rt/vm/src/main/java/org/apidesign/vm4brwsr/VM.java
author Jaroslav Tulach <jaroslav.tulach@apidesign.org>
Sun, 20 Mar 2016 15:26:19 +0100
changeset 1902 c3dee54ecc15
parent 1863 14a122c18d73
child 1917 66c99d4b3532
permissions -rw-r--r--
Don't redefine already exported classes
     1 /**
     2  * Back 2 Browser Bytecode Translator
     3  * Copyright (C) 2012-2015 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
     4  *
     5  * This program is free software: you can redistribute it and/or modify
     6  * it under the terms of the GNU General Public License as published by
     7  * the Free Software Foundation, version 2 of the License.
     8  *
     9  * This program is distributed in the hope that it will be useful,
    10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    12  * GNU General Public License for more details.
    13  *
    14  * You should have received a copy of the GNU General Public License
    15  * along with this program. Look for COPYING file in the top folder.
    16  * If not, see http://opensource.org/licenses/GPL-2.0.
    17  */
    18 package org.apidesign.vm4brwsr;
    19 
    20 import java.io.IOException;
    21 import java.io.InputStream;
    22 import org.apidesign.bck2brwsr.core.JavaScriptBody;
    23 import org.apidesign.vm4brwsr.ByteCodeParser.ClassData;
    24 import org.apidesign.vm4brwsr.ByteCodeParser.FieldData;
    25 import org.apidesign.vm4brwsr.ByteCodeParser.MethodData;
    26 
    27 /** Generator of JavaScript from bytecode of classes on classpath of the VM.
    28  *
    29  * @author Jaroslav Tulach <jtulach@netbeans.org>
    30  */
    31 abstract class VM extends ByteCodeToJavaScript {
    32     protected final ClassDataCache classDataCache;
    33 
    34     private final Bck2Brwsr.Resources resources;
    35     private final ExportedSymbols exportedSymbols;
    36     private final StringBuilder invokerMethods;
    37     private final StringArray asBinary;
    38     int exportedCount;
    39 
    40     private VM(
    41         Appendable out, Bck2Brwsr.Resources resources, 
    42         StringArray explicitlyExported, StringArray asBinary
    43     ) {
    44         super(out);
    45         this.resources = resources;
    46         this.classDataCache = new ClassDataCache(resources);
    47         this.exportedSymbols = new ExportedSymbols(resources, explicitlyExported);
    48         this.invokerMethods = new StringBuilder();
    49         this.asBinary = asBinary;
    50     }
    51 
    52     static {
    53         // uses VMLazy to load dynamic classes
    54         boolean assertsOn = false;
    55         assert assertsOn = true;
    56         if (assertsOn) {
    57             VMLazy.init();
    58             ClassPath.init();
    59         }
    60     }
    61 
    62     @Override
    63     boolean debug(String msg) throws IOException {
    64         return false;
    65     }
    66     
    67     static void compile(Appendable out, 
    68         Bck2Brwsr config
    69     ) throws IOException {
    70         String[] both = config.classes().toArray();
    71         
    72         final StringArray fixedNames = new StringArray();
    73         fixedNames.add(Object.class.getName().replace('.', '/'));
    74         fixedNames.add(Class.class.getName().replace('.', '/'));
    75         fixedNames.add(ArithmeticException.class.getName().replace('.', '/'));
    76         
    77         VM vm;
    78         if (config.isExtension()) {
    79             fixedNames.add(VM.class.getName().replace('.', '/'));
    80             vm = new Extension(out, 
    81                 config.getResources(), both, config.exported(),
    82                 config.allResources(), config.classpath()
    83             );
    84         } else {
    85             if (config.includeVM()) {
    86                 fixedNames.add(VM.class.getName().replace('.', '/'));
    87             }
    88             vm = new Standalone(out, 
    89                 config.getResources(), config.exported(),
    90                 config.allResources()
    91             );
    92         }            
    93         vm.doCompile(fixedNames.addAndNew(both));
    94     }
    95 
    96     private void doCompile(StringArray names) throws IOException {
    97         generatePrologue();
    98         append("\n  var invoker = {};");
    99         append("\n  function registerClass(vm, name, fn) {");
   100         append("\n    if (!vm[name]) vm[name] = fn;");
   101         append("\n    return vm[name];");
   102         append("\n  }");
   103         generateBody(names);
   104         append(invokerMethods);
