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, that is, 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     * Constructs a ConstantPool.
071     *
072     * @param constantPool Array of constants.
073     */
074    public ConstantPool(final Constant... constantPool) {
075        setConstantPool(constantPool);
076    }
077
078    /**
079     * Reads constants from given input stream.
080     *
081     * @param input Input stream.
082     * @throws IOException if problem in readUnsignedShort or readConstant.
083     */
084    public ConstantPool(final DataInput input) throws IOException {
085        byte tag;
086        final int constantPoolCount = input.readUnsignedShort();
087        constantPool = new Constant[constantPoolCount];
088        /*
089         * constantPool[0] is unused by the compiler and may be used freely by the implementation.
090         * constantPool[0] is currently unused by the implementation.
091         */
092        for (int i = 1; i < constantPoolCount; i++) {
093            constantPool[i] = Constant.readConstant(input);
094            /*
095             * 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
096             * pool, then the next item will be numbered n+2"
097             *
098             * Thus we have to increment the index counter.
099             */
100            tag = constantPool[i].getTag();
101            if (tag == Const.CONSTANT_Double || tag == Const.CONSTANT_Long) {
102                i++;
103            }
104        }
105    }
106
107    /**
108     * 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,
109     * attributes, etc. spawns a tree of objects.
110     *
111     * @param v Visitor object.
112     */
113    @Override
114    public void accept(final Visitor v) {
115        v.visitConstantPool(this);
116    }
117
118    /**
119     * Resolves constant to a string representation.
120     *
121     * @param c Constant to be printed.
122     * @return String representation.
123     * @throws IllegalArgumentException if c is unknown constant type.
124     */
125    public String constantToString(Constant c) throws IllegalArgumentException {
126        final String str;
127        final int i;
128        final byte tag = c.getTag();
129        switch (tag) {
130        case Const.CONSTANT_Class:
131            i = ((ConstantClass) c).getNameIndex();
132            c = getConstantUtf8(i);
133            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
134            break;
135        case Const.CONSTANT_String:
136            i = ((ConstantString) c).getStringIndex();
137            c = getConstantUtf8(i);
138            str = "\"" + escape(((ConstantUtf8) c).getBytes()) + "\"";
139            break;
140        case Const.CONSTANT_Utf8:
141            str = ((ConstantUtf8) c).getBytes();
142            break;
143        case Const.CONSTANT_Double:
144            str = String.valueOf(((ConstantDouble) c).getBytes());
145            break;
146        case Const.CONSTANT_Float:
147            str = String.valueOf(((ConstantFloat) c).getBytes());
148            break;
149        case Const.CONSTANT_Long:
150            str = String.valueOf(((ConstantLong) c).getBytes());
151            break;
152        case Const.CONSTANT_Integer:
153            str = String.valueOf(((ConstantInteger) c).getBytes());
154            break;
155        case Const.CONSTANT_NameAndType:
156            str = constantToString(((ConstantNameAndType) c).getNameIndex(), Const.CONSTANT_Utf8) + " "
157                    + constantToString(((ConstantNameAndType) c).getSignatureIndex(), Const.CONSTANT_Utf8);
158            break;
159        case Const.CONSTANT_InterfaceMethodref:
160        case Const.CONSTANT_Methodref:
161        case Const.CONSTANT_Fieldref:
162            str = constantToString(((ConstantCP) c).getClassIndex(), Const.CONSTANT_Class) + "."
163                    + constantToString(((ConstantCP) c).getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
164            break;
165        case Const.CONSTANT_MethodHandle:
166            // Note that the ReferenceIndex may point to a Fieldref, Methodref or
167            // InterfaceMethodref - so we need to peek ahead to get the actual type.
168            final ConstantMethodHandle cmh = (ConstantMethodHandle) c;
169            str = Const.getMethodHandleName(cmh.getReferenceKind()) + " "
170                    + constantToString(cmh.getReferenceIndex(), getConstant(cmh.getReferenceIndex()).getTag());
171            break;
172        case Const.CONSTANT_MethodType:
173            final ConstantMethodType cmt = (ConstantMethodType) c;
174            str = constantToString(cmt.getDescriptorIndex(), Const.CONSTANT_Utf8);
175            break;
176        case Const.CONSTANT_InvokeDynamic:
177            final ConstantInvokeDynamic cid = (ConstantInvokeDynamic) c;
178            str = cid.getBootstrapMethodAttrIndex() + ":" + constantToString(cid.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
179            break;
180        case Const.CONSTANT_Dynamic:
181            final ConstantDynamic cd = (ConstantDynamic) c;
182            str = cd.getBootstrapMethodAttrIndex() + ":" + constantToString(cd.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
183            break;
184        case Const.CONSTANT_Module:
185            i = ((ConstantModule) c).getNameIndex();
186            c = getConstantUtf8(i);
187            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
188            break;
189        case Const.CONSTANT_Package:
190            i = ((ConstantPackage) c).getNameIndex();
191            c = getConstantUtf8(i);
192            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
193            break;
194        default: // Never reached
195            throw new IllegalArgumentException("Unknown constant type " + tag);
196        }
197        return str;
198    }
199
200    /**
201     * Retrieves constant at 'index' from constant pool and resolve it to a string representation.
