1   package org.apache.bcel.classfile;
2   
3   /* ====================================================================
4    * The Apache Software License, Version 1.1
5    *
6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
7    * reserved.
8    *
9    * Redistribution and use in source and binary forms, with or without
10   * modification, are permitted provided that the following conditions
11   * are met:
12   *
13   * 1. Redistributions of source code must retain the above copyright
14   *    notice, this list of conditions and the following disclaimer.
15   *
16   * 2. Redistributions in binary form must reproduce the above copyright
17   *    notice, this list of conditions and the following disclaimer in
18   *    the documentation and/or other materials provided with the
19   *    distribution.
20   *
21   * 3. The end-user documentation included with the redistribution,
22   *    if any, must include the following acknowledgment:
23   *       "This product includes software developed by the
24   *        Apache Software Foundation (http://www.apache.org/)."
25   *    Alternately, this acknowledgment may appear in the software itself,
26   *    if and wherever such third-party acknowledgments normally appear.
27   *
28   * 4. The names "Apache" and "Apache Software Foundation" and
29   *    "Apache BCEL" must not be used to endorse or promote products
30   *    derived from this software without prior written permission. For
31   *    written permission, please contact apache@apache.org.
32   *
33   * 5. Products derived from this software may not be called "Apache",
34   *    "Apache BCEL", nor may "Apache" appear in their name, without
35   *    prior written permission of the Apache Software Foundation.
36   *
37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
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43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48   * SUCH DAMAGE.
49   * ====================================================================
50   *
51   * This software consists of voluntary contributions made by many
52   * individuals on behalf of the Apache Software Foundation.  For more
53   * information on the Apache Software Foundation, please see
54   * <http://www.apache.org/>.
55   */
56  
57  import  org.apache.bcel.Constants;
58  import  java.io.*;
59  import  java.util.zip.*;
60  
61  /***
62   * Wrapper class that parses a given Java .class file. The method <A
63   * href ="#parse">parse</A> returns a <A href ="JavaClass.html">
64   * JavaClass</A> object on success. When an I/O error or an
65   * inconsistency occurs an appropiate exception is propagated back to
66   * the caller.
67   *
68   * The structure and the names comply, except for a few conveniences,
69   * exactly with the <A href="ftp://java.sun.com/docs/specs/vmspec.ps">
70   * JVM specification 1.0</a>. See this paper for
71   * further details about the structure of a bytecode file.
72   *
73   * @version $Id: ClassParser.java,v 1.5 2002/08/09 13:09:31 mdahm Exp $
74   * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A> 
75   */
76  public final class ClassParser {
77    private DataInputStream file;
78    private ZipFile         zip;
79    private String          file_name;
80    private int             class_name_index, superclass_name_index;
81    private int             major, minor; // Compiler version
82    private int             access_flags; // Access rights of parsed class
83    private int[]           interfaces; // Names of implemented interfaces
84    private ConstantPool    constant_pool; // collection of constants
85    private Field[]         fields; // class fields, i.e., its variables
86    private Method[]        methods; // methods defined in the class
87    private Attribute[]     attributes; // attributes defined in the class
88    private boolean         is_zip; // Loaded from zip file
89  
90    private static final int BUFSIZE = 8192;
91  
92    /***
93     * Parse class from the given stream.
94     *
95     * @param file Input stream
96     * @param file_name File name
97     */
98    public ClassParser(InputStream file, String file_name) {
99      this.file_name = file_name;
100 
101     String clazz = file.getClass().getName(); // Not a very clean solution ...
102     is_zip = clazz.startsWith("java.util.zip.") || clazz.startsWith("java.util.jar.");
103 
104     if(file instanceof DataInputStream) // Is already a data stream
105       this.file = (DataInputStream)file;
106     else
107       this.file = new DataInputStream(new BufferedInputStream(file, BUFSIZE));
108   }
109 
110   /*** Parse class from given .class file.
111    *
112    * @param file_name file name
113    * @throws IOException
114    */
115   public ClassParser(String file_name) throws IOException
116   {    
117     is_zip = false;
118     this.file_name = file_name;
119     file = new DataInputStream(new BufferedInputStream
120 			       (new FileInputStream(file_name), BUFSIZE));
121   }
122 
123   /*** Parse class from given .class file in a ZIP-archive
124    *
125    * @param file_name file name
126    * @throws IOException
127    */
128   public ClassParser(String zip_file, String file_name) throws IOException
129   {    
130     is_zip = true;
131     zip = new ZipFile(zip_file);
132     ZipEntry entry = zip.getEntry(file_name);
133   		   
134     this.file_name = file_name;
135 
136     file = new DataInputStream(new BufferedInputStream(zip.getInputStream(entry),
137 						       BUFSIZE));
138   }
139 
140   /***
141    * Parse the given Java class file and return an object that represents
142    * the contained data, i.e., constants, methods, fields and commands.
143    * A <em>ClassFormatException</em> is raised, if the file is not a valid
144    * .class file. (This does not include verification of the byte code as it
145    * is performed by the java interpreter).
