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 * Copyright 2014 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * Licensed 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 io.undertow.util;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;

import io.undertow.UndertowLogger;
import org.xnio.ChannelListener;
import org.xnio.ChannelListeners;
import org.xnio.IoUtils;
import org.xnio.channels.StreamSinkChannel;

A simple write listener that can be used to write out the contents of a String. When the string is written out it closes the channel. This should not be added directly to the channel, instead setup(StreamSinkChannel) should be called, which will attempt a write, and only add the listener if required. 
Author:
Stuart Douglas/**
 * A simple write listener that can be used to write out the contents of a String. When the string is written
 * out it closes the channel.
 *
 * This should not be added directly to the channel, instead {@link #setup(org.xnio.channels.StreamSinkChannel)}
 * should be called, which will attempt a write, and only add the listener if required.
 *
 * @author Stuart Douglas
 */
public class StringWriteChannelListener implements ChannelListener<StreamSinkChannel> {

    private final ByteBuffer buffer;

    public StringWriteChannelListener( final String string) {
        this(string, Charset.defaultCharset());
    }

    public StringWriteChannelListener( final String string, Charset charset) {
        buffer = ByteBuffer.wrap(string.getBytes(charset));
    }

    public void setup(final StreamSinkChannel channel) {
        try {
            int c;
            do {
                c = channel.write(buffer);
            } while (buffer.hasRemaining() && c > 0);
            if (buffer.hasRemaining()) {
                channel.getWriteSetter().set(this);
                channel.resumeWrites();
            } else {
                writeDone(channel);
            }
        } catch (IOException e) {
            handleError(channel, e);
        }
    }

    protected void handleError(StreamSinkChannel channel, IOException e) {
        UndertowLogger.REQUEST_IO_LOGGER.ioException(e);
        IoUtils.safeClose(channel);
    }

    @Override
    public void handleEvent(final StreamSinkChannel channel) {
        try {
            int c;
            do {
                c = channel.write(buffer);
            } while (buffer.hasRemaining() && c > 0);
            if (buffer.hasRemaining()) {
                channel.resumeWrites();
                return;
            } else {
                writeDone(channel);
            }
        } catch (IOException e) {
            handleError(channel, e);
        }
    }

    public boolean hasRemaining() {
        return buffer.hasRemaining();
    }

    protected void writeDone(final StreamSinkChannel channel) {
        try {
            channel.shutdownWrites();

            if (!channel.flush()) {
                channel.getWriteSetter().set(ChannelListeners.flushingChannelListener(new ChannelListener<StreamSinkChannel>() {
                    @Override
                    public void handleEvent(StreamSinkChannel o) {
                        IoUtils.safeClose(channel);
                    }
                }, ChannelListeners.closingChannelExceptionHandler()));
                channel.resumeWrites();

            }
        } catch (IOException e) {
            handleError(channel, e);
        }
    }
}