| } |
| }; |
| } |