code: /*
   * Copyright 2012-2018 Chronicle Map Contributors
   *
   * 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 net.openhft.chronicle.map;
  
  final class MapMethodsSupport {
  
      private MapMethodsSupport() {
      }
  
      static <V> void returnCurrentValueIfPresent(
              MapQueryContext<?, V, ?> q, ReturnValue<V> returnValue) {
          MapEntry<?, V> entry = q.entry();
          if (entry != null)
              returnValue.returnValue(entry.value());
      }
  
      static <V> boolean tryReturnCurrentValueIfPresent(
              MapQueryContext<?, V, ?> q, ReturnValue<V> returnValue) {
          if (q.readLock().tryLock()) {
              MapEntry<?, V> entry = q.entry();
              if (entry != null) {
                  returnValue.returnValue(entry.value());
                  return true;
              }
              // Key is absent
              q.readLock().unlock();
          }
          q.updateLock().lock();
          MapEntry<?, V> entry = q.entry();
          if (entry != null) {
              returnValue.returnValue(entry.value());
              return true;
          }
          return false;
      }
  }
  