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 * @see     Constant
035 * @see     org.apache.bcel.generic.ConstantPoolGen
036 */
037public class ConstantPool implements Cloneable, Node {
038
039    private Constant[] constant_pool;
040
041    /**
042     * @param constant_pool Array of constants
043     */
044    public ConstantPool(final Constant[] constant_pool) {
045        this.constant_pool = constant_pool;
046    }
047
048    /**
049     * Reads constants from given input stream.
050     *
051     * @param input Input stream
052     * @throws IOException
053     * @throws ClassFormatException
054     */
055    public ConstantPool(final DataInput input) throws IOException, ClassFormatException {
056        byte tag;
057        final int constant_pool_count = input.readUnsignedShort();
058        constant_pool = new Constant[constant_pool_count];
059        /* constant_pool[0] is unused by the compiler and may be used freely
060         * by the implementation.
061         */
062        for (int i = 1; i < constant_pool_count; i++) {
063            constant_pool[i] = Constant.readConstant(input);
064            /* Quote from the JVM specification:
065             * "All eight byte constants take up two spots in the constant pool.
066             * If this is the n'th byte in the constant pool, then the next item
067             * will be numbered n+2"
068             *
069             * Thus we have to increment the index counter.
070             */
071            tag = constant_pool[i].getTag();
072            if ((tag == Const.CONSTANT_Double) || (tag == Const.CONSTANT_Long)) {
073                i++;
074            }
075        }
076    }
077
078    /**
079     * Called by objects that are traversing the nodes of the tree implicitely
080     * defined by the contents of a Java class. I.e., the hierarchy of methods,
081     * fields, attributes, etc. spawns a tree of objects.
082     *
083     * @param v Visitor object
084     */
085    @Override
086    public void accept( final Visitor v ) {
087        v.visitConstantPool(this);
088    }
089
090    /**
091     * Resolves constant to a string representation.
092     *
093     * @param  c Constant to be printed
094     * @return String representation
095     */
096    public String constantToString( Constant c ) throws ClassFormatException {
097        String str;
098        int i;
099        final byte tag = c.getTag();
100        switch (tag) {
101            case Const.CONSTANT_Class:
102                i = ((ConstantClass) c).getNameIndex();
103                c = getConstant(i, Const.CONSTANT_Utf8);
104                str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
105                break;
106            case Const.CONSTANT_String:
107                i = ((ConstantString) c).getStringIndex();
108                c = getConstant(i, Const.CONSTANT_Utf8);
109                str = "\"" + escape(((ConstantUtf8) c).getBytes()) + "\"";
110                break;
111            case Const.CONSTANT_Utf8:
112                str = ((ConstantUtf8) c).getBytes();
113                break;
114            case Const.CONSTANT_Double:
115                str = String.valueOf(((ConstantDouble) c).getBytes());
116                break;
117            case Const.CONSTANT_Float:
118                str = String.valueOf(((ConstantFloat) c).getBytes());
119                break;
120            case Const.CONSTANT_Long:
121                str = String.valueOf(((ConstantLong) c).getBytes());
122                break;
123            case Const.CONSTANT_Integer:
124                str = String.valueOf(((ConstantInteger) c).getBytes());
125                break;
126            case Const.CONSTANT_NameAndType:
127                str = constantToString(((ConstantNameAndType) c).getNameIndex(),
128                        Const.CONSTANT_Utf8)
129                        + " " + constantToString(((ConstantNameAndType) c).getSignatureIndex(),
130                        Const.CONSTANT_Utf8);
131                break;
132            case Const.CONSTANT_InterfaceMethodref:
133            case Const.CONSTANT_Methodref:
134            case Const.CONSTANT_Fieldref:
135                str = constantToString(((ConstantCP) c).getClassIndex(), Const.CONSTANT_Class)
136                        + "." + constantToString(((ConstantCP) c).getNameAndTypeIndex(),
137                        Const.CONSTANT_NameAndType);
138                break;
139            case Const.CONSTANT_MethodHandle:
140                // Note that the ReferenceIndex may point to a Fieldref, Methodref or
141                // InterfaceMethodref - so we need to peek ahead to get the actual type.
142                final ConstantMethodHandle cmh = (ConstantMethodHandle) c;
143                str = Const.getMethodHandleName(cmh.getReferenceKind())
144                        + " " + constantToString(cmh.getReferenceIndex(),
145                        getConstant(cmh.getReferenceIndex()).getTag());
146                break;
147            case Const.CONSTANT_MethodType:
148                final ConstantMethodType cmt = (ConstantMethodType) c;
149                str = constantToString(cmt.getDescriptorIndex(), Const.CONSTANT_Utf8);
150                break;
151            case Const.CONSTANT_InvokeDynamic:
152                final ConstantInvokeDynamic cid = (ConstantInvokeDynamic) c;
153                str = cid.getBootstrapMethodAttrIndex()
154                        + ":" + constantToString(cid.getNameAndTypeIndex(),
155                        Const.CONSTANT_NameAndType);
156                break;
157            case Const.CONSTANT_Module:
158                i = ((ConstantModule) c).getNameIndex();
159                c = getConstant(i, Const.CONSTANT_Utf8);
160                str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
161                break;
162            case Const.CONSTANT_Package:
163                i = ((ConstantPackage) c).getNameIndex();
164                c = getConstant(i, Const.CONSTANT_Utf8);
165                str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
166                break;
167            default: // Never reached
168                throw new RuntimeException("Unknown constant type " + tag);
169        }
170        return str;
171    }
172
173    private static String escape( final String str ) {
174        final int len = str.length();
175        final StringBuilder buf = new StringBuilder(len + 5);
176        final char[] ch = str.toCharArray();
177        for (int i = 0; i < len; i++) {
178            switch (ch[i]) {
179                case '\n':
180                    buf.append("\\n");
181                    break;
182                case '\r':
183                    buf.append("\\r");
184                    break;
185                case '\t':
186                    buf.append("\\t");
187                    break;
188                case '\b':
189                    buf.append("\\b");
190                    break;
191                case '"':
192                    buf.append("\\\"");
193                    break;
194                default:
195                    buf.append(ch[i]);
196            }
197        }
198        return buf.toString();
199    }
200
201    /**
202     * Retrieves constant at `index' from constant pool and resolve it to
203     * a string representation.
