ReflogReaderImpl.java

/*
 * Copyright (C) 2009, Robin Rosenberg <robin.rosenberg@dewire.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.internal.storage.file;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ReflogEntry;
import org.eclipse.jgit.lib.ReflogReader;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.util.IO;
import org.eclipse.jgit.util.RawParseUtils;

/**
 * Utility for reading reflog entries
 */
class ReflogReaderImpl implements ReflogReader {
    private File logName;

    /**
     * @param db
     * @param refname
     */
    ReflogReaderImpl(Repository db, String refname) {
        logName = new File(db.getDirectory(), Constants.LOGS + '/' + refname);
    }

    /* (non-Javadoc)
     * @see org.eclipse.jgit.internal.storage.file.ReflogReaader#getLastEntry()
     */
    /** {@inheritDoc} */
    @Override
    public ReflogEntry getLastEntry() throws IOException {
        return getReverseEntry(0);
    }

    /* (non-Javadoc)
     * @see org.eclipse.jgit.internal.storage.file.ReflogReaader#getReverseEntries()
     */
    /** {@inheritDoc} */
    @Override
    public List<ReflogEntry> getReverseEntries() throws IOException {
        return getReverseEntries(Integer.MAX_VALUE);
    }

    /* (non-Javadoc)
     * @see org.eclipse.jgit.internal.storage.file.ReflogReaader#getReverseEntry(int)
     */
    /** {@inheritDoc} */
    @Override
    public ReflogEntry getReverseEntry(int number) throws IOException {
        if (number < 0)
            throw new IllegalArgumentException();

        final byte[] log;
        try {
            log = IO.readFully(logName);
        } catch (FileNotFoundException e) {
            if (logName.exists()) {
                throw e;
            }
            return null;
        }

        int rs = RawParseUtils.prevLF(log, log.length);
        int current = 0;
        while (rs >= 0) {
            rs = RawParseUtils.prevLF(log, rs);
            if (number == current)
                return new ReflogEntryImpl(log, rs < 0 ? 0 : rs + 2);
            current++;
        }
        return null;
    }

    /* (non-Javadoc)
     * @see org.eclipse.jgit.internal.storage.file.ReflogReaader#getReverseEntries(int)
     */
    /** {@inheritDoc} */
    @Override
    public List<ReflogEntry> getReverseEntries(int max) throws IOException {
        final byte[] log;
        try {
            log = IO.readFully(logName);
        } catch (FileNotFoundException e) {
            if (logName.exists()) {
                throw e;
            }
            return Collections.emptyList();
        }

        int rs = RawParseUtils.prevLF(log, log.length);
        List<ReflogEntry> ret = new ArrayList<>();
        while (rs >= 0 && max-- > 0) {
            rs = RawParseUtils.prevLF(log, rs);
            ReflogEntry entry = new ReflogEntryImpl(log, rs < 0 ? 0 : rs + 2);
            ret.add(entry);
        }
        return ret;
    }
}