/*

 * Copyright 2009 Sun Microsystems, Inc.  All Rights Reserved.

 * 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.  Sun designates this

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

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.misc;

import java.io.File;

import java.io.IOException;

/**

 * BootClassLoaderHook defines an interface for a hook to inject

 * into the bootstrap class loader.

 *

 * In jkernel build, the sun.jkernel.DownloadManager is set as

 * a BootClassLoaderHook by the jkernel VM after the VM is initialized.

 *

 * In other JDK builds, no hook is set.

 */

public abstract class BootClassLoaderHook {

    private static BootClassLoaderHook bootLoaderHook = null;

    public static synchronized BootClassLoaderHook getHook() {

        return bootLoaderHook;

    }

    public static synchronized void setHook(BootClassLoaderHook hook) {

        if (!VM.isBooted()) {

            throw new InternalError("hook can only be set after VM is booted");

        }

        if (bootLoaderHook != null) {

            throw new InternalError("hook should not be reinitialized");

        }

        bootLoaderHook = hook;

    }

    protected BootClassLoaderHook() {

    }

    /**

     * A method to be invoked before a class loader loads

     * a bootstrap class.

     *

     * @param classname the binary name of the class

     */

    public static void preLoadClass(String classname) {

        BootClassLoaderHook hook = getHook();

        if (hook != null) {

            hook.loadBootstrapClass(classname);

        }

    }

    /**

     * A method to be invoked before a class loader loads

     * a resource.

     *

     * @param resourcename the resource name

     */

    public static void preLoadResource(String resourcename) {

        BootClassLoaderHook hook = getHook();

        if (hook != null) {

            hook.getBootstrapResource(resourcename);

        }

    }

    /**

     * A method to be invoked before a library is loaded.

     *

     * @param libname the name of the library

     */

    public static void preLoadLibrary(String libname) {

        BootClassLoaderHook hook = getHook();

        if (hook != null) {

            hook.loadLibrary(libname);

        }

    }

    private static final File[] EMPTY_FILE_ARRAY = new File[0];

    /**

     * Returns bootstrap class paths added by the hook.

     */

    public static File[] getBootstrapPaths() {

        BootClassLoaderHook hook = getHook();

        if (hook != null) {

        } else {

            return EMPTY_FILE_ARRAY;

        }

    }

    /**

     * Returns a pathname of a JAR or class that the hook loads

     * per this loadClass request; or null.

     *

     * @param classname the binary name of the class

     */

    public abstract String loadBootstrapClass(String className);

    /**

     * Returns a pathname of a resource file that the hook loads

     * per this getResource request; or null.

     *

     * @param resourceName the resource name

     */

    public abstract String getBootstrapResource(String resourceName);

    /**

     * Returns true if the hook successfully performs an operation per

     * this loadLibrary request; or false if it fails.

     *

     * @param libname the name of the library

     */

    public abstract boolean loadLibrary(String libname);

    /**

     * Returns additional boot class paths added by the hook that

     * should be searched by the boot class loader.

     */

    public abstract File[] getAdditionalBootstrapPaths();

    /**

     * Returns true if the current thread is in the process of doing

     * a prefetching operation.

     */

    public abstract boolean isCurrentThreadPrefetching();

    /**

     * Returns true if the hook successfully prefetches the specified file.

     *

     * @param name a platform independent pathname

     */

    public abstract boolean prefetchFile(String name);

}