202     *
203     * @param index of constant in constant pool.
204     * @param tag   expected type.
205     * @return String representation.
206     */
207    public String constantToString(final int index, final byte tag) {
208        return constantToString(getConstant(index, tag));
209    }
210
211    /**
212     * Creates a deep copy of this constant pool.
213     *
214     * @return deep copy of this constant pool.
215     */
216    public ConstantPool copy() {
217        ConstantPool c = null;
218        try {
219            c = (ConstantPool) clone();
220            c.constantPool = new Constant[constantPool.length];
221            for (int i = 1; i < constantPool.length; i++) {
222                if (constantPool[i] != null) {
223                    c.constantPool[i] = constantPool[i].copy();
224                }
225            }
226        } catch (final CloneNotSupportedException e) {
227            // TODO should this throw?
228        }
229        return c;
230    }
231
232    /**
233     * Dumps constant pool to file stream in binary format.
234     *
235     * @param file Output file stream.
236     * @throws IOException if problem in writeShort or dump
237     */
238    public void dump(final DataOutputStream file) throws IOException {
239        /*
240         * Constants over the size of the constant pool shall not be written out. This is a redundant measure as the ConstantPoolGen should have already
241         * reported an error back in the situation.
242         */
243        final int size = Math.min(constantPool.length, Const.MAX_CP_ENTRIES);
244
245        file.writeShort(size);
246        for (int i = 1; i < size; i++) {
247            if (constantPool[i] != null) {
248                constantPool[i].dump(file);
249            }
250        }
251    }
252
253    /**
254     * Gets constant from constant pool.
255     *
256     * @param <T> the type of the constant.
257     * @param index Index in constant pool.
258     * @return Constant value.
259     * @see Constant
260     * @throws ClassFormatException if index is invalid.
261     */
262    @SuppressWarnings("unchecked")
263    public <T extends Constant> T getConstant(final int index) throws ClassFormatException {
264        return (T) getConstant(index, Constant.class);
265    }
266
267    /**
268     * Gets constant from constant pool and check whether it has the expected type.
269     *
270     * @param <T> the type of the constant.
271     * @param index Index in constant pool.
272     * @param tag   Tag of expected constant, that is, its type.
273     * @return Constant value.
274     * @see Constant
275     * @throws ClassFormatException if constant type does not match tag.
276     */
277    @SuppressWarnings("unchecked")
278    public <T extends Constant> T getConstant(final int index, final byte tag) throws ClassFormatException {
279        return (T) getConstant(index, tag, Constant.class);
280    }
281
282    /**
283     * Gets constant from constant pool and check whether it has the expected type.
284     *
285     * @param <T> the type of the constant.
286     * @param index Index in constant pool.
287     * @param tag   Tag of expected constant, that is, its type.
288     * @param castTo the class to cast to.
289     * @return Constant value.
290     * @see Constant
291     * @throws ClassFormatException if constant type does not match tag.
292     * @since 6.6.0
293     */
294    public <T extends Constant> T getConstant(final int index, final byte tag, final Class<T> castTo) throws ClassFormatException {
295        final T c = getConstant(index);
296        if (c == null || c.getTag() != tag) {
297            throw new ClassFormatException("Expected class '" + Const.getConstantName(tag) + "' at index " + index + " and got " + c);
298        }
299        return c;
300    }
301
302    /**
303     * Gets constant from constant pool.
304     *
305     * @param <T> A {@link Constant} subclass.
306     * @param index Index in constant pool.
307     * @param castTo The {@link Constant} subclass to cast to.
308     * @return Constant value.
309     * @throws ClassFormatException if index is invalid.
