1 /* 2 * Copyright (c) Facebook, Inc. and its affiliates. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.facebook.jni; 18 19 import com.facebook.jni.annotations.DoNotStrip; 20 import java.util.Iterator; 21 import java.util.Map; 22 import javax.annotation.Nullable; 23 24 /** 25 * To iterate over a Map from C++ requires four calls per entry: hasNext(), next(), getKey(), 26 * getValue(). This helper reduces it to one call and two field gets per entry. It does not use a 27 * generic argument, since in C++, the types will be erased, anyway. This is *not* a {@link 28 * java.util.Iterator}. 29 */ 30 @DoNotStrip 31 public class MapIteratorHelper { 32 @DoNotStrip private final Iterator<Map.Entry> mIterator; 33 @DoNotStrip private @Nullable Object mKey; 34 @DoNotStrip private @Nullable Object mValue; 35 36 @DoNotStrip MapIteratorHelper(Map map)37 public MapIteratorHelper(Map map) { 38 mIterator = map.entrySet().iterator(); 39 } 40 41 /** 42 * Moves the helper to the next entry in the map, if any. Returns true iff there is an entry to 43 * read. 44 */ 45 @DoNotStrip hasNext()46 boolean hasNext() { 47 if (mIterator.hasNext()) { 48 Map.Entry entry = mIterator.next(); 49 mKey = entry.getKey(); 50 mValue = entry.getValue(); 51 return true; 52 } else { 53 mKey = null; 54 mValue = null; 55 return false; 56 } 57 } 58 } 59