   105         
   106         for (String r : asBinary.toArray()) {
   107             append("\n  ").append(getExportsObject()).append("['registerResource']('");
   108             append(r).append("', '");
   109             InputStream is = this.resources.get(r);
   110             byte[] arr = new byte[is.available()];
   111             int offset = 0;
   112             for (;;) {
   113                 if (offset == arr.length) {
   114                     byte[] tmp = new byte[arr.length * 2];
   115                     System.arraycopy(arr, 0, tmp, 0, arr.length);
   116                     arr = tmp;
   117                 }
   118                 int len = is.read(arr, offset, arr.length - offset);
   119                 if (len == -1) {
   120                     break;
   121                 }
   122                 offset += len;
   123             }
   124             if (offset != arr.length) {
   125                 byte[] tmp = new byte[offset];
   126                 System.arraycopy(arr, 0, tmp, 0, offset);
   127                 arr = tmp;
   128             }
   129             append(btoa(arr));
   130             append("');");
   131         }
   132         
   133         append("\n");
   134         generateEpilogue();
   135     }
   136 
   137     @JavaScriptBody(args = { "arr" }, body = "return btoa(arr);")
   138     private static String btoa(byte[] arr) {
   139         return javax.xml.bind.DatatypeConverter.printBase64Binary(arr);
   140     }
   141 
   142     protected abstract void generatePrologue() throws IOException;
   143 
   144     protected abstract void generateEpilogue() throws IOException;
   145 
   146     protected abstract String getExportsObject();
   147 
   148     protected abstract boolean isExternalClass(String className);
   149 
   150     protected abstract void lazyReference(Appendable out, String n) throws IOException;
   151     
   152     @Override
   153     protected final void declareClass(ClassData classData, String mangledName)
   154             throws IOException {
   155         if (exportedSymbols.isExported(classData)) {
   156             append("registerClass(").append(getExportsObject()).append(",'")
   157                                                .append(mangledName)
   158                                                .append("',")
   159                             .append(mangledName)
   160                .append(")");
   161             exportedCount++;
   162         } else {
   163             append(mangledName);
   164         }
   165     }
   166 
   167     protected String generateClass(String className) throws IOException {
   168         ClassData classData = classDataCache.getClassData(className);
   169         if (classData == null) {
   170             throw new IOException("Can't find class " + className);
   171         }
   172         return compile(classData);
   173     }
   174 
   175     @Override
   176     protected void declaredField(FieldData fieldData,
   177                                  String destObject,
   178                                  String mangledName) throws IOException {
   179         if (exportedSymbols.isExported(fieldData)) {
   180             exportMember(destObject, mangledName);
   181         }
   182     }
   183 
   184     @Override
   185     protected void declaredMethod(MethodData methodData,
   186                                   String destObject,
   187                                   String mangledName) throws IOException {
   188         if (isHierarchyExported(methodData)) {
   189             exportMember(destObject, mangledName);
   190         }
   191     }
   192 
   193     private void exportMember(String destObject, String memberName)
   194             throws IOException {
   195         append("\n").append(destObject).append("['")
   196         .append(memberName)
   197         .append("'] = m;\n");
   198     }
   199 
   200     private void generateBody(StringArray names) throws IOException {
   201         StringArray processed = new StringArray();
   202         StringArray initCode = new StringArray();
   203         StringArray skipClass = new StringArray();
   204         for (String baseClass : names.toArray()) {
   205             references.add(baseClass);
   206             for (;;) {
   207                 String name = null;
   208                 for (String n : references.toArray()) {
   209                     if (skipClass.contains(n)) {
   210                         continue;
   211                     }
   212                     if (processed.contains(n)) {
   213                         continue;
