SocketTDExercise.java

package com.huyle;


import java.io.IOException;

public class SocketTDExercise {

    private static final int MESSAGE_SIZE = 8;

    private HLSocket socketClient;

    /**
     * An artificial terminal API to fetch the next fixed-length
     * message from an endpoint with the provided address.
     */
    public byte[] nextMessage(String address) throws IOException {
        byte[] buf = new byte[MESSAGE_SIZE];
        int bufOffset = 0;
        int actualRead = 0;
        SocketConnection socket = null;
        try {
            socket = socketClient.connect(address);
            while (bufOffset < MESSAGE_SIZE) {
                actualRead = socketClient.readFromSocket(
                        socket,
                        buf,
                        bufOffset,
                        MESSAGE_SIZE - actualRead);
                if (actualRead == -1) {
                    int errorCode = socketClient.readFromSocket(socket, null, 0, 0);
                    throw new IOException(String.format(
                            "Failed to read data completely from a socket: %s. "
                                    + "Error code: %d", MESSAGE_SIZE, errorCode));
                } else if (actualRead == 0 && bufOffset < MESSAGE_SIZE) {
                    throw new IOException(String.format(
                            "EOF before reaching the requested size %d", MESSAGE_SIZE));
                }
                bufOffset += actualRead;
            }
        } finally {
            if (socket != null) {
                socket.close();
            }
        }
        return buf;
    }

    interface SocketConnection {
        void close();
    }

    interface HLSocket {
        SocketConnection connect(String address);

        int readFromSocket(SocketConnection connection,
                           byte[] buffer,
                           int bufferOffset,
                           int requestSize);
    }

}