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// 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.util;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
/**
* Callback to be invoked when part of a result has been computed. Allows a client interested in
* the result to process it as it is computed, for instance by streaming it, if it is too big to
* fit in memory.
*/
@ThreadSafe
public interface BatchCallback<T, E extends Exception> {
/**
* Called when part of a result has been computed.
*
* <p>Note that this method can be called several times for a single {@code BatchCallback}.
* Implementations should assume that multiple calls can happen.
*
* @param partialResult Part of the result. May contain duplicates, either in the same call or
* across calls.
*/
void process(Iterable<T> partialResult) throws E, InterruptedException;
/** {@link BatchCallback} that does precisely nothing. */
class NullCallback<T> implements BatchCallback<T, RuntimeException> {
private static final NullCallback<Object> INSTANCE = new NullCallback<>();
@Override
public void process(Iterable<T> partialResult) {}
@SuppressWarnings("unchecked")
public static <T> NullCallback<T> instance() {
return (NullCallback<T>) INSTANCE;
}
}
}
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