Add utilities to persist lists of Persistable objects

/*

 * Copyright (C) 2020 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.vcn.util;

import android.annotation.NonNull;

import android.os.PersistableBundle;

import java.util.ArrayList;

import java.util.List;

/** @hide */

public class PersistableBundleUtils {

    private static final String LIST_KEY_FORMAT = "LIST_ITEM_%d";

    private static final String LIST_LENGTH_KEY = "LIST_LENGTH";

    /**

     * Functional interface to convert an object of the specified type to a PersistableBundle.

     *

     * @param <T> the type of the source object

     */

    public interface Serializer<T> {

        /**

         * Converts this object to a PersistableBundle.

         *

         * @return the PersistableBundle representation of this object

         */

        PersistableBundle toPersistableBundle(T obj);

    }

    /**

     * Functional interface used to create an object of the specified type from a PersistableBundle.

     *

     * @param <T> the type of the resultant object

     */

    public interface Deserializer<T> {

        /**

         * Creates an instance of specified type from a PersistableBundle representation.

         *

         * @param in the PersistableBundle representation

         * @return an instance of the specified type

         */

        T fromPersistableBundle(PersistableBundle in);

    }

    /**

     * Converts from a list of Persistable objects to a single PersistableBundle.

     *

     * <p>To avoid key collisions, NO additional key/value pairs should be added to the returned

     * PersistableBundle object.

     *

     * @param <T> the type of the objects to convert to the PersistableBundle

     * @param in the list of objects to be serialized into a PersistableBundle

     * @param serializer an implementation of the {@link Serializer} functional interface that

     *     converts an object of type T to a PersistableBundle

     */

    @NonNull

    public static <T> PersistableBundle fromList(

            @NonNull List<T> in, @NonNull Serializer<T> serializer) {

        final PersistableBundle result = new PersistableBundle();

        result.putInt(LIST_LENGTH_KEY, in.size());

        for (int i = 0; i < in.size(); i++) {

            final String key = String.format(LIST_KEY_FORMAT, i);

            result.putPersistableBundle(key, serializer.toPersistableBundle(in.get(i)));

        }

        return result;

    }

    /**

     * Converts from a PersistableBundle to a list of objects.

     *

     * @param <T> the type of the objects to convert from a PersistableBundle

     * @param in the PersistableBundle containing the persisted list

     * @param deserializer an implementation of the {@link Deserializer} functional interface that

     *     builds the relevant type of objects.

     */

    @NonNull

    public static <T> List<T> toList(

            @NonNull PersistableBundle in, @NonNull Deserializer<T> deserializer) {

        final int listLength = in.getInt(LIST_LENGTH_KEY);

        final ArrayList<T> result = new ArrayList<>(listLength);

        for (int i = 0; i < listLength; i++) {

            final String key = String.format(LIST_KEY_FORMAT, i);

            final PersistableBundle item = in.getPersistableBundle(key);

            result.add(deserializer.fromPersistableBundle(item));

        }

        return result;

    }

}

/*

 * Copyright (C) 2020 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.vcn.util;

import static org.junit.Assert.assertEquals;

import android.os.PersistableBundle;

import androidx.test.filters.SmallTest;

import androidx.test.runner.AndroidJUnit4;

import org.junit.Test;

import org.junit.runner.RunWith;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.Objects;

@RunWith(AndroidJUnit4.class)

@SmallTest

public class PersistableBundleUtilsTest {

    private static final String TEST_KEY = "testKey";

    private static final String TEST_STRING_PREFIX = "testString";

    private static final int[] TEST_INT_ARRAY = new int[] {0, 1, 2, 3, 4};

    private static final int NUM_COLLECTION_ENTRIES = 10;

    private static class TestClass {

        private static final String TEST_INTEGER_KEY = "mTestInteger";

        private final int mTestInteger;

        private static final String TEST_INT_ARRAY_KEY = "mTestIntArray";

        private final int[] mTestIntArray;

        private static final String TEST_STRING_KEY = "mTestString";

        private final String mTestString;

        private static final String TEST_PERSISTABLE_BUNDLE_KEY = "mTestPersistableBundle";

        private final PersistableBundle mTestPersistableBundle;

        TestClass(

                int testInteger,

                int[] testIntArray,

                String testString,

                PersistableBundle testPersistableBundle) {

            mTestInteger = testInteger;

            mTestIntArray = testIntArray;

            mTestString = testString;

            mTestPersistableBundle = testPersistableBundle;

        }

        TestClass(PersistableBundle in) {

            mTestInteger = in.getInt(TEST_INTEGER_KEY);

            mTestIntArray = in.getIntArray(TEST_INT_ARRAY_KEY);

            mTestString = in.getString(TEST_STRING_KEY);

            mTestPersistableBundle = in.getPersistableBundle(TEST_PERSISTABLE_BUNDLE_KEY);

        }

        public PersistableBundle toPersistableBundle() {

            final PersistableBundle result = new PersistableBundle();

            result.putInt(TEST_INTEGER_KEY, mTestInteger);

            result.putIntArray(TEST_INT_ARRAY_KEY, mTestIntArray);

            result.putString(TEST_STRING_KEY, mTestString);

            result.putPersistableBundle(TEST_PERSISTABLE_BUNDLE_KEY, mTestPersistableBundle);

            return result;

        }

        @Override

        public int hashCode() {

            return Objects.hash(

                    mTestInteger,

                    Arrays.hashCode(mTestIntArray),

                    mTestString,

                    mTestPersistableBundle);

        }

        @Override

        public boolean equals(Object o) {

            if (!(o instanceof TestClass)) {

                return false;

            }

            final TestClass other = (TestClass) o;

            // TODO: Add a proper equals() to PersistableBundle. But in the meantime, force

            // TODO: unparcelling in order to allow test comparison.

            if (mTestPersistableBundle.size() != other.mTestPersistableBundle.size()) {

                return false;

            }

            return mTestInteger == other.mTestInteger

                    && Arrays.equals(mTestIntArray, other.mTestIntArray)

                    && mTestString.equals(other.mTestString)

                    && mTestPersistableBundle.kindofEquals(other.mTestPersistableBundle);

        }

    }

    @Test

    public void testConversionLossless() throws Exception {

        final List<TestClass> sourceList = new ArrayList<>();

        for (int i = 0; i < NUM_COLLECTION_ENTRIES; i++) {

            final PersistableBundle innerBundle = new PersistableBundle();

            innerBundle.putInt(TEST_KEY, i);

            sourceList.add(new TestClass(i, TEST_INT_ARRAY, TEST_STRING_PREFIX + i, innerBundle));

        }

        final PersistableBundle bundled =

                PersistableBundleUtils.fromList(sourceList, TestClass::toPersistableBundle);

        final List<TestClass> resultList = PersistableBundleUtils.toList(bundled, TestClass::new);

        assertEquals(sourceList, resultList);

    }

}