CachedObjectDirectory.java

/*
 * Copyright (C) 2010, Constantine Plotnikov <constantine.plotnikov@gmail.com>
 * Copyright (C) 2010, JetBrains s.r.o. 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.IOException;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

import org.eclipse.jgit.internal.storage.file.ObjectDirectory.AlternateHandle;
import org.eclipse.jgit.internal.storage.pack.ObjectToPack;
import org.eclipse.jgit.internal.storage.pack.PackWriter;
import org.eclipse.jgit.lib.AbbreviatedObjectId;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectDatabase;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectIdOwnerMap;
import org.eclipse.jgit.lib.ObjectLoader;
import org.eclipse.jgit.util.FS;

/**
 * The cached instance of an {@link ObjectDirectory}.
 * <p>
 * This class caches the list of loose objects in memory, so the file system is
 * not queried with stat calls.
 */
class CachedObjectDirectory extends FileObjectDatabase {
    /**
     * The set that contains unpacked objects identifiers, it is created when
     * the cached instance is created.
     */
    private ObjectIdOwnerMap<UnpackedObjectId> unpackedObjects;

    private final ObjectDirectory wrapped;

    private CachedObjectDirectory[] alts;

    /**
     * The constructor
     *
     * @param wrapped
     *            the wrapped database
     */
    CachedObjectDirectory(ObjectDirectory wrapped) {
        this.wrapped = wrapped;
        this.unpackedObjects = scanLoose();
    }

    private ObjectIdOwnerMap<UnpackedObjectId> scanLoose() {
        ObjectIdOwnerMap<UnpackedObjectId> m = new ObjectIdOwnerMap<>();
        File objects = wrapped.getDirectory();
        String[] fanout = objects.list();
        if (fanout == null)
            return m;
        for (String d : fanout) {
            if (d.length() != 2)
                continue;
            String[] entries = new File(objects, d).list();
            if (entries == null)
                continue;
            for (String e : entries) {
                if (e.length() != Constants.OBJECT_ID_STRING_LENGTH - 2)
                    continue;
                try {
                    ObjectId id = ObjectId.fromString(d + e);
                    m.add(new UnpackedObjectId(id));
                } catch (IllegalArgumentException notAnObject) {
                    // ignoring the file that does not represent loose object
                }
            }
        }
        return m;
    }

    /** {@inheritDoc} */
    @Override
    public void close() {
        // Don't close anything.
    }

    /** {@inheritDoc} */
    @Override
    public ObjectDatabase newCachedDatabase() {
        return this;
    }

    @Override
    File getDirectory() {
        return wrapped.getDirectory();
    }

    @Override
    File fileFor(AnyObjectId id) {
        return wrapped.fileFor(id);
    }

    @Override
    Config getConfig() {
        return wrapped.getConfig();
    }

    @Override
    FS getFS() {
        return wrapped.getFS();
    }

    @Override
    Set<ObjectId> getShallowCommits() throws IOException {
        return wrapped.getShallowCommits();
    }

    private CachedObjectDirectory[] myAlternates() {
        if (alts == null) {
            ObjectDirectory.AlternateHandle[] src = wrapped.myAlternates();
            alts = new CachedObjectDirectory[src.length];
            for (int i = 0; i < alts.length; i++)
                alts[i] = src[i].db.newCachedFileObjectDatabase();
        }
        return alts;
    }

    private Set<AlternateHandle.Id> skipMe(Set<AlternateHandle.Id> skips) {
        Set<AlternateHandle.Id> withMe = new HashSet<>();
        if (skips != null) {
            withMe.addAll(skips);
        }
        withMe.add(getAlternateId());
        return withMe;
    }

    @Override
    void resolve(Set<ObjectId> matches, AbbreviatedObjectId id)
            throws IOException {
        wrapped.resolve(matches, id);
    }

    /** {@inheritDoc} */
    @Override
    public boolean has(AnyObjectId objectId) throws IOException {
        return has(objectId, null);
    }

    private boolean has(AnyObjectId objectId, Set<AlternateHandle.Id> skips)
            throws IOException {
        if (unpackedObjects.contains(objectId)) {
            return true;
        }
        if (wrapped.hasPackedObject(objectId)) {
            return true;
        }
        skips = skipMe(skips);
        for (CachedObjectDirectory alt : myAlternates()) {
            if (!skips.contains(alt.getAlternateId())) {
                if (alt.has(objectId, skips)) {
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    ObjectLoader openObject(WindowCursor curs, AnyObjectId objectId)
            throws IOException {
        return openObject(curs, objectId, null);
    }

    private ObjectLoader openObject(final WindowCursor curs,
            final AnyObjectId objectId, Set<AlternateHandle.Id> skips)
            throws IOException {
        ObjectLoader ldr = openLooseObject(curs, objectId);
        if (ldr != null) {
            return ldr;
        }
        ldr = wrapped.openPackedObject(curs, objectId);
        if (ldr != null) {
            return ldr;
        }
        skips = skipMe(skips);
        for (CachedObjectDirectory alt : myAlternates()) {
            if (!skips.contains(alt.getAlternateId())) {
                ldr = alt.openObject(curs, objectId, skips);
                if (ldr != null) {
                    return ldr;
                }
            }
        }
        return null;
    }

    @Override
    long getObjectSize(WindowCursor curs, AnyObjectId objectId)
            throws IOException {
        // Object size is unlikely to be requested from contexts using
        // this type. Don't bother trying to accelerate the lookup.
        return wrapped.getObjectSize(curs, objectId);
    }

    @Override
    ObjectLoader openLooseObject(WindowCursor curs, AnyObjectId id)
            throws IOException {
        if (unpackedObjects.contains(id)) {
            ObjectLoader ldr = wrapped.openLooseObject(curs, id);
            if (ldr != null)
                return ldr;
            unpackedObjects = scanLoose();
        }
        return null;
    }

    @Override
    InsertLooseObjectResult insertUnpackedObject(File tmp, ObjectId objectId,
            boolean createDuplicate) throws IOException {
        InsertLooseObjectResult result = wrapped.insertUnpackedObject(tmp,
                objectId, createDuplicate);
        switch (result) {
        case INSERTED:
        case EXISTS_LOOSE:
            unpackedObjects.addIfAbsent(new UnpackedObjectId(objectId));
            break;

        case EXISTS_PACKED:
        case FAILURE:
            break;
        }
        return result;
    }

    @Override
    Pack openPack(File pack) throws IOException {
        return wrapped.openPack(pack);
    }

    @Override
    void selectObjectRepresentation(PackWriter packer, ObjectToPack otp,
            WindowCursor curs) throws IOException {
        wrapped.selectObjectRepresentation(packer, otp, curs);
    }

    @Override
    Collection<Pack> getPacks() {
        return wrapped.getPacks();
    }

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

    private AlternateHandle.Id getAlternateId() {
        return wrapped.getAlternateId();
    }
}