   214                     }
   215                     name = n;
   216                 }
   217                 if (name == null) {
   218                     break;
   219                 }
   220                 InputStream is = resources.get(name + ".class");
   221                 if (is == null) {
   222                     lazyReference(this, name);
   223                     skipClass.add(name);
   224                     continue;
   225                 }
   226                 try {
   227                     String ic = generateClass(name);
   228                     processed.add(name);
   229                     initCode.add(ic == null ? "" : ic);
   230                 } catch (RuntimeException ex) {
   231                     throw new IOException("Error while compiling " + name + "\n", ex);
   232                 }
   233             }
   234 
   235             for (String resource : scripts.toArray()) {
   236                 while (resource.startsWith("/")) {
   237                     resource = resource.substring(1);
   238                 }
   239                 requireResourceImpl(resource);
   240                 asBinary.remove(resource);
   241             }
   242             scripts = new StringArray();
   243 
   244             StringArray toInit = StringArray.asList(references.toArray());
   245             toInit.reverse();
   246 
   247             for (String ic : toInit.toArray()) {
   248                 int indx = processed.indexOf(ic);
   249                 if (indx >= 0) {
   250                     final String theCode = initCode.toArray()[indx];
   251                     if (!theCode.isEmpty()) {
   252                         append(theCode).append("\n");
   253                     }
   254                     initCode.toArray()[indx] = "";
   255                 }
   256             }
   257         }
   258     }
   259 
   260     final void requireResourceImpl(String resource) throws IOException {
   261         InputStream emul = resources.get(resource);
   262         if (emul == null) {
   263             throw new IOException("Can't find " + resource);
   264         }
   265         append("\n// resource from ").append(resource).append("\n");
   266         readResource(emul, this);
   267         append("\n");
   268     }
   269 
   270     private static void readResource(InputStream emul, Appendable out) throws IOException {
   271         try {
   272             int state = 0;
   273             for (;;) {
   274                 int ch = emul.read();
   275                 if (ch == -1) {
   276                     break;
   277                 }
   278                 if (ch < 0 || ch > 255) {
   279                     throw new IOException("Invalid char in emulation " + ch);
   280                 }
   281                 out.append((char)ch);
   282             }
   283         } finally {
   284             emul.close();
   285         }
   286     }
   287 
   288     static String toString(String name) throws IOException {
   289         StringBuilder sb = new StringBuilder();
   290 //        compile(sb, name);
   291         return sb.toString().toString();
   292     }
   293 
   294     private StringArray scripts = new StringArray();
   295     private StringArray references = new StringArray();
   296     
   297     @Override
   298     protected boolean requireReference(String cn) {
   299         return references.addIfMissing(cn);
   300     }
   301 
   302     @Override
   303     protected void requireScript(String resourcePath) {
   304         scripts.add(resourcePath);
   305     }
   306 
   307     @Override
   308     String assignClass(String className) {
   309         return "vm." + className + " = ";
   310     }
   311     
   312     @Override
   313     String accessClass(String className) {
   314         return "vm." + className;
   315     }
   316 
   317     @Override
   318     protected FieldData findField(String[] fieldInfoName) throws IOException {
   319         FieldData field = classDataCache.findField(
   320             fieldInfoName[0], fieldInfoName[1], fieldInfoName[2]
   321         );
   322         return field != null && canAccessDirectly(field.cls) ? field : null;
   323     }
   324 
   325     @Override
   326     protected String accessField(String object, FieldData field, String[] fieldInfoName)
   327     throws IOException {
   328         if (field != null && !field.isStatic()) {
   329             return "fld_" + object + "_" + field.getName();
   330         } else {
   331             String mangledName = "_" + fieldInfoName[1];
