Merge changes from topic "stats-migration"

* changes:
  Skip PersistentIntTest on S- device
  Don't clobber existing history entries.
  Ensure NetworkStats migrated snapshot is identical
  [MS82.1] Support network stats data migration process
  Add a PersistentInt class.

framework-t/src/android/net/NetworkStatsCollection.java

@@ -865,6 +865,9 @@ public class NetworkStatsCollection implements FileRotator.Reader, FileRotator.W
          * Add association of the history with the specified key in this map.
          *
          * @param key The object used to identify a network, see {@link Key}.
+         *            If history already exists for this key, then the passed-in history is appended
+         *            to the previously-passed in history. The caller must ensure that the history
+         *            passed-in timestamps are greater than all previously-passed-in timestamps.
          * @param history {@link NetworkStatsHistory} instance associated to the given {@link Key}.
          * @return The builder object.
          */
@@ -874,9 +877,21 @@ public class NetworkStatsCollection implements FileRotator.Reader, FileRotator.W
             Objects.requireNonNull(key);
             Objects.requireNonNull(history);
             final List<Entry> historyEntries = history.getEntries();
+            final NetworkStatsHistory existing = mEntries.get(key);
 
+            final int size = historyEntries.size() + ((existing != null) ? existing.size() : 0);
             final NetworkStatsHistory.Builder historyBuilder =
-                    new NetworkStatsHistory.Builder(mBucketDurationMillis, historyEntries.size());
+                    new NetworkStatsHistory.Builder(mBucketDurationMillis, size);
+
+            // TODO: this simply appends the entries to any entries that were already present in
+            // the builder, which requires the caller to pass in entries in order. We might be
+            // able to do better with something like recordHistory.
+            if (existing != null) {
+                for (Entry entry : existing.getEntries()) {
+                    historyBuilder.addEntry(entry);
+                }
+            }
+
             for (Entry entry : historyEntries) {
                 historyBuilder.addEntry(entry);
             }

framework-t/src/android/net/NetworkStatsHistory.java

@@ -32,6 +32,7 @@ import static android.text.format.DateUtils.SECOND_IN_MILLIS;
 import static com.android.net.module.util.NetworkStatsUtils.multiplySafeByRational;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.os.Build;
@@ -949,6 +950,25 @@ public final class NetworkStatsHistory implements Parcelable {
         return writer.toString();
     }
 
+    /**
+     * Same as "equals", but not actually called equals as this would affect public API behavior.
+     * @hide
+     */
+    @Nullable
+    public boolean isSameAs(NetworkStatsHistory other) {
+        return bucketCount == other.bucketCount
+                && Arrays.equals(bucketStart, other.bucketStart)
+                // Don't check activeTime since it can change on import due to the importer using
+                // recordHistory. It's also not exposed by the APIs or present in dumpsys or
+                // toString().
+                && Arrays.equals(rxBytes, other.rxBytes)
+                && Arrays.equals(rxPackets, other.rxPackets)
+                && Arrays.equals(txBytes, other.txBytes)
+                && Arrays.equals(txPackets, other.txPackets)
+                && Arrays.equals(operations, other.operations)
+                && totalBytes == other.totalBytes;
+    }
+
     @UnsupportedAppUsage
     public static final @android.annotation.NonNull Creator<NetworkStatsHistory> CREATOR = new Creator<NetworkStatsHistory>() {
         @Override
@@ -1116,14 +1136,44 @@ public final class NetworkStatsHistory implements Parcelable {
             mOperations = new ArrayList<>(initialCapacity);
         }
 
+        private void addToElement(List<Long> list, int pos, long value) {
+            list.set(pos, list.get(pos) + value);
+        }
+
         /**
          * Add an {@link Entry} into the {@link NetworkStatsHistory} instance.
          *
-         * @param entry The target {@link Entry} object.
+         * @param entry The target {@link Entry} object. The entry timestamp must be greater than
+         *              that of any previously-added entry.
          * @return The builder object.
          */
         @NonNull
         public Builder addEntry(@NonNull Entry entry) {
+            final int lastBucket = mBucketStart.size() - 1;
+            final long lastBucketStart = (lastBucket != -1) ? mBucketStart.get(lastBucket) : 0;
+
+            // If last bucket has the same timestamp, modify it instead of adding another bucket.
+            // This allows callers to pass in the same bucket twice (e.g., to accumulate
+            // data over time), but still requires that entries must be sorted.
+            // The importer will do this in case a rotated file has the same timestamp as
+            // the previous file.
+            if (lastBucket != -1 && entry.bucketStart == lastBucketStart) {
+                addToElement(mActiveTime, lastBucket, entry.activeTime);
+                addToElement(mRxBytes, lastBucket, entry.rxBytes);
+                addToElement(mRxPackets, lastBucket, entry.rxPackets);
+                addToElement(mTxBytes, lastBucket, entry.txBytes);
+                addToElement(mTxPackets, lastBucket, entry.txPackets);
+                addToElement(mOperations, lastBucket, entry.operations);
+                return this;
+            }
+
+            // Inserting in the middle is prohibited for performance reasons.
+            if (entry.bucketStart <= lastBucketStart) {
+                throw new IllegalArgumentException("new bucket start " + entry.bucketStart
+                        + " must be greater than last bucket start " + lastBucketStart);
+            }
+
+            // Common case: add entries at the end of the list.
             mBucketStart.add(entry.bucketStart);
             mActiveTime.add(entry.activeTime);
             mRxBytes.add(entry.rxBytes);