Instruction.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.bcel.generic;

import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.bcel.Const;
import org.apache.bcel.classfile.ConstantPool;
import org.apache.bcel.util.ByteSequence;

/**
 * Abstract super class for all Java byte codes.
 */
public abstract class Instruction implements Cloneable {

    static final Instruction[] EMPTY_ARRAY = {};

    private static InstructionComparator cmp = InstructionComparator.DEFAULT;

    /**
     * Gets Comparator object used in the equals() method to determine equality of instructions.
     *
     * @return currently used comparator for equals()
     * @deprecated (6.0) use the built in comparator, or wrap this class in another object that implements these methods
     */
    @Deprecated
    public static InstructionComparator getComparator() {
        return cmp;
    }

    /**
     * Tests if the value can fit in a byte (signed)
     *
     * @param value the value to check
     * @return true if the value is in range
     * @since 6.0
     */
    public static boolean isValidByte(final int value) {
        return value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE;
    }

    /**
     * Tests if the value can fit in a short (signed)
     *
     * @param value the value to check
     * @return true if the value is in range
     * @since 6.0
     */
    public static boolean isValidShort(final int value) {
        return value >= Short.MIN_VALUE && value <= Short.MAX_VALUE;
    }

    /**
     * Reads an instruction from (byte code) input stream and return the appropriate object.
     * <p>
     * If the Instruction is defined in {@link InstructionConst}, then the singleton instance is returned.
     * </p>
     * @param bytes input stream bytes
     * @return instruction object being read
     * @throws IOException Thrown when an I/O exception of some sort has occurred.
     * @see InstructionConst#getInstruction(int)
     */
    // @since 6.0 no longer final
    public static Instruction readInstruction(final ByteSequence bytes) throws IOException {
        boolean wide = false;
        short opcode = (short) bytes.readUnsignedByte();
        Instruction obj = null;
        if (opcode == Const.WIDE) { // Read next opcode after wide byte
            wide = true;
            opcode = (short) bytes.readUnsignedByte();
        }
        final Instruction instruction = InstructionConst.getInstruction(opcode);
        if (instruction != null) {
            return instruction; // Used predefined immutable object, if available
        }

