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The KSC SDK for Java - Core module holds the classes that is used by the individual service clients to interact with KSC Web Services. Users need to depend on KSC-java-sdk artifact for accessing individual client classes.
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/*
 * Copyright 2010-2016 ksyun.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Portions copyright 2006-2009 James Murty. Please see LICENSE.txt
 * for applicable license terms and NOTICE.txt for applicable notices.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://ksyun.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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.ksc.util;

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

/**
 * Utilities for encoding and decoding binary data to and from different forms.
 */
public class BinaryUtils {
    /**
     * Converts byte data to a Hex-encoded string in lower case.
     *
     * @param data
     *            data to hex encode.
     *
     * @return hex-encoded string.
     */
    public static String toHex(byte[] data) {
        return Base16Lower.encodeAsString(data);
    }

    /**
     * Converts a Hex-encoded data string to the original byte data.
     *
     * @param hexData
     *            hex-encoded data to decode.
     * @return decoded data from the hex string.
     */
    public static byte[] fromHex(String hexData) {
        return Base16Lower.decode(hexData);
    }

    /**
     * Converts byte data to a Base64-encoded string.
     *
     * @param data
     *            data to Base64 encode.
     * @return encoded Base64 string.
     */
    public static String toBase64(byte[] data) {
        return Base64.encodeAsString(data);
    }

    /**
     * Converts a Base64-encoded string to the original byte data.
     *
     * @param b64Data
     *            a Base64-encoded string to decode.
     *
     * @return bytes decoded from a Base64 string.
     */
    public static byte[] fromBase64(String b64Data) {
        return b64Data == null ? null : Base64.decode(b64Data);
    }

    /**
     * Wraps a ByteBuffer in an InputStream. If the input {@code byteBuffer}
     * is null, returns an empty stream.
     *
     * @param byteBuffer The ByteBuffer to wrap.
     *
     * @return An InputStream wrapping the ByteBuffer content.
     */
    public static ByteArrayInputStream toStream(ByteBuffer byteBuffer) {
        if (byteBuffer == null) {
            return new ByteArrayInputStream(new byte[0]);
        }
        return new ByteArrayInputStream(copyBytesFrom(byteBuffer));
    }

    /**
     * Returns a copy of all the bytes from the given ByteBuffer,
     * from the beginning to the buffer's limit; or null if the input is null.
     * 
     * The internal states of the given byte buffer will be restored when this
     * method completes execution.
     * 

     * When handling ByteBuffer from user's input, it's typical to
     * call the {@link #copyBytesFrom(ByteBuffer)} instead of
     * {@link #copyAllBytesFrom(ByteBuffer)} so as to account for the position
     * of the input ByteBuffer. The opposite is typically true,
     * however, when handling ByteBuffer from withint the
     * unmarshallers of the low-level clients.
     */
    public static byte[] copyAllBytesFrom(ByteBuffer bb) {
        if (bb == null) {
            return null;
        }

        if (bb.hasArray()) {
            return Arrays.copyOfRange(
                    bb.array(),
                    bb.arrayOffset(),
                    bb.arrayOffset() + bb.limit());
        }

        ByteBuffer copy = bb.asReadOnlyBuffer();
        copy.rewind();

        byte[] dst = new byte[copy.remaining()];
        copy.get(dst);
        return dst;
    }

    /**
     * Returns a copy of the bytes from the given ByteBuffer,
     * ranging from the the buffer's current position to the buffer's limit; or
     * null if the input is null.
     * 

     * The internal states of the given byte buffer will be restored when this
     * method completes execution.
     * 
     * When handling ByteBuffer from user's input, it's typical to
     * call the {@link #copyBytesFrom(ByteBuffer)} instead of
     * {@link #copyAllBytesFrom(ByteBuffer)} so as to account for the position
     * of the input ByteBuffer. The opposite is typically true,
     * however, when handling ByteBuffer from withint the
     * unmarshallers of the low-level clients.
     */
    public static byte[] copyBytesFrom(ByteBuffer bb) {
        if (bb == null) {
            return null;
        }

        if (bb.hasArray()) {
            return Arrays.copyOfRange(
                    bb.array(),
                    bb.arrayOffset() + bb.position(),
                    bb.arrayOffset() + bb.limit());
        }

        byte[] dst = new byte[bb.remaining()];
        bb.asReadOnlyBuffer().get(dst);
        return dst;
    }

}