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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 $Id$
     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 }
    140