jaroslav@298: /**
jaroslav@298:  * Back 2 Browser Bytecode Translator
jaroslav@298:  * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
jaroslav@298:  *
jaroslav@298:  * This program is free software: you can redistribute it and/or modify
jaroslav@298:  * it under the terms of the GNU General Public License as published by
jaroslav@298:  * the Free Software Foundation, version 2 of the License.
jaroslav@298:  *
jaroslav@298:  * This program is distributed in the hope that it will be useful,
jaroslav@298:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
jaroslav@298:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
jaroslav@298:  * GNU General Public License for more details.
jaroslav@298:  *
jaroslav@298:  * You should have received a copy of the GNU General Public License
jaroslav@298:  * along with this program. Look for COPYING file in the top folder.
jaroslav@298:  * If not, see http://opensource.org/licenses/GPL-2.0.
jaroslav@298:  */
jaroslav@298: package org.apidesign.vm4brwsr;
jaroslav@298: 
jaroslav@298: import java.io.IOException;
jaroslav@298: import java.io.InputStream;
jaroslav@298: import java.net.URL;
jaroslav@298: import java.util.Enumeration;
jaroslav@298: 
jaroslav@298: /** Build your own virtual machine! Use methods in this class to generate
jaroslav@298:  * a skeleton JVM in JavaScript that contains pre-compiled classes of your
jaroslav@298:  * choice. The generated script defines one JavaScript method that can
jaroslav@298:  * be used to bootstrap and load the virtual machine: <pre>
jaroslav@298:  * var vm = bck2brwsr();
jaroslav@298:  * var main = vm.loadClass('org.your.pkg.Main');
jaroslav@298:  * main.main__V_3Ljava_lang_String_2(null);
jaroslav@298:  * </pre>
jaroslav@298:  * In case one wants to initialize the virtual machine with ability to
jaroslav@298:  * load classes lazily when needed, one can provide a loader function to
jaroslav@298:  * when creating the virtual machine: <pre>
jaroslav@298:  * var vm = bck2brwsr(function(resource) { 
jaroslav@298:  *   return null; // byte[] for the resource
jaroslav@298:  * });
jaroslav@298:  * </pre>
jaroslav@298:  * In this scenario, when a request for a unknown class is made, the loader
jaroslav@298:  * function is asked for its byte code and the system dynamically transforms
jaroslav@298:  * it to JavaScript.
jaroslav@298:  *
jaroslav@298:  * @author Jaroslav Tulach <jtulach@netbeans.org>
jaroslav@298:  */
jaroslav@298: public final class Bck2Brwsr {
jaroslav@298:     private Bck2Brwsr() {
jaroslav@298:     }
jaroslav@298:     
jaroslav@298:     /** Generates virtual machine from bytes served by a <code>resources</code>
jaroslav@298:      * provider.
jaroslav@298:      * 
jaroslav@298:      * @param out the output to write the generated JavaScript to
jaroslav@298:      * @param resources provider of class files to use
jaroslav@298:      * @param classes additional classes to include in the generated script
jaroslav@298:      * @throws IOException I/O exception can be thrown when something goes wrong
jaroslav@298:      */
jaroslav@298:     public static void generate(Appendable out, Resources resources, String... classes) throws IOException {
jaroslav@298:         StringArray arr = StringArray.asList(classes);
jaroslav@298:         arr.add(VM.class.getName().replace('.', '/'));
jaroslav@298:         VM.compile(resources, out, arr);
jaroslav@298:     }
jaroslav@298:     
jaroslav@298:     /** Generates virtual machine from bytes served by a class loader.
jaroslav@298:      * 
jaroslav@298:      * @param out the output to write the generated JavaScript to
jaroslav@298:      * @param loader class loader to load needed classes from
jaroslav@298:      * @param classes additional classes to include in the generated script
jaroslav@298:      * @throws IOException I/O exception can be thrown when something goes wrong
jaroslav@298:      */
jaroslav@298:     public static void generate(Appendable out, final ClassLoader loader, String... classes) throws IOException {
jaroslav@298:         class R implements Resources {
jaroslav@298:             @Override
jaroslav@298:             public InputStream get(String name) throws IOException {
jaroslav@298:                 Enumeration<URL> en = loader.getResources(name);
jaroslav@298:                 URL u = null;
jaroslav@298:                 while (en.hasMoreElements()) {
jaroslav@298:                     u = en.nextElement();
jaroslav@298:                 }
jaroslav@298:                 if (u == null) {
jaroslav@298:                     throw new IOException("Can't find " + name);
jaroslav@298:                 }
jaroslav@298:                 return u.openStream();
jaroslav@298:             }
jaroslav@298:         }
jaroslav@298:         generate(out, new R(), classes);
jaroslav@298:     }
jaroslav@298:     
jaroslav@298:     /** Provider of resources (classes and other files). The 
jaroslav@298:      * {@link #generate(java.lang.Appendable, org.apidesign.vm4brwsr.Bck2Brwsr.Resources, java.lang.String[]) 
jaroslav@298:      * generator method} will call back here for all classes needed during
jaroslav@298:      * translation to JavaScript.
jaroslav@298:      */
jaroslav@298:     public interface Resources {
jaroslav@298:         /** Loads given resource (class or other file like image). The 
jaroslav@298:          * resource name to load bytes for the {@link String} class
jaroslav@298:          * would be <code>"java/lang/String.class"</code>.
jaroslav@298:          * 
jaroslav@298:          * @param resource path to resource to load
jaroslav@298:          * @return the input stream for the resource 
jaroslav@298:          * @throws IOException can be thrown if the loading fails on some error
jaroslav@298:          *   or the file cannot be found
jaroslav@298:          */
jaroslav@298:         public InputStream get(String resource) throws IOException;
jaroslav@298:     }
jaroslav@298: }