    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.bcel.generic;
    020
    021import java.io.DataOutputStream;
    022import java.io.IOException;
    023
    024import org.apache.bcel.ExceptionConst;
    025import org.apache.bcel.util.ByteSequence;
    026
    027/**
    028 * LDC - Push item from constant pool.
    029 *
    030 * <PRE>
    031 * Stack: ... -&gt; ..., item
    032 * </PRE>
    033 */
    034public class LDC extends CPInstruction implements PushInstruction, ExceptionThrower {
    035
    036    /**
    037     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
    038     */
    039    LDC() {
    040    }
    041
    042    public LDC(final int index) {
    043        super(org.apache.bcel.Const.LDC_W, index);
    044        setSize();
    045    }
    046
    047    /**
    048     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
    049     * methods according to the class hierarchy in descending order, that is, the most specific visitXXX() call comes last.
    050     *
    051     * @param v Visitor object.
    052     */
    053    @Override
    054    public void accept(final Visitor v) {
    055        v.visitStackProducer(this);
    056        v.visitPushInstruction(this);
    057        v.visitExceptionThrower(this);
    058        v.visitTypedInstruction(this);
    059        v.visitCPInstruction(this);
    060        v.visitLDC(this);
    061    }
    062
    063    /**
    064     * Dumps instruction as byte code to stream out.
    065     *
    066     * @param out Output stream.
    067     */
    068    @Override
    069    public void dump(final DataOutputStream out) throws IOException {
    070        out.writeByte(super.getOpcode());
    071        if (super.getLength() == 2) { // TODO useless check?
    072            out.writeByte(super.getIndex());
    073        } else {
    074            out.writeShort(super.getIndex());
    075        }
    076    }
    077
    078    @Override
    079    public Class<?>[] getExceptions() {
    080        return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_STRING_RESOLUTION);
    081    }
    082
    083    @Override
    084    public Type getType(final ConstantPoolGen cpg) {
    085        switch (cpg.getConstantPool().getConstant(super.getIndex()).getTag()) {
    086        case org.apache.bcel.Const.CONSTANT_String:
    087            return Type.STRING;
    088        case org.apache.bcel.Const.CONSTANT_Float:
    089            return Type.FLOAT;
    090        case org.apache.bcel.Const.CONSTANT_Integer:
    091            return Type.INT;
    092        case org.apache.bcel.Const.CONSTANT_Class:
    093            return Type.CLASS;
    094        case org.apache.bcel.Const.CONSTANT_Dynamic:
    095            return Type.OBJECT;
    096        default: // Never reached
    097            throw new IllegalArgumentException("Unknown or invalid constant type at " + super.getIndex());
    098        }
    099    }
    100
    101    public Object getValue(final ConstantPoolGen cpg) {
    102        org.apache.bcel.classfile.Constant c = cpg.getConstantPool().getConstant(super.getIndex());
    103        switch (c.getTag()) {
    104        case org.apache.bcel.Const.CONSTANT_String:
    105            final int i = ((org.apache.bcel.classfile.ConstantString) c).getStringIndex();
    106            c = cpg.getConstantPool().getConstant(i);
    107            return ((org.apache.bcel.classfile.ConstantUtf8) c).getBytes();
    108        case org.apache.bcel.Const.CONSTANT_Float:
    109            return Float.valueOf(((org.apache.bcel.classfile.ConstantFloat) c).getBytes());
    110        case org.apache.bcel.Const.CONSTANT_Integer:
    111            return Integer.valueOf(((org.apache.bcel.classfile.ConstantInteger) c).getBytes());
    112        case org.apache.bcel.Const.CONSTANT_Class:
    113            final int nameIndex = ((org.apache.bcel.classfile.ConstantClass) c).getNameIndex();
    114            c = cpg.getConstantPool().getConstant(nameIndex);
    115            return Type.getType(Type.internalTypeNameToSignature(((org.apache.bcel.classfile.ConstantUtf8) c).getBytes()));
    116        case org.apache.bcel.Const.CONSTANT_Dynamic:
    117            // Really not sure what to return here, maybe a BootstrapMethod instance but how do we get it?
    118            return c;
    119        default: // Never reached
    120            throw new IllegalArgumentException("Unknown or invalid constant type at " + super.getIndex());
    121        }
    122    }
    123
    124    /**
    125     * Reads needed data (for example index) from file.
    126     */
    127    @Override
    128    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
    129        super.setLength(2);
    130        super.setIndex(bytes.readUnsignedByte());
    131    }
    132
    133    /**
    134     * Sets the index to constant pool and adjust size.
    135     */
    136    @Override
    137    public final void setIndex(final int index) {
    138        super.setIndex(index);
    139        setSize();
    140    }
    141
    142    // Adjust to proper size
    143    protected final void setSize() {
    144        if (super.getIndex() <= org.apache.bcel.Const.MAX_BYTE) { // Fits in one byte?
    145            super.setOpcode(org.apache.bcel.Const.LDC);
    146            super.setLength(2);
    147        } else {
    148            super.setOpcode(org.apache.bcel.Const.LDC_W);
    149            super.setLength(3);
    150        }
    151    }
    152}