code: /*
   * 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.
   */
  
  /**
   * <p>This package provides high performance primitive and primitive array access to direct (native),
   * off-heap memory and memory-mapped file resources, consistent views into
   * {@link java.nio.ByteBuffer}, and on-heap primitive arrays. It can be used as a more
   * comprehensive and flexible replacement for {@link java.nio.ByteBuffer}.
   * </p>
   *
   * <p>In addition, this package provides:</p>
   *
   * <ul><li>Two different access APIs: read-only {@link org.apache.datasketches.memory.Memory} and
   * {@link org.apache.datasketches.memory.WritableMemory} for absolute offset access,
   * and read-only {@link org.apache.datasketches.memory.Buffer} and
   * {@link org.apache.datasketches.memory.WritableBuffer}
   * for relative positional access (similar to ByteBuffer).</li>
   *
   * <li>Clean separation of Read-only API from Writable API, which makes writable versus read-only
   * resources detectable at compile time.</li>
   *
   * <li>The conversion from Writable to read-only is just a cast, so no unnecessary objects are
   * created. For example:
   * <blockquote><pre>
   *     WritableMemory wMem = ...
   *     Memory mem = wMem;
   * </pre></blockquote>
   * </li>
   *
   * <li> {@link java.lang.AutoCloseable} for the external resources that require it,
   * which enables compile-time checks for non-closed resources.</li>
   *
   * <li>Immediate invalidation of all downstream references of an AutoCloseable
   * resource when that resource is closed, either manually or by the JVM.
   * This virtually eliminates the possibility of accidentally writing into the memory space
   * previously owned by a closed resource.</li>
   *
   * <li>Improved performance over the prior Memory implementation.</li>
   *
   * <li>Cleaner internal architecture, which will make it easier to extend in the future.</li>
   *
   * <li>No external dependencies, which makes it simple to install in virtually any Java environment.
   * </li>
   * </ul>
   *
   * <p>More specifically, this package provides access to four different types of resources using
   * two different access APIs. These resources can be viewed as contiguous blobs of bytes that provide at least
   * byte-level read and write access. The four resources are:</p>
   *
   * <ul><li>Direct (a.k.a. Native) off-heap memory allocated by the user.</li>
   * <li>Memory-mapped files, both writable and read-only.</li>
   * <li>{@code ByteBuffers}, both heap-based and direct, writable and read-only.</li>
   * <li>Heap-based primitive arrays, which can be accessed as writable or read-only.</li>
   * </ul>
   *
   * <p>The two different access APIs are:</p>
   * <ul><li><i>Memory, WritableMemory</i>: Absolute offset addressing into a resource.</li>
   * <li><i>Buffer, WritableBuffer</i>: Position relative addressing into a resource.</li>
   * </ul>
   *
   * <p>In addition, all combinations of access APIs and backing resources can be accessed via
   * multibyte primitive methods (e.g.
   * <i>getLong(...), getLongArray(...), putLong(...), putLongArray(...)</i>) as either
   * {@link java.nio.ByteOrder#BIG_ENDIAN} or {@link java.nio.ByteOrder#LITTLE_ENDIAN}.</p>
   *
   * <p>The resources don't know or care about the access APIs, and the access
   * APIs don't really know or care what resource they are accessing.</p>
   *
   * <p>A Direct or memory-mapped file resource can also be explicitly closed by the user</p>
   * <blockquote><pre>
   *     //Using try-with-resources block:
   *     try (WritableMemory wmem = WritableMemory.map(File file)) {
   *       doWork(wMem) // read and write to memory mapped file.
   *     }
   *
   *     //Using explicit close():
   *     WritableMemory wmem = WritableMemory.map(File file);
   *     doWork(wMem) // read and write to memory mapped file.
   *     wmem.close();
   * </pre></blockquote>
   *
   * <p>Whatever thread of your process is responsible for allocating a direct or memory-mapped resource
   * must be responsible for closing it or making sure it gets closed. This is also true for the special
   * memory-mapping methods load(), isLoaded() and force().</p>
   *
   *<p>Moving back and forth between <i>Memory</i> and <i>Buffer</i>:</p>
   *<blockquote><pre>
   *    Memory mem = ...
   *    Buffer buf = mem.asBuffer();
   *    ...
   *    Memory mem2 = buf.asMemory();
   *    ...
   * </pre></blockquote>
   *
   * <p>Hierarchical memory regions can be easily created:</p>
   * <blockquote><pre>
   *     WritableMemory wMem = ...
   *     WritableMemory wReg = wMem.writableRegion(offset, length); //OR
   *     Memory region = wMem.region(offset, length);
   * </pre></blockquote>
   *
   * <p>All methods are checked for bounds violations.</p>
   *
   * <p>The classes in this package are not thread-safe.</p>
   *
   * @author Lee Rhodes
   */
  package org.apache.datasketches.memory;
  