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/*
 * Copyright  1999-2004 The Apache Software Foundation.
 *
 *  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
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package com.sun.org.apache.xml.internal.security.transforms;

import java.io.IOException;
import java.io.OutputStream;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.HashMap;
import java.util.Map;
import javax.xml.parsers.ParserConfigurationException;

import com.sun.org.apache.xml.internal.security.c14n.CanonicalizationException;
import com.sun.org.apache.xml.internal.security.c14n.InvalidCanonicalizerException;
import com.sun.org.apache.xml.internal.security.exceptions.AlgorithmAlreadyRegisteredException;
import com.sun.org.apache.xml.internal.security.exceptions.XMLSecurityException;
import com.sun.org.apache.xml.internal.security.signature.XMLSignatureInput;
import com.sun.org.apache.xml.internal.security.utils.Constants;
import com.sun.org.apache.xml.internal.security.utils.HelperNodeList;
import com.sun.org.apache.xml.internal.security.utils.SignatureElementProxy;
import com.sun.org.apache.xml.internal.security.utils.XMLUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

/**
 * Implements the behaviour of the <code>ds:Transform</code> element.
 *
 * This <code>Transform</code>(Factory) class acts as the Factory and Proxy of
 * the implementing class that supports the functionality of <a
 * href=http://www.w3.org/TR/xmldsig-core/#sec-TransformAlg>a Transform
 * algorithm</a>.
 * Implements the Factory and Proxy pattern for ds:Transform algorithms.
 *
 * @author Christian Geuer-Pollmann
 * @see Transforms
 * @see TransformSpi
 *
 */
public final class Transform extends SignatureElementProxy {

    /** {@link java.util.logging} logging facility */
    static java.util.logging.Logger log =
        java.util.logging.Logger.getLogger(Transform.class.getName());

    /** Field _alreadyInitialized */
    private static boolean alreadyInitialized = false;

    /** All available Transform classes are registered here */
    private static Map<String, Class<?>> transformClassHash = null;

    private static Map<String, TransformSpi> transformSpiHash = new HashMap<String, TransformSpi>();

    private TransformSpi transformSpi = null;

    /**
     * Constructs {@link Transform}
     *
     * @param doc the {@link Document} in which <code>Transform</code> will be
     * placed
     * @param algorithmURI URI representation of
     * <code>Transform algorithm</code> which will be specified as parameter of
     * {@link #getInstance(Document, String)}, when generated. </br>
     * @param contextNodes the child node list of <code>Transform</code> element
     * @throws InvalidTransformException
     */
    public Transform(Document doc, String algorithmURI, NodeList contextNodes)
        throws InvalidTransformException {

        super(doc);

        this._constructionElement.setAttributeNS
            (null, Constants._ATT_ALGORITHM, algorithmURI);

        transformSpi = getTransformSpi(algorithmURI);
        if (transformSpi == null) {
             Object exArgs[] = { algorithmURI };
             throw new InvalidTransformException(
                "signature.Transform.UnknownTransform", exArgs);
        }

        if (log.isLoggable(java.util.logging.Level.FINE)) {
            log.log(java.util.logging.Level.FINE, "Create URI \"" + algorithmURI + "\" class \""
                   + transformSpi.getClass() + "\"");
            log.log(java.util.logging.Level.FINE, "The NodeList is " + contextNodes);
        }

        // give it to the current document
        if (contextNodes != null) {
            for (int i = 0; i < contextNodes.getLength(); i++) {
               this._constructionElement.appendChild
                   (contextNodes.item(i).cloneNode(true));
            }
        }
    }

    /**
     * This constructor can only be called from the {@link Transforms} object,
     * so it's protected.
     *
     * @param element <code>ds:Transform</code> element
     * @param BaseURI the URI of the resource where the XML instance was stored
     * @throws InvalidTransformException
     * @throws TransformationException
     * @throws XMLSecurityException
     */
    public Transform(Element element, String BaseURI)
        throws InvalidTransformException, TransformationException,
               XMLSecurityException {

        super(element, BaseURI);

