    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        setConstantPool(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         * constantPool[0] is currently unused by the implementation.
    087         */
    088        for (int i = 1; i < constantPoolCount; 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 == null || 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 <T> A {@link Constant} subclass
    296     * @param index Index in constant pool
    297     * @param castTo The {@link Constant} subclass to cast to.
    298     * @return Constant value
    299     * @see Constant
    300     * @throws ClassFormatException if index is invalid
    301     * @since 6.6.0
    302     */
    303    public <T extends Constant> T getConstant(final int index, final Class<T> castTo) throws ClassFormatException {
    304        if (index >= constantPool.length || index < 1) {
    305            throw new ClassFormatException("Invalid constant pool reference using index: " + index + ". Constant pool size is: " + constantPool.length);
    306        }
    307        if (constantPool[index] != null && !castTo.isAssignableFrom(constantPool[index].getClass())) {
    308            throw new ClassFormatException("Invalid constant pool reference at index: " + index +
    309                    ". Expected " + castTo + " but was " + constantPool[index].getClass());
    310        }
    311        if (index > 1) {
    312            final Constant prev = constantPool[index - 1];
    313            if (prev != null && (prev.getTag() == Const.CONSTANT_Double || prev.getTag() == Const.CONSTANT_Long)) {
    314                throw new ClassFormatException("Constant pool at index " + index + " is invalid. The index is unused due to the preceeding "
    315                        + Const.getConstantName(prev.getTag()) + ".");
    316            }
    317        }
    318        // Previous check ensures this won't throw a ClassCastException
    319        final T c = castTo.cast(constantPool[index]);
    320        if (c == null) {
    321            throw new ClassFormatException("Constant pool at index " + index + " is null.");
    322        }
    323        return c;
    324    }
    325
    326    /**
    327     * Gets constant from constant pool and check whether it has the expected type.
    328     *
    329     * @param index Index in constant pool
    330     * @return ConstantInteger value
    331     * @see ConstantInteger
    332     * @throws ClassFormatException if constant type does not match tag
    333     */
    334    public ConstantInteger getConstantInteger(final int index) {
    335        return getConstant(index, Const.CONSTANT_Integer, ConstantInteger.class);
    336    }
    337
    338    /**
    339     * @return Array of constants.
    340     * @see Constant
    341     */
    342    public Constant[] getConstantPool() {
    343        return constantPool;
    344    }
    345
    346    /**
    347     * Gets string from constant pool and bypass the indirection of 'ConstantClass' and 'ConstantString' objects. I.e. these classes have an index field that
    348     * points to another entry of the constant pool of type 'ConstantUtf8' which contains the real data.
    349     *
    350     * @param index Index in constant pool
    351     * @param tag   Tag of expected constant, either ConstantClass or ConstantString
    352     * @return Contents of string reference
    353     * @see ConstantClass
    354     * @see ConstantString
    355     * @throws IllegalArgumentException if tag is invalid
    356     */
    357    public String getConstantString(final int index, final byte tag) throws IllegalArgumentException {
    358        int i;
    359        /*
    360         * 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
    361         * 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
    362         * subclassing.
    363         */
    364        switch (tag) {
    365        case Const.CONSTANT_Class:
    366            i = getConstant(index, ConstantClass.class).getNameIndex();
    367            break;
    368        case Const.CONSTANT_String:
    369            i = getConstant(index, ConstantString.class).getStringIndex();
    370            break;
    371        case Const.CONSTANT_Module:
    372            i = getConstant(index, ConstantModule.class).getNameIndex();
    373            break;
    374        case Const.CONSTANT_Package:
    375            i = getConstant(index, ConstantPackage.class).getNameIndex();
    376            break;
    377        case Const.CONSTANT_Utf8:
    378            return getConstantUtf8(index).getBytes();
    379        default:
    380            throw new IllegalArgumentException("getConstantString called with illegal tag " + tag);
    381        }
    382        // Finally get the string from the constant pool
    383        return getConstantUtf8(i).getBytes();
    384    }
    385
    386    /**
    387     * Gets constant from constant pool and check whether it has the expected type.
    388     *
    389     * @param index Index in constant pool
    390     * @return ConstantUtf8 value
    391     * @see ConstantUtf8
    392     * @throws ClassFormatException if constant type does not match tag
    393     */
    394    public ConstantUtf8 getConstantUtf8(final int index) throws ClassFormatException {
    395        return getConstant(index, Const.CONSTANT_Utf8, ConstantUtf8.class);
    396    }
    397
    398    /**
    399     * @return Length of constant pool.
    400     */
    401    public int getLength() {
    402        return constantPool.length;
    403    }
    404
    405    @Override
    406    public Iterator<Constant> iterator() {
    407        return Arrays.stream(constantPool).iterator();
    408    }
    409
    410    /**
    411     * @param constant Constant to set
    412     */
    413    public void setConstant(final int index, final Constant constant) {
    414        constantPool[index] = constant;
    415    }
    416
    417    /**
    418     * @param constantPool
    419     */
    420    public void setConstantPool(final Constant[] constantPool) {
    421        this.constantPool = constantPool != null ? constantPool : Constant.EMPTY_ARRAY;
    422    }
    423
    424    /**
    425     * @return String representation.
    426     */
    427    @Override
    428    public String toString() {
    429        final StringBuilder buf = new StringBuilder();
    430        for (int i = 1; i < constantPool.length; i++) {
    431            buf.append(i).append(")").append(constantPool[i]).append("\n");
    432        }
    433        return buf.toString();
    434    }
    435}