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;
023
024import org.apache.bcel.Const;
025
026/**
027 * This class represents the constant pool, i.e., a table of constants, of
028 * a parsed classfile. It may contain null references, due to the JVM
029 * specification that skips an entry after an 8-byte constant (double,
030 * long) entry.  Those interested in generating constant pools
031 * programatically should see <a href="../generic/ConstantPoolGen.html">
032 * ConstantPoolGen</a>.
033
034 * @version $Id: ConstantPool.java 1749603 2016-06-21 20:50:19Z ggregory $
035 * @see     Constant
036 * @see     org.apache.bcel.generic.ConstantPoolGen
037 */
038public class ConstantPool implements Cloneable, Node {
039
040    private Constant[] constant_pool;
041
042
043    /**
044     * @param constant_pool Array of constants
045     */
046    public ConstantPool(final Constant[] constant_pool) {
047        this.constant_pool = constant_pool;
048    }
049
050
051    /**
052     * Read constants from given input stream.
053     *
054     * @param input Input stream
055     * @throws IOException
056     * @throws ClassFormatException
057     */
058    public ConstantPool(final DataInput input) throws IOException, ClassFormatException {
059        byte tag;
060        final int constant_pool_count = input.readUnsignedShort();
061        constant_pool = new Constant[constant_pool_count];
062        /* constant_pool[0] is unused by the compiler and may be used freely
063         * by the implementation.
064         */
065        for (int i = 1; i < constant_pool_count; i++) {
066            constant_pool[i] = Constant.readConstant(input);
067            /* Quote from the JVM specification:
068             * "All eight byte constants take up two spots in the constant pool.
069             * If this is the n'th byte in the constant pool, then the next item
070             * will be numbered n+2"
071             * 
072             * Thus we have to increment the index counter.
073             */
074            tag = constant_pool[i].getTag();
075            if ((tag == Const.CONSTANT_Double) || (tag == Const.CONSTANT_Long)) {
076                i++;
077            }
078        }
079    }
080
081
082    /**
083     * Called by objects that are traversing the nodes of the tree implicitely
084     * defined by the contents of a Java class. I.e., the hierarchy of methods,
085     * fields, attributes, etc. spawns a tree of objects.
086     *
087     * @param v Visitor object
088     */
089    @Override
090    public void accept( final Visitor v ) {
091        v.visitConstantPool(this);
092    }
093
094
095    /**
096     * Resolve constant to a string representation.
097     *
098     * @param  c Constant to be printed
099     * @return String representation
100     */
101    public String constantToString( Constant c ) throws ClassFormatException {
102        String str;
103        int i;
104        final byte tag = c.getTag();
105        switch (tag) {
106            case Const.CONSTANT_Class:
107                i = ((ConstantClass) c).getNameIndex();
108                c = getConstant(i, Const.CONSTANT_Utf8);
109                str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
110                break;
111            case Const.CONSTANT_String:
112                i = ((ConstantString) c).getStringIndex();
113                c = getConstant(i, Const.CONSTANT_Utf8);
114                str = "\"" + escape(((ConstantUtf8) c).getBytes()) + "\"";
115                break;
116            case Const.CONSTANT_Utf8:
117                str = ((ConstantUtf8) c).getBytes();
118                break;
119            case Const.CONSTANT_Double:
120                str = String.valueOf(((ConstantDouble) c).getBytes());
121                break;
122            case Const.CONSTANT_Float:
123                str = String.valueOf(((ConstantFloat) c).getBytes());
124                break;
125            case Const.CONSTANT_Long:
126                str = String.valueOf(((ConstantLong) c).getBytes());
127                break;
128            case Const.CONSTANT_Integer:
129                str = String.valueOf(((ConstantInteger) c).getBytes());
130                break;
131            case Const.CONSTANT_NameAndType:
132                str = constantToString(((ConstantNameAndType) c).getNameIndex(),
133                        Const.CONSTANT_Utf8)
134                        + ":" + constantToString(((ConstantNameAndType) c).getSignatureIndex(),
135                        Const.CONSTANT_Utf8);
136                break;
137            case Const.CONSTANT_InterfaceMethodref:
138            case Const.CONSTANT_Methodref:
139            case Const.CONSTANT_Fieldref:
140                str = constantToString(((ConstantCP) c).getClassIndex(), Const.CONSTANT_Class)
141                        + "." + constantToString(((ConstantCP) c).getNameAndTypeIndex(),
142                        Const.CONSTANT_NameAndType);
143                break;
144            case Const.CONSTANT_MethodHandle:
145                // Note that the ReferenceIndex may point to a Fieldref, Methodref or
146                // InterfaceMethodref - so we need to peek ahead to get the actual type.
147                final ConstantMethodHandle cmh = (ConstantMethodHandle) c;
148                str = Const.getMethodHandleName(cmh.getReferenceKind())
149                        + " " + constantToString(cmh.getReferenceIndex(),
150                        getConstant(cmh.getReferenceIndex()).getTag());
151                break;            
152            case Const.CONSTANT_MethodType:
153                final ConstantMethodType cmt = (ConstantMethodType) c;
154                str = constantToString(cmt.getDescriptorIndex(), Const.CONSTANT_Utf8);
155                break;
156            case Const.CONSTANT_InvokeDynamic:
157                final ConstantInvokeDynamic cid = (ConstantInvokeDynamic) c;
158                str = cid.getBootstrapMethodAttrIndex()
159                        + ":" + constantToString(cid.getNameAndTypeIndex(),
160                        Const.CONSTANT_NameAndType);
161                break;
162            default: // Never reached
163                throw new RuntimeException("Unknown constant type " + tag);
164        }
165        return str;
166    }
167
168
169    private static String escape( final String str ) {
170        final int len = str.length();
171        final StringBuilder buf = new StringBuilder(len + 5);
172        final char[] ch = str.toCharArray();
173        for (int i = 0; i < len; i++) {
174            switch (ch[i]) {
175                case '\n':
176                    buf.append("\\n");
177                    break;
178                case '\r':
179                    buf.append("\\r");
180                    break;
181                case '\t':
182                    buf.append("\\t");
183                    break;
184                case '\b':
185                    buf.append("\\b");
186                    break;
187                case '"':
188                    buf.append("\\\"");
189                    break;
190                default:
191                    buf.append(ch[i]);
192            }
193        }
194        return buf.toString();
195    }
196
197
198    /**
199     * Retrieve constant at `index' from constant pool and resolve it to
200     * a string representation.
