src/test/java/org/apache/bcel/data/ConstantPoolX.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.bcel.data;

/*
 * This file is a modified copy of org.apache.bcel.classfile.ConstantPool.java.
 * It was chosen as it generates both tableswitch and lookupswitch byte codes.
 * It has been modified to compile stand alone within the BCEL test environment.
 * The code is not executed but the classfile is used as input to a BCEL test case.
 */

import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.bcel.Const;
import org.apache.bcel.classfile.ClassFormatException;
import org.apache.bcel.classfile.Constant;
import org.apache.bcel.classfile.ConstantCP;
import org.apache.bcel.classfile.ConstantClass;
import org.apache.bcel.classfile.ConstantDouble;
import org.apache.bcel.classfile.ConstantFloat;
import org.apache.bcel.classfile.ConstantInteger;
import org.apache.bcel.classfile.ConstantInvokeDynamic;
import org.apache.bcel.classfile.ConstantLong;
import org.apache.bcel.classfile.ConstantMethodHandle;
import org.apache.bcel.classfile.ConstantMethodType;
import org.apache.bcel.classfile.ConstantModule;
import org.apache.bcel.classfile.ConstantNameAndType;
import org.apache.bcel.classfile.ConstantPackage;
import org.apache.bcel.classfile.ConstantString;
import org.apache.bcel.classfile.ConstantUtf8;
import org.apache.bcel.classfile.Node;
import org.apache.bcel.classfile.Utility;

/**
 * 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 skips an entry after an 8-byte constant (double, long) entry. Those
 * interested in generating constant pools programatically should see <a href="../generic/ConstantPoolGen.html">
 * ConstantPoolGen</a>.
 *
 * @see Constant
 * @see org.apache.bcel.generic.ConstantPoolGen
 */
public abstract class ConstantPoolX implements Cloneable, Node {

    private static String escape(final String str) {
        final int len = str.length();
        final StringBuilder buf = new StringBuilder(len + 5);
        final char[] ch = str.toCharArray();
        for (int i = 0; i < len; i++) {
            switch (ch[i]) {
            case '\n':
                buf.append("\\n");
                break;
            case '\r':
                buf.append("\\r");
                break;
            case '\t':
                buf.append("\\t");
                break;
            case '\b':
                buf.append("\\b");
                break;
            case '"':
                buf.append("\\\"");
                break;
            default:
                buf.append(ch[i]);
            }
        }
        return buf.toString();
    }

    private Constant[] constantPool;

    /**
     * Resolves constant to a string representation.
     *
     * @param c Constant to be printed.
     * @return String representation.
     */
    public String constantToString(Constant c) throws ClassFormatException {
        final String str;
        final int i;
        final byte tag = c.getTag();
        switch (tag) {
        case Const.CONSTANT_Class:
            i = ((ConstantClass) c).getNameIndex();
            c = getConstant(i, Const.CONSTANT_Utf8);
            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
            break;
        case Const.CONSTANT_String:
            i = ((ConstantString) c).getStringIndex();
            c = getConstant(i, Const.CONSTANT_Utf8);
            str = "\"" + escape(((ConstantUtf8) c).getBytes()) + "\"";
            break;
        case Const.CONSTANT_Utf8:
            str = ((ConstantUtf8) c).getBytes();
            break;
        case Const.CONSTANT_Double:
            str = String.valueOf(((ConstantDouble) c).getBytes());
            break;
        case Const.CONSTANT_Float:
            str = String.valueOf(((ConstantFloat) c).getBytes());
            break;
        case Const.CONSTANT_Long:
            str = String.valueOf(((ConstantLong) c).getBytes());
            break;
        case Const.CONSTANT_Integer:
            str = String.valueOf(((ConstantInteger) c).getBytes());
            break;
        case Const.CONSTANT_NameAndType:
            str = constantToString(((ConstantNameAndType) c).getNameIndex(), Const.CONSTANT_Utf8) + " "
                + constantToString(((ConstantNameAndType) c).getSignatureIndex(), Const.CONSTANT_Utf8);
            break;
        case Const.CONSTANT_InterfaceMethodref:
        case Const.CONSTANT_Methodref:
        case Const.CONSTANT_Fieldref:
            str = constantToString(((ConstantCP) c).getClassIndex(), Const.CONSTANT_Class) + "."
                + constantToString(((ConstantCP) c).getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
            break;
        case Const.CONSTANT_MethodHandle:
            // Note that the ReferenceIndex may point to a Fieldref, Methodref or
            // InterfaceMethodref - so we need to peek ahead to get the actual type.
            final ConstantMethodHandle cmh = (ConstantMethodHandle) c;
            str = Const.getMethodHandleName(cmh.getReferenceKind()) + " "
                + constantToString(cmh.getReferenceIndex(), getConstant(cmh.getReferenceIndex()).getTag());
            break;
        case Const.CONSTANT_MethodType:
            final ConstantMethodType cmt = (ConstantMethodType) c;
            str = constantToString(cmt.getDescriptorIndex(), Const.CONSTANT_Utf8);
            break;
        case Const.CONSTANT_InvokeDynamic:
            final ConstantInvokeDynamic cid = (ConstantInvokeDynamic) c;
            str = cid.getBootstrapMethodAttrIndex() + ":" + constantToString(cid.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
            break;
        case Const.CONSTANT_Module:
            i = ((ConstantModule) c).getNameIndex();
            c = getConstant(i, Const.CONSTANT_Utf8);
            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
            break;
        case Const.CONSTANT_Package:
            i = ((ConstantPackage) c).getNameIndex();
            c = getConstant(i, Const.CONSTANT_Utf8);
            str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
            break;
        default: // Never reached
            throw new IllegalArgumentException("Unknown constant type " + tag);
        }
        return str;
    }

