1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.bcel.classfile;
18
19 import java.io.BufferedInputStream;
20 import java.io.DataInputStream;
21 import java.io.FileInputStream;
22 import java.io.IOException;
23 import java.io.InputStream;
24 import java.util.zip.ZipEntry;
25 import java.util.zip.ZipFile;
26
27 import org.apache.bcel.Const;
28
29 /**
30 * Wrapper class that parses a given Java .class file. The method <a href ="#parse">parse</a> returns a
31 * <a href ="JavaClass.html"> JavaClass</a> object on success. When an I/O error or an inconsistency occurs an
32 * appropriate exception is propagated back to the caller.
33 *
34 * The structure and the names comply, except for a few conveniences, exactly with the
35 * <a href="https://docs.oracle.com/javase/specs/"> JVM specification 1.0</a>. See this paper for further details about
36 * the structure of a bytecode file.
37 */
38 public final class ClassParser {
39
40 private static final int BUFSIZE = 8192;
41 private DataInputStream dataInputStream;
42 private final boolean fileOwned;
43 private final String fileName;
44 private String zipFile;
45 private int classNameIndex;
46 private int superclassNameIndex;
47 private int major; // Compiler version
48 private int minor; // Compiler version
49 private int accessFlags; // Access rights of parsed class
50 private int[] interfaces; // Names of implemented interfaces
51 private ConstantPool constantPool; // collection of constants
52 private Field[] fields; // class fields, i.e., its variables
53 private Method[] methods; // methods defined in the class
54 private Attribute[] attributes; // attributes defined in the class
55 private final boolean isZip; // Loaded from ZIP file
56
57 /**
58 * Parses class from the given stream.
59 *
60 * @param inputStream Input stream
61 * @param fileName File name
62 */
63 public ClassParser(final InputStream inputStream, final String fileName) {
64 this.fileName = fileName;
65 this.fileOwned = false;
66 final String clazz = inputStream.getClass().getName(); // Not a very clean solution ...
67 this.isZip = clazz.startsWith("java.util.zip.") || clazz.startsWith("java.util.jar.");
68 if (inputStream instanceof DataInputStream) {
69 this.dataInputStream = (DataInputStream) inputStream;
70 } else {
71 this.dataInputStream = new DataInputStream(new BufferedInputStream(inputStream, BUFSIZE));
72 }
73 }
74
75 /**
76 * Parses class from given .class file.
77 *
78 * @param fileName file name
79 */
80 public ClassParser(final String fileName) {
81 this.isZip = false;
82 this.fileName = fileName;
83 this.fileOwned = true;
84 }
85
86 /**
87 * Parses class from given .class file in a ZIP-archive
88 *
89 * @param zipFile ZIP file name
90 * @param fileName file name
91 */
92 public ClassParser(final String zipFile, final String fileName) {
93 this.isZip = true;
94 this.fileOwned = true;
95 this.zipFile = zipFile;
96 this.fileName = fileName;
97 }
98
99 /**
100 * Parses the given Java class file and return an object that represents the contained data, i.e., constants, methods,
101 * fields and commands. A <em>ClassFormatException</em> is raised, if the file is not a valid .class file. (This does
102 * not include verification of the byte code as it is performed by the Java interpreter).
103 *
104 * @return Class object representing the parsed class file
105 * @throws IOException if an I/O error occurs.
106 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
107 */
108 public JavaClass parse() throws IOException, ClassFormatException {
109 ZipFile zip = null;
110 try {
111 if (fileOwned) {
112 if (isZip) {
113 zip = new ZipFile(zipFile);
114 final ZipEntry entry = zip.getEntry(fileName);
115
116 if (entry == null) {
117 throw new IOException("File " + fileName + " not found");
118 }
119
120 dataInputStream = new DataInputStream(new BufferedInputStream(zip.getInputStream(entry), BUFSIZE));
121 } else {
122 dataInputStream = new DataInputStream(new BufferedInputStream(new FileInputStream(fileName), BUFSIZE));
123 }
124 }
125 /****************** Read headers ********************************/
126 // Check magic tag of class file
127 readID();
128 // Get compiler version
129 readVersion();
130 /****************** Read constant pool and related **************/
131 // Read constant pool entries
132 readConstantPool();
133 // Get class information
134 readClassInfo();
135 // Get interface information, i.e., implemented interfaces
136 readInterfaces();
137 /****************** Read class fields and methods ***************/
138 // Read class fields, i.e., the variables of the class
139 readFields();
140 // Read class methods, i.e., the functions in the class
141 readMethods();
142 // Read class attributes
143 readAttributes();
144 // Check for unknown variables
145 // Unknown[] u = Unknown.getUnknownAttributes();
146 // for (int i=0; i < u.length; i++)
147 // System.err.println("WARNING: " + u[i]);
148 // Everything should have been read now
149 // if (file.available() > 0) {
150 // int bytes = file.available();
151 // byte[] buf = new byte[bytes];
152 // file.read(buf);
153 // if (!(isZip && (buf.length == 1))) {
154 // System.err.println("WARNING: Trailing garbage at end of " + fileName);
155 // System.err.println(bytes + " extra bytes: " + Utility.toHexString(buf));
156 // }
157 // }
158 } finally {
159 // Read everything of interest, so close the file
160 if (fileOwned) {
161 try {
162 if (dataInputStream != null) {
163 dataInputStream.close();
164 }
165 } catch (final IOException ignored) {
166 // ignore close exceptions
167 }
168 }
169 try {
170 if (zip != null) {
171 zip.close();
172 }
173 } catch (final IOException ignored) {
174 // ignore close exceptions
175 }
176 }
177 // Return the information we have gathered in a new object
178 return new JavaClass(classNameIndex, superclassNameIndex, fileName, major, minor, accessFlags, constantPool, interfaces, fields, methods, attributes,
179 isZip ? JavaClass.ZIP : JavaClass.FILE);
180 }
181
182 /**
183 * Reads information about the attributes of the class.
