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    1   package org.apache.bcel.generic;
    2
    3   /* ====================================================================
    4    * The Apache Software License, Version 1.1
    5    *
    6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
    7    * reserved.
    8    *
    9    * Redistribution and use in source and binary forms, with or without
    10   * modification, are permitted provided that the following conditions
    11   * are met:
    12   *
    13   * 1. Redistributions of source code must retain the above copyright
    14   *    notice, this list of conditions and the following disclaimer.
    15   *
    16   * 2. Redistributions in binary form must reproduce the above copyright
    17   *    notice, this list of conditions and the following disclaimer in
    18   *    the documentation and/or other materials provided with the
    19   *    distribution.
    20   *
    21   * 3. The end-user documentation included with the redistribution,
    22   *    if any, must include the following acknowledgment:
    23   *       "This product includes software developed by the
    24   *        Apache Software Foundation (http://www.apache.org/)."
    25   *    Alternately, this acknowledgment may appear in the software itself,
    26   *    if and wherever such third-party acknowledgments normally appear.
    27   *
    28   * 4. The names "Apache" and "Apache Software Foundation" and
    29   *    "Apache BCEL" must not be used to endorse or promote products
    30   *    derived from this software without prior written permission. For
    31   *    written permission, please contact apache@apache.org.
    32   *
    33   * 5. Products derived from this software may not be called "Apache",
    34   *    "Apache BCEL", nor may "Apache" appear in their name, without
    35   *    prior written permission of the Apache Software Foundation.
    36   *
    37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
    41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    42   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    44   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    48   * SUCH DAMAGE.
    49   * ====================================================================
    50   *
    51   * This software consists of voluntary contributions made by many
    52   * individuals on behalf of the Apache Software Foundation.  For more
    53   * information on the Apache Software Foundation, please see
    54   * <http://www.apache.org/>;.
    55   */
    56  import java.io.*;
    57  import org.apache.bcel.util.ByteSequence;
    58
    59  /***
    60   * LDC - Push item from constant pool.
    61   *
    62   * <PRE>Stack: ... -> ..., item</PRE>
    63   *
    64   * @version $Id: LDC.java,v 1.1.1.1 2001/10/29 20:00:21 jvanzyl Exp $
    65   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
    66   */
    67  public class LDC extends CPInstruction
    68    implements PushInstruction, ExceptionThrower, TypedInstruction {
    69    /***
    70     * Empty constructor needed for the Class.newInstance() statement in
    71     * Instruction.readInstruction(). Not to be used otherwise.
    72     */
    73    LDC() {}
    74
    75    public LDC(int index) {
    76      super(org.apache.bcel.Constants.LDC_W, index);
    77      setSize();
    78    }
    79
    80    // Adjust to proper size
    81    protected final void setSize() {
    82      if(index <= org.apache.bcel.Constants.MAX_BYTE) { // Fits in one byte?
    83        opcode = org.apache.bcel.Constants.LDC;
    84        length = 2;
    85      } else {
    86        opcode = org.apache.bcel.Constants.LDC_W;
    87        length = 3;
    88      }
    89    }
    90
    91    /***
    92     * Dump instruction as byte code to stream out.
    93     * @param out Output stream
    94     */
    95    public void dump(DataOutputStream out) throws IOException {
    96      out.writeByte(opcode);
    97
    98      if(length == 2)
    99        out.writeByte(index);
    100     else // Applies for LDC_W
    101       out.writeShort(index);
    102   }
    103
    104   /***
    105    * Set the index to constant pool and adjust size.
    106    */
    107   public final void setIndex(int index) {
    108     super.setIndex(index);
    109     setSize();
    110   }
    111
    112   /***
    113    * Read needed data (e.g. index) from file.
    114    */
    115   protected void initFromFile(ByteSequence bytes, boolean wide)
    116        throws IOException
    117   {
    118     length = 2;
    119     index  = bytes.readUnsignedByte();
    120   }
    121
    122   public Object getValue(ConstantPoolGen cpg) {
    123     org.apache.bcel.classfile.Constant c = cpg.getConstantPool().getConstant(index);
    124
    125     switch(c.getTag()) {
    126       case org.apache.bcel.Constants.CONSTANT_String:
    127 	int i = ((org.apache.bcel.classfile.ConstantString)c).getStringIndex();
    128 	c = cpg.getConstantPool().getConstant(i);
    129 	return ((org.apache.bcel.classfile.ConstantUtf8)c).getBytes();
    130
    131     case org.apache.bcel.Constants.CONSTANT_Float:
    132 	return new Float(((org.apache.bcel.classfile.ConstantFloat)c).getBytes());
    133
    134     case org.apache.bcel.Constants.CONSTANT_Integer:
    135 	return new Integer(((org.apache.bcel.classfile.ConstantInteger)c).getBytes());
    136
    137     default: // Never reached
    138       throw new RuntimeException("Unknown or invalid constant type at " + index);
    139       }
    140   }
    141
    142   public Type getType(ConstantPoolGen cpg) {
    143     switch(cpg.getConstantPool().getConstant(index).getTag()) {
    144     case org.apache.bcel.Constants.CONSTANT_String:  return Type.STRING;
    145     case org.apache.bcel.Constants.CONSTANT_Float:   return Type.FLOAT;
    146     case org.apache.bcel.Constants.CONSTANT_Integer: return Type.INT;
    147     default: // Never reached
    148       throw new RuntimeException("Unknown or invalid constant type at " + index);
    149     }
    150   }
    151
    152   public Class[] getExceptions() {
    153     return org.apache.bcel.ExceptionConstants.EXCS_STRING_RESOLUTION;
    154   }
    155
    156   /***
    157    * Call corresponding visitor method(s). The order is:
    158    * Call visitor methods of implemented interfaces first, then
    159    * call methods according to the class hierarchy in descending order,
    160    * i.e., the most specific visitXXX() call comes last.
    161    *
    162    * @param v Visitor object
    163    */
    164   public void accept(Visitor v) {
    165     v.visitStackProducer(this);
    166     v.visitPushInstruction(this);
    167     v.visitExceptionThrower(this);
    168     v.visitTypedInstruction(this);
    169     v.visitCPInstruction(this);
    170     v.visitLDC(this);
    171   }
    172 }

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