1 /*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5 /*
6 * Licensed to the Apache Software Foundation (ASF) under one or more
7 * contributor license agreements. See the NOTICE file distributed with
8 * this work for additional information regarding copyright ownership.
9 * The ASF licenses this file to You under the Apache License, Version 2.0
10 * (the "License"); you may not use this file except in compliance with
11 * the License. You may obtain a copy of the License at
12 *
13 * http://www.apache.org/licenses/LICENSE-2.0
14 *
15 * Unless required by applicable law or agreed to in writing, software
16 * distributed under the License is distributed on an "AS IS" BASIS,
17 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
18 * See the License for the specific language governing permissions and
19 * limitations under the License.
20 */
21
22 package com.sun.org.apache.bcel.internal.util;
23
24 import com.sun.org.apache.bcel.internal.classfile.*;
25 import com.sun.org.apache.bcel.internal.generic.*;
26 import com.sun.org.apache.bcel.internal.Repository;
27 import com.sun.org.apache.bcel.internal.Constants;
28 import java.io.*;
29
30 /**
31 * This class takes a given JavaClass object and converts it to a
32 * Java program that creates that very class using BCEL. This
33 * gives new users of BCEL a useful example showing how things
34 * are done with BCEL. It does not cover all features of BCEL,
35 * but tries to mimic hand-written code as close as possible.
36 *
37 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
38 */
39 public class BCELifier extends com.sun.org.apache.bcel.internal.classfile.EmptyVisitor {
40 private JavaClass _clazz;
41 private PrintWriter _out;
42 private ConstantPoolGen _cp;
43
44 /** @param clazz Java class to "decompile"
45 * @param out where to output Java program
46 */
47 public BCELifier(JavaClass clazz, OutputStream out) {
48 _clazz = clazz;
49 _out = new PrintWriter(out);
50 _cp = new ConstantPoolGen(_clazz.getConstantPool());
51 }
52
53 /** Start Java code generation
54 */
55 public void start() {
56 visitJavaClass(_clazz);
57 _out.flush();
58 }
59
60 public void visitJavaClass(JavaClass clazz) {
61 String class_name = clazz.getClassName();
62 String super_name = clazz.getSuperclassName();
63 String package_name = clazz.getPackageName();
64 String inter = Utility.printArray(clazz.getInterfaceNames(),
65 false, true);
66 if(!"".equals(package_name)) {
67 class_name = class_name.substring(package_name.length() + 1);
68 _out.println("package " + package_name + ";\n");
69 }
70
71 _out.println("import com.sun.org.apache.bcel.internal.generic.*;");
72 _out.println("import com.sun.org.apache.bcel.internal.classfile.*;");
73 _out.println("import com.sun.org.apache.bcel.internal.*;");
74 _out.println("import java.io.*;\n");
75
76 _out.println("public class " + class_name + "Creator implements Constants {");
77 _out.println(" private InstructionFactory _factory;");
78 _out.println(" private ConstantPoolGen _cp;");
79 _out.println(" private ClassGen _cg;\n");
80
81 _out.println(" public " + class_name + "Creator() {");
82 _out.println(" _cg = new ClassGen(\"" +
83 (("".equals(package_name))? class_name :
84 package_name + "." + class_name) +
85 "\", \"" + super_name + "\", " +
86 "\"" + clazz.getSourceFileName() + "\", " +
87 printFlags(clazz.getAccessFlags(), true) + ", " +
88 "new String[] { " + inter + " });\n");
89
90 _out.println(" _cp = _cg.getConstantPool();");
91 _out.println(" _factory = new InstructionFactory(_cg, _cp);");
92 _out.println(" }\n");
93
94 printCreate();
95
96 Field[] fields = clazz.getFields();
97
98 if(fields.length > 0) {
99 _out.println(" private void createFields() {");
100 _out.println(" FieldGen field;");
101
102 for(int i=0; i < fields.length; i++) {
103 fields[i].accept(this);
104 }
105
106 _out.println(" }\n");
107 }
108
109 Method[] methods = clazz.getMethods();
110
111 for(int i=0; i < methods.length; i++) {
112 _out.println(" private void createMethod_" + i + "() {");
113
114 methods[i].accept(this);
115 _out.println(" }\n");
116 }
117
118 printMain();
119 _out.println("}");
120 }
121
122 private void printCreate() {
123 _out.println(" public void create(OutputStream out) throws IOException {");
124
125 Field[] fields = _clazz.getFields();
126 if(fields.length > 0) {
