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.generic; 019 020import java.io.DataOutputStream; 021import java.io.IOException; 022 023import org.apache.bcel.ExceptionConst; 024import org.apache.bcel.util.ByteSequence; 025 026/** 027 * LDC - Push item from constant pool. 028 * 029 * <PRE> 030 * Stack: ... -> ..., item 031 * </PRE> 032 * 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, i.e., 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 * Dump 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 default: // Never reached 095 throw new IllegalArgumentException("Unknown or invalid constant type at " + super.getIndex()); 096 } 097 } 098 099 public Object getValue(final ConstantPoolGen cpg) { 100 org.apache.bcel.classfile.Constant c = cpg.getConstantPool().getConstant(super.getIndex()); 101 switch (c.getTag()) { 102 case org.apache.bcel.Const.CONSTANT_String: 103 final int i = ((org.apache.bcel.classfile.ConstantString) c).getStringIndex(); 104 c = cpg.getConstantPool().getConstant(i); 105 return ((org.apache.bcel.classfile.ConstantUtf8) c).getBytes(); 106 case org.apache.bcel.Const.CONSTANT_Float: 107 return Float.valueOf(((org.apache.bcel.classfile.ConstantFloat) c).getBytes()); 108 case org.apache.bcel.Const.CONSTANT_Integer: 109 return Integer.valueOf(((org.apache.bcel.classfile.ConstantInteger) c).getBytes()); 110 case org.apache.bcel.Const.CONSTANT_Class: 111 final int nameIndex = ((org.apache.bcel.classfile.ConstantClass) c).getNameIndex(); 112 c = cpg.getConstantPool().getConstant(nameIndex); 113 return new ObjectType(((org.apache.bcel.classfile.ConstantUtf8) c).getBytes()); 114 default: // Never reached 115 throw new IllegalArgumentException("Unknown or invalid constant type at " + super.getIndex()); 116 } 117 } 118 119 /** 120 * Read needed data (e.g. index) from file. 121 */ 122 @Override 123 protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException { 124 super.setLength(2); 125 super.setIndex(bytes.readUnsignedByte()); 126 } 127 128 /** 129 * Set the index to constant pool and adjust size. 130 */ 131 @Override 132 public final void setIndex(final int index) { 133 super.setIndex(index); 134 setSize(); 135 } 136 137 // Adjust to proper size 138 protected final void setSize() { 139 if (super.getIndex() <= org.apache.bcel.Const.MAX_BYTE) { // Fits in one byte? 140 super.setOpcode(org.apache.bcel.Const.LDC); 141 super.setLength(2); 142 } else { 143 super.setOpcode(org.apache.bcel.Const.LDC_W); 144 super.setLength(3); 145 } 146 } 147}