ObjectDirectory.java

/*
 * Copyright (C) 2009, 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 static org.eclipse.jgit.internal.storage.pack.PackExt.PACK;
import static org.eclipse.jgit.internal.storage.pack.PackExt.BITMAP_INDEX;
import static org.eclipse.jgit.internal.storage.pack.PackExt.INDEX;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.file.Files;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.atomic.AtomicReference;

import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.internal.storage.pack.ObjectToPack;
import org.eclipse.jgit.internal.storage.pack.PackExt;
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.ObjectLoader;
import org.eclipse.jgit.lib.RepositoryCache;
import org.eclipse.jgit.lib.RepositoryCache.FileKey;
import org.eclipse.jgit.util.FS;
import org.eclipse.jgit.util.FileUtils;

/**
 * Traditional file system based {@link org.eclipse.jgit.lib.ObjectDatabase}.
 * <p>
 * This is the classical object database representation for a Git repository,
 * where objects are stored loose by hashing them into directories by their
 * {@link org.eclipse.jgit.lib.ObjectId}, or are stored in compressed containers
 * known as {@link org.eclipse.jgit.internal.storage.file.Pack}s.
 * <p>
 * Optionally an object database can reference one or more alternates; other
 * ObjectDatabase instances that are searched in addition to the current
 * database.
 * <p>
 * Databases are divided into two halves: a half that is considered to be fast
 * to search (the {@code PackFile}s), and a half that is considered to be slow
 * to search (loose objects). When alternates are present the fast half is fully
 * searched (recursively through all alternates) before the slow half is
 * considered.
 */
public class ObjectDirectory extends FileObjectDatabase {
    /** Maximum number of candidates offered as resolutions of abbreviation. */
    private static final int RESOLVE_ABBREV_LIMIT = 256;

    private final AlternateHandle handle = new AlternateHandle(this);

    private final Config config;

    private final File objects;

    private final File infoDirectory;

    private final LooseObjects loose;

    private final PackDirectory packed;

    private final PackDirectory preserved;

    private final File alternatesFile;

    private final FS fs;

    private final AtomicReference<AlternateHandle[]> alternates;

    private final File shallowFile;

    private FileSnapshot shallowFileSnapshot = FileSnapshot.DIRTY;

    private Set<ObjectId> shallowCommitsIds;

    /**
     * Initialize a reference to an on-disk object directory.
     *
     * @param cfg
     *            configuration this directory consults for write settings.
     * @param dir
     *            the location of the <code>objects</code> directory.
     * @param alternatePaths
     *            a list of alternate object directories
     * @param fs
     *            the file system abstraction which will be necessary to perform
     *            certain file system operations.
     * @param shallowFile
     *            file which contains IDs of shallow commits, null if shallow
     *            commits handling should be turned off
     * @throws java.io.IOException
     *             an alternate object cannot be opened.
     */
    public ObjectDirectory(final Config cfg, final File dir,
            File[] alternatePaths, FS fs, File shallowFile) throws IOException {
        config = cfg;
        objects = dir;
        infoDirectory = new File(objects, "info"); //$NON-NLS-1$
        File packDirectory = new File(objects, "pack"); //$NON-NLS-1$
        File preservedDirectory = new File(packDirectory, "preserved"); //$NON-NLS-1$
        alternatesFile = new File(objects, Constants.INFO_ALTERNATES);
        loose = new LooseObjects(objects);
        packed = new PackDirectory(config, packDirectory);
        preserved = new PackDirectory(config, preservedDirectory);
        this.fs = fs;
        this.shallowFile = shallowFile;

        alternates = new AtomicReference<>();
        if (alternatePaths != null) {
            AlternateHandle[] alt;

            alt = new AlternateHandle[alternatePaths.length];
            for (int i = 0; i < alternatePaths.length; i++)
                alt[i] = openAlternate(alternatePaths[i]);
            alternates.set(alt);
        }
    }

    /** {@inheritDoc} */
    @Override
    public final File getDirectory() {
        return loose.getDirectory();
    }

