1 /*
   2  * Copyright (c) 1999, 2016, 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 com.sun.tools.javac.jvm;
  26 
  27 import com.sun.tools.javac.util.ByteBuffer;
  28 import com.sun.tools.javac.util.Name.NameMapper;
  29 
  30 import java.io.IOException;
  31 import java.io.InputStream;
  32 import java.nio.file.Files;
  33 import java.nio.file.Path;
  34 
  35 import javax.tools.JavaFileObject;
  36 
  37 import static com.sun.tools.javac.jvm.ClassFile.*;
  38 
  39 
  40 /**
  41  * Stripped down ClassReader, just sufficient to read module names from module-info.class files
  42  * while analyzing the module path.
  43  *
  44  * <p>
  45  * <b>This is NOT part of any supported API. If you write code that depends on this, you do so at
  46  * your own risk. This code and its internal interfaces are subject to change or deletion without
  47  * notice.</b>
  48  */
  49 public class ModuleNameReader {
  50     public static class BadClassFile extends Exception {
  51         private static final long serialVersionUID = 0;
  52         BadClassFile(String msg) {
  53             super(msg);
  54         }
  55     }
  56 
  57     private static final int INITIAL_BUFFER_SIZE = 0x0fff0;
  58 
  59     /** The buffer containing the currently read class file.
  60      */
  61     private ByteBuffer buf = new ByteBuffer(INITIAL_BUFFER_SIZE);
  62 
  63     /** The current input pointer.
  64      */
  65     private int bp;
  66 
  67     /** The constant pool reader.
  68      */
  69     private PoolReader reader;
  70 
  71     public ModuleNameReader() {
  72     }
  73 
  74     public String readModuleName(Path p) throws IOException, BadClassFile {
  75         try (InputStream in = Files.newInputStream(p)) {
  76             return readModuleName(in);
  77         }
  78     }
  79 
  80     public String readModuleName(JavaFileObject jfo) throws IOException, BadClassFile {
  81         try (InputStream in = jfo.openInputStream()) {
  82             return readModuleName(in);
  83         }
  84     }
  85 
  86     public String readModuleName(InputStream in) throws IOException, BadClassFile {
  87         bp = 0;
  88         buf.reset();
  89         buf.appendStream(in);
  90 
  91         int magic = nextInt();
  92         if (magic != JAVA_MAGIC)
  93             throw new BadClassFile("illegal.start.of.class.file");
  94 
  95         int minorVersion = nextChar();
  96         int majorVersion = nextChar();
  97         if (majorVersion < 53)
  98             throw new BadClassFile("bad major version number for module: " + majorVersion);
  99 
 100         reader = new PoolReader(buf);
 101         bp = reader.readPool(buf, bp);
 102 
 103         int access_flags = nextChar();
 104         if (access_flags != 0x8000)
 105             throw new BadClassFile("invalid access flags for module: 0x" + Integer.toHexString(access_flags));
 106 
 107         int this_class = nextChar();
 108         // could, should, check this_class == CONSTANT_Class("module-info")
 109         checkZero(nextChar(), "super_class");
 110         checkZero(nextChar(), "interface_count");
 111         checkZero(nextChar(), "fields_count");
 112         checkZero(nextChar(), "methods_count");
 113         int attributes_count = nextChar();
 114         for (int i = 0; i < attributes_count; i++) {
 115             int attr_name = nextChar();
 116             int attr_length = nextInt();
 117             if (reader.peekName(attr_name, utf8Mapper(false)).equals("Module") && attr_length > 2) {
 118                 return reader.peekModuleName(nextChar(), utf8Mapper(true));
 119             } else {
 120                 // skip over unknown attributes
 121                 bp += attr_length;
 122             }
 123         }
 124         throw new BadClassFile("no Module attribute");
 125     }
 126 
 127     void checkZero(int count, String name) throws BadClassFile {
 128         if (count != 0)
 129             throw new BadClassFile("invalid " + name + " for module: " + count);
 130     }
 131 
 132     /** Read a character.
 133      */
 134     char nextChar() {
 135         char res = buf.getChar(bp);
 136         bp += 2;
 137         return res;
 138     }
 139 
 140     /** Read an integer.
 141      */
 142     int nextInt() {
 143         int res = buf.getInt(bp);
 144         bp += 4;
 145         return res;
 146     }
 147 
 148     NameMapper<String> utf8Mapper(boolean internalize) {
 149         return internalize ?
 150                 (buf, offset, len) -> new String(ClassFile.internalize(buf, offset, len)) :
 151                 String::new;
 152     }
 153 
 154 }