View Javadoc

1   /*
2    * Copyright  2000-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License"); 
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License. 
15   *
16   */
17  package org.apache.bcel.generic;
18  
19  import java.io.DataOutputStream;
20  import java.io.IOException;
21  import org.apache.bcel.classfile.Constant;
22  import org.apache.bcel.classfile.ConstantClass;
23  import org.apache.bcel.classfile.ConstantPool;
24  import org.apache.bcel.util.ByteSequence;
25  
26  /*** 
27   * Abstract super class for instructions that use an index into the 
28   * constant pool such as LDC, INVOKEVIRTUAL, etc.
29   *
30   * @see ConstantPoolGen
31   * @see LDC
32   * @see INVOKEVIRTUAL
33   *
34   * @version $Id: CPInstruction.java 386056 2006-03-15 11:31:56Z tcurdt $
35   * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
36   */
37  public abstract class CPInstruction extends Instruction implements TypedInstruction,
38          IndexedInstruction {
39  
40      protected int index; // index to constant pool
41  
42  
43      /***
44       * Empty constructor needed for the Class.newInstance() statement in
45       * Instruction.readInstruction(). Not to be used otherwise.
46       */
47      CPInstruction() {
48      }
49  
50  
51      /***
52       * @param index to constant pool
53       */
54      protected CPInstruction(short opcode, int index) {
55          super(opcode, (short) 3);
56          setIndex(index);
57      }
58  
59  
60      /***
61       * Dump instruction as byte code to stream out.
62       * @param out Output stream
63       */
64      public void dump( DataOutputStream out ) throws IOException {
65          out.writeByte(opcode);
66          out.writeShort(index);
67      }
68  
69  
70      /***
71       * Long output format:
72       *
73       * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]" 
74       * "("&lt;length of instruction&gt;")" "&lt;"&lt; constant pool index&gt;"&gt;"
75       *
76       * @param verbose long/short format switch
77       * @return mnemonic for instruction
78       */
79      public String toString( boolean verbose ) {
80          return super.toString(verbose) + " " + index;
81      }
82  
83  
84      /***
85       * @return mnemonic for instruction with symbolic references resolved
86       */
87      public String toString( ConstantPool cp ) {
88          Constant c = cp.getConstant(index);
89          String str = cp.constantToString(c);
90          if (c instanceof ConstantClass) {
91              str = str.replace('.', '/');
92          }
93          return org.apache.bcel.Constants.OPCODE_NAMES[opcode] + " " + str;
94      }
95  
96  
97      /***
98       * Read needed data (i.e., index) from file.
99       * @param bytes input stream
100      * @param wide wide prefix?
101      */
102     protected void initFromFile( ByteSequence bytes, boolean wide ) throws IOException {
103         setIndex(bytes.readUnsignedShort());
104         length = 3;
105     }
106 
107 
108     /***
109      * @return index in constant pool referred by this instruction.
110      */
111     public final int getIndex() {
112         return index;
113     }
114 
115 
116     /***
117      * Set the index to constant pool.
118      * @param index in  constant pool.
119      */
120     public void setIndex( int index ) {
121         if (index < 0) {
122             throw new ClassGenException("Negative index value: " + index);
123         }
124         this.index = index;
125     }
126 
127 
128     /*** @return type related with this instruction.
129      */
130     public Type getType( ConstantPoolGen cpg ) {
131         ConstantPool cp = cpg.getConstantPool();
132         String name = cp.getConstantString(index, org.apache.bcel.Constants.CONSTANT_Class);
133         if (!name.startsWith("[")) {
134             name = "L" + name + ";";
135         }
136         return Type.getType(name);
137     }
138 }