diff --git a/services/java/com/android/server/net/NetworkStatsRecorder.java b/services/java/com/android/server/net/NetworkStatsRecorder.java
new file mode 100644
index 0000000..e7ba358
--- /dev/null
+++ b/services/java/com/android/server/net/NetworkStatsRecorder.java
@@ -0,0 +1,341 @@
+/*
+ * Copyright (C) 2012 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.server.net;
+
+import static android.net.NetworkStats.TAG_NONE;
+import static com.android.internal.util.Preconditions.checkNotNull;
+
+import android.net.NetworkStats;
+import android.net.NetworkStats.NonMonotonicObserver;
+import android.net.NetworkStatsHistory;
+import android.net.NetworkTemplate;
+import android.net.TrafficStats;
+import android.util.Log;
+import android.util.Slog;
+
+import com.android.internal.util.FileRotator;
+import com.android.internal.util.IndentingPrintWriter;
+import com.google.android.collect.Sets;
+
+import java.io.DataOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.lang.ref.WeakReference;
+import java.util.HashSet;
+import java.util.Map;
+
+/**
+ * Logic to record deltas between periodic {@link NetworkStats} snapshots into
+ * {@link NetworkStatsHistory} that belong to {@link NetworkStatsCollection}.
+ * Keeps pending changes in memory until they pass a specific threshold, in
+ * bytes. Uses {@link FileRotator} for persistence logic.
+ * <p>
+ * Not inherently thread safe.
+ */
+public class NetworkStatsRecorder {
+    private static final String TAG = "NetworkStatsRecorder";
+    private static final boolean LOGD = true;
+
+    private final FileRotator mRotator;
+    private final NonMonotonicObserver<String> mObserver;
+    private final String mCookie;
+
+    private final long mBucketDuration;
+    private final long mPersistThresholdBytes;
+    private final boolean mOnlyTags;
+
+    private NetworkStats mLastSnapshot;
+
+    private final NetworkStatsCollection mPending;
+    private final NetworkStatsCollection mSinceBoot;
+
+    private final CombiningRewriter mPendingRewriter;
+
+    private WeakReference<NetworkStatsCollection> mComplete;
+
+    public NetworkStatsRecorder(FileRotator rotator, NonMonotonicObserver<String> observer,
+            String cookie, long bucketDuration, long persistThresholdBytes, boolean onlyTags) {
+        mRotator = checkNotNull(rotator, "missing FileRotator");
+        mObserver = checkNotNull(observer, "missing NonMonotonicObserver");
+        mCookie = cookie;
+
+        mBucketDuration = bucketDuration;
+        mPersistThresholdBytes = persistThresholdBytes;
+        mOnlyTags = onlyTags;
+
+        mPending = new NetworkStatsCollection(bucketDuration);
+        mSinceBoot = new NetworkStatsCollection(bucketDuration);
+
+        mPendingRewriter = new CombiningRewriter(mPending);
+    }
+
+    public void resetLocked() {
+        mLastSnapshot = null;
+        mPending.reset();
+        mSinceBoot.reset();
+        mComplete.clear();
+    }
+
+    public NetworkStats.Entry getTotalSinceBootLocked(NetworkTemplate template) {
+        return mSinceBoot.getSummary(template, Long.MIN_VALUE, Long.MAX_VALUE).getTotal(null);
+    }
+
+    /**
+     * Load complete history represented by {@link FileRotator}. Caches
+     * internally as a {@link WeakReference}, and updated with future
+     * {@link #recordSnapshotLocked(NetworkStats, Map, long)} snapshots as long
+     * as reference is valid.
+     */
+    public NetworkStatsCollection getOrLoadCompleteLocked() {
+        NetworkStatsCollection complete = mComplete != null ? mComplete.get() : null;
+        if (complete == null) {
+            if (LOGD) Slog.d(TAG, "getOrLoadCompleteLocked() reading from disk for " + mCookie);
+            try {
+                complete = new NetworkStatsCollection(mBucketDuration);
+                mRotator.readMatching(complete, Long.MIN_VALUE, Long.MAX_VALUE);
+                complete.recordCollection(mPending);
+                mComplete = new WeakReference<NetworkStatsCollection>(complete);
+            } catch (IOException e) {
+                Log.wtf(TAG, "problem completely reading network stats", e);
+            }
+        }
+        return complete;
+    }
+
+    /**
+     * Record any delta that occurred since last {@link NetworkStats} snapshot,
+     * using the given {@link Map} to identify network interfaces. First
+     * snapshot is considered bootstrap, and is not counted as delta.
