com.google.devtools.build.lib.query2.engine.AllPathsFunction.java Source code

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Here is the source code for com.google.devtools.build.lib.query2.engine.AllPathsFunction.java

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// Copyright 2014 The Bazel Authors. 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.devtools.build.lib.query2.engine;

import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.Argument;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.ArgumentType;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.QueryFunction;

import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ForkJoinPool;

/**
 * Implementation of the <code>allpaths()</code> function.
 */
public class AllPathsFunction implements QueryFunction {
    AllPathsFunction() {
    }

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

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

    @Override
    public List<ArgumentType> getArgumentTypes() {
        return ImmutableList.of(ArgumentType.EXPRESSION, ArgumentType.EXPRESSION);
    }

    @Override
    public <T> void eval(QueryEnvironment<T> env, VariableContext<T> context, QueryExpression expression,
            List<Argument> args, Callback<T> callback) throws QueryException, InterruptedException {

        Set<T> fromValue = QueryUtil.evalAll(env, context, args.get(0).getExpression());
        Set<T> toValue = QueryUtil.evalAll(env, context, args.get(1).getExpression());

        // Algorithm: compute "reachableFromX", the forward transitive closure of
        // the "from" set, then find the intersection of "reachableFromX" with the
        // reverse transitive closure of the "to" set.  The reverse transitive
        // closure and intersection operations are interleaved for efficiency.
        // "result" holds the intersection.

        env.buildTransitiveClosure(expression, fromValue, Integer.MAX_VALUE);

        Set<T> reachableFromX = env.getTransitiveClosure(fromValue);
        Predicate<T> reachable = Predicates.in(reachableFromX);
        Uniquifier<T> uniquifier = env.createUniquifier();
        Collection<T> result = uniquifier.unique(intersection(reachableFromX, toValue));
        callback.process(result);
        Collection<T> worklist = result;
        while (!worklist.isEmpty()) {
            Collection<T> reverseDeps = env.getReverseDeps(worklist);
            worklist = uniquifier.unique(Iterables.filter(reverseDeps, reachable));
            callback.process(worklist);
        }
    }

    @Override
    public <T> void parEval(QueryEnvironment<T> env, VariableContext<T> context, QueryExpression expression,
            List<Argument> args, ThreadSafeCallback<T> callback, ForkJoinPool forkJoinPool)
            throws QueryException, InterruptedException {
        eval(env, context, expression, args, callback);
    }

    /**
     * Returns a (new, mutable, unordered) set containing the intersection of the
     * two specified sets.
     */
    private static <T> Set<T> intersection(Set<T> x, Set<T> y) {
        Set<T> result = new HashSet<>();
        if (x.size() > y.size()) {
            Sets.intersection(y, x).copyInto(result);
        } else {
            Sets.intersection(x, y).copyInto(result);
        }
        return result;
    }
}