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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   https://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.apache.bcel.classfile;
20  
21  import java.io.DataInput;
22  import java.io.DataOutputStream;
23  import java.io.IOException;
24  import java.util.Arrays;
25  import java.util.Iterator;
26  
27  import org.apache.bcel.Const;
28  
29  /**
30   * This class represents the constant pool, i.e., a table of constants, of a parsed classfile. It may contain null references, due to the JVM specification that
31   * skips an entry after an 8-byte constant (double, long) entry. Those interested in generating constant pools programmatically should see
32   * <a href="../generic/ConstantPoolGen.html"> ConstantPoolGen</a>.
33   *
34   * @see Constant
35   * @see org.apache.bcel.generic.ConstantPoolGen
36   */
37  public class ConstantPool implements Cloneable, Node, Iterable<Constant> {
38  
39      private static String escape(final String str) {
40          final int len = str.length();
41          final StringBuilder buf = new StringBuilder(len + 5);
42          final char[] ch = str.toCharArray();
43          for (int i = 0; i < len; i++) {
44              switch (ch[i]) {
45              case '\n':
46                  buf.append("\\n");
47                  break;
48              case '\r':
49                  buf.append("\\r");
50                  break;
51              case '\t':
52                  buf.append("\\t");
53                  break;
54              case '\b':
55                  buf.append("\\b");
56                  break;
57              case '"':
58                  buf.append("\\\"");
59                  break;
60              default:
61                  buf.append(ch[i]);
62              }
63          }
64          return buf.toString();
65      }
66  
67      private Constant[] constantPool;
68  
69      /**
70       * @param constantPool Array of constants
71       */
72      public ConstantPool(final Constant[] constantPool) {
73          setConstantPool(constantPool);
74      }
75  
76      /**
77       * Reads constants from given input stream.
78       *
79       * @param input Input stream
80       * @throws IOException if problem in readUnsignedShort or readConstant
81       */
82      public ConstantPool(final DataInput input) throws IOException {
83          byte tag;
84          final int constantPoolCount = input.readUnsignedShort();
85          constantPool = new Constant[constantPoolCount];
86          /*
87           * constantPool[0] is unused by the compiler and may be used freely by the implementation.
88           * constantPool[0] is currently unused by the implementation.
89           */
90          for (int i = 1; i < constantPoolCount; i++) {
91              constantPool[i] = Constant.readConstant(input);
92              /*
93               * Quote from the JVM specification: "All eight byte constants take up two spots in the constant pool. If this is the n'th byte in the constant
94               * pool, then the next item will be numbered n+2"
95               *
96               * Thus we have to increment the index counter.
97               */
98              tag = constantPool[i].getTag();
99              if (tag == Const.CONSTANT_Double || tag == Const.CONSTANT_Long) {
100                 i++;
101             }
102         }
103     }
104 
105     /**
106      * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class. I.e., the hierarchy of methods, fields,
107      * attributes, etc. spawns a tree of objects.
108      *
109      * @param v Visitor object
110      */
111     @Override
112     public void accept(final Visitor v) {
113         v.visitConstantPool(this);
114     }
115 
116     /**
117      * Resolves constant to a string representation.
118      *
119      * @param c Constant to be printed
120      * @return String representation
121      * @throws IllegalArgumentException if c is unknown constant type
122      */
123     public String constantToString(Constant c) throws IllegalArgumentException {
124         final String str;
125         final int i;
126         final byte tag = c.getTag();
127         switch (tag) {
128         case Const.CONSTANT_Class:
129             i = ((ConstantClass) c).getNameIndex();
130             c = getConstantUtf8(i);
131             str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
132             break;
133         case Const.CONSTANT_String:
134             i = ((ConstantString) c).getStringIndex();
135             c = getConstantUtf8(i);
136             str = "\"" + escape(((ConstantUtf8) c).getBytes()) + "\"";
137             break;
138         case Const.CONSTANT_Utf8:
139             str = ((ConstantUtf8) c).getBytes();
140             break;
141         case Const.CONSTANT_Double:
142             str = String.valueOf(((ConstantDouble) c).getBytes());
143             break;
144         case Const.CONSTANT_Float:
145             str = String.valueOf(((ConstantFloat) c).getBytes());
146             break;
147         case Const.CONSTANT_Long:
148             str = String.valueOf(((ConstantLong) c).getBytes());
149             break;
150         case Const.CONSTANT_Integer:
151             str = String.valueOf(((ConstantInteger) c).getBytes());
152             break;
153         case Const.CONSTANT_NameAndType:
154             str = constantToString(((ConstantNameAndType) c).getNameIndex(), Const.CONSTANT_Utf8) + " "
155                     + constantToString(((ConstantNameAndType) c).getSignatureIndex(), Const.CONSTANT_Utf8);
156             break;
157         case Const.CONSTANT_InterfaceMethodref:
158         case Const.CONSTANT_Methodref:
159         case Const.CONSTANT_Fieldref:
160             str = constantToString(((ConstantCP) c).getClassIndex(), Const.CONSTANT_Class) + "."
