/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package com.sun.tools.internal.xjc.api.util;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.File;

import java.net.URL;

import java.net.URLClassLoader;

import java.net.MalformedURLException;

import com.sun.istack.internal.Nullable;

/**

 * {@link ClassLoader} that loads Annotation Processing and specified classes

 * both into the same classloader, so that they can reference each other.

 *

 * @author Bhakti Mehta

 * @since 2.0 beta

 */

public final class ApClassLoader extends URLClassLoader {

    /**

     * List of package prefixes we want to mask the

     * parent classLoader from loading

     */

    private final String[] packagePrefixes;

    /**

     *

     * @param packagePrefixes

     *      The package prefixes that are forced to resolve within this class loader.

     * @param parent

     *      The parent class loader to delegate to. Null to indicate bootstrap classloader.

     */

    public ApClassLoader(@Nullable ClassLoader parent, String[] packagePrefixes) throws ToolsJarNotFoundException {

        super(getToolsJar(parent),parent);

        if(getURLs().length==0)

            // if tools.jar was found in our classloader, no need to create

            // a parallel classes

            this.packagePrefixes = new String[0];

        else

            this.packagePrefixes = packagePrefixes;

    }

    public Class loadClass(String className) throws ClassNotFoundException {

        for( String prefix : packagePrefixes ) {

            if (className.startsWith(prefix) ) {

                // we need to load those classes in this class loader

                // without delegation.

                return findClass(className);

            }

        }

        return super.loadClass(className);

    }

    protected Class findClass(String name) throws ClassNotFoundException {

        StringBuilder sb = new StringBuilder(name.length() + 6);

        sb.append(name.replace('.','/')).append(".class");

        InputStream is = getResourceAsStream(sb.toString());

        if (is==null)

            throw new ClassNotFoundException("Class not found" + sb);

        try {

            ByteArrayOutputStream baos = new ByteArrayOutputStream();

            byte[] buf = new byte[1024];

            int len;

            while((len=is.read(buf))>=0)

                baos.write(buf,0,len);

            buf = baos.toByteArray();

            // define package if not defined yet

            int i = name.lastIndexOf('.');

            if (i != -1) {

                String pkgname = name.substring(0, i);

                Package pkg = getPackage(pkgname);

                if(pkg==null)

                    definePackage(pkgname, null, null, null, null, null, null, null);

            }

            return defineClass(name,buf,0,buf.length);

        } catch (IOException e) {

            throw new ClassNotFoundException(name,e);

        } finally {

            try {

                is.close();

            } catch (IOException ioe) {

                //ignore

            }

        }

    }

    /**

     * Returns a class loader that can load classes from JDK tools.jar.

     * @param parent

     */

    private static URL[] getToolsJar(@Nullable ClassLoader parent) throws ToolsJarNotFoundException {

        try {

            Class.forName("com.sun.tools.javac.Main", false, parent);

            return new URL[0];

            // we can already load them in the parent class loader.

            // so no need to look for tools.jar.

            // this happens when we are run inside IDE/Ant, or

            // in Mac OS.

        } catch (ClassNotFoundException e) {

            // otherwise try to find tools.jar

        }

        File jreHome = new File(System.getProperty("java.home"));

        File toolsJar = new File( jreHome.getParent(), "lib/tools.jar" );

        if (!toolsJar.exists()) {

            throw new ToolsJarNotFoundException(toolsJar);

        }

        try {

            return new URL[]{toolsJar.toURL()};

        } catch (MalformedURLException e) {

            // impossible

            throw new AssertionError(e);

        }

    }

}