Merge "Add geo targeting implementation" (df2293f6) · Commits · e / os / android_frameworks_base

telephony/java/com/android/internal/telephony/CbGeoUtils.java

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		/*
		* Copyright (C) 2019 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 com.android.internal.telephony;

		import android.annotation.NonNull;
		import android.telephony.Rlog;
		import android.text.TextUtils;

		import java.util.ArrayList;
		import java.util.List;
		import java.util.stream.Collectors;


		/**
		* This utils class is specifically used for geo-targeting of CellBroadcast messages.
		* The coordinates used by this utils class are latitude and longitude, but some algorithms in this
		* class only use them as coordinates on plane, so the calculation will be inaccurate. So don't use
		* this class for anything other then geo-targeting of cellbroadcast messages.
		*/
		public class CbGeoUtils {
		/** Geometric interface. */
		public interface Geometry {
		/**
		* Determines if the given point {@code p} is inside the geometry.
		* @param p point in latitude, longitude format.
		* @return {@code True} if the given point is inside the geometry.
		*/
		boolean contains(LatLng p);
		}

		/**
		* Tolerance for determining if the value is 0. If the absolute value of a value is less than
		* this tolerance, it will be treated as 0.
		*/
		public static final double EPS = 1e-7;

		/** The radius of earth. */
		public static final int EARTH_RADIUS_METER = 6371 * 1000;

		private static final String TAG = "CbGeoUtils";

		/** The identifier of geometry in the encoded string. */
		private static final String CIRCLE_SYMBOL = "circle";
		private static final String POLYGON_SYMBOL = "polygon";

		/** Point represent by (latitude, longitude). */
		public static class LatLng {
		public final double lat;
		public final double lng;

		/**
		* Constructor.
		* @param lat latitude, range [-90, 90]
		* @param lng longitude, range [-180, 180]
		*/
		public LatLng(double lat, double lng) {
		this.lat = lat;
		this.lng = lng;
		}

		/**
		* @param p the point use to calculate the subtraction result.
		* @return the result of this point subtract the given point {@code p}.
		*/
		public LatLng subtract(LatLng p) {
		return new LatLng(lat - p.lat, lng - p.lng);
		}

		/**
		* Calculate the distance in meter between this point and the given point {@code p}.
		* @param p the point use to calculate the distance.
		* @return the distance in meter.
		*/
		public double distance(LatLng p) {
		double dlat = Math.sin(0.5 * Math.toRadians(lat - p.lat));
		double dlng = Math.sin(0.5 * Math.toRadians(lng - p.lng));
		double x = dlat * dlat
		+ dlng * dlng * Math.cos(Math.toRadians(lat)) * Math.cos(Math.toRadians(p.lat));
		return 2 * Math.atan2(Math.sqrt(x), Math.sqrt(1 - x)) * EARTH_RADIUS_METER;
		}
		}

		/**
		* The class represents a simple polygon with at least 3 points.
		*/
		public static class Polygon implements Geometry {
		/**
		* In order to reduce the loss of precision in floating point calculations, all vertices
		* of the polygon are scaled. Set the value of scale to 1000 can take into account the
		* actual distance accuracy of 1 meter if the EPS is 1e-7 during the calculation.
		*/
		private static final double SCALE = 1000.0;

		private final List<LatLng> mVertices;
		private final List<Point> mScaledVertices;
		private final LatLng mOrigin;

		/**
		* Constructs a simple polygon from the given vertices. The adjacent two vertices are
		* connected to form an edge of the polygon. The polygon has at least 3 vertices, and the
		* last vertices and the first vertices must be adjacent.
		*
		* The longitude difference in the vertices should be less than 180 degree.
		*/
		public Polygon(@NonNull List<LatLng> vertices) {
		mVertices = vertices;

