Use the latest fbjni

libs/fbjni/java/com/facebook/jni/IteratorHelper.java

@@ -0,0 +1,58 @@
+/**
+ * Copyright 2018-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.jni;
+
+import com.facebook.jni.annotations.DoNotStrip;
+import java.util.Iterator;
+import javax.annotation.Nullable;
+
+/**
+ * To iterate over an Iterator from C++ requires two calls per entry: hasNext() and next(). This
+ * helper reduces it to one call and one field get per entry. It does not use a generic argument,
+ * since in C++, the types will be erased, anyway. This is *not* a {@link java.util.Iterator}.
+ */
+@DoNotStrip
+public class IteratorHelper {
+  private final Iterator mIterator;
+
+  // This is private, but accessed via JNI.
+  @DoNotStrip private @Nullable Object mElement;
+
+  @DoNotStrip
+  public IteratorHelper(Iterator iterator) {
+    mIterator = iterator;
+  }
+
+  @DoNotStrip
+  public IteratorHelper(Iterable iterable) {
+    mIterator = iterable.iterator();
+  }
+
+  /**
+   * Moves the helper to the next entry in the map, if any. Returns true iff there is an entry to
+   * read.
+   */
+  @DoNotStrip
+  boolean hasNext() {
+    if (mIterator.hasNext()) {
+      mElement = mIterator.next();
+      return true;
+    } else {
+      mElement = null;
+      return false;
+    }
+  }
+}