Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 */
017package org.apache.bcel.classfile;
018
019import java.io.DataInput;
020import java.io.DataOutputStream;
021import java.io.IOException;
022import java.util.Arrays;
023import java.util.Iterator;
024
025import org.apache.bcel.Const;
026
027/**
028 * 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
029 * skips an entry after an 8-byte constant (double, long) entry. Those interested in generating constant pools programmatically should see
030 * <a href="../generic/ConstantPoolGen.html"> ConstantPoolGen</a>.
031 *
032 * @see Constant
033 * @see org.apache.bcel.generic.ConstantPoolGen
034 */
035public class ConstantPool implements Cloneable, Node, Iterable<Constant> {
036
037    private static String escape(final String str) {
038        final int len = str.length();
039        final StringBuilder buf = new StringBuilder(len + 5);
040        final char[] ch = str.toCharArray();
041        for (int i = 0; i < len; i++) {
042            switch (ch[i]) {
043            case '\n':
044                buf.append("\\n");
045                break;
046            case '\r':
047                buf.append("\\r");
048                break;
049            case '\t':
050                buf.append("\\t");
051                break;
052            case '\b':
053                buf.append("\\b");
054                break;
055            case '"':
056                buf.append("\\\"");
057                break;
058            default:
059                buf.append(ch[i]);
060            }
061        }
062        return buf.toString();
063    }
064
065    private Constant[] constantPool;
066
067    /**
068     * @param constantPool Array of constants
069     */
070    public ConstantPool(final Constant[] constantPool) {
071        setConstantPool(constantPool);
072    }
073
074    /**
075     * Reads constants from given input stream.
076     *
077     * @param input Input stream
078     * @throws IOException if problem in readUnsignedShort or readConstant
079     */
080    public ConstantPool(final DataInput input) throws IOException {
081        byte tag;
082        final int constantPoolCount = input.readUnsignedShort();
083        constantPool = new Constant[constantPoolCount];
084        /*
085         * constantPool[0] is unused by the compiler and may be used freely by the implementation.
086         * constantPool[0] is currently unused by the implementation.
087         */
088        for (int i = 1; i < constantPoolCount; i++) {
089            constantPool[i] = Constant.readConstant(input);
090            /*
091             * 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
092             * pool, then the next item will be numbered n+2"
093             *
094             * Thus we have to increment the index counter.
095             */
096            tag = constantPool[i].getTag();
097            if (tag == Const.CONSTANT_Double || tag == Const.CONSTANT_Long) {
098                i++;
099            }
100        }
101    }
102
103    /**
104     * 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,
105     * attributes, etc. spawns a tree of objects.
106     *
107     * @param v Visitor object
108     */
109    @Override
110    public void accept(final Visitor v) {
111        v.visitConstantPool(this);
112    }
113
114    /**
115     * Resolves constant to a string representation.
116     *
117     * @param c Constant to be printed
118     * @return String representation
119     * @throws IllegalArgumentException if c is unknown constant type
120     */
121    public String constantToString(Constant c) throws IllegalArgumentException {
122        String str;
123        int i;
124        final byte tag = c.getTag();
125        switch (tag) {
126        case Const.CONSTANT_Class:
127            i = ((ConstantClass) c).getNameIndex();
128            c = getConstantUtf8(i);
129            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
130            break;
131        case Const.CONSTANT_String:
132            i = ((ConstantString) c).getStringIndex();
133            c = getConstantUtf8(i);
134            str = "\"" + escape(((ConstantUtf8) c).getBytes()) + "\"";
135            break;
136        case Const.CONSTANT_Utf8:
137            str = ((ConstantUtf8) c).getBytes();
138            break;
139        case Const.CONSTANT_Double:
140            str = String.valueOf(((ConstantDouble) c).getBytes());
141            break;
142        case Const.CONSTANT_Float:
143            str = String.valueOf(((ConstantFloat) c).getBytes());
144            break;
145        case Const.CONSTANT_Long:
146            str = String.valueOf(((ConstantLong) c).getBytes());
147            break;
148        case Const.CONSTANT_Integer:
149            str = String.valueOf(((ConstantInteger) c).getBytes());
150            break;
151        case Const.CONSTANT_NameAndType:
152            str = constantToString(((ConstantNameAndType) c).getNameIndex(), Const.CONSTANT_Utf8) + " "
153                    + constantToString(((ConstantNameAndType) c).getSignatureIndex(), Const.CONSTANT_Utf8);
154            break;
155        case Const.CONSTANT_InterfaceMethodref:
156        case Const.CONSTANT_Methodref:
157        case Const.CONSTANT_Fieldref:
158            str = constantToString(((ConstantCP) c).getClassIndex(), Const.CONSTANT_Class) + "."
159                    + constantToString(((ConstantCP) c).getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
160            break;
161        case Const.CONSTANT_MethodHandle:
162            // Note that the ReferenceIndex may point to a Fieldref, Methodref or
163            // InterfaceMethodref - so we need to peek ahead to get the actual type.