    /**
     * <p>Getter for the field <code>packDirectory</code>.</p>
     *
     * @return the location of the <code>pack</code> directory.
     */
    public final File getPackDirectory() {
        return packed.getDirectory();
    }

    /**
     * <p>Getter for the field <code>preservedDirectory</code>.</p>
     *
     * @return the location of the <code>preserved</code> directory.
     */
    public final File getPreservedDirectory() {
        return preserved.getDirectory();
    }

    /** {@inheritDoc} */
    @Override
    public boolean exists() {
        return fs.exists(objects);
    }

    /** {@inheritDoc} */
    @Override
    public void create() throws IOException {
        loose.create();
        FileUtils.mkdir(infoDirectory);
        packed.create();
    }

    /** {@inheritDoc} */
    @Override
    public ObjectDirectoryInserter newInserter() {
        return new ObjectDirectoryInserter(this, config);
    }

    /**
     * Create a new inserter that inserts all objects as pack files, not loose
     * objects.
     *
     * @return new inserter.
     */
    public PackInserter newPackInserter() {
        return new PackInserter(this);
    }

    /** {@inheritDoc} */
    @Override
    public void close() {
        loose.close();

        packed.close();

        // Fully close all loaded alternates and clear the alternate list.
        AlternateHandle[] alt = alternates.get();
        if (alt != null && alternates.compareAndSet(alt, null)) {
            for(AlternateHandle od : alt)
                od.close();
        }
    }

    /** {@inheritDoc} */
    @Override
    public Collection<Pack> getPacks() {
        return packed.getPacks();
    }

    /**
     * {@inheritDoc}
     * <p>
     * Add a single existing pack to the list of available pack files.
     */
    @Override
    public Pack openPack(File pack) throws IOException {
        PackFile pf;
        try {
            pf = new PackFile(pack);
        } catch (IllegalArgumentException e) {
            throw new IOException(
                    MessageFormat.format(JGitText.get().notAValidPack, pack),
                    e);
        }

        String p = pf.getName();
        // TODO(nasserg): See if PackFile can do these checks instead
        if (p.length() != 50 || !p.startsWith("pack-") //$NON-NLS-1$
                || !pf.getPackExt().equals(PACK)) {
            throw new IOException(
                    MessageFormat.format(JGitText.get().notAValidPack, pack));
        }

        PackFile bitmapIdx = pf.create(BITMAP_INDEX);
        Pack res = new Pack(pack, bitmapIdx.exists() ? bitmapIdx : null);
        packed.insert(res);
        return res;
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        return "ObjectDirectory[" + getDirectory() + "]"; //$NON-NLS-1$ //$NON-NLS-2$
    }

    /** {@inheritDoc} */
    @Override
    public boolean has(AnyObjectId objectId) {
        return loose.hasCached(objectId)
                || hasPackedOrLooseInSelfOrAlternate(objectId)
                || (restoreFromSelfOrAlternate(objectId, null)
                        && hasPackedOrLooseInSelfOrAlternate(objectId));
    }

    private boolean hasPackedOrLooseInSelfOrAlternate(AnyObjectId objectId) {
        return hasPackedInSelfOrAlternate(objectId, null)
                || hasLooseInSelfOrAlternate(objectId, null);
    }

    private boolean hasPackedInSelfOrAlternate(AnyObjectId objectId,
            Set<AlternateHandle.Id> skips) {
        if (hasPackedObject(objectId)) {
            return true;
        }
        skips = addMe(skips);
        for (AlternateHandle alt : myAlternates()) {
            if (!skips.contains(alt.getId())) {
                if (alt.db.hasPackedInSelfOrAlternate(objectId, skips)) {
                    return true;
                }
            }
        }
        return false;
    }

    private boolean hasLooseInSelfOrAlternate(AnyObjectId objectId,
            Set<AlternateHandle.Id> skips) {
        if (loose.has(objectId)) {
            return true;
        }
        skips = addMe(skips);
        for (AlternateHandle alt : myAlternates()) {
            if (!skips.contains(alt.getId())) {
                if (alt.db.hasLooseInSelfOrAlternate(objectId, skips)) {
                    return true;
                }
            }
        }
        return false;
    }

    boolean hasPackedObject(AnyObjectId objectId) {
        return packed.has(objectId);
    }

