1 /*
2 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
3 */
4 /*
5 * Licensed to the Apache Software Foundation (ASF) under one or more
6 * contributor license agreements. See the NOTICE file distributed with
7 * this work for additional information regarding copyright ownership.
8 * The ASF licenses this file to You under the Apache License, Version 2.0
9 * (the "License"); you may not use this file except in compliance with
10 * the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20
21 package com.sun.org.apache.bcel.internal.generic;
22
23 import java.io.*;
24 import com.sun.org.apache.bcel.internal.util.ByteSequence;
25
26 /**
27 * LDC - Push item from constant pool.
28 *
29 * <PRE>Stack: ... -> ..., item</PRE>
30 *
31 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
32 */
33 public class LDC extends CPInstruction
34 implements PushInstruction, ExceptionThrower, TypedInstruction {
35 /**
36 * Empty constructor needed for the Class.newInstance() statement in
37 * Instruction.readInstruction(). Not to be used otherwise.
38 */
39 LDC() {}
40
41 public LDC(int index) {
42 super(com.sun.org.apache.bcel.internal.Constants.LDC_W, index);
43 setSize();
44 }
45
46 // Adjust to proper size
47 protected final void setSize() {
48 if(index <= com.sun.org.apache.bcel.internal.Constants.MAX_BYTE) { // Fits in one byte?
49 opcode = com.sun.org.apache.bcel.internal.Constants.LDC;
50 length = 2;
51 } else {
52 opcode = com.sun.org.apache.bcel.internal.Constants.LDC_W;
53 length = 3;
54 }
55 }
56
57 /**
58 * Dump instruction as byte code to stream out.
59 * @param out Output stream
60 */
61 public void dump(DataOutputStream out) throws IOException {
62 out.writeByte(opcode);
63
64 if(length == 2)
65 out.writeByte(index);
66 else // Applies for LDC_W
67 out.writeShort(index);
68 }
69
70 /**
71 * Set the index to constant pool and adjust size.
72 */
73 public final void setIndex(int index) {
74 super.setIndex(index);
75 setSize();
76 }
77
78 /**
79 * Read needed data (e.g. index) from file.
80 */
81 protected void initFromFile(ByteSequence bytes, boolean wide)
82 throws IOException
83 {
84 length = 2;
85 index = bytes.readUnsignedByte();
86 }
87
88 public Object getValue(ConstantPoolGen cpg) {
89 com.sun.org.apache.bcel.internal.classfile.Constant c = cpg.getConstantPool().getConstant(index);
90
91 switch(c.getTag()) {
92 case com.sun.org.apache.bcel.internal.Constants.CONSTANT_String:
93 int i = ((com.sun.org.apache.bcel.internal.classfile.ConstantString)c).getStringIndex();
94 c = cpg.getConstantPool().getConstant(i);
95 return ((com.sun.org.apache.bcel.internal.classfile.ConstantUtf8)c).getBytes();
96
97 case com.sun.org.apache.bcel.internal.Constants.CONSTANT_Float:
98 return Float.valueOf(((com.sun.org.apache.bcel.internal.classfile.ConstantFloat)c).getBytes());
99
100 case com.sun.org.apache.bcel.internal.Constants.CONSTANT_Integer:
101 return Integer.valueOf(((com.sun.org.apache.bcel.internal.classfile.ConstantInteger)c).getBytes());
102
103 default: // Never reached
104 throw new RuntimeException("Unknown or invalid constant type at " + index);
105 }
106 }
107
108 public Type getType(ConstantPoolGen cpg) {
109 switch(cpg.getConstantPool().getConstant(index).getTag()) {
110 case com.sun.org.apache.bcel.internal.Constants.CONSTANT_String: return Type.STRING;
111 case com.sun.org.apache.bcel.internal.Constants.CONSTANT_Float: return Type.FLOAT;
112 case com.sun.org.apache.bcel.internal.Constants.CONSTANT_Integer: return Type.INT;
113 default: // Never reached
114 throw new RuntimeException("Unknown or invalid constant type at " + index);
115 }
116 }
117
118 public Class[] getExceptions() {
119 return com.sun.org.apache.bcel.internal.ExceptionConstants.EXCS_STRING_RESOLUTION;
120 }
121
122 /**
123 * Call corresponding visitor method(s). The order is:
124 * Call visitor methods of implemented interfaces first, then
125 * call methods according to the class hierarchy in descending order,
126 * i.e., the most specific visitXXX() call comes last.
127 *
128 * @param v Visitor object
129 */
130 public void accept(Visitor v) {
131 v.visitStackProducer(this);
132 v.visitPushInstruction(this);
133 v.visitExceptionThrower(this);
134 v.visitTypedInstruction(this);
135 v.visitCPInstruction(this);
136 v.visitLDC(this);
137 }
138 }