LocationFudger: Avoid division by zero

Following internal discussions, this CL removes a rarely-occuring bug.

At latitudes -+90°, cos() is 0, leading to a division by zero.
This exception happens only if the device location (plus offset) is exactly at the North or South pole, so I assume it never happened in practice.

Change-Id: I6e91791e1b7e87ed88e48cff13a0af9b3a680908
Test: atest FrameworksMockingServicesTests:LocationFudgerTest
Bug: 388189593
Flag: EXEMPT Bug Fix

1 files changed, 10 insertions, 1 deletions

diff --git a/services/core/java/com/android/server/location/fudger/LocationFudger.java b/services/core/java/com/android/server/location/fudger/LocationFudger.java
index 88a269706470..27ad555f3701 100644
--- a/services/core/java/com/android/server/location/fudger/LocationFudger.java
+++ b/services/core/java/com/android/server/location/fudger/LocationFudger.java
@@ -239,6 +239,15 @@ public class LocationFudger {
 
     // requires latitude since longitudinal distances change with distance from equator.
     private static double metersToDegreesLongitude(double distance, double lat) {
-        return distance / APPROXIMATE_METERS_PER_DEGREE_AT_EQUATOR / Math.cos(Math.toRadians(lat));
+        // Needed to convert from longitude distance to longitude degree.
+        // X meters near the poles is more degrees than at the equator.
+        double cosLat = Math.cos(Math.toRadians(lat));
+        // If we are right on top of the pole, the degree is always 0.
+        // We return a very small value instead to avoid divide by zero errors
+        // later on.
+        if (cosLat == 0.0) {
+            return 0.0001;
+        }
+        return distance / APPROXIMATE_METERS_PER_DEGREE_AT_EQUATOR / cosLat;
     }
 }