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

    private void resolve(Set<ObjectId> matches, AbbreviatedObjectId id,
            Set<AlternateHandle.Id> skips)
            throws IOException {
        if (!packed.resolve(matches, id, RESOLVE_ABBREV_LIMIT))
            return;

        if (!loose.resolve(matches, id, RESOLVE_ABBREV_LIMIT))
            return;

        skips = addMe(skips);
        for (AlternateHandle alt : myAlternates()) {
            if (!skips.contains(alt.getId())) {
                alt.db.resolve(matches, id, skips);
                if (matches.size() > RESOLVE_ABBREV_LIMIT) {
                    return;
                }
            }
        }
    }

    @Override
    ObjectLoader openObject(WindowCursor curs, AnyObjectId objectId)
            throws IOException {
        ObjectLoader ldr = openObjectWithoutRestoring(curs, objectId);
        if (ldr == null && restoreFromSelfOrAlternate(objectId, null)) {
            ldr = openObjectWithoutRestoring(curs, objectId);
        }
        return ldr;
    }

    private ObjectLoader openObjectWithoutRestoring(WindowCursor curs, AnyObjectId objectId)
            throws IOException {
        if (loose.hasCached(objectId)) {
            ObjectLoader ldr = openLooseObject(curs, objectId);
            if (ldr != null) {
                return ldr;
            }
        }
        ObjectLoader ldr = openPackedFromSelfOrAlternate(curs, objectId, null);
        if (ldr != null) {
            return ldr;
        }
        return openLooseFromSelfOrAlternate(curs, objectId, null);
    }

    private ObjectLoader openPackedFromSelfOrAlternate(WindowCursor curs,
            AnyObjectId objectId, Set<AlternateHandle.Id> skips) {
        ObjectLoader ldr = openPackedObject(curs, objectId);
        if (ldr != null) {
            return ldr;
        }
        skips = addMe(skips);
        for (AlternateHandle alt : myAlternates()) {
            if (!skips.contains(alt.getId())) {
                ldr = alt.db.openPackedFromSelfOrAlternate(curs, objectId, skips);
                if (ldr != null) {
                    return ldr;
                }
            }
        }
        return null;
    }

    private ObjectLoader openLooseFromSelfOrAlternate(WindowCursor curs,
            AnyObjectId objectId, Set<AlternateHandle.Id> skips)
                    throws IOException {
        ObjectLoader ldr = openLooseObject(curs, objectId);
        if (ldr != null) {
            return ldr;
        }
        skips = addMe(skips);
        for (AlternateHandle alt : myAlternates()) {
            if (!skips.contains(alt.getId())) {
                ldr = alt.db.openLooseFromSelfOrAlternate(curs, objectId, skips);
                if (ldr != null) {
                    return ldr;
                }
            }
        }
        return null;
    }

    ObjectLoader openPackedObject(WindowCursor curs, AnyObjectId objectId) {
        return packed.open(curs, objectId);
    }

    @Override
    ObjectLoader openLooseObject(WindowCursor curs, AnyObjectId id)
            throws IOException {
        return loose.open(curs, id);
    }

    @Override
    long getObjectSize(WindowCursor curs, AnyObjectId id) throws IOException {
        long sz = getObjectSizeWithoutRestoring(curs, id);
        if (0 > sz && restoreFromSelfOrAlternate(id, null)) {
            sz = getObjectSizeWithoutRestoring(curs, id);
        }
        return sz;
    }

    private long getObjectSizeWithoutRestoring(WindowCursor curs,
            AnyObjectId id) throws IOException {
        if (loose.hasCached(id)) {
            long len = loose.getSize(curs, id);
            if (0 <= len) {
                return len;
            }
        }
        long len = getPackedSizeFromSelfOrAlternate(curs, id, null);
        if (0 <= len) {
            return len;
        }
        return getLooseSizeFromSelfOrAlternate(curs, id, null);
    }

