    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 *
    017 */
    018package org.apache.bcel.generic;
    019
    020import java.io.DataOutputStream;
    021import java.io.IOException;
    022
    023import org.apache.bcel.Const;
    024import org.apache.bcel.util.ByteSequence;
    025
    026/**
    027 * Abstract super class for instructions dealing with local variables.
    028 *
    029 * @version $Id$
    030 */
    031public abstract class LocalVariableInstruction extends Instruction implements TypedInstruction,
    032        IndexedInstruction {
    033
    034    /**
    035     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
    036     */
    037    @Deprecated
    038    protected int n = -1; // index of referenced variable
    039
    040    private short c_tag = -1; // compact version, such as ILOAD_0
    041    private short canon_tag = -1; // canonical tag such as ILOAD
    042
    043
    044    private boolean wide() {
    045        return n > Const.MAX_BYTE;
    046    }
    047
    048
    049    /**
    050     * Empty constructor needed for Instruction.readInstruction.
    051     * Not to be used otherwise.
    052     * tag and length are defined in readInstruction and initFromFile, respectively.
    053     */
    054    LocalVariableInstruction(final short canon_tag, final short c_tag) {
    055        super();
    056        this.canon_tag = canon_tag;
    057        this.c_tag = c_tag;
    058    }
    059
    060
    061    /**
    062     * Empty constructor needed for Instruction.readInstruction.
    063     * Also used by IINC()!
    064     */
    065    LocalVariableInstruction() {
    066    }
    067
    068
    069    /**
    070     * @param opcode Instruction opcode
    071     * @param c_tag Instruction number for compact version, ALOAD_0, e.g.
    072     * @param n local variable index (unsigned short)
    073     */
    074    protected LocalVariableInstruction(final short opcode, final short c_tag, final int n) {
    075        super(opcode, (short) 2);
    076        this.c_tag = c_tag;
    077        canon_tag = opcode;
    078        setIndex(n);
    079    }
    080
    081
    082    /**
    083     * Dump instruction as byte code to stream out.
    084     * @param out Output stream
    085     */
    086    @Override
    087    public void dump( final DataOutputStream out ) throws IOException {
    088        if (wide()) {
    089            out.writeByte(Const.WIDE);
    090        }
    091        out.writeByte(super.getOpcode());
    092        if (super.getLength() > 1) { // Otherwise ILOAD_n, instruction, e.g.
    093            if (wide()) {
    094                out.writeShort(n);
    095            } else {
    096                out.writeByte(n);
    097            }
    098        }
    099    }
    100
    101
    102    /**
    103     * Long output format:
    104     *
    105     * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]"
    106     * "("&lt;length of instruction&gt;")" "&lt;"&lt; local variable index&gt;"&gt;"
    107     *
    108     * @param verbose long/short format switch
    109     * @return mnemonic for instruction
    110     */
    111    @Override
    112    public String toString( final boolean verbose ) {
    113        final short _opcode = super.getOpcode();
    114        if (((_opcode >= Const.ILOAD_0) && (_opcode <= Const.ALOAD_3))
    115         || ((_opcode >= Const.ISTORE_0) && (_opcode <= Const.ASTORE_3))) {
    116            return super.toString(verbose);
    117        }
    118        return super.toString(verbose) + " " + n;
    119    }
    120
    121
    122    /**
    123     * Read needed data (e.g. index) from file.
    124     * <pre>
    125     * (ILOAD &lt;= tag &lt;= ALOAD_3) || (ISTORE &lt;= tag &lt;= ASTORE_3)
    126     * </pre>
    127     */
    128    @Override
    129    protected void initFromFile( final ByteSequence bytes, final boolean wide ) throws IOException {
    130        if (wide) {
    131            n = bytes.readUnsignedShort();
    132            super.setLength(4);
    133        } else {
    134            final short _opcode = super.getOpcode();
    135            if (((_opcode >= Const.ILOAD) && (_opcode <= Const.ALOAD))
    136             || ((_opcode >= Const.ISTORE) && (_opcode <= Const.ASTORE))) {
    137                n = bytes.readUnsignedByte();
    138                super.setLength(2);
    139            } else if (_opcode <= Const.ALOAD_3) { // compact load instruction such as ILOAD_2
    140                n = (_opcode - Const.ILOAD_0) % 4;
    141                super.setLength(1);
    142            } else { // Assert ISTORE_0 <= tag <= ASTORE_3
    143                n = (_opcode - Const.ISTORE_0) % 4;
    144                super.setLength(1);
    145            }
    146        }
    147    }
    148
    149
    150    /**
    151     * @return local variable index (n) referred by this instruction.
    152     */
    153    @Override
    154    public final int getIndex() {
    155        return n;
    156    }
    157
    158
    159    /**
    160     * Set the local variable index.
    161     * also updates opcode and length
    162     * TODO Why?
    163     * @see #setIndexOnly(int)
    164     */
    165    @Override
    166    public void setIndex( final int n ) { // TODO could be package-protected?
    167        if ((n < 0) || (n > Const.MAX_SHORT)) {
    168            throw new ClassGenException("Illegal value: " + n);
    169        }
    170        this.n = n;
    171        // Cannot be < 0 as this is checked above
    172        if (n <= 3) { // Use more compact instruction xLOAD_n
    173            super.setOpcode((short) (c_tag + n));
    174            super.setLength(1);
    175        } else {
    176            super.setOpcode(canon_tag);
    177            if (wide()) {
    178                super.setLength(4);
    179            } else {
    180                super.setLength(2);
    181            }
    182        }
    183    }
    184
    185
    186    /** @return canonical tag for instruction, e.g., ALOAD for ALOAD_0
    187     */
    188    public short getCanonicalTag() {
    189        return canon_tag;
    190    }
    191
    192
    193    /**
    194     * Returns the type associated with the instruction -
    195     * in case of ALOAD or ASTORE Type.OBJECT is returned.
    196     * This is just a bit incorrect, because ALOAD and ASTORE
    197     * may work on every ReferenceType (including Type.NULL) and
    198     * ASTORE may even work on a ReturnaddressType .
    199     * @return type associated with the instruction
    200     */
    201    @Override
    202    public Type getType( final ConstantPoolGen cp ) {
    203        switch (canon_tag) {
    204            case Const.ILOAD:
    205            case Const.ISTORE:
    206                return Type.INT;
    207            case Const.LLOAD:
    208            case Const.LSTORE:
    209                return Type.LONG;
    210            case Const.DLOAD:
    211            case Const.DSTORE:
    212                return Type.DOUBLE;
    213            case Const.FLOAD:
    214            case Const.FSTORE:
    215                return Type.FLOAT;
    216            case Const.ALOAD:
    217            case Const.ASTORE:
    218                return Type.OBJECT;
    219            default:
    220                throw new ClassGenException("Oops: unknown case in switch" + canon_tag);
    221        }
    222    }
    223
    224    /**
    225     * Sets the index of the referenced variable (n) only
    226     * @since 6.0
    227     * @see #setIndex(int)
    228     */
    229    final void setIndexOnly(final int n) {
    230        this.n = n;
    231    }
    232}