1 /*
   2  * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package jdk.internal.module;
  26 
  27 import java.io.IOException;
  28 import java.io.OutputStream;
  29 import java.lang.module.ModuleDescriptor;
  30 import java.nio.ByteBuffer;
  31 import java.util.stream.Stream;
  32 
  33 import jdk.internal.org.objectweb.asm.ClassWriter;
  34 import jdk.internal.org.objectweb.asm.Opcodes;
  35 
  36 import static jdk.internal.module.ClassFileAttributes.*;
  37 import static jdk.internal.module.ClassFileConstants.ACC_MODULE;
  38 
  39 /**
  40  * Utility class to write a ModuleDescriptor as a module-info.class.
  41  */
  42 
  43 public final class ModuleInfoWriter {
  44 
  45     private ModuleInfoWriter() { }
  46 
  47     /**
  48      * Writes the given module descriptor to a module-info.class file,
  49      * returning it in a byte array.
  50      */
  51     private static byte[] toModuleInfo(ModuleDescriptor md, ModuleTarget target) {
  52         ClassWriter cw = new ClassWriter(0);
  53         cw.visit(Opcodes.V1_9, ACC_MODULE, "module-info", null, null, null);
  54         cw.visitAttribute(new ModuleAttribute(md));
  55 
  56         // for tests: write the ModulePackages attribute when there are packages
  57         // that aren't exported or open
  58         Stream<String> exported = md.exports().stream()
  59                 .map(ModuleDescriptor.Exports::source);
  60         Stream<String> open = md.opens().stream()
  61                 .map(ModuleDescriptor.Opens::source);
  62         long exportedOrOpen = Stream.concat(exported, open).distinct().count();
  63         if (md.packages().size() > exportedOrOpen)
  64             cw.visitAttribute(new ModulePackagesAttribute(md.packages()));
  65 
  66         // write ModuleMainClass if the module has a main class
  67         md.mainClass().ifPresent(mc -> cw.visitAttribute(new ModuleMainClassAttribute(mc)));
  68 
  69         // write ModuleTarget if there is a target platform
  70         if (target != null) {
  71             cw.visitAttribute(new ModuleTargetAttribute(target.targetPlatform()));
  72         }
  73 
  74         cw.visitEnd();
  75         return cw.toByteArray();
  76     }
  77 
  78     /**
  79      * Writes a module descriptor to the given output stream as a
  80      * module-info.class.
  81      */
  82     public static void write(ModuleDescriptor descriptor,
  83                              ModuleTarget target,
  84                              OutputStream out)
  85         throws IOException
  86     {
  87         byte[] bytes = toModuleInfo(descriptor, target);
  88         out.write(bytes);
  89     }
  90 
  91     /**
  92      * Writes a module descriptor to the given output stream as a
  93      * module-info.class.
  94      */
  95     public static void write(ModuleDescriptor descriptor, OutputStream out)
  96         throws IOException
  97     {
  98         write(descriptor, null, out);
  99     }
 100 
 101     /**
 102      * Returns a {@code ByteBuffer} containing the given module descriptor
 103      * in module-info.class format.
 104      */
 105     public static ByteBuffer toByteBuffer(ModuleDescriptor descriptor) {
 106         byte[] bytes = toModuleInfo(descriptor, null);
 107         return ByteBuffer.wrap(bytes);
 108     }
 109 }