    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.bcel.generic;
    020
    021import java.io.DataOutputStream;
    022import java.io.IOException;
    023
    024import org.apache.bcel.Const;
    025import org.apache.bcel.ExceptionConst;
    026import org.apache.bcel.classfile.ConstantPool;
    027import org.apache.bcel.util.ByteSequence;
    028
    029/**
    030 * INVOKEINTERFACE - Invoke interface method
    031 *
    032 * <PRE>
    033 * Stack: ..., objectref, [arg1, [arg2 ...]] -&gt; ...
    034 * </PRE>
    035 *
    036 * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-6.html#jvms-6.5.invokeinterface"> The
    037 *      invokeinterface instruction in The Java Virtual Machine Specification</a>
    038 */
    039public final class INVOKEINTERFACE extends InvokeInstruction {
    040
    041    private int nargs; // Number of arguments on stack (number of stack slots), called "count" in vmspec2
    042
    043    /**
    044     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
    045     */
    046    INVOKEINTERFACE() {
    047    }
    048
    049    public INVOKEINTERFACE(final int index, final int nargs) {
    050        super(Const.INVOKEINTERFACE, index);
    051        super.setLength(5);
    052        if (nargs < 1) {
    053            throw new ClassGenException("Number of arguments must be > 0 " + nargs);
    054        }
    055        this.nargs = nargs;
    056    }
    057
    058    /**
    059     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
    060     * methods according to the class hierarchy in descending order, that is, the most specific visitXXX() call comes last.
    061     *
    062     * @param v Visitor object.
    063     */
    064    @Override
    065    public void accept(final Visitor v) {
    066        v.visitExceptionThrower(this);
    067        v.visitTypedInstruction(this);
    068        v.visitStackConsumer(this);
    069        v.visitStackProducer(this);
    070        v.visitLoadClass(this);
    071        v.visitCPInstruction(this);
    072        v.visitFieldOrMethod(this);
    073        v.visitInvokeInstruction(this);
    074        v.visitINVOKEINTERFACE(this);
    075    }
    076
    077    @Override
    078    public int consumeStack(final ConstantPoolGen cpg) { // nargs is given in byte-code
    079        return nargs; // nargs includes this reference
    080    }
    081
    082    /**
    083     * Dumps instruction as byte code to stream out.
    084     *
    085     * @param out Output stream.
    086     */
    087    @Override
    088    public void dump(final DataOutputStream out) throws IOException {
    089        out.writeByte(super.getOpcode());
    090        out.writeShort(super.getIndex());
    091        out.writeByte(nargs);
    092        out.writeByte(0);
    093    }
    094
    095    /**
    096     * The <strong>count</strong> argument according to the Java Language Specification, Second Edition.
    097     */
    098    public int getCount() {
    099        return nargs;
    100    }
    101
    102    @Override
    103    public Class<?>[] getExceptions() {
    104        return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_INTERFACE_METHOD_RESOLUTION, ExceptionConst.UNSATISFIED_LINK_ERROR,
    105            ExceptionConst.ABSTRACT_METHOD_ERROR, ExceptionConst.ILLEGAL_ACCESS_ERROR, ExceptionConst.INCOMPATIBLE_CLASS_CHANGE_ERROR);
    106    }
    107
    108    /**
    109     * Reads needed data (that is, index) from file.
    110     */
    111    @Override
    112    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
    113        super.initFromFile(bytes, wide);
    114        super.setLength(5);
    115        nargs = bytes.readUnsignedByte();
    116        bytes.readByte(); // Skip 0 byte
    117    }
    118
    119    /**
    120     * @return mnemonic for instruction with symbolic references resolved.
    121     */
    122    @Override
    123    public String toString(final ConstantPool cp) {
    124        return super.toString(cp) + " " + nargs;
    125    }
    126}