diff --git a/sample_updater/src/com/example/android/systemupdatersample/util/PayloadSpecs.java b/sample_updater/src/com/example/android/systemupdatersample/util/PayloadSpecs.java
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+++ b/sample_updater/src/com/example/android/systemupdatersample/util/PayloadSpecs.java
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+/*
+ * Copyright (C) 2018 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.example.android.systemupdatersample.util;
+
+import android.annotation.TargetApi;
+import android.os.Build;
+
+import com.example.android.systemupdatersample.PayloadSpec;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
+
+/** The helper class that creates {@link PayloadSpec}. */
+@TargetApi(Build.VERSION_CODES.N)
+public final class PayloadSpecs {
+
+    /**
+     * The payload PAYLOAD_ENTRY is stored in the zip package to comply with the Android OTA package
+     * format. We want to find out the offset of the entry, so that we can pass it over to the A/B
+     * updater without making an extra copy of the payload.
+     *
+     * <p>According to Android docs, the entries are listed in the order in which they appear in the
+     * zip file. So we enumerate the entries to identify the offset of the payload file.
+     * http://developer.android.com/reference/java/util/zip/ZipFile.html#entries()
+     */
+    public static PayloadSpec forNonStreaming(File packageFile) throws IOException {
+        boolean payloadFound = false;
+        long payloadOffset = 0;
+        long payloadSize = 0;
+
+        List<String> properties = new ArrayList<>();
+        try (ZipFile zip = new ZipFile(packageFile)) {
+            Enumeration<? extends ZipEntry> entries = zip.entries();
+            long offset = 0;
+            while (entries.hasMoreElements()) {
+                ZipEntry entry = entries.nextElement();
+                String name = entry.getName();
+                // Zip local file header has 30 bytes + filename + sizeof extra field.
+                // https://en.wikipedia.org/wiki/Zip_(file_format)
+                long extraSize = entry.getExtra() == null ? 0 : entry.getExtra().length;
+                offset += 30 + name.length() + extraSize;
+
+                if (entry.isDirectory()) {
+                    continue;
+                }
+
+                long length = entry.getCompressedSize();
+                if (PackagePropertyFiles.PAYLOAD_BINARY_FILE_NAME.equals(name)) {
+                    if (entry.getMethod() != ZipEntry.STORED) {
+                        throw new IOException("Invalid compression method.");
+                    }
+                    payloadFound = true;
+                    payloadOffset = offset;
+                    payloadSize = length;
+                } else if (PackagePropertyFiles.PAYLOAD_PROPERTIES_FILE_NAME.equals(name)) {
+                    InputStream inputStream = zip.getInputStream(entry);
+                    if (inputStream != null) {
+                        BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
+                        String line;
+                        while ((line = br.readLine()) != null) {
+                            properties.add(line);
+                        }
+                    }
+                }
+                offset += length;
+            }
+        }
+
+        if (!payloadFound) {
+            throw new IOException("Failed to find payload entry in the given package.");
+        }
+        return PayloadSpec.newBuilder()
+                        .url("file://" + packageFile.getAbsolutePath())
+                        .offset(payloadOffset)
+                        .size(payloadSize)
+                        .properties(properties)
+                        .build();
+    }
+
+    /**
+     * Converts an {@link PayloadSpec} to a string.
+     */
+    public static String toString(PayloadSpec payloadSpec) {
+        return "<PayloadSpec url=" + payloadSpec.getUrl()
+                + ", offset=" + payloadSpec.getOffset()
+                + ", size=" + payloadSpec.getSize()
+                + ", properties=" + Arrays.toString(
+                        payloadSpec.getProperties().toArray(new String[0]))
+                + ">";
+    }
+
+    private PayloadSpecs() {}
+
+}