LazyObjectIdSetFile.java

/*
 * Copyright (C) 2015, 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.file;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;

import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.MutableObjectId;
import org.eclipse.jgit.lib.ObjectIdOwnerMap;
import org.eclipse.jgit.lib.ObjectIdSet;

/**
 * Lazily loads a set of ObjectIds, one per line.
 */
public class LazyObjectIdSetFile implements ObjectIdSet {
    private final File src;
    private ObjectIdOwnerMap<Entry> set;

    /**
     * Create a new lazy set from a file.
     *
     * @param src
     *            the source file.
     */
    public LazyObjectIdSetFile(File src) {
        this.src = src;
    }

    /** {@inheritDoc} */
    @Override
    public boolean contains(AnyObjectId objectId) {
        if (set == null) {
            set = load();
        }
        return set.contains(objectId);
    }

    private ObjectIdOwnerMap<Entry> load() {
        ObjectIdOwnerMap<Entry> r = new ObjectIdOwnerMap<>();
        try (FileInputStream fin = new FileInputStream(src);
                Reader rin = new InputStreamReader(fin, UTF_8);
                BufferedReader br = new BufferedReader(rin)) {
            MutableObjectId id = new MutableObjectId();
            for (String line; (line = br.readLine()) != null;) {
                id.fromString(line);
                if (!r.contains(id)) {
                    r.add(new Entry(id));
                }
            }
        } catch (IOException e) {
            // Ignore IO errors accessing the lazy set.
        }
        return r;
    }

    static class Entry extends ObjectIdOwnerMap.Entry {
        Entry(AnyObjectId id) {
            super(id);
        }
    }
}