   332            return accessNonVirtualMember(
   333                object, mangledName, field != null ? field.cls : null
   334            );
   335          }
   336     }
   337 
   338     @Override
   339     protected String accessStaticMethod(
   340                              String object,
   341                              String mangledName,
   342                              String[] fieldInfoName) throws IOException {
   343         final MethodData method =
   344                 classDataCache.findMethod(fieldInfoName[0],
   345                                           fieldInfoName[1],
   346                                           fieldInfoName[2]);
   347         return accessNonVirtualMember(object, mangledName,
   348                                       (method != null) ? method.cls : null);
   349     }
   350 
   351     @Override
   352     protected String accessVirtualMethod(
   353             String object, 
   354             String mangledName, 
   355             String[] fieldInfoName, 
   356             int params
   357     ) throws IOException {
   358         final ClassData referencedClass =
   359                 classDataCache.getClassData(fieldInfoName[0]);
   360         final MethodData method =
   361                 classDataCache.findMethod(referencedClass,
   362                                           fieldInfoName[1],
   363                                           fieldInfoName[2]);
   364 
   365         if ((method != null)
   366                 && !isExternalClass(method.cls.getClassName())
   367                 && (((method.access & ByteCodeParser.ACC_FINAL) != 0)
   368                         || ((referencedClass.getAccessFlags()
   369                                  & ByteCodeParser.ACC_FINAL) != 0)
   370                         || !isHierarchyExported(method))) {
   371             return object + "." + mangledName + '(';
   372         }
   373 
   374         return accessThroughInvoker(object, mangledName, params);
   375     }
   376 
   377     private String accessThroughInvoker(String object, String mangledName, int params) 
   378     throws IOException {
   379         String def = "\n  invoker." + mangledName + " = function(target";
   380         if (invokerMethods.indexOf(def) == -1) {
   381             invokerMethods.append(def);
   382             for (int j = 0; j < params; j++) {
   383                 invokerMethods.append(", p").append(j);
   384             }
   385             invokerMethods.append(") {\n    return target['").
   386                 append(mangledName).append("'](");
   387             for (int j = 0; j < params; j++) {
   388                 if (j > 0) {
   389                     invokerMethods.append(",");
   390                 }
   391                 invokerMethods.append("p").append(j);
   392             }
   393             invokerMethods.append(");\n  };");
   394         }
   395         return "invoker." + mangledName + '(' + object + (params > 1 ? "," : "");
   396     }
   397 
   398     private boolean isHierarchyExported(final MethodData methodData)
   399             throws IOException {
   400         if (exportedSymbols.isExported(methodData)) {
   401             return true;
   402         }
   403         if ((methodData.access & (ByteCodeParser.ACC_PRIVATE
   404                                       | ByteCodeParser.ACC_STATIC)) != 0) {
   405             return false;
   406         }
   407 
   408         final ExportedMethodFinder exportedMethodFinder =
   409                 new ExportedMethodFinder(exportedSymbols);
   410 
   411         classDataCache.findMethods(
   412                 methodData.cls,
   413                 methodData.getName(),
   414                 methodData.getInternalSig(),
   415                 exportedMethodFinder);
   416 
   417         return (exportedMethodFinder.getFound() != null);
   418     }
   419 
   420     private boolean canAccessDirectly(ClassData declaringClass) {
   421         if (declaringClass == null) {
   422             return false;
   423         }
   424         final String className = declaringClass.getClassName();
   425         if (
   426             "java/lang/Object".equals(className) ||
   427             "java/lang/reflect/Array".equals(className) ||
   428             isExternalClass(className)
   429         ) {
   430             return false;
   431         }
   432         return true;
   433     }
   434 
   435     private String accessNonVirtualMember(
   436         String object, String mangledName, ClassData declaringClass
   437     ) {
   438         return canAccessDirectly(declaringClass) ?
