/*
 * 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.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.SeekableByteChannel;

import com.google.common.base.Preconditions;

Rough equivalent of BufferedInputStream and DataInputStream wrapping the input stream of a File or Socket
Created to work around the fact that when BIS + DIS delegate to NIO for socket IO they will allocate large
thread local direct byte buffers when a large array is used to read.
There may also be some performance improvement due to using a DBB as the underlying buffer for IO and the removal
of some indirection and delegation when it comes to reading out individual values, but that is not the goal.
Closing NIODataInputStream will invoke close on the ReadableByteChannel provided at construction.
NIODataInputStream is not thread safe.
/**
 * Rough equivalent of BufferedInputStream and DataInputStream wrapping the input stream of a File or Socket
 * Created to work around the fact that when BIS + DIS delegate to NIO for socket IO they will allocate large
 * thread local direct byte buffers when a large array is used to read.
 *
 * There may also be some performance improvement due to using a DBB as the underlying buffer for IO and the removal
 * of some indirection and delegation when it comes to reading out individual values, but that is not the goal.
 *
 * Closing NIODataInputStream will invoke close on the ReadableByteChannel provided at construction.
 *
 * NIODataInputStream is not thread safe.
 */
public class NIODataInputStream extends RebufferingInputStream
{
    protected final ReadableByteChannel channel;

    private static ByteBuffer makeBuffer(int bufferSize)
    {
        ByteBuffer buffer = ByteBuffer.allocateDirect(bufferSize);
        buffer.position(0);
        buffer.limit(0);

        return buffer;
    }

    public NIODataInputStream(ReadableByteChannel channel, int bufferSize)
    {
        super(makeBuffer(bufferSize));

        Preconditions.checkNotNull(channel);
        this.channel = channel;
    }

    @Override
    protected void reBuffer() throws IOException
    {
        Preconditions.checkState(buffer.remaining() == 0);
        buffer.clear();

        while ((channel.read(buffer)) == 0) {}

        buffer.flip();
    }

    @Override
    public void close() throws IOException
    {
        channel.close();
        super.close();
        FileUtils.clean(buffer);
        buffer = null;
    }

    @Override
    public int available() throws IOException
    {
        if (channel instanceof SeekableByteChannel)
        {
            SeekableByteChannel sbc = (SeekableByteChannel) channel;
            long remainder = Math.max(0, sbc.size() - sbc.position());
            return (remainder > Integer.MAX_VALUE) ? Integer.MAX_VALUE : (int)(remainder + buffer.remaining());
        }
        return buffer.remaining();
    }
}