        // retrieve Algorithm Attribute from ds:Transform
        String algorithmURI = element.getAttributeNS(null, Constants._ATT_ALGORITHM);

        if (algorithmURI == null || algorithmURI.length() == 0) {
            Object exArgs[] = { Constants._ATT_ALGORITHM,
                                Constants._TAG_TRANSFORM };
            throw new TransformationException("xml.WrongContent", exArgs);
        }

        transformSpi = getTransformSpi(algorithmURI);
        if (transformSpi == null) {
            Object exArgs[] = { algorithmURI };
            throw new InvalidTransformException(
                "signature.Transform.UnknownTransform", exArgs);
        }
    }

    /**
     * Generates a Transform object that implements the specified
     * <code>Transform algorithm</code> URI.
     *
     * @param algorithmURI <code>Transform algorithm</code> URI representation,
     * such as specified in
     * <a href=http://www.w3.org/TR/xmldsig-core/#sec-TransformAlg>Transform algorithm </a>
     * @param doc the proxy {@link Document}
     * @return <code>{@link Transform}</code> object
     * @throws InvalidTransformException
     */
    public static Transform getInstance(
        Document doc, String algorithmURI) throws InvalidTransformException {
        return getInstance(doc, algorithmURI, (NodeList) null);
    }

    /**
     * Generates a Transform object that implements the specified
     * <code>Transform algorithm</code> URI.
     *
     * @param algorithmURI <code>Transform algorithm</code> URI representation,
     * such as specified in
     * <a href=http://www.w3.org/TR/xmldsig-core/#sec-TransformAlg>Transform algorithm </a>
     * @param contextChild the child element of <code>Transform</code> element
     * @param doc the proxy {@link Document}
     * @return <code>{@link Transform}</code> object
     * @throws InvalidTransformException
     */
    public static Transform getInstance(
        Document doc, String algorithmURI, Element contextChild)
        throws InvalidTransformException {

        HelperNodeList contextNodes = new HelperNodeList();

        XMLUtils.addReturnToElement(doc, contextNodes);
        contextNodes.appendChild(contextChild);
        XMLUtils.addReturnToElement(doc, contextNodes);

        return getInstance(doc, algorithmURI, contextNodes);
    }

    /**
     * Generates a Transform object that implements the specified
     * <code>Transform algorithm</code> URI.
     *
     * @param algorithmURI <code>Transform algorithm</code> URI form, such as
     * specified in <a href=http://www.w3.org/TR/xmldsig-core/#sec-TransformAlg>
     * Transform algorithm </a>
     * @param contextNodes the child node list of <code>Transform</code> element
     * @param doc the proxy {@link Document}
     * @return <code>{@link Transform}</code> object
     * @throws InvalidTransformException
     */
    public static Transform getInstance(
        Document doc, String algorithmURI, NodeList contextNodes)
        throws InvalidTransformException {
        return new Transform(doc, algorithmURI, contextNodes);
    }

    /**
     * Initalizes for this {@link Transform}.
     */
    public static void init() {
        if (!alreadyInitialized) {
            transformClassHash = new HashMap<String,Class<?>>(10);
            // make sure builtin algorithms are all registered first
            com.sun.org.apache.xml.internal.security.Init.init();
            alreadyInitialized = true;
        }
    }

    /**
     * Registers implementing class of the Transform algorithm with algorithmURI
     *
     * @param algorithmURI algorithmURI URI representation of
     * <code>Transform algorithm</code> will be specified as parameter of
     * {@link #getInstance(Document, String)}, when generate. </br>
     * @param implementingClass <code>implementingClass</code> the implementing
     * class of {@link TransformSpi}
     * @throws AlgorithmAlreadyRegisteredException if specified algorithmURI
     * is already registered
     */
    public static void register(String algorithmURI, String implementingClass)
        throws AlgorithmAlreadyRegisteredException {

        // are we already registered?
        Class<? extends TransformSpi> registeredClass = getImplementingClass(algorithmURI);
        if ((registeredClass != null) ) {
            Object exArgs[] = { algorithmURI, registeredClass };
            throw new AlgorithmAlreadyRegisteredException(
               "algorithm.alreadyRegistered", exArgs);
        }

