org.acmsl.katas.antlr4netty.InterpreterServerChannelHandler.java Source code

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Here is the source code for org.acmsl.katas.antlr4netty.InterpreterServerChannelHandler.java

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/*
                    kata-antlr4-netty
    
Copyright (C) 2002-today  Jose San Leandro Armendariz
                          chous@acm-sl.org
    
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2 of the License, or any later version.
    
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.
    
You should have received a copy of the GNU General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    
Thanks to ACM S.L. for distributing this library under the GPL license.
Contact info: jose.sanleandro@acm-sl.com
    
 ******************************************************************************
 *
 * Filename: InterpreterServerChannelHandler.java
 *
 * Author: Jose San Leandro Armendariz
 *
 * Description: Gets spawned on incoming connections and calculates the input.
 *
 * Date: 2014/07/17
 * Time: 07:22
 *
 */
package org.acmsl.katas.antlr4netty;

/*
 * Importing Netty classes.
 */
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.CharsetUtil;
import io.netty.util.ReferenceCountUtil;

/*
 * Importing JetBrains annotations.
 */
import org.jetbrains.annotations.NotNull;

/*
 * Importing checkthread.org annotations.
 */
import org.checkthread.annotations.ThreadSafe;

/*
 * Importing JDK classes.
 */
import java.math.BigDecimal;

/**
 * Gets spawned on incoming connections and calculates the input.
 * @author <a href="mailto:queryj@acm-sl.org">Jose San Leandro</a>
 * @since 3.0
 * Created: 2014/07/17 07:22
 */
@ThreadSafe
@Sharable
public class InterpreterServerChannelHandler extends ChannelHandlerAdapter {
    /**
     * {@inheritDoc}
     */
    @Override
    public void channelRead(@NotNull final ChannelHandlerContext ctx, @NotNull final Object msg) throws Exception {
        @NotNull
        final String input;

        @NotNull
        final ByteBuf buffer = (ByteBuf) msg;

        @NotNull
        final byte[] aux = new byte[buffer.readableBytes()];

        for (int index = 0; index < aux.length; index++) {
            aux[index] = buffer.readByte();
        }

        ReferenceCountUtil.release(msg);

        input = new String(aux, CharsetUtil.UTF_8);

        @NotNull
        final BigDecimal output = calculate(input);

        @NotNull
        final ByteBuf out = Unpooled.copiedBuffer(("" + output + "\n").getBytes(CharsetUtil.UTF_8));

        ctx.writeAndFlush(out);
    }

    /**
     * Performs the arithmetic calculations expressed in given input,
     * according to Interpreter grammar.
     * @param input the input.
     * @return the outcome of the calculation.
     */
    @NotNull
    public BigDecimal calculate(@NotNull final String input) {
        return new Interpreter().eval(input);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void channelReadComplete(final ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void exceptionCaught(final ChannelHandlerContext ctx, final Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}