161                     + constantToString(((ConstantCP) c).getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
162             break;
163         case Const.CONSTANT_MethodHandle:
164             // Note that the ReferenceIndex may point to a Fieldref, Methodref or
165             // InterfaceMethodref - so we need to peek ahead to get the actual type.
166             final ConstantMethodHandle cmh = (ConstantMethodHandle) c;
167             str = Const.getMethodHandleName(cmh.getReferenceKind()) + " "
168                     + constantToString(cmh.getReferenceIndex(), getConstant(cmh.getReferenceIndex()).getTag());
169             break;
170         case Const.CONSTANT_MethodType:
171             final ConstantMethodType cmt = (ConstantMethodType) c;
172             str = constantToString(cmt.getDescriptorIndex(), Const.CONSTANT_Utf8);
173             break;
174         case Const.CONSTANT_InvokeDynamic:
175             final ConstantInvokeDynamic cid = (ConstantInvokeDynamic) c;
176             str = cid.getBootstrapMethodAttrIndex() + ":" + constantToString(cid.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
177             break;
178         case Const.CONSTANT_Dynamic:
179             final ConstantDynamic cd = (ConstantDynamic) c;
180             str = cd.getBootstrapMethodAttrIndex() + ":" + constantToString(cd.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
181             break;
182         case Const.CONSTANT_Module:
183             i = ((ConstantModule) c).getNameIndex();
184             c = getConstantUtf8(i);
185             str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
186             break;
187         case Const.CONSTANT_Package:
188             i = ((ConstantPackage) c).getNameIndex();
189             c = getConstantUtf8(i);
190             str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
191             break;
192         default: // Never reached
193             throw new IllegalArgumentException("Unknown constant type " + tag);
194         }
195         return str;
196     }
197 
198     /**
199      * Retrieves constant at 'index' from constant pool and resolve it to a string representation.
200      *
201      * @param index of constant in constant pool
202      * @param tag   expected type
203      * @return String representation
204      */
205     public String constantToString(final int index, final byte tag) {
206         return constantToString(getConstant(index, tag));
207     }
208 
209     /**
210      * @return deep copy of this constant pool
211      */
212     public ConstantPool copy() {
213         ConstantPool c = null;
214         try {
215             c = (ConstantPool) clone();
216             c.constantPool = new Constant[constantPool.length];
217             for (int i = 1; i < constantPool.length; i++) {
218                 if (constantPool[i] != null) {
219                     c.constantPool[i] = constantPool[i].copy();
220                 }
221             }
222         } catch (final CloneNotSupportedException e) {
223             // TODO should this throw?
224         }
225         return c;
226     }
227 
228     /**
229      * Dump constant pool to file stream in binary format.
230      *
231      * @param file Output file stream
232      * @throws IOException if problem in writeShort or dump
233      */
234     public void dump(final DataOutputStream file) throws IOException {
235         /*
236          * Constants over the size of the constant pool shall not be written out. This is a redundant measure as the ConstantPoolGen should have already
237          * reported an error back in the situation.
238          */
239         final int size = Math.min(constantPool.length, Const.MAX_CP_ENTRIES);
240 
241         file.writeShort(size);
242         for (int i = 1; i < size; i++) {
243             if (constantPool[i] != null) {
244                 constantPool[i].dump(file);
245             }
246         }
247     }
248 
249     /**
250      * Gets constant from constant pool.
251      *
252      * @param index Index in constant pool
253      * @return Constant value
254      * @see Constant
255      * @throws ClassFormatException if index is invalid
256      */
257     @SuppressWarnings("unchecked")
258     public <T extends Constant> T getConstant(final int index) throws ClassFormatException {
259         return (T) getConstant(index, Constant.class);
260     }
261 
262     /**
263      * Gets constant from constant pool and check whether it has the expected type.
264      *
265      * @param index Index in constant pool
266      * @param tag   Tag of expected constant, i.e., its type
267      * @return Constant value
268      * @see Constant
269      * @throws ClassFormatException if constant type does not match tag
270      */
271     @SuppressWarnings("unchecked")
272     public <T extends Constant> T getConstant(final int index, final byte tag) throws ClassFormatException {
273         return (T) getConstant(index, tag, Constant.class);
274     }
275 
276     /**
277      * Gets constant from constant pool and check whether it has the expected type.
278      *
279      * @param index Index in constant pool
280      * @param tag   Tag of expected constant, i.e., its type
281      * @return Constant value
282      * @see Constant
283      * @throws ClassFormatException if constant type does not match tag
284      * @since 6.6.0
285      */
286     public <T extends Constant> T getConstant(final int index, final byte tag, final Class<T> castTo) throws ClassFormatException {
287         final T c = getConstant(index);
288         if (c == null || c.getTag() != tag) {
289             throw new ClassFormatException("Expected class '" + Const.getConstantName(tag) + "' at index " + index + " and got " + c);
290         }
291         return c;
292     }
293 
294     /**
295      * Gets constant from constant pool.
296      *
297      * @param <T> A {@link Constant} subclass
298      * @param index Index in constant pool
299      * @param castTo The {@link Constant} subclass to cast to.
