    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 *  Unless required by applicable law or agreed to in writing, software
    012 *  distributed under the License is distributed on an "AS IS" BASIS,
    013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 *  See the License for the specific language governing permissions and
    015 *  limitations under the License.
    016 *
    017 */
    018package org.apache.bcel.classfile;
    019
    020import java.io.BufferedInputStream;
    021import java.io.DataInputStream;
    022import java.io.FileInputStream;
    023import java.io.IOException;
    024import java.io.InputStream;
    025import java.util.zip.ZipEntry;
    026import java.util.zip.ZipFile;
    027
    028import org.apache.bcel.Const;
    029
    030/**
    031 * Wrapper class that parses a given Java .class file. The method <A
    032 * href ="#parse">parse</A> returns a <A href ="JavaClass.html">
    033 * JavaClass</A> object on success. When an I/O error or an
    034 * inconsistency occurs an appropiate exception is propagated back to
    035 * the caller.
    036 *
    037 * The structure and the names comply, except for a few conveniences,
    038 * exactly with the <A href="http://docs.oracle.com/javase/specs/">
    039 * JVM specification 1.0</a>. See this paper for
    040 * further details about the structure of a bytecode file.
    041 *
    042 * @version $Id: ClassParser.java 1749603 2016-06-21 20:50:19Z ggregory $
    043 */
    044public final class ClassParser {
    045
    046    private DataInputStream dataInputStream;
    047    private final boolean fileOwned;
    048    private final String file_name;
    049    private String zip_file;
    050    private int class_name_index;
    051    private int superclass_name_index;
    052    private int major; // Compiler version
    053    private int minor; // Compiler version
    054    private int access_flags; // Access rights of parsed class
    055    private int[] interfaces; // Names of implemented interfaces
    056    private ConstantPool constant_pool; // collection of constants
    057    private Field[] fields; // class fields, i.e., its variables
    058    private Method[] methods; // methods defined in the class
    059    private Attribute[] attributes; // attributes defined in the class
    060    private final boolean is_zip; // Loaded from zip file
    061    private static final int BUFSIZE = 8192;
    062
    063
    064    /**
    065     * Parse class from the given stream.
    066     *
    067     * @param inputStream Input stream
    068     * @param file_name File name
    069     */
    070    public ClassParser(final InputStream inputStream, final String file_name) {
    071        this.file_name = file_name;
    072        fileOwned = false;
    073        final String clazz = inputStream.getClass().getName(); // Not a very clean solution ...
    074        is_zip = clazz.startsWith("java.util.zip.") || clazz.startsWith("java.util.jar.");
    075        if (inputStream instanceof DataInputStream) {
    076            this.dataInputStream = (DataInputStream) inputStream;
    077        } else {
    078            this.dataInputStream = new DataInputStream(new BufferedInputStream(inputStream, BUFSIZE));
    079        }
    080    }
    081
    082
    083    /** Parse class from given .class file.
    084     *
    085     * @param file_name file name
    086     */
    087    public ClassParser(final String file_name) {
    088        is_zip = false;
    089        this.file_name = file_name;
    090        fileOwned = true;
    091    }
    092
    093
    094    /** Parse class from given .class file in a ZIP-archive
    095     *
    096     * @param zip_file zip file name
    097     * @param file_name file name
    098     */
    099    public ClassParser(final String zip_file, final String file_name) {
    100        is_zip = true;
    101        fileOwned = true;
    102        this.zip_file = zip_file;
    103        this.file_name = file_name;
    104    }
    105
    106
    107    /**
    108     * Parse the given Java class file and return an object that represents
    109     * the contained data, i.e., constants, methods, fields and commands.
    110     * A <em>ClassFormatException</em> is raised, if the file is not a valid
    111     * .class file. (This does not include verification of the byte code as it
    112     * is performed by the java interpreter).
    113     *
    114     * @return Class object representing the parsed class file
    115     * @throws  IOException
    116     * @throws  ClassFormatException
    117     */
    118    public JavaClass parse() throws IOException, ClassFormatException {
    119        ZipFile zip = null;
    120        try {
    121            if (fileOwned) {
    122                if (is_zip) {
    123                    zip = new ZipFile(zip_file);
    124                    final ZipEntry entry = zip.getEntry(file_name);
    125
    126                    if (entry == null) {
    127                        throw new IOException("File " + file_name + " not found");
    128                    }
    129
    130                    dataInputStream = new DataInputStream(new BufferedInputStream(zip.getInputStream(entry),
    131                            BUFSIZE));
    132                } else {
    133                    dataInputStream = new DataInputStream(new BufferedInputStream(new FileInputStream(
    134                            file_name), BUFSIZE));
    135                }
    136            }
    137            /****************** Read headers ********************************/
    138            // Check magic tag of class file
    139            readID();
    140            // Get compiler version
    141            readVersion();
    142            /****************** Read constant pool and related **************/
    143            // Read constant pool entries
    144            readConstantPool();
    145            // Get class information
    146            readClassInfo();
    147            // Get interface information, i.e., implemented interfaces
    148            readInterfaces();
    149            /****************** Read class fields and methods ***************/
    150            // Read class fields, i.e., the variables of the class
    151            readFields();
    152            // Read class methods, i.e., the functions in the class
    153            readMethods();
    154            // Read class attributes
    155            readAttributes();
    156            // Check for unknown variables
    157            //Unknown[] u = Unknown.getUnknownAttributes();
    158            //for (int i=0; i < u.length; i++)
    159            //  System.err.println("WARNING: " + u[i]);
    160            // Everything should have been read now
    161            //      if(file.available() > 0) {
    162            //        int bytes = file.available();
    163            //        byte[] buf = new byte[bytes];
    164            //        file.read(buf);
    165            //        if(!(is_zip && (buf.length == 1))) {
    166            //      System.err.println("WARNING: Trailing garbage at end of " + file_name);
    167            //      System.err.println(bytes + " extra bytes: " + Utility.toHexString(buf));
    168            //        }
    169            //      }
    170        } finally {
    171            // Read everything of interest, so close the file
    172            if (fileOwned) {
    173                try {
    174                    if (dataInputStream != null) {
    175                        dataInputStream.close();
    176                    }
    177                } catch (final IOException ioe) {
    178                    //ignore close exceptions
    179                }
    180            }
    181            try {
    182                if (zip != null) {
    183                    zip.close();
    184                }
    185            } catch (final IOException ioe) {
    186                //ignore close exceptions
    187            }
    188        }
    189        // Return the information we have gathered in a new object
    190        return new JavaClass(class_name_index, superclass_name_index, file_name, major, minor,
    191                access_flags, constant_pool, interfaces, fields, methods, attributes, is_zip
    192                        ? JavaClass.ZIP
    193                        : JavaClass.FILE);
    194    }
    195
    196
    197    /**
    198     * Read information about the attributes of the class.
