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.cassandra.io.util;
  
  import java.io.DataInput;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.primitives.Ints;
  
  import org.apache.cassandra.utils.memory.MemoryUtil;
  
  public class MemoryInputStream extends RebufferingInputStream implements DataInput
  {
      private final Memory mem;
      private final int bufferSize;
      private long offset;
  
  
      public MemoryInputStream(Memory mem)
      {
          this(mem, Ints.saturatedCast(mem.size));
      }
  
      @VisibleForTesting
      public MemoryInputStream(Memory mem, int bufferSize)
      {
          super(getByteBuffer(mem.peer, bufferSize));
          this.mem = mem;
          this.bufferSize = bufferSize;
          this.offset = mem.peer + bufferSize;
      }
  
      @Override
      protected void reBuffer() throws IOException
      {
          if (offset - mem.peer >= mem.size())
              return;
  
          buffer = getByteBuffer(offset, Math.min(bufferSize, Ints.saturatedCast(memRemaining())));
          offset += buffer.capacity();
      }
  
      @Override
      public int available()
      {
          return Ints.saturatedCast(buffer.remaining() + memRemaining());
      }
  
      private long memRemaining()
      {
          return mem.size + mem.peer - offset;
      }
  
      private static ByteBuffer getByteBuffer(long offset, int length)
      {
          return MemoryUtil.getByteBuffer(offset, length, ByteOrder.BIG_ENDIAN);
      }
  }
  