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/*******************************************************************************
 * Copyright (c) 2015 LegSem.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser Public License v2.1
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * 
 * Contributors:
 *     LegSem - initial API and implementation
 ******************************************************************************/
package com.legstar.coxb.transform;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.legstar.coxb.CobolContext;
import com.legstar.coxb.CobolElementVisitor;
import com.legstar.coxb.ICobolComplexBinding;
import com.legstar.coxb.host.HostException;

/**
 * Generic methods to transform java value object to host data.
 * 
 * Implementing classes should inherit from AbstractJavaToHostTransformer and
 * implement the getBinding method.
 * 

 * This is sample code with dynamic binding:
 * 
 * 
 * public class JavaToHostLsfileaeTransformer extends
 *         AbstractJavaToHostTransformer {
 *     public ICobolComplexBinding getBinding() throws BindingException {
 *         try {
 *             CComplexReflectBinding binding = new CComplexReflectBinding(
 *                     new com.legstar.test.coxb.lsfileae.ObjectFactory(),
 *                     com.legstar.test.coxb.lsfileae.Dfhcommarea.class);
 *             return binding;
 *         } catch (ReflectBindingException e) {
 *             throw new BindingException(e);
 *         }
 *     }
 * }
 * 
 * 
 * This is sample code with static binding:
 * 
 * 
 * public class JavaToHostLsfileaeTransformer extends
 *         AbstractJavaToHostTransformer {
 *     public ICobolComplexBinding getBinding() throws BindingException {
 *         return new com.legstar.test.coxb.lsfileae.DfhcommareaBinding();
 *     }
 * }
 * 
 */
public abstract class AbstractJavaToHostTransformer extends AbstractTransformer
        implements IJavaToHostTransformer {

    /** Maximum size of a level 01 data item. */
    private static final int MAX_HOST_DATA_SIZE = 134217727;

    /** Logger. */
    private final Log _log = LogFactory
            .getLog(AbstractJavaToHostTransformer.class);

    /**
     * Create a Java to Host transformer using default COBOL parameters.
     */
    public AbstractJavaToHostTransformer() {
        super();
    }

    /**
     * Create a Java to Host transformer using a specific host character set
     * while other COBOL parameters are set by default.
     * 
     * @param hostCharset the host character set
     */
    public AbstractJavaToHostTransformer(final String hostCharset) {
        super(hostCharset);
    }

    /**
     * Create a Java to Host transformer using a specific COBOL parameters set.
     * 
     * @param cobolContext the COBOL parameters set.
     */
    public AbstractJavaToHostTransformer(final CobolContext cobolContext) {
        super(cobolContext);
    }

    /**
     * Transforms java to host data with a specific host character set.
     * 
     * @param valueObject a java value object
     * @param hostCharset the host character set
     * @return a byte array with host data
     * @throws HostTransformException if transformation fails
     */
    public byte[] transform(final Object valueObject, final String hostCharset)
            throws HostTransformException {
        return transform(valueObject, hostCharset, new HostTransformStatus());
    }

    /**
     * Transforms java to host data with a specific host character set.
     * 
     * @param valueObject a java value object
     * @param hostCharset the host character set
     * @param status will contain information on the transformation after it is
     *            executed
     * @return a byte array with host data
     * @throws HostTransformException if transformation fails
     */
    public byte[] transform(final Object valueObject, final String hostCharset,
            final HostTransformStatus status) throws HostTransformException {
        if (hostCharset != null && hostCharset.length() > 0) {
            getCobolConverters().getCobolContext().setHostCharsetName(
                    hostCharset);
        }
        return transform(valueObject, status);
    }

    /**
     * Transforms java data object to host data.
     * 
     * @param valueObject a java value object
     * @return a byte array with host data
     * @throws HostTransformException if transformation fails
     */
    public byte[] transform(final Object valueObject)
            throws HostTransformException {
        return transform(valueObject, new HostTransformStatus());
    }

    /**
     * Transforms java data object to host data.
     * 
     * @param valueObject a java value object
     * @param status will contain information on the transformation after it is
     *            executed
     * @return a byte array with host data
     * @throws HostTransformException if transformation fails
     */
    public byte[] transform(final Object valueObject,
            final HostTransformStatus status) throws HostTransformException {

        long start = System.currentTimeMillis();
        if (_log.isDebugEnabled()) {
            _log.debug("Java to Host transformation started");
        }

        try {
            /* Reuse binding if possible get a new one otherwise */
            ICobolComplexBinding binding = getCachedBinding();
            binding.setObjectValue(valueObject);

            /*
             * Allocate a byte array large enough to accommodate the largest
             * object but not too large as to get memory errors.
             */
            int size = binding.getByteLength();
            if (size > MAX_HOST_DATA_SIZE) {
                _log.warn("Expected host data size of " + size
                        + " exceeds the maximum allowed of "
                        + MAX_HOST_DATA_SIZE);
                size = MAX_HOST_DATA_SIZE;
            }
            byte[] hostData = new byte[size];

            /* create the outbound buffer by marshalling the java object tree */
            CobolElementVisitor marshaler = getCobolBindingVisitorsFactory()
                    .createMarshalVisitor(hostData, 0, getCobolConverters());

            /*
             * Traverse the object structure, visiting each node with the
             * visitor
             */
            binding.accept(marshaler);

            /* Get the actual bytes marshalled */
            int bytesMarshalled = marshaler.getOffset();

            /*
             * If the byte array was allocated too large (this happens with
             * variable size arrays for instance), reallocate.
             */
            byte[] adjustedHostData;
            if (bytesMarshalled < size) {
                adjustedHostData = new byte[bytesMarshalled];
                System.arraycopy(hostData, 0, adjustedHostData, 0,
                        bytesMarshalled);
            } else {
                adjustedHostData = hostData;
            }

            if (_log.isDebugEnabled()) {
                long end = System.currentTimeMillis();
                _log.debug("Java to Host transformation ended. Processed: "
                        + Integer.toString(bytesMarshalled) + " bytes "
                        + "elapse:" + Long.toString(end - start) + " ms");
            }
            status.setHostBytesProcessed(bytesMarshalled);
            status.setBinding(binding);

            return adjustedHostData;

        } catch (HostException he) {
            throw new HostTransformException(he);
        }
    }

}