+     */
+    public void recordSnapshotLocked(NetworkStats snapshot,
+            Map<String, NetworkIdentitySet> ifaceIdent, long currentTimeMillis) {
+        final HashSet<String> unknownIfaces = Sets.newHashSet();
+
+        // assume first snapshot is bootstrap and don't record
+        if (mLastSnapshot == null) {
+            mLastSnapshot = snapshot;
+            return;
+        }
+
+        final NetworkStatsCollection complete = mComplete != null ? mComplete.get() : null;
+
+        final NetworkStats delta = NetworkStats.subtract(
+                snapshot, mLastSnapshot, mObserver, mCookie);
+        final long end = currentTimeMillis;
+        final long start = end - delta.getElapsedRealtime();
+
+        NetworkStats.Entry entry = null;
+        for (int i = 0; i < delta.size(); i++) {
+            entry = delta.getValues(i, entry);
+            final NetworkIdentitySet ident = ifaceIdent.get(entry.iface);
+            if (ident == null) {
+                unknownIfaces.add(entry.iface);
+                continue;
+            }
+
+            // skip when no delta occured
+            if (entry.isEmpty()) continue;
+
+            // only record tag data when requested
+            if ((entry.tag == TAG_NONE) != mOnlyTags) {
+                mPending.recordData(ident, entry.uid, entry.set, entry.tag, start, end, entry);
+
+                // also record against boot stats when present
+                if (mSinceBoot != null) {
+                    mSinceBoot.recordData(ident, entry.uid, entry.set, entry.tag, start, end, entry);
+                }
+
+                // also record against complete dataset when present
+                if (complete != null) {
+                    complete.recordData(ident, entry.uid, entry.set, entry.tag, start, end, entry);
+                }
+            }
+        }
+
+        mLastSnapshot = snapshot;
+
+        if (LOGD && unknownIfaces.size() > 0) {
+            Slog.w(TAG, "unknown interfaces " + unknownIfaces + ", ignoring those stats");
+        }
+    }
+
+    /**
+     * Consider persisting any pending deltas, if they are beyond
+     * {@link #mPersistThresholdBytes}.
+     */
+    public void maybePersistLocked(long currentTimeMillis) {
+        final long pendingBytes = mPending.getTotalBytes();
+        if (pendingBytes >= mPersistThresholdBytes) {
+            forcePersistLocked(currentTimeMillis);
+        } else {
+            mRotator.maybeRotate(currentTimeMillis);
+        }
+    }
+
+    /**
+     * Force persisting any pending deltas.
+     */
+    public void forcePersistLocked(long currentTimeMillis) {
+        if (mPending.isDirty()) {
+            if (LOGD) Slog.d(TAG, "forcePersistLocked() writing for " + mCookie);
+            try {
+                mRotator.rewriteActive(mPendingRewriter, currentTimeMillis);
+                mRotator.maybeRotate(currentTimeMillis);
+                mPending.reset();
+            } catch (IOException e) {
+                Log.wtf(TAG, "problem persisting pending stats", e);
+            }
+        }
+    }
+
+    /**
+     * Remove the given UID from all {@link FileRotator} history, migrating it
+     * to {@link TrafficStats#UID_REMOVED}.
+     */
+    public void removeUidLocked(int uid) {
+        try {
+            // process all existing data to migrate uid
+            mRotator.rewriteAll(new RemoveUidRewriter(mBucketDuration, uid));
+        } catch (IOException e) {
+            Log.wtf(TAG, "problem removing UID " + uid, e);
+        }
+
+        // clear UID from current stats snapshot
+        if (mLastSnapshot != null) {
+            mLastSnapshot = mLastSnapshot.withoutUid(uid);
+        }
+    }
+
+    /**
+     * Rewriter that will combine current {@link NetworkStatsCollection} values
+     * with anything read from disk, and write combined set to disk. Clears the
+     * original {@link NetworkStatsCollection} when finished writing.
