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

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Here is the source code for com.google.devtools.build.lib.query2.engine.SomePathFunction.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.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import com.google.common.collect.Sets.SetView;
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.List;
import java.util.Set;
import java.util.concurrent.ForkJoinPool;

/**
 * A somepath(x, y) query expression, which computes the set of nodes
 * on some arbitrary path from a target in set x to a target in set y.
 *
 * <pre>expr ::= SOMEPATH '(' expr ',' expr ')'</pre>
 */
class SomePathFunction implements QueryFunction {
    SomePathFunction() {
    }

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

    @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, final 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());

        // Implementation strategy: for each x in "from", compute its forward
        // transitive closure.  If it intersects "to", then do a path search from x
        // to an arbitrary node in the intersection, and return the path.  This
        // avoids computing the full transitive closure of "from" in some cases.

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

        // This set contains all nodes whose TC does not intersect "toValue".
        Uniquifier<T> uniquifier = env.createUniquifier();

        for (T x : uniquifier.unique(fromValue)) {
            Set<T> xtc = env.getTransitiveClosure(ImmutableSet.of(x));
            SetView<T> result;
            if (xtc.size() > toValue.size()) {
                result = Sets.intersection(toValue, xtc);
            } else {
                result = Sets.intersection(xtc, toValue);
            }
            if (!result.isEmpty()) {
                callback.process(env.getNodesOnPath(x, result.iterator().next()));
                return;
            }
            uniquifier.unique(xtc);
        }
        callback.process(ImmutableSet.<T>of());
    }

    @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);
    }
}