310     * @see Constant
311     * @since 6.6.0
312     */
313    public <T extends Constant> T getConstant(final int index, final Class<T> castTo) throws ClassFormatException {
314        if (index >= constantPool.length || index < 1) {
315            throw new ClassFormatException("Invalid constant pool reference using index: " + index + ". Constant pool size is: " + constantPool.length);
316        }
317        if (constantPool[index] != null && !castTo.isAssignableFrom(constantPool[index].getClass())) {
318            throw new ClassFormatException("Invalid constant pool reference at index: " + index +
319                    ". Expected " + castTo + " but was " + constantPool[index].getClass());
320        }
321        if (index > 1) {
322            final Constant prev = constantPool[index - 1];
323            if (prev != null && (prev.getTag() == Const.CONSTANT_Double || prev.getTag() == Const.CONSTANT_Long)) {
324                throw new ClassFormatException("Constant pool at index " + index + " is invalid. The index is unused due to the preceeding "
325                        + Const.getConstantName(prev.getTag()) + ".");
326            }
327        }
328        // Previous check ensures this won't throw a ClassCastException
329        final T c = castTo.cast(constantPool[index]);
330        if (c == null) {
331            throw new ClassFormatException("Constant pool at index " + index + " is null.");
332        }
333        return c;
334    }
335
336    /**
337     * Gets constant from constant pool and check whether it has the expected type.
338     *
339     * @param index Index in constant pool.
340     * @return ConstantInteger value.
341     * @throws ClassFormatException if constant type does not match tag.
342     * @see ConstantInteger
343     */
344    public ConstantInteger getConstantInteger(final int index) {
345        return getConstant(index, Const.CONSTANT_Integer, ConstantInteger.class);
346    }
347
348    /**
349     * Gets the array of constants.
350     *
351     * @return Array of constants.
352     * @see Constant
353     */
354    public Constant[] getConstantPool() {
355        return constantPool;
356    }
357
358    /**
359     * Gets string from constant pool and bypass the indirection of 'ConstantClass' and 'ConstantString' objects. I.e. these classes have an index field that
360     * points to another entry of the constant pool of type 'ConstantUtf8' which contains the real data.
361     *
362     * @param index Index in constant pool.
363     * @param tag   Tag of expected constant, either ConstantClass or ConstantString.
364     * @return Contents of string reference.
365     * @throws IllegalArgumentException if tag is invalid.
366     * @see ConstantClass
367     * @see ConstantString
368     */
369    public String getConstantString(final int index, final byte tag) throws IllegalArgumentException {
370        final int i;
371        /*
372         * 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
373         * 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
374         * subclassing.
375         */
376        switch (tag) {
377        case Const.CONSTANT_Class:
378            i = getConstant(index, ConstantClass.class).getNameIndex();
379            break;
380        case Const.CONSTANT_String:
381            i = getConstant(index, ConstantString.class).getStringIndex();
382            break;
383        case Const.CONSTANT_Module:
384            i = getConstant(index, ConstantModule.class).getNameIndex();
385            break;
386        case Const.CONSTANT_Package:
387            i = getConstant(index, ConstantPackage.class).getNameIndex();
388            break;
389        case Const.CONSTANT_Utf8:
390            return getConstantUtf8(index).getBytes();
391        default:
392            throw new IllegalArgumentException("getConstantString called with illegal tag " + tag);
393        }
394        // Finally get the string from the constant pool
395        return getConstantUtf8(i).getBytes();
396    }
397
398    /**
399     * Gets constant from constant pool and check whether it has the expected type.
400     *
401     * @param index Index in constant pool.
402     * @return ConstantUtf8 value.
403     * @throws ClassFormatException if constant type does not match tag.
404     * @see ConstantUtf8
405     */
406    public ConstantUtf8 getConstantUtf8(final int index) throws ClassFormatException {
407        return getConstant(index, Const.CONSTANT_Utf8, ConstantUtf8.class);
408    }
409
410    /**
411     * Gets the length of constant pool.
412     *
413     * @return Length of constant pool.
414     */
415    public int getLength() {
416        return constantPool.length;
417    }
418
419    @Override
420    public Iterator<Constant> iterator() {
421        return Arrays.stream(constantPool).iterator();
422    }
423
424    /**
425     * Sets a constant at the specified index.
426     *
427     * @param index the index in the constant pool.
428     * @param constant Constant to set.
429     */
430    public void setConstant(final int index, final Constant constant) {
431        constantPool[index] = constant;
432    }
433
434    /**
435     * Sets the constant pool.
436     *
437     * @param constantPool the constant pool array.
438     */
439    public void setConstantPool(final Constant[] constantPool) {
440        this.constantPool = constantPool != null ? constantPool : Constant.EMPTY_ARRAY;
441    }
442
443    /**
444     * @return String representation.
445     */
446    @Override
447    public String toString() {
448        final StringBuilder buf = new StringBuilder();
449        for (int i = 1; i < constantPool.length; i++) {
450            buf.append(i).append(")").append(constantPool[i]).append("\n");
451        }
452        return buf.toString();
453    }
454}