| /* |
| * Copyright 2014-present Facebook, Inc. |
| * |
| * 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.facebook.buck.util; |
| |
| import com.google.common.collect.ImmutableList; |
| import com.google.common.collect.Lists; |
| |
| import java.util.Iterator; |
| import java.util.List; |
| |
| public class MoreIterables { |
| |
| private MoreIterables() {} |
| |
| private static <T> ImmutableList<Iterator<T>> iterators(Iterable<T> inputs[]) { |
| ImmutableList.Builder<Iterator<T>> iterators = ImmutableList.builder(); |
| for (Iterable<T> input : inputs) { |
| iterators.add(input.iterator()); |
| } |
| return iterators.build(); |
| } |
| |
| /** |
| * Combine the given iterables by peeling off items one at a time from each of the input |
| * iterables until any one of the iterables are exhausted. |
| */ |
| @SafeVarargs |
| public static <T> Iterable<T> zipAndConcat(Iterable<T>... inputs) { |
| |
| // If no inputs were seen, just return an empty list. |
| if (inputs.length == 0) { |
| return ImmutableList.of(); |
| } |
| |
| ImmutableList.Builder<T> result = ImmutableList.builder(); |
| ImmutableList<Iterator<T>> iterators = iterators(inputs); |
| |
| // Keep grabbing rounds from the input iterators until we've exhausted one |
| // of them, then return. |
| List<T> round = Lists.newArrayListWithCapacity(inputs.length); |
| while (true) { |
| for (Iterator<T> iterator : iterators) { |
| if (!iterator.hasNext()) { |
| return result.build(); |
| } |
| round.add(iterator.next()); |
| } |
| result.addAll(round); |
| round.clear(); |
| } |
| } |
| |
| } |