164            final ConstantMethodHandle cmh = (ConstantMethodHandle) c;
165            str = Const.getMethodHandleName(cmh.getReferenceKind()) + " "
166                    + constantToString(cmh.getReferenceIndex(), getConstant(cmh.getReferenceIndex()).getTag());
167            break;
168        case Const.CONSTANT_MethodType:
169            final ConstantMethodType cmt = (ConstantMethodType) c;
170            str = constantToString(cmt.getDescriptorIndex(), Const.CONSTANT_Utf8);
171            break;
172        case Const.CONSTANT_InvokeDynamic:
173            final ConstantInvokeDynamic cid = (ConstantInvokeDynamic) c;
174            str = cid.getBootstrapMethodAttrIndex() + ":" + constantToString(cid.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
175            break;
176        case Const.CONSTANT_Dynamic:
177            final ConstantDynamic cd = (ConstantDynamic) c;
178            str = cd.getBootstrapMethodAttrIndex() + ":" + constantToString(cd.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
179            break;
180        case Const.CONSTANT_Module:
181            i = ((ConstantModule) c).getNameIndex();
182            c = getConstantUtf8(i);
183            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
184            break;
185        case Const.CONSTANT_Package:
186            i = ((ConstantPackage) c).getNameIndex();
187            c = getConstantUtf8(i);
188            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
189            break;
190        default: // Never reached
191            throw new IllegalArgumentException("Unknown constant type " + tag);
192        }
193        return str;
194    }
195
196    /**
197     * Retrieves constant at 'index' from constant pool and resolve it to a string representation.
198     *
199     * @param index of constant in constant pool
200     * @param tag   expected type
201     * @return String representation
202     */
203    public String constantToString(final int index, final byte tag) {
204        return constantToString(getConstant(index, tag));
205    }
206
207    /**
208     * @return deep copy of this constant pool
209     */
210    public ConstantPool copy() {
211        ConstantPool c = null;
212        try {
213            c = (ConstantPool) clone();
214            c.constantPool = new Constant[constantPool.length];
215            for (int i = 1; i < constantPool.length; i++) {
216                if (constantPool[i] != null) {
217                    c.constantPool[i] = constantPool[i].copy();
218                }
219            }
220        } catch (final CloneNotSupportedException e) {
221            // TODO should this throw?
222        }
223        return c;
224    }
225
226    /**
227     * Dump constant pool to file stream in binary format.
228     *
229     * @param file Output file stream
230     * @throws IOException if problem in writeShort or dump
231     */
232    public void dump(final DataOutputStream file) throws IOException {
233        /*
234         * Constants over the size of the constant pool shall not be written out. This is a redundant measure as the ConstantPoolGen should have already
235         * reported an error back in the situation.
236         */
237        final int size = Math.min(constantPool.length, Const.MAX_CP_ENTRIES);
238
239        file.writeShort(size);
240        for (int i = 1; i < size; i++) {
241            if (constantPool[i] != null) {
242                constantPool[i].dump(file);
243            }
244        }
245    }
246
247    /**
248     * Gets constant from constant pool.
249     *
250     * @param index Index in constant pool
251     * @return Constant value
252     * @see Constant
253     * @throws ClassFormatException if index is invalid
254     */
255    @SuppressWarnings("unchecked")
256    public <T extends Constant> T getConstant(final int index) throws ClassFormatException {
257        return (T) getConstant(index, Constant.class);
258    }
259
260    /**
261     * Gets constant from constant pool and check whether it has the expected type.
262     *
263     * @param index Index in constant pool
264     * @param tag   Tag of expected constant, i.e., its type
265     * @return Constant value
266     * @see Constant
267     * @throws ClassFormatException if constant type does not match tag
268     */
269    @SuppressWarnings("unchecked")
270    public <T extends Constant> T getConstant(final int index, final byte tag) throws ClassFormatException {
271        return (T) getConstant(index, tag, Constant.class);
272    }
273
274    /**
275     * Gets constant from constant pool and check whether it has the expected type.
276     *
277     * @param index Index in constant pool
278     * @param tag   Tag of expected constant, i.e., its type
279     * @return Constant value
280     * @see Constant
281     * @throws ClassFormatException if constant type does not match tag
282     * @since 6.6.0
283     */
284    public <T extends Constant> T getConstant(final int index, final byte tag, final Class<T> castTo) throws ClassFormatException {
285        final T c = getConstant(index);
286        if (c == null || c.getTag() != tag) {
287            throw new ClassFormatException("Expected class '" + Const.getConstantName(tag) + "' at index " + index + " and got " + c);
288        }
289        return c;
290    }
291
292    /**
293     * Gets constant from constant pool.
294     *
295     * @param <T> A {@link Constant} subclass
296     * @param index Index in constant pool
297     * @param castTo The {@link Constant} subclass to cast to.
