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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   *
17   */
18  package org.apache.bcel.generic;
19  
20  import java.io.DataOutputStream;
21  import java.io.IOException;
22  
23  import org.apache.bcel.Const;
24  import org.apache.bcel.ExceptionConst;
25  import org.apache.bcel.classfile.ConstantPool;
26  import org.apache.bcel.util.ByteSequence;
27  
28  /**
29   * INVOKEINTERFACE - Invoke interface method
30   * <PRE>Stack: ..., objectref, [arg1, [arg2 ...]] -&gt; ...</PRE>
31   *
32   * @version $Id: INVOKEINTERFACE.html 1021978 2017-12-09 17:38:21Z ggregory $
33   * @see
34   * <a href="http://docs.oracle.com/javase/specs/jvms/se8/html/jvms-6.html#jvms-6.5.invokeinterface">
35   * The invokeinterface instruction in The Java Virtual Machine Specification</a>
36   */
37  public final class INVOKEINTERFACE extends InvokeInstruction {
38  
39      private int nargs; // Number of arguments on stack (number of stack slots), called "count" in vmspec2
40  
41  
42      /**
43       * Empty constructor needed for Instruction.readInstruction.
44       * Not to be used otherwise.
45       */
46      INVOKEINTERFACE() {
47      }
48  
49  
50      public INVOKEINTERFACE(final int index, final int nargs) {
51          super(Const.INVOKEINTERFACE, index);
52          super.setLength(5);
53          if (nargs < 1) {
54              throw new ClassGenException("Number of arguments must be > 0 " + nargs);
55          }
56          this.nargs = nargs;
57      }
58  
59  
60      /**
61       * Dump instruction as byte code to stream out.
62       * @param out Output stream
63       */
64      @Override
65      public void dump( final DataOutputStream out ) throws IOException {
66          out.writeByte(super.getOpcode());
67          out.writeShort(super.getIndex());
68          out.writeByte(nargs);
69          out.writeByte(0);
70      }
71  
72  
73      /**
74       * The <B>count</B> argument according to the Java Language Specification,
75       * Second Edition.
76       */
77      public int getCount() {
78          return nargs;
79      }
80  
81  
82      /**
83       * Read needed data (i.e., index) from file.
84       */
85      @Override
86      protected void initFromFile( final ByteSequence bytes, final boolean wide ) throws IOException {
87          super.initFromFile(bytes, wide);
88          super.setLength(5);
89          nargs = bytes.readUnsignedByte();
90          bytes.readByte(); // Skip 0 byte
91      }
92  
93  
94      /**
95       * @return mnemonic for instruction with symbolic references resolved
96       */
97      @Override
98      public String toString( final ConstantPool cp ) {
99          return super.toString(cp) + " " + nargs;
100     }
101 
102 
103     @Override
104     public int consumeStack( final ConstantPoolGen cpg ) { // nargs is given in byte-code
105         return nargs; // nargs includes this reference
106     }
107 
108 
109     @Override
110     public Class<?>[] getExceptions() {
111         return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_INTERFACE_METHOD_RESOLUTION,
112             ExceptionConst.UNSATISFIED_LINK_ERROR,
113             ExceptionConst.ABSTRACT_METHOD_ERROR,
114             ExceptionConst.ILLEGAL_ACCESS_ERROR,
115             ExceptionConst.INCOMPATIBLE_CLASS_CHANGE_ERROR);
116     }
117 
118 
119     /**
120      * Call corresponding visitor method(s). The order is:
121      * Call visitor methods of implemented interfaces first, then
122      * call methods according to the class hierarchy in descending order,
123      * i.e., the most specific visitXXX() call comes last.
124      *
125      * @param v Visitor object
126      */
127     @Override
128     public void accept( final Visitor v ) {
129         v.visitExceptionThrower(this);
130         v.visitTypedInstruction(this);
131         v.visitStackConsumer(this);
132         v.visitStackProducer(this);
133         v.visitLoadClass(this);
134         v.visitCPInstruction(this);
135         v.visitFieldOrMethod(this);
136         v.visitInvokeInstruction(this);
137         v.visitINVOKEINTERFACE(this);
138     }
139 }