        switch (opcode) {
        case Const.BIPUSH:
            obj = new BIPUSH();
            break;
        case Const.SIPUSH:
            obj = new SIPUSH();
            break;
        case Const.LDC:
            obj = new LDC();
            break;
        case Const.LDC_W:
            obj = new LDC_W();
            break;
        case Const.LDC2_W:
            obj = new LDC2_W();
            break;
        case Const.ILOAD:
            obj = new ILOAD();
            break;
        case Const.LLOAD:
            obj = new LLOAD();
            break;
        case Const.FLOAD:
            obj = new FLOAD();
            break;
        case Const.DLOAD:
            obj = new DLOAD();
            break;
        case Const.ALOAD:
            obj = new ALOAD();
            break;
        case Const.ILOAD_0:
            obj = new ILOAD(0);
            break;
        case Const.ILOAD_1:
            obj = new ILOAD(1);
            break;
        case Const.ILOAD_2:
            obj = new ILOAD(2);
            break;
        case Const.ILOAD_3:
            obj = new ILOAD(3);
            break;
        case Const.LLOAD_0:
            obj = new LLOAD(0);
            break;
        case Const.LLOAD_1:
            obj = new LLOAD(1);
            break;
        case Const.LLOAD_2:
            obj = new LLOAD(2);
            break;
        case Const.LLOAD_3:
            obj = new LLOAD(3);
            break;
        case Const.FLOAD_0:
            obj = new FLOAD(0);
            break;
        case Const.FLOAD_1:
            obj = new FLOAD(1);
            break;
        case Const.FLOAD_2:
            obj = new FLOAD(2);
            break;
        case Const.FLOAD_3:
            obj = new FLOAD(3);
            break;
        case Const.DLOAD_0:
            obj = new DLOAD(0);
            break;
        case Const.DLOAD_1:
            obj = new DLOAD(1);
            break;
        case Const.DLOAD_2:
            obj = new DLOAD(2);
            break;
        case Const.DLOAD_3:
            obj = new DLOAD(3);
            break;
        case Const.ALOAD_0:
            obj = new ALOAD(0);
            break;
        case Const.ALOAD_1:
            obj = new ALOAD(1);
            break;
        case Const.ALOAD_2:
            obj = new ALOAD(2);
            break;
        case Const.ALOAD_3:
            obj = new ALOAD(3);
            break;
        case Const.ISTORE:
            obj = new ISTORE();
            break;
        case Const.LSTORE:
            obj = new LSTORE();
            break;
        case Const.FSTORE:
            obj = new FSTORE();
            break;
        case Const.DSTORE:
            obj = new DSTORE();
            break;
        case Const.ASTORE:
            obj = new ASTORE();
            break;
        case Const.ISTORE_0:
            obj = new ISTORE(0);
            break;
        case Const.ISTORE_1:
            obj = new ISTORE(1);
            break;
        case Const.ISTORE_2:
            obj = new ISTORE(2);
            break;
        case Const.ISTORE_3:
            obj = new ISTORE(3);
            break;
        case Const.LSTORE_0:
            obj = new LSTORE(0);
            break;
        case Const.LSTORE_1:
            obj = new LSTORE(1);
            break;
        case Const.LSTORE_2:
            obj = new LSTORE(2);
            break;
        case Const.LSTORE_3:
            obj = new LSTORE(3);
            break;
        case Const.FSTORE_0:
            obj = new FSTORE(0);
            break;
        case Const.FSTORE_1:
            obj = new FSTORE(1);
            break;
        case Const.FSTORE_2:
            obj = new FSTORE(2);
            break;
        case Const.FSTORE_3:
            obj = new FSTORE(3);
            break;
        case Const.DSTORE_0:
            obj = new DSTORE(0);
            break;
        case Const.DSTORE_1:
            obj = new DSTORE(1);
            break;
        case Const.DSTORE_2:
            obj = new DSTORE(2);
            break;
        case Const.DSTORE_3:
            obj = new DSTORE(3);
            break;
        case Const.ASTORE_0:
            obj = new ASTORE(0);
            break;
        case Const.ASTORE_1:
            obj = new ASTORE(1);
            break;
        case Const.ASTORE_2:
            obj = new ASTORE(2);
            break;
        case Const.ASTORE_3:
            obj = new ASTORE(3);
            break;
        case Const.IINC:
            obj = new IINC();
            break;
        case Const.IFEQ:
            obj = new IFEQ();
            break;
        case Const.IFNE:
            obj = new IFNE();
            break;
        case Const.IFLT:
            obj = new IFLT();
            break;
        case Const.IFGE:
            obj = new IFGE();
            break;
        case Const.IFGT:
            obj = new IFGT();
            break;
        case Const.IFLE:
            obj = new IFLE();
            break;
        case Const.IF_ICMPEQ:
            obj = new IF_ICMPEQ();
            break;
        case Const.IF_ICMPNE:
            obj = new IF_ICMPNE();
            break;
        case Const.IF_ICMPLT:
            obj = new IF_ICMPLT();
            break;
        case Const.IF_ICMPGE:
            obj = new IF_ICMPGE();
            break;
        case Const.IF_ICMPGT:
            obj = new IF_ICMPGT();
            break;
        case Const.IF_ICMPLE:
            obj = new IF_ICMPLE();
            break;
        case Const.IF_ACMPEQ:
            obj = new IF_ACMPEQ();
            break;
        case Const.IF_ACMPNE:
            obj = new IF_ACMPNE();
            break;
        case Const.GOTO:
            obj = new GOTO();
            break;
        case Const.JSR:
            obj = new JSR();
            break;
        case Const.RET:
            obj = new RET();
            break;
        case Const.TABLESWITCH:
            obj = new TABLESWITCH();
            break;
        case Const.LOOKUPSWITCH:
            obj = new LOOKUPSWITCH();
            break;
        case Const.GETSTATIC:
            obj = new GETSTATIC();
            break;
        case Const.PUTSTATIC:
            obj = new PUTSTATIC();
            break;
        case Const.GETFIELD:
            obj = new GETFIELD();
            break;
        case Const.PUTFIELD:
            obj = new PUTFIELD();
            break;
        case Const.INVOKEVIRTUAL:
            obj = new INVOKEVIRTUAL();
            break;
        case Const.INVOKESPECIAL:
            obj = new INVOKESPECIAL();
            break;
        case Const.INVOKESTATIC:
            obj = new INVOKESTATIC();
            break;
        case Const.INVOKEINTERFACE:
            obj = new INVOKEINTERFACE();
            break;
        case Const.INVOKEDYNAMIC:
            obj = new INVOKEDYNAMIC();
            break;
        case Const.NEW:
            obj = new NEW();
            break;
        case Const.NEWARRAY:
            obj = new NEWARRAY();
            break;
        case Const.ANEWARRAY:
            obj = new ANEWARRAY();
            break;
        case Const.CHECKCAST:
            obj = new CHECKCAST();
            break;
        case Const.INSTANCEOF:
            obj = new INSTANCEOF();
            break;
        case Const.MULTIANEWARRAY:
            obj = new MULTIANEWARRAY();
            break;
        case Const.IFNULL:
            obj = new IFNULL();
            break;
        case Const.IFNONNULL:
            obj = new IFNONNULL();
            break;
        case Const.GOTO_W:
            obj = new GOTO_W();
            break;
        case Const.JSR_W:
            obj = new JSR_W();
            break;
        case Const.BREAKPOINT:
            obj = new BREAKPOINT();
            break;
        case Const.IMPDEP1:
            obj = new IMPDEP1();
            break;
        case Const.IMPDEP2:
            obj = new IMPDEP2();
            break;
        default:
            throw new ClassGenException("Illegal opcode detected: " + opcode);

