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.util.ByteSequence;
026
027/**
028 * RET - Return from subroutine
029 *
030 * <pre>
031 * Stack: ... -&gt; ...
032 * </pre>
033 */
034public class RET extends Instruction implements IndexedInstruction, TypedInstruction {
035
036    private boolean wide;
037    private int index; // index to local variable containing the return address
038
039    /**
040     * Default constructor needed for Instruction.readInstruction. Not to be used otherwise.
041     */
042    RET() {
043    }
044
045    /**
046     * Constructs a RET instruction.
047     *
048     * @param index index of local variable containing the return address.
049     */
050    public RET(final int index) {
051        super(Const.RET, (short) 2);
052        setIndex(index); // May set wide as side effect
053    }
054
055    /**
056     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
057     * methods according to the class hierarchy in descending order, that is, the most specific visitXXX() call comes last.
058     *
059     * @param v Visitor object.
060     */
061    @Override
062    public void accept(final Visitor v) {
063        v.visitRET(this);
064    }
065
066    /**
067     * Dumps instruction as byte code to stream out.
068     *
069     * @param out Output stream.
070     */
071    @Override
072    public void dump(final DataOutputStream out) throws IOException {
073        if (wide) {
074            out.writeByte(Const.WIDE);
075        }
076        out.writeByte(super.getOpcode());
077        if (wide) {
078            out.writeShort(index);
079        } else {
080            out.writeByte(index);
081        }
082    }
083
084    /**
085     * Gets the index of the local variable containing the return address.
086     *
087     * @return index of local variable containing the return address.
088     */
089    @Override
090    public final int getIndex() {
091        return index;
092    }
093
094    /**
095     * Gets the return address type.
096     *
097     * @return return address type.
098     */
099    @Override
100    public Type getType(final ConstantPoolGen cp) {
101        return ReturnaddressType.NO_TARGET;
102    }
103
104    /**
105     * Reads needed data (for example index) from file.
106     */
107    @Override
108    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
109        this.wide = wide;
110        if (wide) {
111            index = bytes.readUnsignedShort();
112            super.setLength(4);
113        } else {
114            index = bytes.readUnsignedByte();
115            super.setLength(2);
116        }
117    }
118
119    /**
120     * Sets the index of the local variable containing the return address.
121     *
122     * @param index index of local variable containing the return address.
123     * @throws ClassGenException Thrown if index is out of bounds.
124     */
125    @Override
126    public final void setIndex(final int index) {
127        if (!isNonNegativeUShort(index)) {
128            throw new ClassGenException("Illegal value: " + index);
129        }
130        this.index = index;
131        setWide();
132    }
133
134    private void setWide() {
135        wide = index > Const.MAX_BYTE;
136        if (wide) {
137            super.setLength(4); // Including the wide byte
138        } else {
139            super.setLength(2);
140        }
141    }
142
143    /**
144     * @return mnemonic for instruction.
145     */
146    @Override
147    public String toString(final boolean verbose) {
148        return super.toString(verbose) + " " + index;
149    }
150}