| // Copyright 2016 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.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe; |
| import java.util.concurrent.ForkJoinPool; |
| |
| /** Listener for calls to the internal methods of {@link QueryExpression} used for evaluation. */ |
| @ThreadSafe |
| public interface QueryExpressionEvalListener<T> { |
| /** Called right before {@link QueryExpression#evalImpl} is called. */ |
| void onEval( |
| QueryExpression expr, |
| QueryEnvironment<T> env, |
| VariableContext<T> context, |
| Callback<T> callback); |
| |
| /** Called right before {@link QueryExpression#parEvalImpl} is called. */ |
| void onParEval( |
| QueryExpression expr, |
| QueryEnvironment<T> env, |
| VariableContext<T> context, |
| ThreadSafeCallback<T> callback, |
| ForkJoinPool forkJoinPool); |
| |
| /** A {@link QueryExpressionEvalListener} that does nothing. */ |
| class NullListener<T> implements QueryExpressionEvalListener<T> { |
| private static final NullListener<?> INSTANCE = new NullListener<>(); |
| |
| private NullListener() { |
| } |
| |
| @SuppressWarnings("unchecked") |
| public static <T> NullListener<T> instance() { |
| return (NullListener<T>) INSTANCE; |
| } |
| |
| @Override |
| public void onEval( |
| QueryExpression expr, |
| QueryEnvironment<T> env, |
| VariableContext<T> context, |
| Callback<T> callback) { |
| } |
| |
| @Override |
| public void onParEval( |
| QueryExpression expr, |
| QueryEnvironment<T> env, |
| VariableContext<T> context, |
| ThreadSafeCallback<T> callback, |
| ForkJoinPool forkJoinPool) { |
| } |
| } |
| } |
| |