1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License 15 */ 16 17 package android.net; 18 19 import android.annotation.SystemApi; 20 import android.os.Parcel; 21 import android.os.Parcelable; 22 23 import java.util.Arrays; 24 import java.util.Objects; 25 26 /** 27 * A curve defining the network score over a range of RSSI values. 28 * 29 * <p>For each RSSI bucket, the score may be any byte. Scores have no absolute meaning and are only 30 * considered relative to other scores assigned by the same scorer. Networks with no score are 31 * treated equivalently to a network with score {@link Byte#MIN_VALUE}, and will not be used. 32 * 33 * <p>For example, consider a curve starting at -110 dBm with a bucket width of 10 and the 34 * following buckets: {@code [-20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120]}. 35 * This represents a linear curve between -110 dBm and 30 dBm. It scores progressively higher at 36 * stronger signal strengths. 37 * 38 * <p>A network can be assigned a fixed score independent of RSSI by setting 39 * {@link #rssiBuckets} to a one-byte array whose element is the fixed score. {@link #start} 40 * should be set to the lowest RSSI value at which this fixed score should apply, and 41 * {@link #bucketWidth} should be set such that {@code start + bucketWidth} is equal to the 42 * highest RSSI value at which this fixed score should apply. 43 * 44 * <p>Note that RSSI values below -110 dBm or above 30 dBm are unlikely to cause any difference 45 * in connectivity behavior from those endpoints. That is, the connectivity framework will treat 46 * a network with a -120 dBm signal exactly as it would treat one with a -110 dBm signal. 47 * Therefore, graphs which specify scores outside this range may be truncated to this range by 48 * the system. 49 * 50 * @see ScoredNetwork 51 * @hide 52 */ 53 @SystemApi 54 public class RssiCurve implements Parcelable { 55 private static final int DEFAULT_ACTIVE_NETWORK_RSSI_BOOST = 25; 56 57 /** The starting dBm of the curve. */ 58 public final int start; 59 60 /** The width of each RSSI bucket, in dBm. */ 61 public final int bucketWidth; 62 63 /** The score for each RSSI bucket. */ 64 public final byte[] rssiBuckets; 65 66 /** 67 * The RSSI boost to give this network when active, in dBm. 68 * 69 * <p>When the system is connected to this network, it will pretend that the network has this 70 * much higher of an RSSI. This is to avoid switching networks when another network has only a 71 * slightly higher score. 72 */ 73 public final int activeNetworkRssiBoost; 74 75 /** 76 * Construct a new {@link RssiCurve}. 77 * 78 * @param start the starting dBm of the curve. 79 * @param bucketWidth the width of each RSSI bucket, in dBm. 80 * @param rssiBuckets the score for each RSSI bucket. 81 */ 82 public RssiCurve(int start, int bucketWidth, byte[] rssiBuckets) { 83 this(start, bucketWidth, rssiBuckets, DEFAULT_ACTIVE_NETWORK_RSSI_BOOST); 84 } 85 86 /** 87 * Construct a new {@link RssiCurve}. 88 * 89 * @param start the starting dBm of the curve. 90 * @param bucketWidth the width of each RSSI bucket, in dBm. 91 * @param rssiBuckets the score for each RSSI bucket. 