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.classfile;
23
24
25 import com.sun.org.apache.bcel.internal.Constants;
26 import java.io.*;
27
28 /**
29 * This class represents the constant pool, i.e., a table of constants, of
30 * a parsed classfile. It may contain null references, due to the JVM
31 * specification that skips an entry after an 8-byte constant (double,
32 * long) entry. Those interested in generating constant pools
33 * programatically should see <a href="../generic/ConstantPoolGen.html">
34 * ConstantPoolGen</a>.
35
36 * @see Constant
37 * @see com.sun.org.apache.bcel.internal.generic.ConstantPoolGen
38 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
39 */
40 public class ConstantPool implements Cloneable, Node, Serializable {
41 private int constant_pool_count;
42 private Constant[] constant_pool;
43
44 /**
45 * @param constant_pool Array of constants
46 */
47 public ConstantPool(Constant[] constant_pool)
48 {
49 setConstantPool(constant_pool);
50 }
51
52 /**
53 * Read constants from given file stream.
54 *
55 * @param file Input stream
56 * @throws IOException
57 * @throws ClassFormatException
58 */
59 ConstantPool(DataInputStream file) throws IOException, ClassFormatException
60 {
61 byte tag;
62
63 constant_pool_count = file.readUnsignedShort();
64 constant_pool = new Constant[constant_pool_count];
65
66 /* constant_pool[0] is unused by the compiler and may be used freely
67 * by the implementation.
68 */
69 for(int i=1; i < constant_pool_count; i++) {
70 constant_pool[i] = Constant.readConstant(file);
71
72 /* Quote from the JVM specification:
73 * "All eight byte constants take up two spots in the constant pool.
74 * If this is the n'th byte in the constant pool, then the next item
75 * will be numbered n+2"
76 *
77 * Thus we have to increment the index counter.
78 */
79 tag = constant_pool[i].getTag();
80 if((tag == Constants.CONSTANT_Double) || (tag == Constants.CONSTANT_Long))
81 i++;
82 }
83 }
84
85 /**
86 * Called by objects that are traversing the nodes of the tree implicitely
87 * defined by the contents of a Java class. I.e., the hierarchy of methods,
88 * fields, attributes, etc. spawns a tree of objects.
89 *
90 * @param v Visitor object
91 */
92 public void accept(Visitor v) {
93 v.visitConstantPool(this);
94 }
95
96 /**
97 * Resolve constant to a string representation.
98 *
99 * @param constant Constant to be printed
100 * @return String representation
101 */
102 public String constantToString(Constant c)
103 throws ClassFormatException
104 {
105 String str;
106 int i;
107 byte tag = c.getTag();
108
109 switch(tag) {
110 case Constants.CONSTANT_Class:
111 i = ((ConstantClass)c).getNameIndex();
112 c = getConstant(i, Constants.CONSTANT_Utf8);
113 str = Utility.compactClassName(((ConstantUtf8)c).getBytes(), false);
114 break;
115
116 case Constants.CONSTANT_String:
117 i = ((ConstantString)c).getStringIndex();
118 c = getConstant(i, Constants.CONSTANT_Utf8);
119 str = "\"" + escape(((ConstantUtf8)c).getBytes()) + "\"";
120 break;
121
122 case Constants.CONSTANT_Utf8: str = ((ConstantUtf8)c).getBytes(); break;
123 case Constants.CONSTANT_Double: str = "" + ((ConstantDouble)c).getBytes(); break;
124 case Constants.CONSTANT_Float: str = "" + ((ConstantFloat)c).getBytes(); break;
125 case Constants.CONSTANT_Long: str = "" + ((ConstantLong)c).getBytes(); break;
126 case Constants.CONSTANT_Integer: str = "" + ((ConstantInteger)c).getBytes(); break;
127
128 case Constants.CONSTANT_NameAndType:
129 str = (constantToString(((ConstantNameAndType)c).getNameIndex(),
130 Constants.CONSTANT_Utf8) + " " +
131 constantToString(((ConstantNameAndType)c).getSignatureIndex(),
132 Constants.CONSTANT_Utf8));
133 break;
134
135 case Constants.CONSTANT_InterfaceMethodref: case Constants.CONSTANT_Methodref:
136 case Constants.CONSTANT_Fieldref:
137 str = (constantToString(((ConstantCP)c).getClassIndex(),
138 Constants.CONSTANT_Class) + "." +
139 constantToString(((ConstantCP)c).getNameAndTypeIndex(),
140 Constants.CONSTANT_NameAndType));
141 break;
142
143 default: // Never reached
144 throw new RuntimeException("Unknown constant type " + tag);
145 }
146
147 return str;
148 }
149
150 private static final String escape(String str) {
151 int len = str.length();
152 StringBuffer buf = new StringBuffer(len + 5);
153 char[] ch = str.toCharArray();
154
155 for(int i=0; i < len; i++) {
156 switch(ch[i]) {
157 case '\n' : buf.append("\\n"); break;
158 case '\r' : buf.append("\\r"); break;
159 case '\t' : buf.append("\\t"); break;
160 case '\b' : buf.append("\\b"); break;
161 case '"' : buf.append("\\\""); break;
162 default: buf.append(ch[i]);
163 }
164 }
165
166 return buf.toString();
167 }
168
169
170 /**
171 * Retrieve constant at `index' from constant pool and resolve it to
172 * a string representation.
