    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 */
    017package org.apache.bcel.generic;
    018
    019import java.io.DataOutputStream;
    020import java.io.IOException;
    021
    022import org.apache.bcel.Const;
    023import org.apache.bcel.ExceptionConst;
    024import org.apache.bcel.classfile.ConstantPool;
    025import org.apache.bcel.util.ByteSequence;
    026
    027/**
    028 * INVOKEINTERFACE - Invoke interface method
    029 *
    030 * <PRE>
    031 * Stack: ..., objectref, [arg1, [arg2 ...]] -&gt; ...
    032 * </PRE>
    033 *
    034 * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-6.html#jvms-6.5.invokeinterface"> The
    035 *      invokeinterface instruction in The Java Virtual Machine Specification</a>
    036 */
    037public final class INVOKEINTERFACE extends InvokeInstruction {
    038
    039    private int nargs; // Number of arguments on stack (number of stack slots), called "count" in vmspec2
    040
    041    /**
    042     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
    043     */
    044    INVOKEINTERFACE() {
    045    }
    046
    047    public INVOKEINTERFACE(final int index, final int nargs) {
    048        super(Const.INVOKEINTERFACE, index);
    049        super.setLength(5);
    050        if (nargs < 1) {
    051            throw new ClassGenException("Number of arguments must be > 0 " + nargs);
    052        }
    053        this.nargs = nargs;
    054    }
    055
    056    /**
    057     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
    058     * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last.
    059     *
    060     * @param v Visitor object
    061     */
    062    @Override
    063    public void accept(final Visitor v) {
    064        v.visitExceptionThrower(this);
    065        v.visitTypedInstruction(this);
    066        v.visitStackConsumer(this);
    067        v.visitStackProducer(this);
    068        v.visitLoadClass(this);
    069        v.visitCPInstruction(this);
    070        v.visitFieldOrMethod(this);
    071        v.visitInvokeInstruction(this);
    072        v.visitINVOKEINTERFACE(this);
    073    }
    074
    075    @Override
    076    public int consumeStack(final ConstantPoolGen cpg) { // nargs is given in byte-code
    077        return nargs; // nargs includes this reference
    078    }
    079
    080    /**
    081     * Dump instruction as byte code to stream out.
    082     *
    083     * @param out Output stream
    084     */
    085    @Override
    086    public void dump(final DataOutputStream out) throws IOException {
    087        out.writeByte(super.getOpcode());
    088        out.writeShort(super.getIndex());
    089        out.writeByte(nargs);
    090        out.writeByte(0);
    091    }
    092
    093    /**
    094     * The <B>count</B> argument according to the Java Language Specification, Second Edition.
    095     */
    096    public int getCount() {
    097        return nargs;
    098    }
    099
    100    @Override
    101    public Class<?>[] getExceptions() {
    102        return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_INTERFACE_METHOD_RESOLUTION, ExceptionConst.UNSATISFIED_LINK_ERROR,
    103            ExceptionConst.ABSTRACT_METHOD_ERROR, ExceptionConst.ILLEGAL_ACCESS_ERROR, ExceptionConst.INCOMPATIBLE_CLASS_CHANGE_ERROR);
    104    }
    105
    106    /**
    107     * Read needed data (i.e., index) from file.
    108     */
    109    @Override
    110    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
    111        super.initFromFile(bytes, wide);
    112        super.setLength(5);
    113        nargs = bytes.readUnsignedByte();
    114        bytes.readByte(); // Skip 0 byte
    115    }
    116
    117    /**
    118     * @return mnemonic for instruction with symbolic references resolved
    119     */
    120    @Override
    121    public String toString(final ConstantPool cp) {
    122        return super.toString(cp) + " " + nargs;
    123    }
    124}