146    *
147    * @return Class object representing the parsed class file
148    * @throws  IOException
149    * @throws  ClassFormatException
150    */  
151   public JavaClass parse() throws IOException, ClassFormatException
152   {
153     /******************* Read headers ********************************/
154     // Check magic tag of class file
155     readID();
156 
157     // Get compiler version
158     readVersion();
159 
160     /******************* Read constant pool and related **************/
161     // Read constant pool entries
162     readConstantPool();
163 	
164     // Get class information
165     readClassInfo();
166 
167     // Get interface information, i.e., implemented interfaces
168     readInterfaces();
169 
170     /******************* Read class fields and methods ***************/ 
171     // Read class fields, i.e., the variables of the class
172     readFields();
173 
174     // Read class methods, i.e., the functions in the class
175     readMethods();
176 
177     // Read class attributes
178     readAttributes();
179 
180     // Check for unknown variables
181     //Unknown[] u = Unknown.getUnknownAttributes();
182     //for(int i=0; i < u.length; i++)
183     //  System.err.println("WARNING: " + u[i]);
184 
185     // Everything should have been read now
186     //      if(file.available() > 0) {
187     //        int bytes = file.available();
188     //        byte[] buf = new byte[bytes];
189     //        file.read(buf);
190     
191     //        if(!(is_zip && (buf.length == 1))) {
192     //  	System.err.println("WARNING: Trailing garbage at end of " + file_name);
193     //  	System.err.println(bytes + " extra bytes: " + Utility.toHexString(buf));
194     //        }
195     //      }
196 
197     // Read everything of interest, so close the file
198     file.close();
199     if(zip != null)
200       zip.close();
201 
202     // Return the information we have gathered in a new object
203     return new JavaClass(class_name_index, superclass_name_index, 
204 			 file_name, major, minor, access_flags,
205 			 constant_pool, interfaces, fields,
206 			 methods, attributes, is_zip? JavaClass.ZIP : JavaClass.FILE);
207   }
208 
209   /***
210    * Read information about the attributes of the class.
211    * @throws  IOException
212    * @throws  ClassFormatException
213    */
214   private final void readAttributes() throws IOException, ClassFormatException
215   {
216     int attributes_count;
217 
218     attributes_count = file.readUnsignedShort();
219     attributes       = new Attribute[attributes_count];
220 
221     for(int i=0; i < attributes_count; i++)
222       attributes[i] = Attribute.readAttribute(file, constant_pool);
223   }
224 
225   /***
226    * Read information about the class and its super class.
227    * @throws  IOException
228    * @throws  ClassFormatException
229    */
230   private final void readClassInfo() throws IOException, ClassFormatException
231   {
232     access_flags = file.readUnsignedShort();
233 
234     /* Interfaces are implicitely abstract, the flag should be set
235      * according to the JVM specification.
236      */
237     if((access_flags & Constants.ACC_INTERFACE) != 0)
238       access_flags |= Constants.ACC_ABSTRACT;
239 
240     if(((access_flags & Constants.ACC_ABSTRACT) != 0) && 
241        ((access_flags & Constants.ACC_FINAL)    != 0 ))
242       throw new ClassFormatException("Class can't be both final and abstract");
243 
244     class_name_index      = file.readUnsignedShort();
245     superclass_name_index = file.readUnsignedShort();
246   }    
247   /***
248    * Read constant pool entries.
249    * @throws  IOException
250    * @throws  ClassFormatException
251    */
252   private final void readConstantPool() throws IOException, ClassFormatException
253   {
254     constant_pool = new ConstantPool(file);
255   }    
256 
257   /***
258    * Read information about the fields of the class, i.e., its variables.
259    * @throws  IOException
260    * @throws  ClassFormatException
261    */
262   private final void readFields() throws IOException, ClassFormatException
263   {
264     int fields_count;
265 
266     fields_count = file.readUnsignedShort();
267     fields       = new Field[fields_count];
268 
269     for(int i=0; i < fields_count; i++)
270       fields[i] = new Field(file, constant_pool);
271   }    
272 
273   /********************* Private utility methods **********************/
274 
275   /***
276    * Check whether the header of the file is ok.
277    * Of course, this has to be the first action on successive file reads.
278    * @throws  IOException
279    * @throws  ClassFormatException
280    */
281   private final void readID() throws IOException, ClassFormatException
282   {
283     int magic = 0xCAFEBABE;
284 
285     if(file.readInt() != magic)
286       throw new ClassFormatException(file_name + " is not a Java .class file");
287   }    
288   /***
289    * Read information about the interfaces implemented by this class.
290    * @throws  IOException
291    * @throws  ClassFormatException
292    */
293   private final void readInterfaces() throws IOException, ClassFormatException
294   {
295     int interfaces_count;
296 
297     interfaces_count = file.readUnsignedShort();
298     interfaces       = new int[interfaces_count];
299 
300     for(int i=0; i < interfaces_count; i++)
301       interfaces[i] = file.readUnsignedShort();
302   }     
303   /***
304    * Read information about the methods of the class.
305    * @throws  IOException
306    * @throws  ClassFormatException
307    */
308   private final void readMethods() throws IOException, ClassFormatException
309   {
310     int methods_count;
311 
312     methods_count = file.readUnsignedShort();
313     methods       = new Method[methods_count];
314 
315     for(int i=0; i < methods_count; i++)
316       methods[i] = new Method(file, constant_pool);
317   }      
318   /***
319    * Read major and minor version of compiler which created the file.
320    * @throws  IOException
321    * @throws  ClassFormatException
322    */
323   private final void readVersion() throws IOException, ClassFormatException
324   {
325     minor = file.readUnsignedShort();
326     major = file.readUnsignedShort();
327   }    
328 }
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