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