AbstractHasher.java

/*
 * This file is part of Fim - File Integrity Manager
 *
 * Copyright (C) 2017  Etienne Vrignaud
 *
 * Fim 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 3 of the License, or
 * (at your option) any later version.
 *
 * Fim 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 Fim.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.fim.internal.hash;

import org.fim.model.Constants;
import org.fim.model.Context;
import org.fim.model.HashMode;
import org.fim.util.Ascii85Util;

import java.nio.ByteBuffer;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public abstract class AbstractHasher implements Hasher {
    public static final String HASH_ALGORITHM = "SHA-512";

    private final Context context;
    private final boolean active;

    private MessageDigest digest;
    private long bytesHashed;
    private long totalBytesHashed;

    private ThroughputKeeper throughputKeeper;

    public AbstractHasher(Context context) throws NoSuchAlgorithmException {
        this.context = context;
        this.active = isCompatible(context.getHashMode());
        this.totalBytesHashed = 0;

        if (context.isDynamicScaling()) {
            this.throughputKeeper = new ThroughputKeeper();
        }

        if (this.active) {
            this.digest = MessageDigest.getInstance(HASH_ALGORITHM);
        }
    }

    protected abstract boolean isCompatible(HashMode hashMode);

    protected abstract ByteBuffer getNextBlockToHash(long filePosition, long currentPosition, ByteBuffer buffer);

    @Override
    public boolean isActive() {
        return active;
    }

    @Override
    public long getBytesHashed() {
        if (active) {
            return bytesHashed;
        } else {
            return 0;
        }
    }

    @Override
    public long getTotalBytesHashed() {
        return totalBytesHashed;
    }

    @Override
    public String getHash() {
        if (active) {
            byte[] digestBytes = digest.digest();
            return Ascii85Util.encode(digestBytes);
        } else {
            return Constants.NO_HASH;
        }
    }

    @Override
    public void reset(long fileSize) {
        if (active) {
            digest.reset();
            bytesHashed = 0;
        }
    }

    @Override
    public void update(long filePosition, ByteBuffer buffer) {
        if (active) {
            long currentPosition = filePosition;
            long limitPosition = filePosition + buffer.limit();
            ByteBuffer block;
            while ((currentPosition < limitPosition) && ((block = getNextBlockToHash(filePosition, currentPosition, buffer)) != null)) {
                currentPosition = filePosition + block.limit();

                int remaining = block.remaining();
                digest.update(block);

                bytesHashed += remaining;
                totalBytesHashed += remaining;

                if (context.isDynamicScaling()) {
                    throughputKeeper.update(remaining);
                }
            }
        }
    }

    @Override
    public long getInstantThroughput() {
        return throughputKeeper.getInstantThroughput();
    }
}