de.fkoeberle.autocommit.git.HashCacluatingDeltaVisitor.java Source code

Introduction

Here is the source code for de.fkoeberle.autocommit.git.HashCacluatingDeltaVisitor.java

Source

/*
 * Copyright (C) 2012, Florian Kberle <florian@fkoeberle.de>
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package de.fkoeberle.autocommit.git;

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

import org.eclipse.jgit.lib.ObjectId;

public class HashCacluatingDeltaVisitor implements GitFileSetDeltaVisitor {
    private final MessageDigest messageDigest;
    /**
     * 0 can be assumed not to occur in the filename string and can thus be used
     * as marker for an added file
     */
    private static final byte[] ADDED_FILE_MAGIC_WORD = new byte[] { 0, 1 };
    private static final byte[] REMOVED_FILE_MAGIC_WORD = new byte[] { 0, 2 };
    private static final byte[] CHANGED_FILE_MAGIC_WORD = new byte[] { 0, 3 };
    private final byte[] buffer;
    private static final int BYTES_PER_OBJECT_ID = 20;

    public HashCacluatingDeltaVisitor() {
        try {
            messageDigest = MessageDigest.getInstance("SHA");
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
        this.buffer = new byte[BYTES_PER_OBJECT_ID];
    }

    @Override
    public void visitAddedFile(String path, ObjectId newObjectId) throws IOException {
        messageDigest.update(ADDED_FILE_MAGIC_WORD);
        messageDigest.update(path.getBytes());
        newObjectId.copyRawTo(buffer, 0);
        messageDigest.update(buffer);
    }

    @Override
    public void visitRemovedFile(String path, ObjectId oldObjectId) throws IOException {
        messageDigest.update(REMOVED_FILE_MAGIC_WORD);
        messageDigest.update(path.getBytes());
        oldObjectId.copyRawTo(buffer, 0);
        messageDigest.update(buffer);
    }

    @Override
    public void visitChangedFile(String path, ObjectId oldObjectId, ObjectId newObjectId) throws IOException {
        messageDigest.update(CHANGED_FILE_MAGIC_WORD);
        messageDigest.update(path.getBytes());
        oldObjectId.copyRawTo(buffer, 0);
        messageDigest.update(buffer);
        newObjectId.copyRawTo(buffer, 0);
        messageDigest.update(buffer);
    }

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

}