    /**
     * Retrieves constant at 'index' from constant pool and resolve it to a string representation.
     *
     * @param index of constant in constant pool.
     * @param tag expected type.
     * @return String representation.
     */
    public String constantToString(final int index, final byte tag) throws ClassFormatException {
        final Constant c = getConstant(index, tag);
        return constantToString(c);
    }

    /**
     * Dumps constant pool to file stream in binary format.
     *
     * @param file Output file stream.
     * @throws IOException if an I/O error occurs.
     */
    public void dump(final DataOutputStream file) throws IOException {
        file.writeShort(constantPool.length);
        for (int i = 1; i < constantPool.length; i++) {
            if (constantPool[i] != null) {
                constantPool[i].dump(file);
            }
        }
    }

    /**
     * Gets constant from constant pool.
     *
     * @param index Index in constant pool.
     * @return Constant value.
     * @see Constant
     */
    public Constant getConstant(final int index) {
        if (index >= constantPool.length || index < 0) {
            throw new ClassFormatException("Invalid constant pool reference: " + index + ". Constant pool size is: " + constantPool.length);
        }
        return constantPool[index];
    }

    /**
     * Gets constant from constant pool and check whether it has the expected type.
     *
     * @param index Index in constant pool.
     * @param tag Tag of expected constant, that is, its type.
     * @return Constant value.
     * @see Constant
     * @throws ClassFormatException
     */
    public Constant getConstant(final int index, final byte tag) throws ClassFormatException {
        final Constant c = getConstant(index);
        if (c == null) {
            throw new ClassFormatException("Constant pool at index " + index + " is null.");
        }
        if (c.getTag() != tag) {
            throw new ClassFormatException("Expected class '" + Const.getConstantName(tag) + "' at index " + index + " and got " + c);
        }
        return c;
    }

    /**
     * @return Array of constants.
     * @see Constant
     */
    public Constant[] getConstantPool() {
        return constantPool;
    }

    /**
     * Gets string from constant pool and bypass the indirection of 'ConstantClass' and 'ConstantString' objects. I.e. these
     * classes have an index field that points to another entry of the constant pool of type 'ConstantUtf8' which contains
     * the real data.
     *
     * @param index Index in constant pool.
     * @param tag Tag of expected constant, either ConstantClass or ConstantString.
     * @return Contents of string reference.
     * @see ConstantClass
     * @see ConstantString
     * @throws ClassFormatException
     */
    public String getConstantString(final int index, final byte tag) throws ClassFormatException {
        final int i;
        Constant c = getConstant(index, tag);
        /*
         * 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 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 subclassing.
         */
        switch (tag) {
        case Const.CONSTANT_Class:
            i = ((ConstantClass) c).getNameIndex();
            break;
        case Const.CONSTANT_String:
            i = ((ConstantString) c).getStringIndex();
            break;
        case Const.CONSTANT_Module:
            i = ((ConstantModule) c).getNameIndex();
            break;
        case Const.CONSTANT_Package:
            i = ((ConstantPackage) c).getNameIndex();
            break;
        default:
            throw new IllegalArgumentException("getConstantString called with illegal tag " + tag);
        }
        // Finally get the string from the constant pool
        c = getConstant(i, Const.CONSTANT_Utf8);
        return ((ConstantUtf8) c).getBytes();
    }

    /**
     * @return Length of constant pool.
     */
    public int getLength() {
        return constantPool == null ? 0 : constantPool.length;
    }

    /**
     * @param constant Constant to set.
     */
    public void setConstant(final int index, final Constant constant) {
        constantPool[index] = constant;
    }

    /**
     * @param constantPool.
     */
    public void setConstantPool(final Constant[] constantPool) {
        this.constantPool = constantPool;
    }

    /**
     * @return String representation.
     */
    @Override
    public String toString() {
        final StringBuilder buf = new StringBuilder();
        for (int i = 1; i < constantPool.length; i++) {
            buf.append(i).append(")").append(constantPool[i]).append("\n");
        }
        return buf.toString();
    }

}