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.file;

    26 

    27 import java.io.IOException;

    28 import java.io.InputStream;

    29 import java.nio.file.Files;

    30 import java.nio.file.Path;

    31 

    32 import com.sun.tools.javac.jvm.ClassFile;

    33 

    34 import static com.sun.tools.javac.jvm.ClassFile.*;

    35 

    36 

    37 /**

    38  * Stripped down ClassReader, just sufficient to read module names from module-info.class files

    39  * while analyzing the module path.

    40  *

    41  * <p>

    42  * <b>This is NOT part of any supported API. If you write code that depends on this, you do so at

    43  * your own risk. This code and its internal interfaces are subject to change or deletion without

    44  * notice.</b>

    45  */

    46 public class ModuleNameReader {

    47     static class BadClassFile extends Exception {

    48         private static final long serialVersionUID = 0;

    49         BadClassFile(String msg) {

    50             super(msg);

    51         }

    52     }

    53 

    54     private static final int INITIAL_BUFFER_SIZE = 0x0fff0;

    55 

    56     /** The buffer containing the currently read class file.

    57      */

    58     private byte[] buf = new byte[INITIAL_BUFFER_SIZE];

    59 

    60     /** The current input pointer.

    61      */

    62     private int bp;

    63 

    64     /** The objects of the constant pool.

    65      */

    66     private Object[] poolObj;

    67 

    68     /** For every constant pool entry, an index into buf where the

    69      *  defining section of the entry is found.

    70      */

    71     private int[] poolIdx;

    72 

    73     ModuleNameReader() {

    74     }

    75 

    76     String readModuleName(Path p) throws IOException, BadClassFile {

    77         try (InputStream in = Files.newInputStream(p)) {

    78             bp = 0;

    79             buf = readInputStream(buf, in);

    80 

    81             int magic = nextInt();

    82             if (magic != JAVA_MAGIC)

    83                 throw new BadClassFile("illegal.start.of.class.file");

    84 

    85             int minorVersion = nextChar();

    86             int majorVersion = nextChar();

    87 

    88             indexPool();

    89 

    90             int accessflags = nextChar();

    91             return readModuleInfoName(nextChar());

    92         }

    93     }

    94 

    95     /** Extract a character at position bp from buf.

    96      */

    97     char getChar(int bp) {

    98         return

    99             (char)(((buf[bp] & 0xFF) << 8) + (buf[bp+1] & 0xFF));

   100     }

   101 

   102     /** Read a character.

   103      */

   104     char nextChar() {

   105         return (char)(((buf[bp++] & 0xFF) << 8) + (buf[bp++] & 0xFF));

   106     }

   107 

   108     /** Read an integer.

   109      */

   110     int nextInt() {

   111         return

   112             ((buf[bp++] & 0xFF) << 24) +

   113             ((buf[bp++] & 0xFF) << 16) +

   114             ((buf[bp++] & 0xFF) << 8) +

   115             (buf[bp++] & 0xFF);

   116     }

   117 

   118     /** Index all constant pool entries, writing their start addresses into

   119      *  poolIdx.

   120      */

   121     void indexPool() throws BadClassFile {

   122         poolIdx = new int[nextChar()];

   123         poolObj = new Object[poolIdx.length];

   124         int i = 1;

   125         while (i < poolIdx.length) {

   126             poolIdx[i++] = bp;

   127             byte tag = buf[bp++];

   128             switch (tag) {

   129             case CONSTANT_Utf8: case CONSTANT_Unicode: {

   130                 int len = nextChar();

   131                 bp = bp + len;

   132                 break;

   133             }

   134             case CONSTANT_Class:

   135             case CONSTANT_String:

   136             case CONSTANT_MethodType:

   137                 bp = bp + 2;

   138                 break;

   139             case CONSTANT_MethodHandle:

   140                 bp = bp + 3;

   141                 break;

   142             case CONSTANT_Fieldref:

   143             case CONSTANT_Methodref:

   144             case CONSTANT_InterfaceMethodref:

   145             case CONSTANT_NameandType:

   146             case CONSTANT_Integer:

   147             case CONSTANT_Float:

   148             case CONSTANT_InvokeDynamic:

   149                 bp = bp + 4;

   150                 break;

   151             case CONSTANT_Long:

   152             case CONSTANT_Double:

   153                 bp = bp + 8;

   154                 i++;

   155                 break;

   156             default:

   157                 throw new BadClassFile("malformed constant pool");

   158             }

   159         }

   160     }

   161 

   162     /** Read the class name of a module-info.class file.

   163      * The name is stored in a CONSTANT_Class entry, where the

   164      * class name is of the form module-name/module-info.

   165      */

   166     String readModuleInfoName(int i) throws BadClassFile {

   167         int classIndex = poolIdx[i];

   168         if (buf[classIndex] == CONSTANT_Class) {

   169             int utf8Index = poolIdx[getChar(classIndex + 1)];

   170             if (buf[utf8Index] == CONSTANT_Utf8) {

   171                 int len = getChar(utf8Index + 1);

   172                 int start = utf8Index + 3;

   173                 String suffix = "/module-info";

   174                 if (endsWith(buf, start, len, suffix))

   175                     return new String(ClassFile.internalize(buf, start, len - suffix.length()));

   176             }

   177         }

   178         throw new BadClassFile("bad module-info name");

   179     }

   180 

   181     private boolean endsWith(byte[] buf, int start, int len, String suffix) {

   182         if (len <= suffix.length())

   183             return false;

   184         for (int i = 0; i < suffix.length(); i++) {

   185             if (buf[start + len - suffix.length() + i] != suffix.charAt(i))

   186                 return false;

   187         }

   188         return true;

   189     }

   190 

   191     private static byte[] readInputStream(byte[] buf, InputStream s) throws IOException {

   192         try {

   193             buf = ensureCapacity(buf, s.available());

   194             int r = s.read(buf);

   195             int bp = 0;

   196             while (r != -1) {

   197                 bp += r;

   198                 buf = ensureCapacity(buf, bp);

   199                 r = s.read(buf, bp, buf.length - bp);

   200             }

   201             return buf;

   202         } finally {

   203             try {

   204                 s.close();

   205             } catch (IOException e) {

   206                 /* Ignore any errors, as this stream may have already

   207                  * thrown a related exception which is the one that

   208                  * should be reported.

   209                  */

   210             }

   211         }

   212     }

   213 

   214     /*

   215      * ensureCapacity will increase the buffer as needed, taking note that

   216      * the new buffer will always be greater than the needed and never

   217      * exactly equal to the needed size or bp. If equal then the read (above)

   218      * will infinitely loop as buf.length - bp == 0.

   219      */

   220     private static byte[] ensureCapacity(byte[] buf, int needed) {

   221         if (buf.length <= needed) {

   222             byte[] old = buf;

   223             buf = new byte[Integer.highestOneBit(needed) << 1];

   224             System.arraycopy(old, 0, buf, 0, old.length);

   225         }

   226         return buf;

   227     }

   228 }