    199     * @throws  IOException
    200     * @throws  ClassFormatException
    201     */
    202    private void readAttributes() throws IOException, ClassFormatException {
    203        final int attributes_count = dataInputStream.readUnsignedShort();
    204        attributes = new Attribute[attributes_count];
    205        for (int i = 0; i < attributes_count; i++) {
    206            attributes[i] = Attribute.readAttribute(dataInputStream, constant_pool);
    207        }
    208    }
    209
    210
    211    /**
    212     * Read information about the class and its super class.
    213     * @throws  IOException
    214     * @throws  ClassFormatException
    215     */
    216    private void readClassInfo() throws IOException, ClassFormatException {
    217        access_flags = dataInputStream.readUnsignedShort();
    218        /* Interfaces are implicitely abstract, the flag should be set
    219         * according to the JVM specification.
    220         */
    221        if ((access_flags & Const.ACC_INTERFACE) != 0) {
    222            access_flags |= Const.ACC_ABSTRACT;
    223        }
    224        if (((access_flags & Const.ACC_ABSTRACT) != 0)
    225                && ((access_flags & Const.ACC_FINAL) != 0)) {
    226            throw new ClassFormatException("Class " + file_name + " can't be both final and abstract");
    227        }
    228        class_name_index = dataInputStream.readUnsignedShort();
    229        superclass_name_index = dataInputStream.readUnsignedShort();
    230    }
    231
    232
    233    /**
    234     * Read constant pool entries.
    235     * @throws  IOException
    236     * @throws  ClassFormatException
    237     */
    238    private void readConstantPool() throws IOException, ClassFormatException {
    239        constant_pool = new ConstantPool(dataInputStream);
    240    }
    241
    242
    243    /**
    244     * Read information about the fields of the class, i.e., its variables.
    245     * @throws  IOException
    246     * @throws  ClassFormatException
    247     */
    248    private void readFields() throws IOException, ClassFormatException {
    249        final int fields_count = dataInputStream.readUnsignedShort();
    250        fields = new Field[fields_count];
    251        for (int i = 0; i < fields_count; i++) {
    252            fields[i] = new Field(dataInputStream, constant_pool);
    253        }
    254    }
    255
    256
    257    /******************** Private utility methods **********************/
    258    /**
    259     * Check whether the header of the file is ok.
    260     * Of course, this has to be the first action on successive file reads.
    261     * @throws  IOException
    262     * @throws  ClassFormatException
    263     */
    264    private void readID() throws IOException, ClassFormatException {
    265        if (dataInputStream.readInt() != Const.JVM_CLASSFILE_MAGIC) {
    266            throw new ClassFormatException(file_name + " is not a Java .class file");
    267        }
    268    }
    269
    270
    271    /**
    272     * Read information about the interfaces implemented by this class.
    273     * @throws  IOException
    274     * @throws  ClassFormatException
    275     */
    276    private void readInterfaces() throws IOException, ClassFormatException {
    277        final int interfaces_count = dataInputStream.readUnsignedShort();
    278        interfaces = new int[interfaces_count];
    279        for (int i = 0; i < interfaces_count; i++) {
    280            interfaces[i] = dataInputStream.readUnsignedShort();
    281        }
    282    }
    283
    284
    285    /**
    286     * Read information about the methods of the class.
    287     * @throws  IOException
    288     * @throws  ClassFormatException
    289     */
    290    private void readMethods() throws IOException, ClassFormatException {
    291        final int methods_count = dataInputStream.readUnsignedShort();
    292        methods = new Method[methods_count];
    293        for (int i = 0; i < methods_count; i++) {
    294            methods[i] = new Method(dataInputStream, constant_pool);
    295        }
    296    }
    297
    298
    299    /**
    300     * Read major and minor version of compiler which created the file.
    301     * @throws  IOException
    302     * @throws  ClassFormatException
    303     */
    304    private void readVersion() throws IOException, ClassFormatException {
    305        minor = dataInputStream.readUnsignedShort();
    306        major = dataInputStream.readUnsignedShort();
    307    }
    308}