content: /*
   *
   * 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.bookkeeper.util;
  
  import java.nio.ByteBuffer;
  
  /**
   * Zero buffer utility.
   *
   */
  
  public class ZeroBuffer {
      private static final byte[] zeroBytes = new byte[64 * 1024];
  
      /**
       * Fill zeros into given buffer.
       * @param dst
       */
      public static void put(ByteBuffer dst) {
          put(dst, dst.remaining());
      }
  
      /**
       * Fill zeros into given buffer up to given length.
       * @param dst
       * @param length
       */
      public static void put(ByteBuffer dst, int length) {
          while (length > zeroBytes.length) {
              dst.put(zeroBytes);
              length -= zeroBytes.length;
          }
          if (length > 0) {
              dst.put(zeroBytes, 0, length);
          }
      }
  
      /**
       * Returns read-only zero-filled buffer.
       * @param length
       * @return ByteBuffer
       */
      public static ByteBuffer readOnlyBuffer(int length) {
          ByteBuffer buffer;
          if (length <= zeroBytes.length) {
              buffer = ByteBuffer.wrap(zeroBytes, 0, length);
          } else {
              buffer = ByteBuffer.allocate(length);
              put(buffer);
              buffer.rewind();
          }
          return buffer.asReadOnlyBuffer();
      }
  }
  