   439             object + "." + mangledName :
   440             object + "['" + mangledName + "']";
   441     }
   442 
   443     private final class ExportedMethodFinder
   444             implements ClassDataCache.TraversalCallback<MethodData> {
   445         private final ExportedSymbols exportedSymbols;
   446         private MethodData found;
   447 
   448         public ExportedMethodFinder(final ExportedSymbols exportedSymbols) {
   449             this.exportedSymbols = exportedSymbols;
   450         }
   451 
   452         @Override
   453         public boolean traverse(final MethodData methodData) {
   454             try {
   455                 if (
   456                     exportedSymbols.isExported(methodData) ||
   457                     isExternalClass(methodData.cls.getClassName())
   458                 ) {
   459                     found = methodData;
   460                     return false;
   461                 }
   462             } catch (final IOException e) {
   463             }
   464 
   465             return true;
   466         }
   467 
   468         public MethodData getFound() {
   469             return found;
   470         }
   471     }
   472 
   473     private static final class Standalone extends VM {
   474         private Standalone(Appendable out,
   475             Bck2Brwsr.Resources resources, 
   476             StringArray explicitlyExported, StringArray asBinary
   477         ) {
   478             super(out, resources, explicitlyExported, asBinary);
   479         }
   480 
   481         @Override
   482         protected void generatePrologue() throws IOException {
   483             append("(function VM(global) {var fillInVMSkeleton = function(vm) {");
   484         }
   485 
   486         @Override
   487         protected void generateEpilogue() throws IOException {
   488             append(
   489                   "  return vm;\n"
   490                 + "  };\n"
   491                 + "  var extensions = [];\n"
   492                 + "  function replaceAll(s, target, replacement) {\n"
   493                 + "    var pos = 0;\n"
   494                 + "    for (;;) {\n"
   495                 + "      var indx = s.indexOf(target, pos);\n"
   496                 + "      if (indx === -1) {\n"
   497                 + "        return s;\n"
   498                 + "      }\n"
   499                 + "      pos = indx + replacement.length;\n"
   500                 + "      s = s.substring(0, indx) + replacement + s.substring(indx + target.length);\n"
   501                 + "    }\n"
   502                 + "  }\n"
   503                 + "  function mangleClass(name) {\n"
   504                 + "    name = replaceAll(name, '_', '_1');\n"
   505                 + "    name = replaceAll(name, '.', '_');\n"
   506                 + "    return name;\n"
   507                 + "  };\n"
   508                 + "  var pending = [];\n"
   509                 + "  var pendingClasses = [];\n"
   510                 + "  function extensionLoaded(ev) {\n"
   511                 + "    var at = pending.indexOf(ev.target);\n"
   512                 + "    pending.splice(at, 1);\n"
   513                 + "    if (pending.length === 0) {\n"
   514                 + "      for (var i = 0; i < pendingClasses.length; i += 3) {\n"
   515                 + "        invokeMethod(pendingClasses[i], pendingClasses[i + 1], pendingClasses[i + 2]);\n"
   516                 + "      }\n"
   517                 + "      pendingClasses = [];\n"
   518                 + "    }\n"
   519                 + "  }\n"
   520                 + "  function invokeMethod(vm, n, args) {\n"
   521                 + "    var clazz = vm.loadClass(n);\n"
   522                 + "    if (args) {\n"
   523                 + "      var seek = args[0];\n"
   524                 + "      var prefix = seek.indexOf('__') == -1 ? seek + '__' : seek;\n"
   525                 + "      args = Array.prototype.slice.call(args, 1);\n"
   526                 + "      var found = '';\n"
   527                 + "      for (var m in clazz) {\n"
   528                 + "        if (m.indexOf(prefix) === 0) {\n"
   529                 + "          return clazz[m].apply(null, args);\n"
   530                 + "        }\n"
   531                 + "        found += m.toString() + '\\n'\n"
   532                 + "      }\n"
   533                 + "      throw 'Cannot find ' + seek + ' in ' + n + ' found:\\n' + found;\n"
   534                 + "    }\n"
   535                 + "  }\n"
   536                 + "  function extensionError(ev) {\n"
   537                 + "    console.log('error loading ' + ev.target.src);\n"
   538                 + "    extensionLoaded(ev);\n"
   539                 + "  }\n"
   540                 + "  function loadExtension(url) {\n"
   541                 + "      if (url.substring(url.length - 4) == '.jar')\n"