    private long getPackedSizeFromSelfOrAlternate(WindowCursor curs,
            AnyObjectId id, Set<AlternateHandle.Id> skips) {
        long len = packed.getSize(curs, id);
        if (0 <= len) {
            return len;
        }
        skips = addMe(skips);
        for (AlternateHandle alt : myAlternates()) {
            if (!skips.contains(alt.getId())) {
                len = alt.db.getPackedSizeFromSelfOrAlternate(curs, id, skips);
                if (0 <= len) {
                    return len;
                }
            }
        }
        return -1;
    }

    private long getLooseSizeFromSelfOrAlternate(WindowCursor curs,
            AnyObjectId id, Set<AlternateHandle.Id> skips) throws IOException {
        long len = loose.getSize(curs, id);
        if (0 <= len) {
            return len;
        }
        skips = addMe(skips);
        for (AlternateHandle alt : myAlternates()) {
            if (!skips.contains(alt.getId())) {
                len = alt.db.getLooseSizeFromSelfOrAlternate(curs, id, skips);
                if (0 <= len) {
                    return len;
                }
            }
        }
        return -1;
    }

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

    private void selectObjectRepresentation(PackWriter packer, ObjectToPack otp,
            WindowCursor curs, Set<AlternateHandle.Id> skips) throws IOException {
        packed.selectRepresentation(packer, otp, curs);

        skips = addMe(skips);
        for (AlternateHandle h : myAlternates()) {
            if (!skips.contains(h.getId())) {
                h.db.selectObjectRepresentation(packer, otp, curs, skips);
            }
        }
    }

    private boolean restoreFromSelfOrAlternate(AnyObjectId objectId,
            Set<AlternateHandle.Id> skips) {
        if (restoreFromSelf(objectId)) {
            return true;
        }

        skips = addMe(skips);
        for (AlternateHandle alt : myAlternates()) {
            if (!skips.contains(alt.getId())) {
                if (alt.db.restoreFromSelfOrAlternate(objectId, skips)) {
                    return true;
                }
            }
        }
        return false;
    }

    private boolean restoreFromSelf(AnyObjectId objectId) {
        Pack preservedPack = preserved.getPack(objectId);
        if (preservedPack == null) {
            return false;
        }
        PackFile preservedFile = new PackFile(preservedPack.getPackFile());
        // Restore the index last since the set will be considered for use once
        // the index appears.
        for (PackExt ext : PackExt.values()) {
            if (!INDEX.equals(ext)) {
                restore(preservedFile.create(ext));
            }
        }
        restore(preservedFile.create(INDEX));
        return true;
    }

    private boolean restore(PackFile preservedPack) {
        PackFile restored = preservedPack
                .createForDirectory(packed.getDirectory());
        try {
            Files.createLink(restored.toPath(), preservedPack.toPath());
        } catch (IOException e) {
            return false;
        }
        return true;
    }

    @Override
    InsertLooseObjectResult insertUnpackedObject(File tmp, ObjectId id,
            boolean createDuplicate) throws IOException {
        // If the object is already in the repository, remove temporary file.
        //
        if (loose.hasCached(id)) {
            FileUtils.delete(tmp, FileUtils.RETRY);
            return InsertLooseObjectResult.EXISTS_LOOSE;
        }
        if (!createDuplicate && has(id)) {
            FileUtils.delete(tmp, FileUtils.RETRY);
            return InsertLooseObjectResult.EXISTS_PACKED;
        }
        return loose.insert(tmp, id);
    }

