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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 * © COPYRIGHT 2021 Corporation CAICT All rights reserved.
 * http://www.caict.ac.cn
 */
package cn.bif.utils.hash;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Sha256 {
    MessageDigest messageDigest;

    public Sha256() {
        try {
            messageDigest = MessageDigest.getInstance("SHA-256");
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }

    public Sha256(byte[] start) {
        this();
        add(start);
    }

    public Sha256 add(byte[] bytes) {
        messageDigest.update(bytes);
        return this;
    }

    public Sha256 add32(int i) {
        messageDigest.update((byte) ((i >>> 24) & 0xFF));
        messageDigest.update((byte) ((i >>> 16) & 0xFF));
        messageDigest.update((byte) ((i >>> 8)  & 0xFF));
        messageDigest.update((byte) ((i)        & 0xFF));
        return this;
    }

    private byte[] finishTaking(int size) {
        byte[] hash = new byte[size];
        System.arraycopy(messageDigest.digest(), 0, hash, 0, size);
        return hash;
    }

    public byte[] finish128() {
        return finishTaking(16);
    }

    public byte[] finish256() {
        return finishTaking(32);
    }

    public byte[] finish() {
        return messageDigest.digest();
    }
}