   542                 + "        url = url.substring(0, url.length - 4) + '.js';\n"
   543                 + "      var script = document.createElement('script');\n"
   544                 + "      script.type = 'text/javascript';\n"
   545                 + "      script.src = url;\n"
   546                 + "      script.onload = extensionLoaded;\n"
   547                 + "      script.onerror = extensionError;\n"
   548                 + "      document.getElementsByTagName('head')[0].appendChild(script);\n"
   549                 + "      pending.push(script);\n"
   550                 + "  }\n"
   551                 + "  global.bck2brwsr = function() {\n"
   552                 + "    var args = Array.prototype.slice.apply(arguments);\n"
   553                 + "    var resources = {};\n"
   554                 + "    function registerResource(n, a64) {\n"
   555                 + "      var frm = atob || window.atob;\n"
   556                 + "      var str = frm(a64);\n"
   557                 + "      var arr = [];\n"
   558                 + "      for (var i = 0; i < str.length; i++) {\n"
   559                 + "        var ch = str.charCodeAt(i) & 0xff;\n"
   560                 + "        if (ch > 127) ch -= 256;\n"
   561                 + "        arr.push(ch);\n"
   562                 + "      }\n"
   563                 + "      if (!resources[n]) resources[n] = [arr];\n"
   564                 + "      else resources[n].push(arr);\n"
   565                 + "    }\n"
   566                 + "    var vm = fillInVMSkeleton({ 'registerResource' : registerResource });\n"
   567                 + "    function initVM() {\n"
   568                 + "      var clsArray = vm['java_lang_reflect_Array'];\n"
   569                 + "      if (clsArray) clsArray(false);\n"
   570                 + "    }\n"
   571                 + "    for (var i = 0; i < extensions.length; ++i) {\n"
   572                 + "      extensions[i](vm);\n"
   573                 + "    }\n"
   574                 + "    vm['registerResource'] = null;\n"
   575                 + "    var knownExtensions = extensions.length;\n"
   576                 + "    var loader = {};\n"
   577                 + "    var loadBytes = function(name, skip) {\n"
   578                 + "      skip = typeof skip == 'number' ? skip : 0;\n"
   579                 + "      var arr = resources[name];\n"
   580                 + "      if (arr) {\n"
   581                 + "        var arrSize = arr.length;\n"
   582                 + "        if (skip < arrSize) return arr[skip];\n"
   583                 + "        skip -= arrSize;\n"
   584                 + "      } else {\n"
   585                 + "        var arrSize = 0;\n"
   586                 + "      };\n"
   587                 + "      for (var i = 0; i < args.length; i++) {\n"
   588                 + "        var at = args[i];\n"
   589                 + "        if(!at) continue;\n"
   590                 + "        var ret;\n"
   591                 + "        if (typeof at === 'string' && at.substring(at.length - 3) === '.js') {\n"
   592                 + "          loadExtension(at);\n"
   593                 + "          args[i] = null;\n"
   594                 + "        } else if (typeof at === 'function') ret = at(name, skip);\n"
   595                 + "        else {\n"
   596                 + "          var cp = vm['org_apidesign_vm4brwsr_ClassPath'];\n"
   597                 + "          if (!cp) throw 'Core Java library not registered. Cannot load from ' + at;\n"
   598                 + "          ret = cp(false).\n"
   599                 + "            loadBytes___3BLjava_lang_String_2Ljava_lang_Object_2II(name, args, i, skip);\n"
   600                 + "        }\n"
   601                 + "        if (ret) return ret;\n"
   602                 + "      }\n"
   603                 + "      while (knownExtensions < extensions.length) {\n"
   604                 + "        vm['registerResource'] = registerResource;\n"
   605                 + "        extensions[knownExtensions++](vm);\n"
   606                 + "        vm['registerResource'] = null;\n"
   607                 + "        initVM();\n"
   608                 + "      }\n"
   609                 + "      var arr = resources[name];\n"
   610                 + "      return (arr && arr.length > arrSize) ? arr[arrSize] : null;\n"
   611                 + "    }\n"
   612                 + "    var reload = function(name, arr, keep) {\n"
   613                 + "      if (!arr) throw 'Cannot find ' + name;\n"
   614                 + "      var lazy = vm['org_apidesign_vm4brwsr_VMLazy'];\n"
   615                 + "      if (!lazy) throw 'No bck2brwsr VM module to compile ' + name;\n"
   616                 + "      if (!keep) {\n"
   617                 + "        var attr = mangleClass(name);\n"
   618                 + "        delete vm[attr];\n"
   619                 + "      }\n"