        ClassLoader cl = Thread.currentThread().getContextClassLoader();

        try {
            transformClassHash.put
                (algorithmURI, Class.forName(implementingClass, true, cl));
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Returns the URI representation of Transformation algorithm
     *
     * @return the URI representation of Transformation algorithm
     */
    public String getURI() {
        return this._constructionElement.getAttributeNS
            (null, Constants._ATT_ALGORITHM);
    }

    /**
     * Transforms the input, and generates {@link XMLSignatureInput} as output.
     *
     * @param input input {@link XMLSignatureInput} which can supplied Octet
     * Stream and NodeSet as Input of Transformation
     * @return the {@link XMLSignatureInput} class as the result of
     * transformation
     * @throws CanonicalizationException
     * @throws IOException
     * @throws InvalidCanonicalizerException
     * @throws TransformationException
     */
    public XMLSignatureInput performTransform(XMLSignatureInput input)
         throws IOException, CanonicalizationException,
                InvalidCanonicalizerException, TransformationException {

        XMLSignatureInput result = null;

        try {
            result = transformSpi.enginePerformTransform(input, this);
        } catch (ParserConfigurationException ex) {
            Object exArgs[] = { this.getURI(), "ParserConfigurationException" };
            throw new CanonicalizationException(
                "signature.Transform.ErrorDuringTransform", exArgs, ex);
        } catch (SAXException ex) {
            Object exArgs[] = { this.getURI(), "SAXException" };
            throw new CanonicalizationException(
                "signature.Transform.ErrorDuringTransform", exArgs, ex);
        }

        return result;
    }

    /**
     * Transforms the input, and generates {@link XMLSignatureInput} as output.
     *
     * @param input input {@link XMLSignatureInput} which can supplied Octet
     * Stream and NodeSet as Input of Transformation
     * @param os where to output the result of the last transformation
     * @return the {@link XMLSignatureInput} class as the result of
     * transformation
     * @throws CanonicalizationException
     * @throws IOException
     * @throws InvalidCanonicalizerException
     * @throws TransformationException
     */
    public XMLSignatureInput performTransform(XMLSignatureInput input,
        OutputStream os) throws IOException, CanonicalizationException,
        InvalidCanonicalizerException, TransformationException {

        XMLSignatureInput result = null;

        try {
            result = transformSpi.enginePerformTransform(input, os, this);
        } catch (ParserConfigurationException ex) {
            Object exArgs[] = { this.getURI(), "ParserConfigurationException" };
            throw new CanonicalizationException(
                "signature.Transform.ErrorDuringTransform", exArgs, ex);
        } catch (SAXException ex) {
            Object exArgs[] = { this.getURI(), "SAXException" };
            throw new CanonicalizationException(
                "signature.Transform.ErrorDuringTransform", exArgs, ex);
        }

        return result;
    }

    /**
     * Method getImplementingClass
     *
     * @param URI
     * @return The name of the class implementing the URI.
     */
    @SuppressWarnings("unchecked")
    private static Class<? extends TransformSpi> getImplementingClass(String URI) {
        return (Class<? extends TransformSpi>)transformClassHash.get(URI);
    }

    private static TransformSpi getTransformSpi(String URI)
        throws InvalidTransformException {
        try {
            TransformSpi value = transformSpiHash.get(URI);
            if (value != null) {
                return value;
            }
            Class<? extends TransformSpi> cl = getImplementingClass(URI);
            if (cl != null) {
                TransformSpi tr = cl.newInstance();
                transformSpiHash.put(URI, tr);
                return tr;
            }
        } catch (InstantiationException ex) {
            Object exArgs[] = { URI };
            throw new InvalidTransformException(
                "signature.Transform.UnknownTransform", exArgs, ex);
        } catch (IllegalAccessException ex) {
            Object exArgs[] = { URI };
            throw new InvalidTransformException(
                "signature.Transform.UnknownTransform", exArgs, ex);
        }
        return null;
    }

    /** @inheritDoc */
    public String getBaseLocalName() {
        return Constants._TAG_TRANSFORM;
    }
}