204     *
205     * @param  index of constant in constant pool
206     * @param  tag expected type
207     * @return String representation
208     */
209    public String constantToString( final int index, final byte tag ) throws ClassFormatException {
210        final Constant c = getConstant(index, tag);
211        return constantToString(c);
212    }
213
214    /**
215     * Dump constant pool to file stream in binary format.
216     *
217     * @param file Output file stream
218     * @throws IOException
219     */
220    public void dump( final DataOutputStream file ) throws IOException {
221        file.writeShort(constant_pool.length);
222        for (int i = 1; i < constant_pool.length; i++) {
223            if (constant_pool[i] != null) {
224                constant_pool[i].dump(file);
225            }
226        }
227    }
228
229    /**
230     * Gets constant from constant pool.
231     *
232     * @param  index Index in constant pool
233     * @return Constant value
234     * @see    Constant
235     */
236    public Constant getConstant( final int index ) {
237        if (index >= constant_pool.length || index < 0) {
238            throw new ClassFormatException("Invalid constant pool reference: " + index
239                    + ". Constant pool size is: " + constant_pool.length);
240        }
241        return constant_pool[index];
242    }
243
244    /**
245     * Gets 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     * @return Array of constants.
269     * @see    Constant
270     */
271    public Constant[] getConstantPool() {
272        return constant_pool;
273    }
274
275    /**
276     * Gets string from constant pool and bypass the indirection of
277     * `ConstantClass' and `ConstantString' objects. I.e. these classes have
278     * an index field that points to another entry of the constant pool of
279     * type `ConstantUtf8' which contains the real data.
280     *
281     * @param  index Index in constant pool
282     * @param  tag Tag of expected constant, either ConstantClass or ConstantString
283     * @return Contents of string reference
284     * @see    ConstantClass
285     * @see    ConstantString
286     * @throws  ClassFormatException
287     */
288    public String getConstantString( final int index, final byte tag ) throws ClassFormatException {
289        Constant c;
290        int i;
291        c = getConstant(index, tag);
292        /* This switch() is not that elegant, since the four classes have the
293         * same contents, they just differ in the name of the index
294         * field variable.
295         * But we want to stick to the JVM naming conventions closely though
296         * we could have solved these more elegantly by using the same
297         * variable name or by subclassing.
298         */
299        switch (tag) {
300            case Const.CONSTANT_Class:
301                i = ((ConstantClass) c).getNameIndex();
302                break;
303            case Const.CONSTANT_String:
304                i = ((ConstantString) c).getStringIndex();
305                break;
306            case Const.CONSTANT_Module:
307                i = ((ConstantModule) c).getNameIndex();
308                break;
309            case Const.CONSTANT_Package:
310                i = ((ConstantPackage) c).getNameIndex();
311                break;
312            default:
313                throw new RuntimeException("getConstantString called with illegal tag " + tag);
314        }
315        // Finally get the string from the constant pool
316        c = getConstant(i, Const.CONSTANT_Utf8);
317        return ((ConstantUtf8) c).getBytes();
318    }
319
320
321    /**
322     * @return Length of constant pool.
323     */
324    public int getLength() {
325        return constant_pool == null ? 0 : constant_pool.length;
326    }
327
328
329    /**
330     * @param constant Constant to set
331     */
332    public void setConstant( final int index, final Constant constant ) {
333        constant_pool[index] = constant;
334    }
335
336
337    /**
338     * @param constant_pool
339     */
340    public void setConstantPool( final Constant[] constant_pool ) {
341        this.constant_pool = constant_pool;
342    }
343
344
345    /**
346     * @return String representation.
347     */
348    @Override
349    public String toString() {
350        final StringBuilder buf = new StringBuilder();
351        for (int i = 1; i < constant_pool.length; i++) {
352            buf.append(i).append(")").append(constant_pool[i]).append("\n");
353        }
354        return buf.toString();
355    }
356
357
358    /**
359     * @return deep copy of this constant pool
360     */
361    public ConstantPool copy() {
362        ConstantPool c = null;
363        try {
364            c = (ConstantPool) clone();
365            c.constant_pool = new Constant[constant_pool.length];
366            for (int i = 1; i < constant_pool.length; i++) {
367                if (constant_pool[i] != null) {
368                    c.constant_pool[i] = constant_pool[i].copy();
369                }
370            }
371        } catch (final CloneNotSupportedException e) {
372            // TODO should this throw?
373        }
374        return c;
375    }
376}