com.google.gitiles.VisibilityCache.java Source code

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Here is the source code for com.google.gitiles.VisibilityCache.java

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// Copyright 2012 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.gitiles;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Predicates.not;
import static com.google.common.collect.Collections2.filter;

import com.google.common.base.Objects;
import com.google.common.base.Predicate;
import com.google.common.base.Throwables;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefDatabase;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevSort;
import org.eclipse.jgit.revwalk.RevWalk;

import java.io.IOException;
import java.util.Collection;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

/** Cache of per-user object visibility. */
public class VisibilityCache {
    private static class Key {
        private final Object user;
        private final String repositoryName;
        private final ObjectId objectId;

        private Key(Object user, String repositoryName, ObjectId objectId) {
            this.user = checkNotNull(user, "user");
            this.repositoryName = checkNotNull(repositoryName, "repositoryName");
            this.objectId = checkNotNull(objectId, "objectId");
        }

        @Override
        public boolean equals(Object o) {
            if (o instanceof Key) {
                Key k = (Key) o;
                return Objects.equal(user, k.user) && Objects.equal(repositoryName, k.repositoryName)
                        && Objects.equal(objectId, k.objectId);
            }
            return false;
        }

        @Override
        public int hashCode() {
            return Objects.hashCode(user, repositoryName, objectId);
        }

        @Override
        public String toString() {
            return Objects.toStringHelper(this).add("user", user).add("repositoryName", repositoryName)
                    .add("objectId", objectId).toString();
        }
    }

    private final Cache<Key, Boolean> cache;
    private final boolean topoSort;

    public static CacheBuilder<Object, Object> newBuilder() {
        return CacheBuilder.newBuilder().maximumSize(1 << 10).expireAfterWrite(30, TimeUnit.MINUTES);
    }

    public VisibilityCache(boolean topoSort) {
        this(topoSort, newBuilder());
    }

    public VisibilityCache(boolean topoSort, CacheBuilder<Object, Object> builder) {
        this.cache = builder.build();
        this.topoSort = topoSort;
    }

    public Cache<?, Boolean> getCache() {
        return cache;
    }

    boolean isVisible(final Repository repo, final RevWalk walk, GitilesAccess access, final ObjectId id)
            throws IOException {
        try {
            return cache.get(new Key(access.getUserKey(), access.getRepositoryName(), id), new Callable<Boolean>() {
                @Override
                public Boolean call() throws IOException {
                    return isVisible(repo, walk, id);
                }
            });
        } catch (ExecutionException e) {
            Throwables.propagateIfInstanceOf(e.getCause(), IOException.class);
            throw new IOException(e);
        }
    }

    private boolean isVisible(Repository repo, RevWalk walk, ObjectId id) throws IOException {
        RevCommit commit;
        try {
            commit = walk.parseCommit(id);
        } catch (IncorrectObjectTypeException e) {
            return false;
        }

        // If any reference directly points at the requested object, permit display.
        // Common for displays of pending patch sets in Gerrit Code Review, or
        // bookmarks to the commit a tag points at.
        Collection<Ref> allRefs = repo.getRefDatabase().getRefs(RefDatabase.ALL).values();
        for (Ref ref : allRefs) {
            ref = repo.getRefDatabase().peel(ref);
            if (id.equals(ref.getObjectId()) || id.equals(ref.getPeeledObjectId())) {
                return true;
            }
        }

        // Check heads first under the assumption that most requests are for refs
        // close to a head. Tags tend to be much further back in history and just
        // clutter up the priority queue in the common case.
        return isReachableFrom(walk, commit, filter(allRefs, refStartsWith(Constants.R_HEADS)))
                || isReachableFrom(walk, commit, filter(allRefs, refStartsWith(Constants.R_TAGS)))
                || isReachableFrom(walk, commit, filter(allRefs, not(refStartsWith("refs/changes/"))));
    }

    private static Predicate<Ref> refStartsWith(final String prefix) {
        return new Predicate<Ref>() {
            @Override
            public boolean apply(Ref ref) {
                return ref.getName().startsWith(prefix);
            }
        };
    }

    private boolean isReachableFrom(RevWalk walk, RevCommit commit, Collection<Ref> refs) throws IOException {
        walk.reset();
        if (topoSort) {
            walk.sort(RevSort.TOPO);
        }
        walk.markStart(commit);
        for (Ref ref : refs) {
            if (ref.getPeeledObjectId() != null) {
                markUninteresting(walk, ref.getPeeledObjectId());
            } else {
                markUninteresting(walk, ref.getObjectId());
            }
        }
        // If the commit is reachable from any branch head, it will appear to be
        // uninteresting to the RevWalk and no output will be produced.
        return walk.next() == null;
    }

    private static void markUninteresting(RevWalk walk, ObjectId id) throws IOException {
        if (id == null) {
            return;
        }
        try {
            walk.markUninteresting(walk.parseCommit(id));
        } catch (IncorrectObjectTypeException e) {
            // Do nothing, doesn't affect reachability.
        } catch (MissingObjectException e) {
            // Do nothing, doesn't affect reachability.
        }
    }
}