Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.bcel.classfile;
020
021import java.io.DataInput;
022import java.io.DataOutputStream;
023import java.io.IOException;
024import java.util.Arrays;
025import java.util.Iterator;
026
027import org.apache.bcel.Const;
028
029/**
030 * 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
031 * skips an entry after an 8-byte constant (double, long) entry. Those interested in generating constant pools programmatically should see
032 * <a href="../generic/ConstantPoolGen.html"> ConstantPoolGen</a>.
033 *
034 * @see Constant
035 * @see org.apache.bcel.generic.ConstantPoolGen
036 */
037public class ConstantPool implements Cloneable, Node, Iterable<Constant> {
038
039    private static String escape(final String str) {
040        final int len = str.length();
041        final StringBuilder buf = new StringBuilder(len + 5);
042        final char[] ch = str.toCharArray();
043        for (int i = 0; i < len; i++) {
044            switch (ch[i]) {
045            case '\n':
046                buf.append("\\n");
047                break;
048            case '\r':
049                buf.append("\\r");
050                break;
051            case '\t':
052                buf.append("\\t");
053                break;
054            case '\b':
055                buf.append("\\b");
056                break;
057            case '"':
058                buf.append("\\\"");
059                break;
060            default:
061                buf.append(ch[i]);
062            }
063        }
064        return buf.toString();
065    }
066
067    private Constant[] constantPool;
068
069    /**
070     * @param constantPool Array of constants
071     */
072    public ConstantPool(final Constant[] constantPool) {
073        setConstantPool(constantPool);
074    }
075
076    /**
077     * Reads constants from given input stream.
078     *
079     * @param input Input stream
080     * @throws IOException if problem in readUnsignedShort or readConstant
081     */
082    public ConstantPool(final DataInput input) throws IOException {
083        byte tag;
084        final int constantPoolCount = input.readUnsignedShort();
085        constantPool = new Constant[constantPoolCount];
086        /*
087         * constantPool[0] is unused by the compiler and may be used freely by the implementation.
088         * constantPool[0] is currently unused by the implementation.
089         */
090        for (int i = 1; i < constantPoolCount; i++) {
091            constantPool[i] = Constant.readConstant(input);
092            /*
093             * 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
094             * pool, then the next item will be numbered n+2"
095             *
096             * Thus we have to increment the index counter.
097             */
098            tag = constantPool[i].getTag();
099            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}