   620                 + "      return lazy(false)\n"
   621                 + "        ['load__Ljava_lang_Object_2Ljava_lang_Object_2Ljava_lang_String_2_3Ljava_lang_Object_2_3B']\n"
   622                 + "        (vm, name, args, arr);\n"
   623                 + "    };\n"
   624                 + "    var loadClass = function(name) {\n"
   625                 + "      var attr = mangleClass(name);\n"
   626                 + "      var fn = vm[attr];\n"
   627                 + "      if (fn) return fn(false);\n"
   628                 + "      try {\n"
   629                 + "        var arr = loadBytes(replaceAll(name, '.', '/') + '.class');\n"
   630                 + "        return reload(name, arr, true);\n"
   631                 + "      } catch (err) {\n"
   632                 + "        fn = vm[attr];\n"
   633                 + "        if (fn) return fn(false);\n"
   634                 + "        throw err;\n"
   635                 + "      }\n"
   636                 + "    }\n"
   637                 + "    if (vm['loadClass']) {\n"
   638                 + "      throw 'Cannot initialize the bck2brwsr VM twice!';\n"
   639                 + "    }\n"
   640                 + "    vm['loadClass'] = loadClass;\n"
   641                 + "    vm['_reload'] = reload;\n"
   642                 + "    vm['loadBytes'] = loadBytes;\n"
   643                 + "    initVM();\n"
   644                 + "    loader.loadClass = function(name) {\n"
   645                 + "      if (pending.length === 0) {\n"
   646                 + "        try {\n"
   647                 + "          var c = loadClass(name);\n"
   648                 + "          c['invoke'] = function() {\n"
   649                 + "            return invokeMethod(vm, name, arguments);\n"
   650                 + "          };\n"
   651                 + "          return c;\n"
   652                 + "        } catch (err) {\n"
   653                 + "          if (pending.length === 0) throw err;\n"
   654                 + "        }\n"
   655                 + "      }\n"
   656                 + "      pendingClasses.push(vm);\n"
   657                 + "      pendingClasses.push(name);\n"
   658                 + "      pendingClasses.push(null);\n"
   659                 + "      return {\n"
   660                 + "        'invoke' : function() {\n"
   661                 + "          if (pending.length === 0) {\n"
   662                 + "            invokeMethod(vm, name, arguments);\n"
   663                 + "            return;\n"
   664                 + "          }\n"
   665                 + "          pendingClasses.push(vm);\n"
   666                 + "          pendingClasses.push(name);\n"
   667                 + "          pendingClasses.push(arguments);\n"
   668                 + "        }\n"
   669                 + "      };\n"
   670                 + "    }\n"
   671                 + "    return loader;\n"
   672                 + "  };\n");
   673             append(
   674                   "  global.bck2brwsr.register = function(config, extension) {\n"
   675                 + "    if (!config || config['magic'] !== 'kafčo') {\n"
   676                 + "      console.log('Will not register: ' + extension);\n"
   677                 + "      return false;\n"
   678                 + "    }\n"
   679                 + "    var cs = typeof document == 'undefined' ? null : document['currentScript'];\n"
   680                 + "    var prefix = cs ? cs['src']['replace'](/\\/[^\\/]*$/,'/') : '';\n"
   681                 + "    extensions.push(extension);\n"
   682                 + "    var cp = config['classpath'];\n"
   683                 + "    if (cp) for (var i = 0; i < cp.length; i++) {\n"
   684                 + "      loadExtension(prefix + cp[i]);\n"
   685                 + "    }\n"
   686                 + "    return null;\n"
   687                 + "  };\n");
   688             append("}(this));");
   689         }
   690 
   691         @Override
   692         protected String getExportsObject() {
   693             return "vm";
   694         }
   695 
   696         @Override
   697         protected boolean isExternalClass(String className) {
   698             return false;
   699         }
   700         
   701         @Override
   702         protected void lazyReference(Appendable out, String n) throws IOException {
   703             String cls = n.replace('/', '_');
   704             String dot = n.replace('/', '.');
   705 
   706             out.append("\nvm.").append(cls).append(" = function() {");
   707             out.append("\n  var instance = arguments.length == 0 || arguments[0] === true;");
   708             out.append("\n  delete vm.").append(cls).append(";");
   709             out.append("\n  var c = vm.loadClass('").append(dot).append("');");
   710             out.append("\n  return vm.").append(cls).append("(instance);");
   711             out.append("\n}");