127 _out.println(" createFields();");
128 }
129
130 Method[] methods = _clazz.getMethods();
131 for(int i=0; i < methods.length; i++) {
132 _out.println(" createMethod_" + i + "();");
133 }
134
135 _out.println(" _cg.getJavaClass().dump(out);");
136
137 _out.println(" }\n");
138 }
139
140 private void printMain() {
141 String class_name = _clazz.getClassName();
142
143 _out.println(" public static void _main(String[] args) throws Exception {");
144 _out.println(" " + class_name + "Creator creator = new " +
145 class_name + "Creator();");
146 _out.println(" creator.create(new FileOutputStream(\"" + class_name +
147 ".class\"));");
148 _out.println(" }");
149 }
150
151 public void visitField(Field field) {
152 _out.println("\n field = new FieldGen(" +
153 printFlags(field.getAccessFlags()) +
154 ", " + printType(field.getSignature()) + ", \"" +
155 field.getName() + "\", _cp);");
156
157 ConstantValue cv = field.getConstantValue();
158
159 if(cv != null) {
160 String value = cv.toString();
161 _out.println(" field.setInitValue(" + value + ")");
162 }
163
164 _out.println(" _cg.addField(field.getField());");
165 }
166
167 public void visitMethod(Method method) {
168 MethodGen mg = new MethodGen(method, _clazz.getClassName(), _cp);
169
170 Type result_type = mg.getReturnType();
171 Type[] arg_types = mg.getArgumentTypes();
172
173 _out.println(" InstructionList il = new InstructionList();");
174 _out.println(" MethodGen method = new MethodGen(" +
175 printFlags(method.getAccessFlags()) +
176 ", " + printType(result_type) +
177 ", " + printArgumentTypes(arg_types) + ", " +
178 "new String[] { " +
179 Utility.printArray(mg.getArgumentNames(), false, true) +
180 " }, \"" + method.getName() + "\", \"" +
181 _clazz.getClassName() + "\", il, _cp);\n");
182
183 BCELFactory factory = new BCELFactory(mg, _out);
184 factory.start();
185
186 _out.println(" method.setMaxStack();");
187 _out.println(" method.setMaxLocals();");
188 _out.println(" _cg.addMethod(method.getMethod());");
189 _out.println(" il.dispose();");
190 }
191
192 static String printFlags(int flags) {
193 return printFlags(flags, false);
194 }
195
196 static String printFlags(int flags, boolean for_class) {
197 if(flags == 0)
198 return "0";
199
200 StringBuffer buf = new StringBuffer();
201 for(int i=0, pow=1; i <= Constants.MAX_ACC_FLAG; i++) {
202 if((flags & pow) != 0) {
203 if((pow == Constants.ACC_SYNCHRONIZED) && for_class)
204 buf.append("ACC_SUPER | ");
205 else
206 buf.append("ACC_" + Constants.ACCESS_NAMES[i].toUpperCase() + " | ");
207 }
208
209 pow <<= 1;
210 }
211
212 String str = buf.toString();
213 return str.substring(0, str.length() - 3);
214 }
215
216 static String printArgumentTypes(Type[] arg_types) {
217 if(arg_types.length == 0)
218 return "Type.NO_ARGS";
219
220 StringBuffer args = new StringBuffer();
221
222 for(int i=0; i < arg_types.length; i++) {
223 args.append(printType(arg_types[i]));
224
225 if(i < arg_types.length - 1)
226 args.append(", ");
227 }
228
229 return "new Type[] { " + args.toString() + " }";
230 }
231
232 static String printType(Type type) {
233 return printType(type.getSignature());
234 }
235
236 static String printType(String signature) {
237 Type type = Type.getType(signature);
238 byte t = type.getType();
239
240 if(t <= Constants.T_VOID) {
241 return "Type." + Constants.TYPE_NAMES[t].toUpperCase();
242 } else if(type.toString().equals("java.lang.String")) {
243 return "Type.STRING";
244 } else if(type.toString().equals("java.lang.Object")) {
245 return "Type.OBJECT";
246 } else if(type.toString().equals("java.lang.StringBuffer")) {
247 return "Type.STRINGBUFFER";
248 } else if(type instanceof ArrayType) {
249 ArrayType at = (ArrayType)type;
250
251 return "new ArrayType(" + printType(at.getBasicType()) +
252 ", " + at.getDimensions() + ")";
253 } else {
254 return "new ObjectType(\"" + Utility.signatureToString(signature, false) +
255 "\")";
256 }
257 }
258
259 /** Default _main method
260 */
261 public static void _main(String[] argv) throws Exception {
262 JavaClass java_class;
263 String name = argv[0];
264
265 if((java_class = Repository.lookupClass(name)) == null)
266 java_class = new ClassParser(name).parse(); // May throw IOException
267
268 BCELifier bcelifier = new BCELifier(java_class, System.out);
269 bcelifier.start();
270 }
271 }