/*
 * Copyright (C) 2019 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.tradefed.util;

import java.nio.ByteBuffer;
import java.util.Arrays;

/**
 * Utilities to operate on byte array, e.g., convert bytes to integer.
 *
 * <p>Java doesn't have an unsigned value type, so expansion is needed to convert an unsigned
 * integer stored in 4 bytes to a long value, or unsigned short stored in 2 bytes to an integer
 * value.
 */
public class ByteArrayUtil {

    /**
     * Get a {@link ByteBuffer} for the given bytes wrapped in a byte array of given size.
     *
     * <p>java doesn't have an unsigned value type, so expansion is needed to convert an unsigned
     * short stored in 2 bytes to an integer value.
     *
     * @param bytes an array of bytes.
     * @param offset the start offset of the integer data.
     * @param length the length of the integer data.
     * @param containerSize the size of the array to store the given bytes, append zero to unfilled
     *     items.
     * @return a {@link ByteBuffer} for the given bytes wrapped in a byte array of given size.
     */
    private static ByteBuffer getByteBuffer(
            byte[] bytes, int offset, int length, int containerSize) {
        byte[] data = new byte[containerSize];
        for (int i = 0; i < length; i++) {
            data[i] = bytes[offset + i];
        }
        return ByteBuffer.wrap(data).order(java.nio.ByteOrder.LITTLE_ENDIAN);
    }

    /**
     * Get an integer from the given bytes.
     *
     * <p>java doesn't have an unsigned value type, so expansion is needed to convert an unsigned
     * short stored in 2 bytes to an integer value.
     *
     * @param bytes an array of bytes.
     * @param offset the start offset of the integer data.
     * @param length the length of the integer data.
     * @return an int value from the given bytes.
     */
    public static int getInt(byte[] bytes, int offset, int length) {
        return getByteBuffer(bytes, offset, length, 4).getInt();
    }

    /**
     * Get a long value from the given bytes.
     *
     * <p>java doesn't have an unsigned value type, so expansion is needed to convert an unsigned
     * integer stored in 4 bytes to a long value.
     *
     * @param bytes an array of bytes.
     * @param offset the start offset of the long value.
     * @param length the length of the long value.
     * @return a long value from the given bytes.
     */
    public static long getLong(byte[] bytes, int offset, int length) {
        return getByteBuffer(bytes, offset, length, 8).getLong();
    }

    /**
     * Get the string from the given bytes.
     *
     * @param bytes an array of bytes.
     * @param offset the start offset of the string data.
     * @param length the length of the string data.
     */
    public static String getString(byte[] bytes, int offset, int length) {
        return new String(Arrays.copyOfRange(bytes, offset, offset + length));
    }
}