        }

        if (wide && !(obj instanceof LocalVariableInstruction || obj instanceof RET)) {
            throw new ClassGenException("Illegal opcode after wide: " + opcode);
        }
        obj.setOpcode(opcode);
        obj.initFromFile(bytes, wide); // Do further initializations, if any
        return obj;
    }

    /**
     * Sets comparator to be used for equals().
     *
     * @deprecated (6.0) use the built in comparator, or wrap this class in another object that implements these methods
     */
    @Deprecated
    public static void setComparator(final InstructionComparator c) {
        cmp = c;
    }

    /**
     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
     */
    @Deprecated
    protected short length = 1; // Length of instruction in bytes

    /**
     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
     */
    @Deprecated
    protected short opcode = -1; // Opcode number

    /**
     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
     */
    Instruction() {
    }

    public Instruction(final short opcode, final short length) {
        this.length = length;
        this.opcode = opcode;
    }

    /**
     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
     * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last.
     *
     * @param v Visitor object
     */
    public abstract void accept(Visitor v);

    /**
     * This method also gives right results for instructions whose effect on the stack depends on the constant pool entry
     * they reference.
     *
     * @return Number of words consumed from stack by this instruction, or Constants.UNPREDICTABLE, if this can not be
     *         computed statically
     */
    public int consumeStack(final ConstantPoolGen cpg) {
        return Const.getConsumeStack(opcode);
    }

    /**
     * Use with caution, since 'BranchInstruction's have a 'target' reference which is not copied correctly (only basic
     * types are). This also applies for 'Select' instructions with their multiple branch targets.
     *
     * @see BranchInstruction
     * @return (shallow) copy of an instruction
     */
    public Instruction copy() {
        Instruction i = null;
        // "Constant" instruction, no need to duplicate
        if (InstructionConst.getInstruction(getOpcode()) != null) {
            i = this;
        } else {
            try {
                i = (Instruction) clone();
            } catch (final CloneNotSupportedException e) {
                System.err.println(e);
            }
        }
        return i;
    }

    /**
     * Some instructions may be reused, so don't do anything by default.
     */
    void dispose() {
    }

    /**
     * Dumps instruction as byte code to stream out.
     *
     * @param out Output stream
     * @throws IOException Thrown when an I/O exception of some sort has occurred.
     */
    public void dump(final DataOutputStream out) throws IOException {
        out.writeByte(opcode); // Common for all instructions
    }

    /**
     * Tests for equality, delegated to comparator
     *
     * @return true if that is an Instruction and has the same opcode
     */
    @Override
    public boolean equals(final Object that) {
        return that instanceof Instruction && cmp.equals(this, (Instruction) that);
    }

    /**
     * @return length (in bytes) of instruction
     */
    public int getLength() {
        return length;
    }

    /**
     * @return name of instruction, i.e., opcode name
     */
    public String getName() {
        return Const.getOpcodeName(opcode);
    }

    /**
     * @return this instructions opcode
     */
    public short getOpcode() {
        return opcode;
    }

    /**
     * Gets the hashCode of this object.
     *
     * @return the hashCode
     * @since 6.0
     */
    @Override
    public int hashCode() {
        return opcode;
    }

    /**
     * Reads needed data (e.g. index) from file.
     *
     * @param bytes byte sequence to read from
     * @param wide "wide" instruction flag
     * @throws IOException may be thrown if the implementation needs to read data from the file
     */
    @SuppressWarnings("unused") // thrown by subclasses
    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
    }

    /**
     * This method also gives right results for instructions whose effect on the stack depends on the constant pool entry
     * they reference.
     *
     * @return Number of words produced onto stack by this instruction, or Constants.UNPREDICTABLE, if this can not be
     *         computed statically
     */
    public int produceStack(final ConstantPoolGen cpg) {
        return Const.getProduceStack(opcode);
    }

    /**
     * Needed in readInstruction and subclasses in this package
     *
     * @since 6.0
     */
    final void setLength(final int length) {
        this.length = (short) length; // TODO check range?
    }

    /**
     * Needed in readInstruction and subclasses in this package
     */
    final void setOpcode(final short opcode) {
        this.opcode = opcode;
    }

    /**
     * @return mnemonic for instruction in verbose format
     */
    @Override
    public String toString() {
        return toString(true);
    }

    /**
     * Long output format:
     *
     * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]" "("&lt;length of instruction&gt;")"
     *
     * @param verbose long/short format switch
     * @return mnemonic for instruction
     */
    public String toString(final boolean verbose) {
        if (verbose) {
            return getName() + "[" + opcode + "](" + length + ")";
        }
        return getName();
    }

    /**
     * @return mnemonic for instruction with sumbolic references resolved
     */
    public String toString(final ConstantPool cp) {
        return toString(false);
    }
}