/*
 * Copyright (C) 2022 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.net.module.util;

import android.annotation.NonNull;

/**
 * Byte utility functions.
 * @hide
 */
public class ByteUtils {
    /**
     * Returns the index of the first appearance of the value {@code target} in {@code array}.
     *
     * @param array an array of {@code byte} values, possibly empty
     * @param target a primitive {@code byte} value
     * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
     *     such index exists.
     */
    public static int indexOf(@NonNull byte[] array, byte target) {
        return indexOf(array, target, 0, array.length);
    }

    private static int indexOf(byte[] array, byte target, int start, int end) {
        for (int i = start; i < end; i++) {
            if (array[i] == target) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns the values from each provided array combined into a single array. For example, {@code
     * concat(new byte[] {a, b}, new byte[] {}, new byte[] {c}} returns the array {@code {a, b, c}}.
     *
     * @param arrays zero or more {@code byte} arrays
     * @return a single array containing all the values from the source arrays, in order
     */
    public static byte[] concat(@NonNull byte[]... arrays) {
        int length = 0;
        for (byte[] array : arrays) {
            length += array.length;
        }
        byte[] result = new byte[length];
        int pos = 0;
        for (byte[] array : arrays) {
            System.arraycopy(array, 0, result, pos, array.length);
            pos += array.length;
        }
        return result;
    }
}