+     */
+    private static class CombiningRewriter implements FileRotator.Rewriter {
+        private final NetworkStatsCollection mCollection;
+
+        public CombiningRewriter(NetworkStatsCollection collection) {
+            mCollection = checkNotNull(collection, "missing NetworkStatsCollection");
+        }
+
+        /** {@inheritDoc} */
+        public void reset() {
+            // ignored
+        }
+
+        /** {@inheritDoc} */
+        public void read(InputStream in) throws IOException {
+            mCollection.read(in);
+        }
+
+        /** {@inheritDoc} */
+        public boolean shouldWrite() {
+            return true;
+        }
+
+        /** {@inheritDoc} */
+        public void write(OutputStream out) throws IOException {
+            mCollection.write(new DataOutputStream(out));
+            mCollection.reset();
+        }
+    }
+
+    /**
+     * Rewriter that will remove any {@link NetworkStatsHistory} attributed to
+     * the requested UID, only writing data back when modified.
+     */
+    public static class RemoveUidRewriter implements FileRotator.Rewriter {
+        private final NetworkStatsCollection mTemp;
+        private final int mUid;
+
+        public RemoveUidRewriter(long bucketDuration, int uid) {
+            mTemp = new NetworkStatsCollection(bucketDuration);
+            mUid = uid;
+        }
+
+        /** {@inheritDoc} */
+        public void reset() {
+            mTemp.reset();
+        }
+
+        /** {@inheritDoc} */
+        public void read(InputStream in) throws IOException {
+            mTemp.read(in);
+            mTemp.clearDirty();
+            mTemp.removeUid(mUid);
+        }
+
+        /** {@inheritDoc} */
+        public boolean shouldWrite() {
+            return mTemp.isDirty();
+        }
+
+        /** {@inheritDoc} */
+        public void write(OutputStream out) throws IOException {
+            mTemp.write(new DataOutputStream(out));
+        }
+    }
+
+    public void importLegacyNetworkLocked(File file) throws IOException {
+        // legacy file still exists; start empty to avoid double importing
+        mRotator.deleteAll();
+
+        final NetworkStatsCollection collection = new NetworkStatsCollection(mBucketDuration);
+        collection.readLegacyNetwork(file);
+
+        final long startMillis = collection.getStartMillis();
+        final long endMillis = collection.getEndMillis();
+
+        if (!collection.isEmpty()) {
+            // process legacy data, creating active file at starting time, then
+            // using end time to possibly trigger rotation.
+            mRotator.rewriteActive(new CombiningRewriter(collection), startMillis);
+            mRotator.maybeRotate(endMillis);
+        }
+    }
+
+    public void importLegacyUidLocked(File file) throws IOException {
+        // legacy file still exists; start empty to avoid double importing
+        mRotator.deleteAll();
+
+        final NetworkStatsCollection collection = new NetworkStatsCollection(mBucketDuration);
+        collection.readLegacyUid(file, mOnlyTags);
+
+        final long startMillis = collection.getStartMillis();
+        final long endMillis = collection.getEndMillis();
+
+        if (!collection.isEmpty()) {
+            // process legacy data, creating active file at starting time, then
+            // using end time to possibly trigger rotation.
+            mRotator.rewriteActive(new CombiningRewriter(collection), startMillis);
+            mRotator.maybeRotate(endMillis);
+        }
+    }
+
+    public void dumpLocked(IndentingPrintWriter pw, boolean fullHistory) {
+        pw.print("Pending bytes: "); pw.println(mPending.getTotalBytes());
+        if (fullHistory) {
+            pw.println("Complete history:");
+            getOrLoadCompleteLocked().dump(pw);
+        } else {
+            pw.println("History since boot:");
+            mSinceBoot.dump(pw);
+        }
+    }
+}