/*
* 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, rssiBuckets, activeNetworkRssiBoost);
}
@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];
}
};
}
|
