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This nifi-utils module should be a general purpose place to store widely and generally useful functions that any component might want to leverage. NO DEPENDENCIES should be added. This module is likely to be leveraged by every extension and should not bring along any other dependencies. The only dependency intended is the nifi-api and even this is expected to be already provided in any case where it would be used. The typical place this util would be found is within a nar and all nars already have nifi-api as a parent dependency. The nifi-api can be thought of as a NiFi Application Container level dependency.

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/*
 * 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.nifi.remote.io.socket;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.net.SocketTimeoutException;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;
import java.util.concurrent.TimeUnit;

public class SocketChannelInputStream extends InputStream {

    private static final long CHANNEL_EMPTY_WAIT_NANOS = TimeUnit.NANOSECONDS.convert(10, TimeUnit.MILLISECONDS);
    private final SocketChannel channel;
    private volatile int timeoutMillis = 30000;

    private final ByteBuffer oneByteBuffer = ByteBuffer.allocate(1);
    private Byte bufferedByte = null;

    public SocketChannelInputStream(final SocketChannel socketChannel) throws IOException {
        // this class expects a non-blocking channel
        socketChannel.configureBlocking(false);
        this.channel = socketChannel;
    }

    public void setTimeout(final int timeoutMillis) {
        this.timeoutMillis = timeoutMillis;
    }

    public void consume() throws IOException {
        channel.shutdownInput();

        final byte[] b = new byte[4096];
        final ByteBuffer buffer = ByteBuffer.wrap(b);
        int bytesRead;
        do {
            bytesRead = channel.read(buffer);
            buffer.flip();
        } while (bytesRead > 0);
    }

    @Override
    public int read() throws IOException {
        if (bufferedByte != null) {
            final int retVal = bufferedByte & 0xFF;
            bufferedByte = null;
            return retVal;
        }

        oneByteBuffer.flip();
        oneByteBuffer.clear();

        final long maxTime = System.currentTimeMillis() + timeoutMillis;

        final boolean blocking = channel.isBlocking();

        try {
            channel.configureBlocking(true);

            int bytesRead;
            do {
                bytesRead = channel.read(oneByteBuffer);
                if (bytesRead == 0) {
                    if (System.currentTimeMillis() > maxTime) {
                        throw new SocketTimeoutException("Timed out reading from socket");
                    }
                }
            } while (bytesRead == 0);

            if (bytesRead == -1) {
                return -1;
            }

            oneByteBuffer.flip();
            return oneByteBuffer.get() & 0xFF;
        } finally {
            if (!blocking) {
                channel.configureBlocking(false);
            }
        }
    }

    @Override
    public int read(final byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    @Override
    public int read(final byte[] b, final int off, final int len) throws IOException {
        if (bufferedByte != null) {
            final byte retVal = bufferedByte;
            bufferedByte = null;
            b[off] = retVal;
            return 1;
        }

        final ByteBuffer buffer = ByteBuffer.wrap(b, off, len);

        final boolean blocking = channel.isBlocking();
        try {
            channel.configureBlocking(true);

            final long maxTime = System.currentTimeMillis() + timeoutMillis;
            int bytesRead;
            do {
                bytesRead = channel.read(buffer);
                if (bytesRead == 0) {
                    if (System.currentTimeMillis() > maxTime) {
                        throw new SocketTimeoutException("Timed out reading from socket");
                    }
                }
            } while (bytesRead == 0);

            return bytesRead;
        } finally {
            if (!blocking) {
                channel.configureBlocking(false);
            }
        }
    }

    @Override
    public int available() throws IOException {
        if (bufferedByte != null) {
            return 1;
        }

        isDataAvailable(); // attempt to read from socket
        return (bufferedByte == null) ? 0 : 1;
    }

    public boolean isDataAvailable() throws IOException {
        if (bufferedByte != null) {
            return true;
        }

        oneByteBuffer.flip();
        oneByteBuffer.clear();
        final int bytesRead = channel.read(oneByteBuffer);
        if (bytesRead == -1) {
            throw new EOFException("Peer has closed the stream");
        }
        if (bytesRead > 0) {
            oneByteBuffer.flip();
            bufferedByte = oneByteBuffer.get();
            return true;
        }
        return false;
    }

    /**
     * Closes the underlying socket channel.
     *
     * @throws java.io.IOException for issues closing underlying stream
     */
    @Override
    public void close() throws IOException {
        channel.close();
    }
}