173 *
174 * @param index of constant in constant pool
175 * @param tag expected type
176 * @return String representation
177 */
178 public String constantToString(int index, byte tag)
179 throws ClassFormatException
180 {
181 Constant c = getConstant(index, tag);
182 return constantToString(c);
183 }
184
185 /**
186 * Dump constant pool to file stream in binary format.
187 *
188 * @param file Output file stream
189 * @throws IOException
190 */
191 public void dump(DataOutputStream file) throws IOException
192 {
193 file.writeShort(constant_pool_count);
194
195 for(int i=1; i < constant_pool_count; i++)
196 if(constant_pool[i] != null)
197 constant_pool[i].dump(file);
198 }
199
200 /**
201 * Get constant from constant pool.
202 *
203 * @param index Index in constant pool
204 * @return Constant value
205 * @see Constant
206 */
207 public Constant getConstant(int index) {
208 if (index >= constant_pool.length || index < 0)
209 throw new ClassFormatException("Invalid constant pool reference: " +
210 index + ". Constant pool size is: " +
211 constant_pool.length);
212 return constant_pool[index];
213 }
214
215 /**
216 * Get constant from constant pool and check whether it has the
217 * expected type.
218 *
219 * @param index Index in constant pool
220 * @param tag Tag of expected constant, i.e., its type
221 * @return Constant value
222 * @see Constant
223 * @throws ClassFormatException
224 */
225 public Constant getConstant(int index, byte tag)
226 throws ClassFormatException
227 {
228 Constant c;
229
230 c = getConstant(index);
231
232 if(c == null)
233 throw new ClassFormatException("Constant pool at index " + index + " is null.");
234
235 if(c.getTag() == tag)
236 return c;
237 else
238 throw new ClassFormatException("Expected class `" + Constants.CONSTANT_NAMES[tag] +
239 "' at index " + index + " and got " + c);
240 }
241
242 /**
243 * @return Array of constants.
244 * @see Constant
245 */
246 public Constant[] getConstantPool() { return constant_pool; }
247 /**
248 * Get string from constant pool and bypass the indirection of
249 * `ConstantClass' and `ConstantString' objects. I.e. these classes have
250 * an index field that points to another entry of the constant pool of
251 * type `ConstantUtf8' which contains the real data.
252 *
253 * @param index Index in constant pool
254 * @param tag Tag of expected constant, either ConstantClass or ConstantString
255 * @return Contents of string reference
256 * @see ConstantClass
257 * @see ConstantString
258 * @throws ClassFormatException
259 */
260 public String getConstantString(int index, byte tag)
261 throws ClassFormatException
262 {
263 Constant c;
264 int i;
265
266 c = getConstant(index, tag);
267
268 /* This switch() is not that elegant, since the two classes have the
269 * same contents, they just differ in the name of the index
270 * field variable.
271 * But we want to stick to the JVM naming conventions closely though
272 * we could have solved these more elegantly by using the same
273 * variable name or by subclassing.
274 */
275 switch(tag) {
276 case Constants.CONSTANT_Class: i = ((ConstantClass)c).getNameIndex(); break;
277 case Constants.CONSTANT_String: i = ((ConstantString)c).getStringIndex(); break;
278 default:
279 throw new RuntimeException("getConstantString called with illegal tag " + tag);
280 }
281
282 // Finally get the string from the constant pool
283 c = getConstant(i, Constants.CONSTANT_Utf8);
284 return ((ConstantUtf8)c).getBytes();
285 }
286 /**
287 * @return Length of constant pool.
288 */
289 public int getLength()
290 {
291 return constant_pool_count;
292 }
293
294 /**
295 * @param constant Constant to set
296 */
297 public void setConstant(int index, Constant constant) {
298 constant_pool[index] = constant;
299 }
300
301 /**
302 * @param constant_pool
303 */
304 public void setConstantPool(Constant[] constant_pool) {
305 this.constant_pool = constant_pool;
306 constant_pool_count = (constant_pool == null)? 0 : constant_pool.length;
307 }
308 /**
309 * @return String representation.
310 */
311 public String toString() {
312 StringBuffer buf = new StringBuffer();
313
314 for(int i=1; i < constant_pool_count; i++)
315 buf.append(i + ")" + constant_pool[i] + "\n");
316
317 return buf.toString();
318 }
319
320 /**
321 * @return deep copy of this constant pool
322 */
323 public ConstantPool copy() {
324 ConstantPool c = null;
325
326 try {
327 c = (ConstantPool)clone();
328 } catch(CloneNotSupportedException e) {}
329
330 c.constant_pool = new Constant[constant_pool_count];
331
332 for(int i=1; i < constant_pool_count; i++) {
333 if(constant_pool[i] != null)
334 c.constant_pool[i] = constant_pool[i].copy();
335 }
336
337 return c;
338 }
339 }