298     * @return Constant value
299     * @see Constant
300     * @throws ClassFormatException if index is invalid
301     * @since 6.6.0
302     */
303    public <T extends Constant> T getConstant(final int index, final Class<T> castTo) throws ClassFormatException {
304        if (index >= constantPool.length || index < 1) {
305            throw new ClassFormatException("Invalid constant pool reference using index: " + index + ". Constant pool size is: " + constantPool.length);
306        }
307        if (constantPool[index] != null && !castTo.isAssignableFrom(constantPool[index].getClass())) {
308            throw new ClassFormatException("Invalid constant pool reference at index: " + index +
309                    ". Expected " + castTo + " but was " + constantPool[index].getClass());
310        }
311        if (index > 1) {
312            final Constant prev = constantPool[index - 1];
313            if (prev != null && (prev.getTag() == Const.CONSTANT_Double || prev.getTag() == Const.CONSTANT_Long)) {
314                throw new ClassFormatException("Constant pool at index " + index + " is invalid. The index is unused due to the preceeding "
315                        + Const.getConstantName(prev.getTag()) + ".");
316            }
317        }
318        // Previous check ensures this won't throw a ClassCastException
319        final T c = castTo.cast(constantPool[index]);
320        if (c == null) {
321            throw new ClassFormatException("Constant pool at index " + index + " is null.");
322        }
323        return c;
324    }
325
326    /**
327     * Gets constant from constant pool and check whether it has the expected type.
328     *
329     * @param index Index in constant pool
330     * @return ConstantInteger value
331     * @see ConstantInteger
332     * @throws ClassFormatException if constant type does not match tag
333     */
334    public ConstantInteger getConstantInteger(final int index) {
335        return getConstant(index, Const.CONSTANT_Integer, ConstantInteger.class);
336    }
337
338    /**
339     * @return Array of constants.
340     * @see Constant
341     */
342    public Constant[] getConstantPool() {
343        return constantPool;
344    }
345
346    /**
347     * Gets string from constant pool and bypass the indirection of 'ConstantClass' and 'ConstantString' objects. I.e. these classes have an index field that
348     * points to another entry of the constant pool of type 'ConstantUtf8' which contains the real data.
349     *
350     * @param index Index in constant pool
351     * @param tag   Tag of expected constant, either ConstantClass or ConstantString
352     * @return Contents of string reference
353     * @see ConstantClass
354     * @see ConstantString
355     * @throws IllegalArgumentException if tag is invalid
356     */
357    public String getConstantString(final int index, final byte tag) throws IllegalArgumentException {
358        int i;
359        /*
360         * 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
361         * 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
362         * subclassing.
363         */
364        switch (tag) {
365        case Const.CONSTANT_Class:
366            i = getConstant(index, ConstantClass.class).getNameIndex();
367            break;
368        case Const.CONSTANT_String:
369            i = getConstant(index, ConstantString.class).getStringIndex();
370            break;
371        case Const.CONSTANT_Module:
372            i = getConstant(index, ConstantModule.class).getNameIndex();
373            break;
374        case Const.CONSTANT_Package:
375            i = getConstant(index, ConstantPackage.class).getNameIndex();
376            break;
377        case Const.CONSTANT_Utf8:
378            return getConstantUtf8(index).getBytes();
379        default:
380            throw new IllegalArgumentException("getConstantString called with illegal tag " + tag);
381        }
382        // Finally get the string from the constant pool
383        return getConstantUtf8(i).getBytes();
384    }
385
386    /**
387     * Gets constant from constant pool and check whether it has the expected type.
388     *
389     * @param index Index in constant pool
390     * @return ConstantUtf8 value
391     * @see ConstantUtf8
392     * @throws ClassFormatException if constant type does not match tag
393     */
394    public ConstantUtf8 getConstantUtf8(final int index) throws ClassFormatException {
395        return getConstant(index, Const.CONSTANT_Utf8, ConstantUtf8.class);
396    }
397
398    /**
399     * @return Length of constant pool.
400     */
401    public int getLength() {
402        return constantPool.length;
403    }
404
405    @Override
406    public Iterator<Constant> iterator() {
407        return Arrays.stream(constantPool).iterator();
408    }
409
410    /**
411     * @param constant Constant to set
412     */
413    public void setConstant(final int index, final Constant constant) {
414        constantPool[index] = constant;
415    }
416
417    /**
418     * @param constantPool
419     */
420    public void setConstantPool(final Constant[] constantPool) {
421        this.constantPool = constantPool != null ? constantPool : Constant.EMPTY_ARRAY;
422    }
423
424    /**
425     * @return String representation.
426     */
427    @Override
428    public String toString() {
429        final StringBuilder buf = new StringBuilder();
430        for (int i = 1; i < constantPool.length; i++) {
431            buf.append(i).append(")").append(constantPool[i]).append("\n");
432        }
433        return buf.toString();
434    }
435}