DfsStreamKey.java

/*
 * Copyright (C) 2011, 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 static java.nio.charset.StandardCharsets.UTF_8;

import java.util.Arrays;

import org.eclipse.jgit.annotations.Nullable;
import org.eclipse.jgit.internal.storage.pack.PackExt;

/**
 * Key used by {@link org.eclipse.jgit.internal.storage.dfs.DfsBlockCache} to disambiguate streams.
 */
public abstract class DfsStreamKey {
    /**
     * Create a {@code DfsStreamKey}
     *
     * @param repo
     *            description of the containing repository.
     * @param name
     *            compute the key from a string name.
     * @param ext
     *            pack file extension, or {@code null}.
     * @return key for {@code name}
     */
    public static DfsStreamKey of(DfsRepositoryDescription repo, String name,
            @Nullable PackExt ext) {
        return new ByteArrayDfsStreamKey(repo, name.getBytes(UTF_8), ext);
    }

    final int hash;

    final int packExtPos;

    /**
     * Constructor for DfsStreamKey.
     *
     * @param hash
     *            hash of the other identifying components of the key.
     * @param ext
     *            pack file extension, or {@code null}.
     */
    protected DfsStreamKey(int hash, @Nullable PackExt ext) {
        // Multiply by 31 here so we can more directly combine with another
        // value without doing the multiply there.
        this.hash = hash * 31;
        this.packExtPos = ext == null ? 0 : ext.getPosition();
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode() {
        return hash;
    }

    /** {@inheritDoc} */
    @Override
    public abstract boolean equals(Object o);

    /** {@inheritDoc} */
    @SuppressWarnings("boxing")
    @Override
    public String toString() {
        return String.format("DfsStreamKey[hash=%08x]", hash); //$NON-NLS-1$
    }

    private static final class ByteArrayDfsStreamKey extends DfsStreamKey {
        private final DfsRepositoryDescription repo;

        private final byte[] name;

        ByteArrayDfsStreamKey(DfsRepositoryDescription repo, byte[] name,
                @Nullable PackExt ext) {
            super(repo.hashCode() * 31 + Arrays.hashCode(name), ext);
            this.repo = repo;
            this.name = name;
        }

        @Override
        public boolean equals(Object o) {
            if (o instanceof ByteArrayDfsStreamKey) {
                ByteArrayDfsStreamKey k = (ByteArrayDfsStreamKey) o;
                return hash == k.hash && repo.equals(k.repo)
                        && Arrays.equals(name, k.name);
            }
            return false;
        }
    }

    static final class ForReverseIndex extends DfsStreamKey {
        private final DfsStreamKey idxKey;

        ForReverseIndex(DfsStreamKey idxKey) {
            super(idxKey.hash + 1, null);
            this.idxKey = idxKey;
        }

        @Override
        public boolean equals(Object o) {
            return o instanceof ForReverseIndex
                    && idxKey.equals(((ForReverseIndex) o).idxKey);
        }
    }
}