com.google.doubleclick.util.ProtoUtils Maven / Gradle / Ivy
/*
* 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.google.doubleclick.util;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableList;
import com.google.protobuf.MessageLiteOrBuilder;
import java.util.ArrayList;
import java.util.List;
/**
* Partial, private copy of the ProtoUtils class in openrtb-core,
* so we don't need to add a dependency from openrtb-core just for this.
*/
final class ProtoUtils {
private ProtoUtils() {
}
/**
* Runs a filter through a sequence of objects.
*
* @param objs Message-or-builder objects
* @param filter Function that returns {@code true} to retain an object, {@code false} to discard
* @return Retained objects. If some elements are retained and others are discarded,
* this will be a new, mutable {@link List} that contains only the retained elements.
* If all elements are retained, returns the same, unmodified input sequence.
* If all elements are discarded, returns an immutable, empty sequence
*/
public static
List filter(List objs, Predicate filter) {
checkNotNull(filter);
for (int i = 0; i < objs.size(); ++i) {
if (!filter.apply(objs.get(i))) {
// At least one discarded object, go to slow-path.
return filterFrom(objs, filter, i);
}
}
// Optimized common case: all items filtered, return the input sequence.
return objs;
}
private static List filterFrom(
List objs, Predicate filter, int firstDiscarded) {
List filtered;
if (firstDiscarded == 0) {
filtered = null;
} else {
filtered = new ArrayList<>(objs.size() - 1);
for (int i = 0; i < firstDiscarded; ++i) {
filtered.add(objs.get(i));
}
}
for (int i = firstDiscarded + 1; i < objs.size(); ++i) {
M obj = objs.get(i);
if (filter.apply(obj)) {
if (filtered == null) {
filtered = new ArrayList<>(objs.size() - i);
}
filtered.add(obj);
}
}
return filtered == null ? ImmutableList.of() : filtered;
}
}