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: LocalVariableInstruction.java 1812166 2017-10-13 23:48:11Z ggregory $
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     * <name of opcode> "["<opcode number>"]"
106     * "("<length of instruction>")" "<"< local variable index>">"
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}