   712         }
   713 
   714         @Override
   715         protected void requireResource(String resourcePath) throws IOException {
   716             requireResourceImpl(resourcePath);
   717             super.asBinary.remove(resourcePath);
   718         }
   719     }
   720 
   721     private static final class Extension extends VM {
   722         private final StringArray extensionClasses;
   723         private final StringArray classpath;
   724 
   725         private Extension(Appendable out, Bck2Brwsr.Resources resources,
   726             String[] extClassesArray, StringArray explicitlyExported,
   727             StringArray asBinary, StringArray classpath
   728         ) throws IOException {
   729             super(out, resources, explicitlyExported, asBinary);
   730             this.extensionClasses = StringArray.asList(extClassesArray);
   731             this.classpath = classpath;
   732         }
   733 
   734         @Override
   735         protected void generatePrologue() throws IOException {
   736             append(
   737                   "bck2brwsr.register({\n"
   738                 + "  'magic' : 'kafčo'"
   739             );
   740             if (classpath != null && classpath.toArray().length > 0) {
   741                 append(
   742                   ",\n  'classpath' : [\n"
   743                 );
   744                 String sep = "    ";
   745                 for (String s : classpath.toArray()) {
   746                     append(sep).append("'").append(s).append("'");
   747                     sep = ",\n    ";
   748                 }
   749                 append(
   750                   "\n  ]"
   751                 );
   752             }
   753             append(
   754                   "\n}, function(exports) {\n"
   755                 + "  var vm = {};\n");
   756             append("  function link(n, assign) {\n"
   757                 + "    return function() {\n"
   758                 + "      var no_ = n['replace__Ljava_lang_String_2Ljava_lang_CharSequence_2Ljava_lang_CharSequence_2']"
   759                                        + "('_', '_1').toString();\n"
   760                 + "      var cls = no_['replace__Ljava_lang_String_2CC']"
   761                                        + "('/', '_').toString();\n"
   762                 + "      var dot = n['replace__Ljava_lang_String_2CC']"
   763                                        + "('/', '.').toString();\n"
   764                 + "      exports.loadClass(dot);\n"
   765                 + "      assign(exports[cls]);\n"
   766                 + "      return exports[cls](arguments);\n"
   767                 + "    };\n"
   768                 + "  };\n"
   769             );
   770         }
   771 
   772         @Override
   773         protected void generateEpilogue() throws IOException {
   774             append("});");
   775             if (exportedCount == 0) {
   776                 throw new IOException("Creating library without any exported symbols is useless!");
   777             }
   778         }
   779 
   780         @Override
   781         protected String generateClass(String className) throws IOException {
   782             if (isExternalClass(className)) {
   783                 final String cls = className.replace("_", "_1").replace('/', '_');
   784                 append("\n").append(assignClass(cls))
   785                    .append("link('")
   786                    .append(className)
   787                    .append("', function(f) { ").append(assignClass(cls)).append(" f; });");
   788 
   789                 return null;
   790             }
   791 
   792             return super.generateClass(className);
   793         }
   794 
   795         @Override
   796         protected String getExportsObject() {
   797             return "exports";
   798         }
   799 
   800         @Override
   801         protected boolean isExternalClass(String className) {
   802             return !extensionClasses.contains(className);
   803         }
   804         
   805         @Override
   806         protected void lazyReference(Appendable out, String n) throws IOException {
   807             String cls = n.replace('/', '_');
   808 
   809             out.append("\nvm.").append(cls).append(" = function() {");
   810             out.append("\n  var instance = arguments.length == 0 || arguments[0] === true;");
   811             out.append("\n  delete vm.").append(cls).append(";");
   812             out.append("\n  return link('").append(n).append("', function(f) { vm.");
   813             out.append(cls).append(" = f;})(instance);");
   814             out.append("\n}");
   815         }
   816 
   817         @Override
   818         protected void requireResource(String resourcePath) throws IOException {
   819             requireResourceImpl(resourcePath);
   820             super.asBinary.remove(resourcePath);
   821         }
   822     }
   823 }