Alert user on rapid/heavy data usage.

Now that we have accurate information about a user's carrier data
plan, we can alert them if the current usage patterns would end up
with a nasty surprise towards the end of the current billing cycle.

For example, a single abusive app could use 90% of the user's budget
within the first few days of a billing cycle, leaving the user to
limp along for the remainder of the month.

The simple algorithm here extrapolates to see if the average usage
over the last 4 days would be more than 150% of the data limit for
the full billing cycle.  This period is short enough to catch rapid
recent usage, but long enough to smooth over short-term habit
changes, such as a weekend getaway.  This was chosen after
backtesting the proposed algorithm against real-world data usage
from a handful of internal users.

Fix NPMS unit tests, and write new ones, but leave the existing
@Ignored annotation intact for now.

Test: bit FrameworksServicesTests:com.android.server.NetworkPolicyManagerServiceTest
Bug: 64133169
Change-Id: I0d394b133257e8569a9aa2631b57638839d870ce

1 files changed, 4 insertions, 0 deletions

diff --git a/core/java/com/android/internal/util/ArrayUtils.java b/core/java/com/android/internal/util/ArrayUtils.java
index 7b023f412cbc..621619c5134d 100644
--- a/core/java/com/android/internal/util/ArrayUtils.java
+++ b/core/java/com/android/internal/util/ArrayUtils.java
@@ -619,6 +619,10 @@ public class ArrayUtils {
         return size - leftIdx;
     }
 
+    public static @NonNull int[] defeatNullable(@Nullable int[] val) {
+        return (val != null) ? val : EmptyArray.INT;
+    }
+
     public static @NonNull String[] defeatNullable(@Nullable String[] val) {
         return (val != null) ? val : EmptyArray.STRING;
     }