201     *
202     * @param  index of constant in constant pool
203     * @param  tag expected type
204     * @return String representation
205     */
206    public String constantToString( final int index, final byte tag ) throws ClassFormatException {
207        final Constant c = getConstant(index, tag);
208        return constantToString(c);
209    }
210
211
212    /** 
213     * Dump constant pool to file stream in binary format.
214     *
215     * @param file Output file stream
216     * @throws IOException
217     */
218    public void dump( final DataOutputStream file ) throws IOException {
219        file.writeShort(constant_pool.length);
220        for (int i = 1; i < constant_pool.length; i++) {
221            if (constant_pool[i] != null) {
222                constant_pool[i].dump(file);
223            }
224        }
225    }
226
227
228    /**
229     * Get constant from constant pool.
230     *
231     * @param  index Index in constant pool
232     * @return Constant value
233     * @see    Constant
234     */
235    public Constant getConstant( final int index ) {
236        if (index >= constant_pool.length || index < 0) {
237            throw new ClassFormatException("Invalid constant pool reference: " + index
238                    + ". Constant pool size is: " + constant_pool.length);
239        }
240        return constant_pool[index];
241    }
242
243
244    /**
245     * Get constant from constant pool and check whether it has the
246     * expected type.
247     *
248     * @param  index Index in constant pool
249     * @param  tag Tag of expected constant, i.e., its type
250     * @return Constant value
251     * @see    Constant
252     * @throws  ClassFormatException
253     */
254    public Constant getConstant( final int index, final byte tag ) throws ClassFormatException {
255        Constant c;
256        c = getConstant(index);
257        if (c == null) {
258            throw new ClassFormatException("Constant pool at index " + index + " is null.");
259        }
260        if (c.getTag() != tag) {
261            throw new ClassFormatException("Expected class `" + Const.getConstantName(tag)
262                    + "' at index " + index + " and got " + c);
263        }
264        return c;
265    }
266
267
268    /**
269     * @return Array of constants.
270     * @see    Constant
271     */
272    public Constant[] getConstantPool() {
273        return constant_pool;
274    }
275
276
277    /**
278     * Get string from constant pool and bypass the indirection of 
279     * `ConstantClass' and `ConstantString' objects. I.e. these classes have
280     * an index field that points to another entry of the constant pool of
281     * type `ConstantUtf8' which contains the real data.
282     *
283     * @param  index Index in constant pool
284     * @param  tag Tag of expected constant, either ConstantClass or ConstantString
285     * @return Contents of string reference
286     * @see    ConstantClass
287     * @see    ConstantString
288     * @throws  ClassFormatException
289     */
290    public String getConstantString( final int index, final byte tag ) throws ClassFormatException {
291        Constant c;
292        int i;
293        c = getConstant(index, tag);
294        /* This switch() is not that elegant, since the two classes have the
295         * same contents, they just differ in the name of the index
296         * field variable.
297         * But we want to stick to the JVM naming conventions closely though
298         * we could have solved these more elegantly by using the same
299         * variable name or by subclassing.
300         */
301        switch (tag) {
302            case Const.CONSTANT_Class:
303                i = ((ConstantClass) c).getNameIndex();
304                break;
305            case Const.CONSTANT_String:
306                i = ((ConstantString) c).getStringIndex();
307                break;
308            default:
309                throw new RuntimeException("getConstantString called with illegal tag " + tag);
310        }
311        // Finally get the string from the constant pool
312        c = getConstant(i, Const.CONSTANT_Utf8);
313        return ((ConstantUtf8) c).getBytes();
314    }
315
316
317    /**
318     * @return Length of constant pool.
319     */
320    public int getLength() {
321        return constant_pool == null ? 0 : constant_pool.length;
322    }
323
324
325    /**
326     * @param constant Constant to set
327     */
328    public void setConstant( final int index, final Constant constant ) {
329        constant_pool[index] = constant;
330    }
331
332
333    /**
334     * @param constant_pool
335     */
336    public void setConstantPool( final Constant[] constant_pool ) {
337        this.constant_pool = constant_pool;
338    }
339
340
341    /**
342     * @return String representation.
343     */
344    @Override
345    public String toString() {
346        final StringBuilder buf = new StringBuilder();
347        for (int i = 1; i < constant_pool.length; i++) {
348            buf.append(i).append(")").append(constant_pool[i]).append("\n");
349        }
350        return buf.toString();
351    }
352
353
354    /**
355     * @return deep copy of this constant pool
356     */
357    public ConstantPool copy() {
358        ConstantPool c = null;
359        try {
360            c = (ConstantPool) clone();
361            c.constant_pool = new Constant[constant_pool.length];
362            for (int i = 1; i < constant_pool.length; i++) {
363                if (constant_pool[i] != null) {
364                    c.constant_pool[i] = constant_pool[i].copy();
365                }
366            }
367        } catch (final CloneNotSupportedException e) {
368            // TODO should this throw?
369        }
370        return c;
371    }
372}