		// Find the point with smallest longitude as the mOrigin point.
		int idx = 0;
		for (int i = 1; i < vertices.size(); i++) {
		if (vertices.get(i).lng < vertices.get(idx).lng) {
		idx = i;
		}
		}
		mOrigin = vertices.get(idx);

		mScaledVertices = vertices.stream()
		.map(latLng -> convertAndScaleLatLng(latLng))
		.collect(Collectors.toList());
		}

		public List<LatLng> getVertices() {
		return mVertices;
		}

		/**
		* Check if the given point {@code p} is inside the polygon. This method counts the number
		* of times the polygon winds around the point P, A.K.A "winding number". The point is
		* outside only when this "winding number" is 0.
		*
		* If a point is on the edge of the polygon, it is also considered to be inside the polygon.
		*/
		@Override
		public boolean contains(LatLng latLng) {
		Point p = convertAndScaleLatLng(latLng);

		int n = mScaledVertices.size();
		int windingNumber = 0;
		for (int i = 0; i < n; i++) {
		Point a = mScaledVertices.get(i);
		Point b = mScaledVertices.get((i + 1) % n);

		// CCW is counterclockwise
		// CCW = ab x ap
		// CCW > 0 -> ap is on the left side of ab
		// CCW == 0 -> ap is on the same line of ab
		// CCW < 0 -> ap is on the right side of ab
		int ccw = sign(crossProduct(b.subtract(a), p.subtract(a)));

		if (ccw == 0) {
		if (Math.min(a.x, b.x) <= p.x && p.x <= Math.max(a.x, b.x)
		&& Math.min(a.y, b.y) <= p.y && p.y <= Math.max(a.y, b.y)) {
		return true;
		}
		} else {
		if (sign(a.y - p.y) <= 0) {
		// upward crossing
		if (ccw > 0 && sign(b.y - p.y) > 0) {
		++windingNumber;
		}
		} else {
		// downward crossing
		if (ccw < 0 && sign(b.y - p.y) <= 0) {
		--windingNumber;
		}
		}
		}
		}
		return windingNumber != 0;
		}

		/**
		* Move the given point {@code latLng} to the coordinate system with {@code mOrigin} as the
		* origin and scale it. {@code mOrigin} is selected from the vertices of a polygon, it has
		* the smallest longitude value among all of the polygon vertices.
		*
		* @param latLng the point need to be converted and scaled.
		* @Return a {@link Point} object.
		*/
		private Point convertAndScaleLatLng(LatLng latLng) {
		double x = latLng.lat - mOrigin.lat;
		double y = latLng.lng - mOrigin.lng;

		// If the point is in different hemispheres(western/eastern) than the mOrigin, and the
		// edge between them cross the 180th meridian, then its relative coordinates will be
		// extended.
		// For example, suppose the longitude of the mOrigin is -178, and the longitude of the
		// point to be converted is 175, then the longitude after the conversion is -8.
		// calculation: (-178 - 8) - (-178).
		if (sign(mOrigin.lng) != 0 && sign(mOrigin.lng) != sign(latLng.lng)) {
		double distCross0thMeridian = Math.abs(mOrigin.lng) + Math.abs(latLng.lng);
		if (sign(distCross0thMeridian * 2 - 360) > 0) {
		y = sign(mOrigin.lng) * (360 - distCross0thMeridian);
		}
		}
		return new Point(x * SCALE, y * SCALE);
		}

		private static double crossProduct(Point a, Point b) {
		return a.x * b.y - a.y * b.x;
		}

		static final class Point {
		public final double x;
		public final double y;

		Point(double x, double y) {
		this.x = x;
		this.y = y;
		}

		public Point subtract(Point p) {
		return new Point(x - p.x, y - p.y);
		}
		}
		}

		/** The class represents a circle. */
		public static class Circle implements Geometry {
		private final LatLng mCenter;
		private final double mRadiusMeter;

		public Circle(LatLng center, double radiusMeter) {
		this.mCenter = center;
		this.mRadiusMeter = radiusMeter;
		}

		public LatLng getCenter() {
		return mCenter;
		}

		public double getRadius() {
		return mRadiusMeter;
		}

		@Override
		public boolean contains(LatLng p) {
		return mCenter.distance(p) <= mRadiusMeter;
		}
		}

