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 *
017 */
018package org.apache.bcel.classfile;
019
020import java.io.DataInput;
021import java.io.DataOutputStream;
022import java.io.IOException;
023import java.util.Arrays;
024import java.util.Iterator;
025
026import org.apache.bcel.Const;
027
028/**
029 * 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
030 * skips an entry after an 8-byte constant (double, long) entry. Those interested in generating constant pools programmatically should see
031 * <a href="../generic/ConstantPoolGen.html"> ConstantPoolGen</a>.
032 *
033 * @see Constant
034 * @see org.apache.bcel.generic.ConstantPoolGen
035 */
036public class ConstantPool implements Cloneable, Node, Iterable<Constant> {
037
038    private static String escape(final String str) {
039        final int len = str.length();
040        final StringBuilder buf = new StringBuilder(len + 5);
041        final char[] ch = str.toCharArray();
042        for (int i = 0; i < len; i++) {
043            switch (ch[i]) {
044            case '\n':
045                buf.append("\\n");
046                break;
047            case '\r':
048                buf.append("\\r");
049                break;
050            case '\t':
051                buf.append("\\t");
052                break;
053            case '\b':
054                buf.append("\\b");
055                break;
056            case '"':
057                buf.append("\\\"");
058                break;
059            default:
060                buf.append(ch[i]);
061            }
062        }
063        return buf.toString();
064    }
065
066    private Constant[] constantPool;
067
068    /**
069     * @param constantPool Array of constants
070     */
071    public ConstantPool(final Constant[] constantPool) {
072        this.constantPool = constantPool;
073    }
074
075    /**
076     * Reads constants from given input stream.
077     *
078     * @param input Input stream
079     * @throws IOException if problem in readUnsignedShort or readConstant
080     */
081    public ConstantPool(final DataInput input) throws IOException {
082        byte tag;
083        final int constant_pool_count = input.readUnsignedShort();
084        constantPool = new Constant[constant_pool_count];
085        /*
086         * constantPool[0] is unused by the compiler and may be used freely by the implementation.
087         */
088        for (int i = 1; i < constant_pool_count; 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.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 index Index in constant pool
296     * @return Constant value
297     * @see Constant
298     * @throws ClassFormatException if index is invalid
299     * @since 6.6.0
300     */
301    public <T extends Constant> T getConstant(final int index, final Class<T> castTo) throws ClassFormatException {
302        if (index >= constantPool.length || index < 0) {
303            throw new ClassFormatException("Invalid constant pool reference: " + index + ". Constant pool size is: " + constantPool.length);
304        }
305        final T c = castTo.cast(constantPool[index]);
306        if (c == null) {
307            throw new ClassFormatException("Constant pool at index " + index + " is null.");
308        }
309        return c;
310    }
311
312    /**
313     * Gets constant from constant pool and check whether it has the expected type.
314     *
315     * @param index Index in constant pool
316     * @return ConstantInteger value
317     * @see ConstantInteger
318     * @throws ClassFormatException if constant type does not match tag
319     */
320    public ConstantInteger getConstantInteger(final int index) {
321        return getConstant(index, Const.CONSTANT_Integer, ConstantInteger.class);
322    }
323
324    /**
325     * @return Array of constants.
326     * @see Constant
327     */
328    public Constant[] getConstantPool() {
329        return constantPool;
330    }
331
332    /**
333     * Gets string from constant pool and bypass the indirection of `ConstantClass' and `ConstantString' objects. I.e. these classes have an index field that
334     * points to another entry of the constant pool of type `ConstantUtf8' which contains the real data.
335     *
336     * @param index Index in constant pool
337     * @param tag   Tag of expected constant, either ConstantClass or ConstantString
338     * @return Contents of string reference
339     * @see ConstantClass
340     * @see ConstantString
341     * @throws IllegalArgumentException if tag is invalid
342     */
343    public String getConstantString(final int index, final byte tag) throws IllegalArgumentException {
344        int i;
345        /*
346         * 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
347         * 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
348         * subclassing.
349         */
350        switch (tag) {
351        case Const.CONSTANT_Class:
352            i = getConstant(index, ConstantClass.class).getNameIndex();
353            break;
354        case Const.CONSTANT_String:
355            i = getConstant(index, ConstantString.class).getStringIndex();
356            break;
357        case Const.CONSTANT_Module:
358            i = getConstant(index, ConstantModule.class).getNameIndex();
359            break;
360        case Const.CONSTANT_Package:
361            i = getConstant(index, ConstantPackage.class).getNameIndex();
362            break;
363        case Const.CONSTANT_Utf8:
364            return getConstantUtf8(index).getBytes();
365        // fallthrough
366        default:
367            throw new IllegalArgumentException("getConstantString called with illegal tag " + tag);
368        }
369        // Finally get the string from the constant pool
370        return getConstantUtf8(i).getBytes();
371    }
372
373    /**
374     * Gets constant from constant pool and check whether it has the expected type.
375     *
376     * @param index Index in constant pool
377     * @return ConstantUtf8 value
378     * @see ConstantUtf8
379     * @throws ClassFormatException if constant type does not match tag
380     */
381    public ConstantUtf8 getConstantUtf8(final int index) throws ClassFormatException {
382        return getConstant(index, Const.CONSTANT_Utf8, ConstantUtf8.class);
383    }
384
385    /**
386     * @return Length of constant pool.
387     */
388    public int getLength() {
389        return constantPool == null ? 0 : constantPool.length;
390    }
391
392    @Override
393    public Iterator<Constant> iterator() {
394        return Arrays.stream(constantPool).iterator();
395    }
396
397    /**
398     * @param constant Constant to set
399     */
400    public void setConstant(final int index, final Constant constant) {
401        constantPool[index] = constant;
402    }
403
404    /**
405     * @param constantPool
406     */
407    public void setConstantPool(final Constant[] constantPool) {
408        this.constantPool = constantPool;
409    }
410
411    /**
412     * @return String representation.
413     */
414    @Override
415    public String toString() {
416        final StringBuilder buf = new StringBuilder();
417        for (int i = 1; i < constantPool.length; i++) {
418            buf.append(i).append(")").append(constantPool[i]).append("\n");
419        }
420        return buf.toString();
421    }
422}