org.wildfly.swarm.plugin.utils.ChecksumUtil Maven / Gradle / Ivy

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/**
 * Copyright 2018 Red Hat, Inc, and individual contributors.
 * 
 * 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 org.wildfly.swarm.plugin.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * @author Michal Szynkiewicz, [email protected]
 * 

 * Date: 8/7/18
 */
public class ChecksumUtil {
    private static final char[] DIGITS = "0123456789abcdef".toCharArray();

    private ChecksumUtil() {
    }

    public static String calculateChecksum(File file) throws IOException, NoSuchAlgorithmException {
        try (FileInputStream in = new FileInputStream(file)) {
            byte[] buf = new byte[1024];
            int len = 0;

            MessageDigest md = MessageDigest.getInstance("SHA1");

            while ((len = in.read(buf)) >= 0) {
                md.update(buf, 0, len);
            }

            return toHex(md.digest());
        }
    }

    protected static String toHex(byte[] digest) {
        char[] result = new char[digest.length * 2];

        for (int i = 0; i < digest.length; i++) {
            toChars(digest[i], result, i * 2);
        }
        return new String(result);
    }

    private static void toChars(byte b, char[] result, int position) {
        result[position + 1] = DIGITS[b & 0xF]; // hex digit for the last (least significant) 4 bits of the byte
        result[position] = DIGITS[(b >> 4) & 0xF]; // first bits moved to the last, 0xF to handle "negative" numbers
    }
}