92 * @param activeNetworkRssiBoost the RSSI boost to apply when this network is active, in dBm. 93 */ 94 public RssiCurve(int start, int bucketWidth, byte[] rssiBuckets, int activeNetworkRssiBoost) { 95 this.start = start; 96 this.bucketWidth = bucketWidth; 97 if (rssiBuckets == null || rssiBuckets.length == 0) { 98 throw new IllegalArgumentException("rssiBuckets must be at least one element large."); 99 } 100 this.rssiBuckets = rssiBuckets; 101 this.activeNetworkRssiBoost = activeNetworkRssiBoost; 102 } 103 104 private RssiCurve(Parcel in) { 105 start = in.readInt(); 106 bucketWidth = in.readInt(); 107 int bucketCount = in.readInt(); 108 rssiBuckets = new byte[bucketCount]; 109 in.readByteArray(rssiBuckets); 110 activeNetworkRssiBoost = in.readInt(); 111 } 112 113 @Override 114 public int describeContents() { 115 return 0; 116 } 117 118 @Override 119 public void writeToParcel(Parcel out, int flags) { 120 out.writeInt(start); 121 out.writeInt(bucketWidth); 122 out.writeInt(rssiBuckets.length); 123 out.writeByteArray(rssiBuckets); 124 out.writeInt(activeNetworkRssiBoost); 125 } 126 127 /** 128 * Lookup the score for a given RSSI value. 129 * 130 * @param rssi The RSSI to lookup. If the RSSI falls below the start of the curve, the score at 131 * the start of the curve will be returned. If it falls after the end of the curve, the 132 * score at the end of the curve will be returned. 133 * @return the score for the given RSSI. 134 */ 135 public byte lookupScore(int rssi) { 136 return lookupScore(rssi, false /* isActiveNetwork */); 137 } 138 139 /** 140 * Lookup the score for a given RSSI value. 141 * 142 * @param rssi The RSSI to lookup. If the RSSI falls below the start of the curve, the score at 143 * the start of the curve will be returned. If it falls after the end of the curve, the 144 * score at the end of the curve will be returned. 145 * @param isActiveNetwork Whether this network is currently active. 146 * @return the score for the given RSSI. 147 */ 148 public byte lookupScore(int rssi, boolean isActiveNetwork) { 149 if (isActiveNetwork) { 150 rssi += activeNetworkRssiBoost; 151 } 152 153 int index = (rssi - start) / bucketWidth; 154 155 // Snap the index to the closest bucket if it falls outside the curve. 156 if (index < 0) { 157 index = 0; 158 } else if (index > rssiBuckets.length - 1) { 159 index = rssiBuckets.length - 1; 160 } 161 162 return rssiBuckets[index]; 163 } 164 165 /** 166 * Determine if two RSSI curves are defined in the same way. 167 * 168 * <p>Note that two curves can be equivalent but defined differently, e.g. if one bucket in one 169 * curve is split into two buckets in another. For the purpose of this method, these curves are 170 * not considered equal to each other. 171 */ 172 @Override 173 public boolean equals(Object o) { 174 if (this == o) return true; 175 if (o == null || getClass() != o.getClass()) return false; 176 177 RssiCurve rssiCurve = (RssiCurve) o; 178 179 return start == rssiCurve.start && 180 bucketWidth == rssiCurve.bucketWidth && 181 Arrays.equals(rssiBuckets, rssiCurve.rssiBuckets) && 182 activeNetworkRssiBoost == rssiCurve.activeNetworkRssiBoost; 183 } 184 185 @Override 186 public int hashCode() { 187 return Objects.hash(start, bucketWidth, activeNetworkRssiBoost) ^ Arrays.hashCode(rssiBuckets); 188 } 189 190 @Override 191 public String toString() { 192 StringBuilder sb = new StringBuilder(); 193 sb.append("RssiCurve[start=") 194 .append(start) 195 .append(",bucketWidth=") 196 .append(bucketWidth) 197 .append(",activeNetworkRssiBoost=") 198 .append(activeNetworkRssiBoost); 199 200 sb.append(",buckets="); 201 for (int i = 0; i < rssiBuckets.length; i++) { 202 sb.append(rssiBuckets[i]); 203 if (i < rssiBuckets.length - 1) { 204 sb.append(","); 205 } 206 } 207 sb.append("]"); 208 209 return sb.toString(); 210 } 211 212 public static final Creator<RssiCurve> CREATOR = 213 new Creator<RssiCurve>() { 214 @Override 215 public RssiCurve createFromParcel(Parcel in) { 216 return new RssiCurve(in); 217 } 218 219 @Override 220 public RssiCurve[] newArray(int size) { 221 return new RssiCurve[size]; 222 } 223 }; 224 } 225
