Java tutorial
/* * Copyright (C) 2015 PRIS Quentin * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ package com.playonlinux.core.utils; import static com.playonlinux.core.lang.Localisation.translate; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.function.Consumer; import org.apache.commons.codec.binary.Hex; import org.apache.commons.io.FileUtils; import com.playonlinux.core.entities.ProgressEntity; public class ChecksumCalculator { private static final int BLOCK_SIZE = 2048; private static final String WAIT_MESSAGE = translate("Please wait while we are verifying the file..."); private Consumer<ProgressEntity> onChange; public String calculate(File fileToCheck, String algorithm) throws IOException { final long fileSize = FileUtils.sizeOf(fileToCheck); try (final FileInputStream inputStream = new FileInputStream(fileToCheck)) { MessageDigest messageDigest; try { messageDigest = MessageDigest.getInstance(algorithm); } catch (NoSuchAlgorithmException e) { throw new IllegalArgumentException(e); } byte[] digest = getDigest(inputStream, messageDigest, fileSize); return Hex.encodeHexString(digest); } } private byte[] getDigest(InputStream inputStream, MessageDigest messageDigest, long sizeInBytes) throws IOException { messageDigest.reset(); byte[] bytes = new byte[BLOCK_SIZE]; int numBytes; int readBytes = 0; while ((numBytes = inputStream.read(bytes)) != -1) { messageDigest.update(bytes, 0, numBytes); readBytes += numBytes; if (sizeInBytes != 0L) { double percentage = (double) readBytes / (double) sizeInBytes * (double) 100; changeState(percentage); } } return messageDigest.digest(); } private void changeState(double percentage) { if (onChange != null) { onChange.accept( new ProgressEntity.Builder().withPercent(percentage).withProgressText(WAIT_MESSAGE).build()); } } public void setOnChange(Consumer<ProgressEntity> onChange) { this.onChange = onChange; } }