# PassThroughMessageHandler.java

    /*
     *  Copyright (c) 2022, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
     *
     *  WSO2 Inc. 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.synapse.transport.util;

    import org.apache.axis2.context.MessageContext;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.synapse.transport.passthru.PassThroughConstants;
    import org.apache.synapse.transport.passthru.Pipe;
    import org.apache.synapse.transport.passthru.config.PassThroughConfiguration;
    import org.apache.synapse.transport.passthru.util.RelayUtils;

    import java.io.BufferedInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.nio.ByteBuffer;
    import java.nio.channels.Channels;
    import java.nio.channels.ReadableByteChannel;
    import java.nio.channels.WritableByteChannel;
    import javax.xml.stream.XMLStreamException;

    /**
     * Message handler to handle the messages coming through Pass-Through transport.
     */
    public class PassThroughMessageHandler implements MessageHandler {

        private static final Log LOG = LogFactory.getLog(PassThroughMessageHandler.class);

        @Override
        public InputStream getMessageDataStream(MessageContext context) throws IOException {

            Pipe pipe = (Pipe) context.getProperty(PassThroughConstants.PASS_THROUGH_PIPE);

            if (pipe != null && context.getProperty(PassThroughConstants.BUFFERED_INPUT_STREAM) != null) {
                BufferedInputStream bufferedInputStream =
                        (BufferedInputStream) context.getProperty(PassThroughConstants.BUFFERED_INPUT_STREAM);
                try {
                    bufferedInputStream.reset();
                    bufferedInputStream.mark(0);
                } catch (Exception e) {
                    //just ignore the error
                }
                return bufferedInputStream;
            }

            if (pipe != null) {
                BufferedInputStream bufferedInputStream = new BufferedInputStream(pipe.getInputStream());
                // Multiplied it by two because we always need a bigger read-limit than the buffer size.
                bufferedInputStream.mark(PassThroughConfiguration.getInstance().getIOBufferSize() * 2);
                OutputStream resetOutStream = pipe.resetOutputStream();

                ReadableByteChannel inputChannel = Channels.newChannel(bufferedInputStream);
                WritableByteChannel outputChannel = Channels.newChannel(resetOutStream);

                if (!isMessageBiggerThanBuffer(inputChannel, outputChannel)) {
                    //TODO:need to find a proper solution
                    try {
                        bufferedInputStream.reset();
                        context.setProperty(PassThroughConstants.BUFFERED_INPUT_STREAM, bufferedInputStream);
                        MessageHandlerProvider.getMessageHandler(context).buildMessage(context);
                    } catch (Exception e) {
                        LOG.error("Error while building message", e);
                    }
                    return null;
                }
                try {
                    bufferedInputStream.reset();
                } catch (Exception e) {
                    // just ignore the error
                }

                pipe.setRawSerializationComplete(true);

                return bufferedInputStream;
            }
            return null;
        }

        @Override
        public void buildMessage(MessageContext messageContext) throws XMLStreamException, IOException {
            RelayUtils.buildMessage(messageContext);
        }

        @Override
        public void buildMessage(MessageContext messageContext, boolean earlyBuild) throws XMLStreamException, IOException {
            RelayUtils.buildMessage(messageContext, earlyBuild);
        }

        public boolean isMessageBiggerThanBuffer(final ReadableByteChannel src, final WritableByteChannel dest) throws IOException {

            int bufferSizeSupport = PassThroughConfiguration.getInstance().getIOBufferSize();

            // Added one to make sure temp buffer is always bigger than the io_buffer
            final ByteBuffer buffer = ByteBuffer.allocate(bufferSizeSupport + 1);

            while (src.read(buffer) != -1) {
                if (bufferSizeSupport < buffer.position()) {
                    return false;
                }
            }

            buffer.flip();
            dest.write(buffer);

            return true;
        }
    }