    @Override
    Config getConfig() {
        return config;
    }

    @Override
    FS getFS() {
        return fs;
    }

    @Override
    Set<ObjectId> getShallowCommits() throws IOException {
        if (shallowFile == null || !shallowFile.isFile())
            return Collections.emptySet();

        if (shallowFileSnapshot == null
                || shallowFileSnapshot.isModified(shallowFile)) {
            shallowCommitsIds = new HashSet<>();

            try (BufferedReader reader = open(shallowFile)) {
                String line;
                while ((line = reader.readLine()) != null) {
                    try {
                        shallowCommitsIds.add(ObjectId.fromString(line));
                    } catch (IllegalArgumentException ex) {
                        throw new IOException(MessageFormat
                                .format(JGitText.get().badShallowLine, line),
                                ex);
                    }
                }
            }

            shallowFileSnapshot = FileSnapshot.save(shallowFile);
        }

        return shallowCommitsIds;
    }

    void closeAllPackHandles(File packFile) {
        // if the packfile already exists (because we are rewriting a
        // packfile for the same set of objects maybe with different
        // PackConfig) then make sure we get rid of all handles on the file.
        // Windows will not allow for rename otherwise.
        if (packFile.exists()) {
            for (Pack p : packed.getPacks()) {
                if (packFile.getPath().equals(p.getPackFile().getPath())) {
                    p.close();
                    break;
                }
            }
        }
    }

    AlternateHandle[] myAlternates() {
        AlternateHandle[] alt = alternates.get();
        if (alt == null) {
            synchronized (alternates) {
                alt = alternates.get();
                if (alt == null) {
                    try {
                        alt = loadAlternates();
                    } catch (IOException e) {
                        alt = new AlternateHandle[0];
                    }
                    alternates.set(alt);
                }
            }
        }
        return alt;
    }

    Set<AlternateHandle.Id> addMe(Set<AlternateHandle.Id> skips) {
        if (skips == null) {
            skips = new HashSet<>();
        }
        skips.add(handle.getId());
        return skips;
    }

    private AlternateHandle[] loadAlternates() throws IOException {
        final List<AlternateHandle> l = new ArrayList<>(4);
        try (BufferedReader br = open(alternatesFile)) {
            String line;
            while ((line = br.readLine()) != null) {
                l.add(openAlternate(line));
            }
        }
        return l.toArray(new AlternateHandle[0]);
    }

    private static BufferedReader open(File f)
            throws IOException, FileNotFoundException {
        return Files.newBufferedReader(f.toPath(), UTF_8);
    }

    private AlternateHandle openAlternate(String location)
            throws IOException {
        final File objdir = fs.resolve(objects, location);
        return openAlternate(objdir);
    }

    private AlternateHandle openAlternate(File objdir) throws IOException {
        final File parent = objdir.getParentFile();
        if (FileKey.isGitRepository(parent, fs)) {
            FileKey key = FileKey.exact(parent, fs);
            FileRepository db = (FileRepository) RepositoryCache.open(key);
            return new AlternateRepository(db);
        }

        ObjectDirectory db = new ObjectDirectory(config, objdir, null, fs, null);
        return new AlternateHandle(db);
    }

    /**
     * Compute the location of a loose object file.
     */
    @Override
    public File fileFor(AnyObjectId objectId) {
        return loose.fileFor(objectId);
    }

    static class AlternateHandle {
        static class Id {
            String alternateId;

            public Id(File object) {
                try {
                    this.alternateId = object.getCanonicalPath();
                } catch (Exception e) {
                    alternateId = null;
                }
            }

            @Override
            public boolean equals(Object o) {
                if (o == this) {
                    return true;
                }
                if (o == null || !(o instanceof Id)) {
                    return false;
                }
                Id aId = (Id) o;
                return Objects.equals(alternateId, aId.alternateId);
            }

            @Override
            public int hashCode() {
                if (alternateId == null) {
                    return 1;
                }
                return alternateId.hashCode();
            }
        }

        final ObjectDirectory db;

        AlternateHandle(ObjectDirectory db) {
            this.db = db;
        }

        void close() {
            db.close();
        }

        public Id getId(){
            return db.getAlternateId();
        }
    }

    static class AlternateRepository extends AlternateHandle {
        final FileRepository repository;

        AlternateRepository(FileRepository r) {
            super(r.getObjectDatabase());
            repository = r;
        }

        @Override
        void close() {
            repository.close();
        }
    }

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

    CachedObjectDirectory newCachedFileObjectDatabase() {
        return new CachedObjectDirectory(this);
    }

    AlternateHandle.Id getAlternateId() {
        return new AlternateHandle.Id(objects);
    }
}