300      * @return Constant value
301      * @see Constant
302      * @throws ClassFormatException if index is invalid
303      * @since 6.6.0
304      */
305     public <T extends Constant> T getConstant(final int index, final Class<T> castTo) throws ClassFormatException {
306         if (index >= constantPool.length || index < 1) {
307             throw new ClassFormatException("Invalid constant pool reference using index: " + index + ". Constant pool size is: " + constantPool.length);
308         }
309         if (constantPool[index] != null && !castTo.isAssignableFrom(constantPool[index].getClass())) {
310             throw new ClassFormatException("Invalid constant pool reference at index: " + index +
311                     ". Expected " + castTo + " but was " + constantPool[index].getClass());
312         }
313         if (index > 1) {
314             final Constant prev = constantPool[index - 1];
315             if (prev != null && (prev.getTag() == Const.CONSTANT_Double || prev.getTag() == Const.CONSTANT_Long)) {
316                 throw new ClassFormatException("Constant pool at index " + index + " is invalid. The index is unused due to the preceeding "
317                         + Const.getConstantName(prev.getTag()) + ".");
318             }
319         }
320         // Previous check ensures this won't throw a ClassCastException
321         final T c = castTo.cast(constantPool[index]);
322         if (c == null) {
323             throw new ClassFormatException("Constant pool at index " + index + " is null.");
324         }
325         return c;
326     }
327 
328     /**
329      * Gets constant from constant pool and check whether it has the expected type.
330      *
331      * @param index Index in constant pool
332      * @return ConstantInteger value
333      * @see ConstantInteger
334      * @throws ClassFormatException if constant type does not match tag
335      */
336     public ConstantInteger getConstantInteger(final int index) {
337         return getConstant(index, Const.CONSTANT_Integer, ConstantInteger.class);
338     }
339 
340     /**
341      * @return Array of constants.
342      * @see Constant
343      */
344     public Constant[] getConstantPool() {
345         return constantPool;
346     }
347 
348     /**
349      * Gets string from constant pool and bypass the indirection of 'ConstantClass' and 'ConstantString' objects. I.e. these classes have an index field that
350      * points to another entry of the constant pool of type 'ConstantUtf8' which contains the real data.
351      *
352      * @param index Index in constant pool
353      * @param tag   Tag of expected constant, either ConstantClass or ConstantString
354      * @return Contents of string reference
355      * @see ConstantClass
356      * @see ConstantString
357      * @throws IllegalArgumentException if tag is invalid
358      */
359     public String getConstantString(final int index, final byte tag) throws IllegalArgumentException {
360         final int i;
361         /*
362          * This switch() is not that elegant, since the four classes have the same contents, they just differ in the name of the index field variable. But we
363          * want to stick to the JVM naming conventions closely though we could have solved these more elegantly by using the same variable name or by
364          * subclassing.
365          */
366         switch (tag) {
367         case Const.CONSTANT_Class:
368             i = getConstant(index, ConstantClass.class).getNameIndex();
369             break;
370         case Const.CONSTANT_String:
371             i = getConstant(index, ConstantString.class).getStringIndex();
372             break;
373         case Const.CONSTANT_Module:
374             i = getConstant(index, ConstantModule.class).getNameIndex();
375             break;
376         case Const.CONSTANT_Package:
377             i = getConstant(index, ConstantPackage.class).getNameIndex();
378             break;
379         case Const.CONSTANT_Utf8:
380             return getConstantUtf8(index).getBytes();
381         default:
382             throw new IllegalArgumentException("getConstantString called with illegal tag " + tag);
383         }
384         // Finally get the string from the constant pool
385         return getConstantUtf8(i).getBytes();
386     }
387 
388     /**
389      * Gets constant from constant pool and check whether it has the expected type.
390      *
391      * @param index Index in constant pool
392      * @return ConstantUtf8 value
393      * @see ConstantUtf8
394      * @throws ClassFormatException if constant type does not match tag
395      */
396     public ConstantUtf8 getConstantUtf8(final int index) throws ClassFormatException {
397         return getConstant(index, Const.CONSTANT_Utf8, ConstantUtf8.class);
398     }
399 
400     /**
401      * @return Length of constant pool.
402      */
403     public int getLength() {
404         return constantPool.length;
405     }
406 
407     @Override
408     public Iterator<Constant> iterator() {
409         return Arrays.stream(constantPool).iterator();
410     }
411 
412     /**
413      * @param constant Constant to set
414      */
415     public void setConstant(final int index, final Constant constant) {
416         constantPool[index] = constant;
417     }
418 
419     /**
420      * @param constantPool
421      */
422     public void setConstantPool(final Constant[] constantPool) {
423         this.constantPool = constantPool != null ? constantPool : Constant.EMPTY_ARRAY;
424     }
425 
426     /**
427      * @return String representation.
428      */
429     @Override
430     public String toString() {
431         final StringBuilder buf = new StringBuilder();
432         for (int i = 1; i < constantPool.length; i++) {
433             buf.append(i).append(")").append(constantPool[i]).append("\n");
434         }
435         return buf.toString();
436     }
437 }