Add HidlSupport.java for utility methods for HIDL.

/*

 * Copyright (C) 2017 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 android.os;

import java.util.Arrays;

import java.util.Collection;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.Objects;

import java.util.stream.IntStream;

/** @hide */

public class HidlSupport {

    /**

     * Similar to Objects.deepEquals, but also take care of lists.

     * Two objects of HIDL types are considered equal if:

     * 1. Both null

     * 2. Both non-null, and of the same class, and:

     * 2.1 Both are primitive arrays / enum arrays, elements are equal using == check

     * 2.2 Both are object arrays, elements are checked recursively

     * 2.3 Both are Lists, elements are checked recursively

     * 2.4 (If both are collections other than lists or maps, throw an error)

     * 2.5 lft.equals(rgt) returns true

     */

    public static boolean deepEquals(Object lft, Object rgt) {

        if (lft == rgt) {

            return true;

        }

        if (lft == null || rgt == null) {

            return false;

        }

        Class<?> lftClazz = lft.getClass();

        Class<?> rgtClazz = rgt.getClass();

        if (lftClazz != rgtClazz) {

            return false;

        }

        if (lftClazz.isArray()) {

            Class<?> lftElementType = lftClazz.getComponentType();

            if (lftElementType != rgtClazz.getComponentType()) {

                return false;

            }

            if (lftElementType.isPrimitive()) {

                return Objects.deepEquals(lft, rgt);

            }

            Object[] lftArray = (Object[])lft;

            Object[] rgtArray = (Object[])rgt;

            return (lftArray.length == rgtArray.length) &&

                   IntStream.range(0, lftArray.length).allMatch(

                        i -> deepEquals(lftArray[i], rgtArray[i]));

        }

        if (lft instanceof List<?>) {

            List<Object> lftList = (List<Object>)lft;

            List<Object> rgtList = (List<Object>)rgt;

            if (lftList.size() != rgtList.size()) {

                return false;

            }

            Iterator<Object> lftIter = lftList.iterator();

            return rgtList.stream()

                    .allMatch(rgtElement -> deepEquals(lftIter.next(), rgtElement));

        }

        throwErrorIfUnsupportedType(lft);

        return lft.equals(rgt);

    }

    /**

     * Similar to Arrays.deepHashCode, but also take care of lists.

     */

    public static int deepHashCode(Object o) {

        if (o == null) {

            return 0;

        }

        Class<?> clazz = o.getClass();

        if (clazz.isArray()) {

            Class<?> elementType = clazz.getComponentType();

            if (elementType.isPrimitive()) {

                return primitiveArrayHashCode(o);

            }

            return Arrays.hashCode(Arrays.stream((Object[])o)

                    .mapToInt(element -> deepHashCode(element))

                    .toArray());

        }

        if (o instanceof List<?>) {

            return Arrays.hashCode(((List<Object>)o).stream()

                    .mapToInt(element -> deepHashCode(element))

                    .toArray());

        }

        throwErrorIfUnsupportedType(o);

        return o.hashCode();

    }

    private static void throwErrorIfUnsupportedType(Object o) {

        if (o instanceof Collection<?> && !(o instanceof List<?>)) {

            throw new UnsupportedOperationException(

                    "Cannot check equality on collections other than lists: " +

                    o.getClass().getName());

        }

        if (o instanceof Map<?, ?>) {

            throw new UnsupportedOperationException(

                    "Cannot check equality on maps");

        }

    }

    private static int primitiveArrayHashCode(Object o) {

        Class<?> elementType = o.getClass().getComponentType();

        if (elementType == boolean.class) {

            return Arrays.hashCode(((boolean[])o));

        }

        if (elementType == byte.class) {

            return Arrays.hashCode(((byte[])o));

        }

        if (elementType == char.class) {

            return Arrays.hashCode(((char[])o));

        }

        if (elementType == double.class) {

            return Arrays.hashCode(((double[])o));

        }

        if (elementType == float.class) {

            return Arrays.hashCode(((float[])o));

        }

        if (elementType == int.class) {

            return Arrays.hashCode(((int[])o));

        }

        if (elementType == long.class) {

            return Arrays.hashCode(((long[])o));

        }

        if (elementType == short.class) {

            return Arrays.hashCode(((short[])o));

        }

        // Should not reach here.

        throw new UnsupportedOperationException();

    }

}