		/**
		* Parse the geometries from the encoded string {@code str}. The string must follow the
		* geometry encoding specified by {@link android.provider.Telephony.CellBroadcasts#GEOMETRIES}.
		*/
		@NonNull
		public static List<Geometry> parseGeometriesFromString(@NonNull String str) {
		List<Geometry> geometries = new ArrayList<>();
		for (String geometryStr : str.split("\\s;\\s")) {
		String[] geoParameters = geometryStr.split("\\s\\\|\\s");
		switch (geoParameters[0]) {
		case CIRCLE_SYMBOL:
		geometries.add(new Circle(parseLatLngFromString(geoParameters[1]),
		Double.parseDouble(geoParameters[2])));
		break;
		case POLYGON_SYMBOL:
		List<LatLng> vertices = new ArrayList<>(geoParameters.length - 1);
		for (int i = 1; i < geoParameters.length; i++) {
		vertices.add(parseLatLngFromString(geoParameters[i]));
		}
		geometries.add(new Polygon(vertices));
		break;
		default:
		Rlog.e(TAG, "Invalid geometry format " + geometryStr);
		}
		}
		return geometries;
		}

		/**
		* Encode a list of geometry objects to string. The encoding format is specified by
		* {@link android.provider.Telephony.CellBroadcasts#GEOMETRIES}.
		*
		* @param geometries the list of geometry objects need to be encoded.
		* @return the encoded string.
		*/
		@NonNull
		public static String encodeGeometriesToString(@NonNull List<Geometry> geometries) {
		return geometries.stream()
		.map(geometry -> encodeGeometryToString(geometry))
		.filter(encodedStr -> !TextUtils.isEmpty(encodedStr))
		.collect(Collectors.joining(";"));
		}


		/**
		* Encode the geometry object to string. The encoding format is specified by
		* {@link android.provider.Telephony.CellBroadcasts#GEOMETRIES}.
		* @param geometry the geometry object need to be encoded.
		* @return the encoded string.
		*/
		@NonNull
		private static String encodeGeometryToString(@NonNull Geometry geometry) {
		StringBuilder sb = new StringBuilder();
		if (geometry instanceof Polygon) {
		sb.append(POLYGON_SYMBOL);
		for (LatLng latLng : ((Polygon) geometry).getVertices()) {
		sb.append("\|");
		sb.append(latLng.lat);
		sb.append(",");
		sb.append(latLng.lng);
		}
		} else if (geometry instanceof Circle) {
		sb.append(CIRCLE_SYMBOL);
		Circle circle = (Circle) geometry;

		// Center
		sb.append("\|");
		sb.append(circle.getCenter().lat);
		sb.append(",");
		sb.append(circle.getCenter().lng);

		// Radius
		sb.append("\|");
		sb.append(circle.getRadius());
		} else {
		Rlog.e(TAG, "Unsupported geometry object " + geometry);
		return null;
		}
		return sb.toString();
		}

		/**
		* Parse {@link LatLng} from {@link String}. Latitude and longitude are separated by ",".
		* Example: "13.56,-55.447".
		*
		* @param str encoded lat/lng string.
		* @Return {@link LatLng} object.
		*/
		@NonNull
		public static LatLng parseLatLngFromString(@NonNull String str) {
		String[] latLng = str.split("\\s,\\s");
		return new LatLng(Double.parseDouble(latLng[0]), Double.parseDouble(latLng[1]));
		}

		/**
		* @Return the sign of the given value {@code value} with the specified tolerance. Return 1
		* means the sign is positive, -1 means negative, 0 means the value will be treated as 0.
		*/
		public static int sign(double value) {
		if (value > EPS) return 1;
		if (value < -EPS) return -1;
		return 0;
		}
		}