com.facebook.buck.query.AllPathsFunction.java Source code

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Here is the source code for com.facebook.buck.query.AllPathsFunction.java

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/*
 * Copyright 2015-present Facebook, Inc.
 *
 * 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.
 */

// Copyright 2014 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.facebook.buck.query;

import com.facebook.buck.query.QueryEnvironment.Argument;
import com.facebook.buck.query.QueryEnvironment.ArgumentType;
import com.facebook.buck.query.QueryEnvironment.QueryFunction;
import com.facebook.buck.util.MoreSets;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.ListeningExecutorService;

import java.util.Collection;
import java.util.Set;

/**
 * A allpaths(from, to) expression, which computes all paths between the
 * build targets in the set 'from' and the build targets in the set 'to',
 * by following the dependencies between nodes in the target graph.
 *
 * <pre>expr ::= ALLPATHS '(' expr ',' expr ')'</pre>
 */
public class AllPathsFunction implements QueryFunction {

    private static final ImmutableList<ArgumentType> ARGUMENT_TYPES = ImmutableList.of(ArgumentType.EXPRESSION,
            ArgumentType.EXPRESSION);

    public AllPathsFunction() {
    }

    @Override
    public String getName() {
        return "allpaths";
    }

    @Override
    public int getMandatoryArguments() {
        return 2;
    }

    @Override
    public ImmutableList<ArgumentType> getArgumentTypes() {
        return ARGUMENT_TYPES;
    }

    @Override
    public Set<QueryTarget> eval(QueryEnvironment env, ImmutableList<Argument> args,
            ListeningExecutorService executor) throws QueryException, InterruptedException {
        QueryExpression from = args.get(0).getExpression();
        QueryExpression to = args.get(1).getExpression();

        Set<QueryTarget> fromSet = from.eval(env, executor);
        Set<QueryTarget> toSet = to.eval(env, executor);

        // Algorithm:
        // 1) compute "reachableFromX", the forward transitive closure of the "from" set;
        // 2) find the intersection of "reachableFromX" with the "to" set, and traverse the graph using
        //    the reverse dependencies. This will effectively compute the intersection between the nodes
        //    reachable from the "from" set and the reverse transitive closure of the "to" set.

        env.buildTransitiveClosure(fromSet, Integer.MAX_VALUE, executor);

        Set<QueryTarget> reachableFromX = env.getTransitiveClosure(fromSet);
        Set<QueryTarget> result = MoreSets.intersection(reachableFromX, toSet);
        Collection<QueryTarget> worklist = result;
        while (!worklist.isEmpty()) {
            Collection<QueryTarget> reverseDeps = env.getReverseDeps(worklist);
            worklist = Lists.newArrayList();
            for (QueryTarget target : reverseDeps) {
                if (reachableFromX.contains(target) && result.add(target)) {
                    worklist.add(target);
                }
            }
        }
        return result;
    }

}