core/src/main/java/org/apache/airavata/mft/core/CircularStreamingBuffer.java

/*
 * 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.airavata.mft.core;

import java.io.*;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.Semaphore;

public class CircularStreamingBuffer {

    private int bufferSize = 18192;
    private ArrayBlockingQueue<Byte> buffer = new ArrayBlockingQueue<>(bufferSize);

    private boolean osClosed = false;
    private Semaphore readSem = new Semaphore(0);

    private OutputStream outputStream = new CSBOutputStream();
    private InputStream inputStream = new CSBInputStream();

    public OutputStream getOutputStream() {
        return outputStream;
    }

    public InputStream getInputStream() {
        return inputStream;
    }

    private void updateRead(boolean forced) {
        if (forced || readSem.availablePermits() == 0) {
            //System.out.println("Read sem released");
            readSem.release();
        }
    }

    public class CSBOutputStream extends OutputStream {

        @Override
        public void flush() throws IOException {
        }

        @Override
        public void close() throws IOException {
            osClosed = true;
            updateRead(true);
        }

        @Override
        public void write(int b) throws IOException {
            try {
                buffer.put((byte)b);
                //System.out.println("Writing");
                updateRead(false);
            } catch (InterruptedException e) {
                throw new IOException(e);
            }
        }
    }

    public class CSBInputStream extends InputStream {

        @Override
        public int read() throws IOException {
            //System.out.println("Read int");
            Byte res = buffer.poll();
            //System.out.println("Done read int");
            if (res == null) {
                //System.out.println("Received null in is.read()");
                if (osClosed) return -1;
                try {
                    //System.out.println("Read sem acquired");
                    readSem.acquire();
                    //System.out.println("Read Released");
                    return read();
                } catch (InterruptedException e) {
                    throw new IOException(e);
                }
            } else {
                return res & 0xff;
            }
        }
    }
}