184 *
185 * @throws IOException if an I/O error occurs.
186 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
187 */
188 private void readAttributes() throws IOException, ClassFormatException {
189 final int attributesCount = dataInputStream.readUnsignedShort();
190 attributes = new Attribute[attributesCount];
191 for (int i = 0; i < attributesCount; i++) {
192 attributes[i] = Attribute.readAttribute(dataInputStream, constantPool);
193 }
194 }
195
196 /**
197 * Reads information about the class and its super class.
198 *
199 * @throws IOException if an I/O error occurs.
200 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
201 */
202 private void readClassInfo() throws IOException, ClassFormatException {
203 accessFlags = dataInputStream.readUnsignedShort();
204 /*
205 * Interfaces are implicitly abstract, the flag should be set according to the JVM specification.
206 */
207 if ((accessFlags & Const.ACC_INTERFACE) != 0) {
208 accessFlags |= Const.ACC_ABSTRACT;
209 }
210 if ((accessFlags & Const.ACC_ABSTRACT) != 0 && (accessFlags & Const.ACC_FINAL) != 0) {
211 throw new ClassFormatException("Class " + fileName + " can't be both final and abstract");
212 }
213 classNameIndex = dataInputStream.readUnsignedShort();
214 superclassNameIndex = dataInputStream.readUnsignedShort();
215 }
216
217 /**
218 * Reads constant pool entries.
219 *
220 * @throws IOException if an I/O error occurs.
221 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
222 */
223 private void readConstantPool() throws IOException, ClassFormatException {
224 constantPool = new ConstantPool(dataInputStream);
225 }
226
227 /**
228 * Reads information about the fields of the class, i.e., its variables.
229 *
230 * @throws IOException if an I/O error occurs.
231 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
232 */
233 private void readFields() throws IOException, ClassFormatException {
234 final int fieldsCount = dataInputStream.readUnsignedShort();
235 fields = new Field[fieldsCount];
236 for (int i = 0; i < fieldsCount; i++) {
237 fields[i] = new Field(dataInputStream, constantPool);
238 }
239 }
240
241 /******************** Private utility methods **********************/
242 /**
243 * Checks whether the header of the file is ok. Of course, this has to be the first action on successive file reads.
244 *
245 * @throws IOException if an I/O error occurs.
246 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
247 */
248 private void readID() throws IOException, ClassFormatException {
249 if (dataInputStream.readInt() != Const.JVM_CLASSFILE_MAGIC) {
250 throw new ClassFormatException(fileName + " is not a Java .class file");
251 }
252 }
253
254 /**
255 * Reads information about the interfaces implemented by this class.
256 *
257 * @throws IOException if an I/O error occurs.
258 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
259 */
260 private void readInterfaces() throws IOException, ClassFormatException {
261 final int interfacesCount = dataInputStream.readUnsignedShort();
262 interfaces = new int[interfacesCount];
263 for (int i = 0; i < interfacesCount; i++) {
264 interfaces[i] = dataInputStream.readUnsignedShort();
265 }
266 }
267
268 /**
269 * Reads information about the methods of the class.
270 *
271 * @throws IOException if an I/O error occurs.
272 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
273 */
274 private void readMethods() throws IOException {
275 final int methodsCount = dataInputStream.readUnsignedShort();
276 methods = new Method[methodsCount];
277 for (int i = 0; i < methodsCount; i++) {
278 methods[i] = new Method(dataInputStream, constantPool);
279 }
280 }
281
282 /**
283 * Reads major and minor version of compiler which created the file.
284 *
285 * @throws IOException if an I/O error occurs.
286 * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
287 */
288 private void readVersion() throws IOException, ClassFormatException {
289 minor = dataInputStream.readUnsignedShort();
290 major = dataInputStream.readUnsignedShort();
291 }
292 }