PatchIdDiffFormatter.java

/*
 * Copyright (C) 2011, Stefan Lay <stefan.lay@.com> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
package org.eclipse.jgit.diff;

import java.io.IOException;
import java.io.OutputStream;
import java.security.DigestOutputStream;
import java.security.MessageDigest;

import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.util.io.NullOutputStream;

/**
 * A DiffFormatter used to calculate the patch-id of the diff.
 */
public class PatchIdDiffFormatter extends DiffFormatter {

    private final MessageDigest digest;

    /**
     * Initialize a formatter to compute a patch id.
     */
    public PatchIdDiffFormatter() {
        super(new DigestOutputStream(NullOutputStream.INSTANCE,
                Constants.newMessageDigest()));
        digest = ((DigestOutputStream) getOutputStream()).getMessageDigest();
    }

    /**
     * Should be called after having called one of the format methods
     *
     * @return the patch id calculated for the provided diff.
     */
    public ObjectId getCalulatedPatchId() {
        return ObjectId.fromRaw(digest.digest());
    }

    /** {@inheritDoc} */
    @Override
    protected void writeHunkHeader(int aStartLine, int aEndLine,
            int bStartLine, int bEndLine) throws IOException {
        // The hunk header is not taken into account for patch id calculation
    }

    /** {@inheritDoc} */
    @Override
    protected void formatIndexLine(OutputStream o, DiffEntry ent)
            throws IOException {
        // The index line is not taken into account for patch id calculation
    }
}