Refactoring of deleting stats in NetworkStats based on uids.

In follow-up commits, current API would create new NetworkStats
every time when 464xlatAdjustment wants to filtered out some
uids.

This commit refactors it to delete stats in-place to get better
performance.

Bug: 118602783
Test: atest FrameworksNetTests
Change-Id: I858f95d1fa7733111786243b4e261ce8a70a068d

core/java/android/net/NetworkStats.java

@@ -44,6 +44,7 @@ import java.util.Objects;
  *
  * @hide
  */
+// @NotThreadSafe
 public class NetworkStats implements Parcelable {
     private static final String TAG = "NetworkStats";
     /** {@link #iface} value when interface details unavailable. */
@@ -443,6 +444,26 @@ public class NetworkStats implements Parcelable {
         return entry;
     }
 
+    /**
+     * If @{code dest} is not equal to @{code src}, copy entry from index @{code src} to index
+     * @{code dest}.
+     */
+    private void maybeCopyEntry(int dest, int src) {
+        if (dest == src) return;
+        iface[dest] = iface[src];
+        uid[dest] = uid[src];
+        set[dest] = set[src];
+        tag[dest] = tag[src];
+        metered[dest] = metered[src];
+        roaming[dest] = roaming[src];
+        defaultNetwork[dest] = defaultNetwork[src];
+        rxBytes[dest] = rxBytes[src];
+        rxPackets[dest] = rxPackets[src];
+        txBytes[dest] = txBytes[src];
+        txPackets[dest] = txPackets[src];
+        operations[dest] = operations[src];
+    }
+
     public long getElapsedRealtime() {
         return elapsedRealtime;
     }
@@ -941,21 +962,18 @@ public class NetworkStats implements Parcelable {
     }
 
     /**
-     * Return all rows except those attributed to the requested UID; doesn't
-     * mutate the original structure.
+     * Remove all rows that match one of specified UIDs.
      */
-    public NetworkStats withoutUids(int[] uids) {
-        final NetworkStats stats = new NetworkStats(elapsedRealtime, 10);
-
-        Entry entry = new Entry();
+    public void removeUids(int[] uids) {
+        int nextOutputEntry = 0;
         for (int i = 0; i < size; i++) {
-            entry = getValues(i, entry);
-            if (!ArrayUtils.contains(uids, entry.uid)) {
-                stats.addValues(entry);
+            if (!ArrayUtils.contains(uids, uid[i])) {
+                maybeCopyEntry(nextOutputEntry, i);
+                nextOutputEntry++;
             }
         }
 
-        return stats;
+        size = nextOutputEntry;
     }
 
     /**