package com.blakequ.bluetooth_manager_lib.device.ibeacon;
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import com.blakequ.bluetooth_manager_lib.util.ByteUtils;
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final class IBeaconUtils {
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private static final double DISTANCE_THRESHOLD_WTF = 0.0;
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private static final double DISTANCE_THRESHOLD_IMMEDIATE = 0.5;
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private static final double DISTANCE_THRESHOLD_NEAR = 3.0;
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private IBeaconUtils(){
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// TO AVOID INSTANTIATION
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}
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/**
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* Calculates the accuracy of an RSSI reading.
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* <p/>
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* The code was taken from <a href="http://stackoverflow.com/questions/20416218/understanding-ibeacon-distancing" /a>
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*
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* @param txPower the calibrated TX power of an iBeacon
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* @param rssi the RSSI value of the iBeacon
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* @return the calculated Accuracy
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*/
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public static double calculateAccuracy(final int txPower, final double rssi) {
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if (rssi == 0) {
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return -1.0; // if we cannot determine accuracy, return -1.
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}
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final double ratio = rssi * 1.0 / txPower;
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if (ratio < 1.0) {
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return Math.pow(ratio, 10);
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} else {
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return (0.89976) * Math.pow(ratio, 7.7095) + 0.111;
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}
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}
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public static String calculateUuidString(final byte[] uuid) {
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final StringBuilder sb = new StringBuilder();
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for (int i = 0; i < uuid.length; i++) {
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if (i == 4) {
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sb.append('-');
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}
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if (i == 6) {
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sb.append('-');
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}
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if (i == 8) {
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sb.append('-');
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}
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if (i == 10) {
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sb.append('-');
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}
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final int intFromByte = ByteUtils.getIntFromByte(uuid[i]);
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if(intFromByte <= 0xF){
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sb.append('0');
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}
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sb.append(Integer.toHexString(intFromByte));
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}
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return sb.toString();
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}
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public static IBeaconDistanceDescriptor getDistanceDescriptor(final double accuracy) {
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if (accuracy < DISTANCE_THRESHOLD_WTF) {
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return IBeaconDistanceDescriptor.UNKNOWN;
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}
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if (accuracy < DISTANCE_THRESHOLD_IMMEDIATE) {
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return IBeaconDistanceDescriptor.IMMEDIATE;
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}
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if (accuracy < DISTANCE_THRESHOLD_NEAR) {
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return IBeaconDistanceDescriptor.NEAR;
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}
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return IBeaconDistanceDescriptor.FAR;
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}
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}
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