src/main/java/org/apache/datasketches/memory/Map.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.datasketches.memory;

/**
 * Read only interface for a memory mapped file
 *
 * @author Roman Leventov
 * @author Lee Rhodes
 * @author Praveenkumar Venkatesan
 */
interface Map extends AutoCloseable {

  /**
   * Loads content into physical memory. This method makes a best effort to ensure that, when it
   * returns, this buffer's content is resident in physical memory. Invoking this method may cause
   * some number of page faults and I/O operations to occur.
   *
   * @see <a href="https://docs.oracle.com/javase/8/docs/api/java/nio/MappedByteBuffer.html#load--">
   * java/nio/MappedByteBuffer.load</a>
   */
  void load();

  /**
   * Tells whether or not the content is resident in physical memory. A return value of true implies
   * that it is highly likely that all of the data in this buffer is resident in physical memory and
   * may therefore be accessed without incurring any virtual-memory page faults or I/O operations. A
   * return value of false does not necessarily imply that the content is not resident in physical
   * memory. The returned value is a hint, rather than a guarantee, because the underlying operating
   * system may have paged out some of the buffer's data by the time that an invocation of this
   * method returns.
   *
   * @return true if loaded
   *
   * @see <a href=
   * "https://docs.oracle.com/javase/8/docs/api/java/nio/MappedByteBuffer.html#isLoaded--"> java
   * /nio/MappedByteBuffer.isLoaded</a>
   */
  boolean isLoaded();

}