DfsReftableStack.java

/*
 * Copyright (C) 2017, Google Inc. 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.dfs;

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

import org.eclipse.jgit.internal.storage.reftable.ReftableReader;

/**
 * Tracks multiple open
 * {@link org.eclipse.jgit.internal.storage.reftable.ReftableReader} instances.
 */
public class DfsReftableStack implements AutoCloseable {
    /**
     * Opens a stack of tables for reading.
     *
     * @param ctx
     *            context to read the tables with. This {@code ctx} will be
     *            retained by the stack and each of the table readers.
     * @param files
     *            the tables to open.
     * @return stack reference to close the tables.
     * @throws java.io.IOException
     *             a table could not be opened
     */
    public static DfsReftableStack open(DfsReader ctx, List<DfsReftable> files)
            throws IOException {
        DfsReftableStack stack = new DfsReftableStack(files.size());
        boolean close = true;
        try {
            for (DfsReftable t : files) {
                stack.files.add(t);
                stack.tables.add(t.open(ctx));
            }
            close = false;
            return stack;
        } finally {
            if (close) {
                stack.close();
            }
        }
    }

    private final List<DfsReftable> files;
    private final List<ReftableReader> tables;

    private DfsReftableStack(int tableCnt) {
        this.files = new ArrayList<>(tableCnt);
        this.tables = new ArrayList<>(tableCnt);
    }

    /**
     * Get unmodifiable list of DfsRefatble files
     *
     * @return unmodifiable list of DfsRefatble files, in the same order the
     *         files were passed to {@link #open(DfsReader, List)}.
     */
    public List<DfsReftable> files() {
        return Collections.unmodifiableList(files);
    }

    /**
     * Get unmodifiable list of tables
     *
     * @return unmodifiable list of tables, in the same order the files were
     *         passed to {@link #open(DfsReader, List)}.
     */
    public List<ReftableReader> readers() {
        return Collections.unmodifiableList(tables);
    }

    /** {@inheritDoc} */
    @Override
    public void close() {
        for (ReftableReader t : tables) {
            try {
                t.close();
            } catch (IOException e) {
                // Ignore close failures.
            }
        }
    }
}