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package com.sun.org.apache.bcel.internal.generic;

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

import com.sun.org.apache.bcel.internal.util.ByteSequence;

Abstract super class for branching instructions like GOTO, IFEQ, etc.. Branch
instructions may have a variable length, namely GOTO, JSR, LOOKUPSWITCH and
TABLESWITCH.
See Also:
InstructionList
Version:
$Id: BranchInstruction.java 1749603 2016-06-21 20:50:19Z ggregory $/**
 * Abstract super class for branching instructions like GOTO, IFEQ, etc.. Branch
 * instructions may have a variable length, namely GOTO, JSR, LOOKUPSWITCH and
 * TABLESWITCH.
 *
 * @see InstructionList
 * @version $Id: BranchInstruction.java 1749603 2016-06-21 20:50:19Z ggregory $
 */
public abstract class BranchInstruction extends Instruction implements InstructionTargeter {

    private int index; // Branch target relative to this instruction
    private InstructionHandle target; // Target object in instruction list
    private int position; // Byte code offset

    
Empty constructor needed for the Class.newInstance() statement in
Instruction.readInstruction(). Not to be used otherwise.
/**
     * Empty constructor needed for the Class.newInstance() statement in
     * Instruction.readInstruction(). Not to be used otherwise.
     */
    BranchInstruction() {
    }

    
Common super constructor
Params:
opcode – Instruction opcode
target – instruction to branch to/**
     * Common super constructor
     *
     * @param opcode Instruction opcode
     * @param target instruction to branch to
     */
    protected BranchInstruction(final short opcode, final InstructionHandle target) {
        super(opcode, (short) 3);
        setTarget(target);
    }

    
Dump instruction as byte code to stream out.
Params:
out – Output stream/**
     * Dump instruction as byte code to stream out.
     *
     * @param out Output stream
     */
    @Override
    public void dump(final DataOutputStream out) throws IOException {
        out.writeByte(super.getOpcode());
        index = getTargetOffset();
        if (!isValidShort(index)) {
            throw new ClassGenException("Branch target offset too large for short: " + index);
        }
        out.writeShort(index); // May be negative, i.e., point backwards
    }

    
Params:
_target – branch target
Returns:
the offset to `target' relative to this instruction/**
     * @param _target branch target
     * @return the offset to `target' relative to this instruction
     */
    protected int getTargetOffset(final InstructionHandle _target) {
        if (_target == null) {
            throw new ClassGenException("Target of " + super.toString(true)
                    + " is invalid null handle");
        }
        final int t = _target.getPosition();
        if (t < 0) {
            throw new ClassGenException("Invalid branch target position offset for "
                    + super.toString(true) + ":" + t + ":" + _target);
        }
        return t - position;
    }

    
Returns:
the offset to this instruction's target/**
     * @return the offset to this instruction's target
     */
    protected int getTargetOffset() {
        return getTargetOffset(target);
    }

    
Called by InstructionList.setPositions when setting the position for
every instruction. In the presence of variable length instructions
`setPositions' performs multiple passes over the instruction list to
calculate the correct (byte) positions and offsets by calling this
function.
Params:
offset – additional offset caused by preceding (variable length)
instructions
max_offset – the maximum offset that may be caused by these
instructions
Returns:
additional offset caused by possible change of this instruction's
length/**
     * Called by InstructionList.setPositions when setting the position for
     * every instruction. In the presence of variable length instructions
     * `setPositions' performs multiple passes over the instruction list to
     * calculate the correct (byte) positions and offsets by calling this
     * function.
     *
     * @param offset additional offset caused by preceding (variable length)
     * instructions
     * @param max_offset the maximum offset that may be caused by these
     * instructions
     * @return additional offset caused by possible change of this instruction's
     * length
     */
    protected int updatePosition(final int offset, final int max_offset) {
        position += offset;
        return 0;
    }

    
Long output format:
<position in byte code> <name of opcode> "["<opcode
number>"]" "("<length of instruction>")" "<"<target
instruction>">" "@"<branch target offset>
Params:
verbose – long/short format switch
Returns:
mnemonic for instruction/**
     * Long output format:
     *
     * &lt;position in byte code&gt; &lt;name of opcode&gt; "["&lt;opcode
     * number&gt;"]" "("&lt;length of instruction&gt;")" "&lt;"&lt;target
     * instruction&gt;"&gt;" "@"&lt;branch target offset&gt;
     *
     * @param verbose long/short format switch
     * @return mnemonic for instruction
     */
    @Override
    public String toString(final boolean verbose) {
        final String s = super.toString(verbose);
        String t = "null";
        if (verbose) {
            if (target != null) {
                if (target.getInstruction() == this) {
                    t = "<points to itself>";
                } else if (target.getInstruction() == null) {
                    t = "<null instruction!!!?>";
                } else {
                    // I'm more interested in the address of the target then
                    // the instruction located there.
                    //t = target.getInstruction().toString(false); // Avoid circles
                    t = "" + target.getPosition();
                }
            }
        } else {
            if (target != null) {
                index = target.getPosition();
                // index = getTargetOffset();  crashes if positions haven't been set
                // t = "" + (index + position);
                t = "" + index;
            }
        }
        return s + " -> " + t;
    }

    
Read needed data (e.g. index) from file. Conversion to a
InstructionHandle is done in InstructionList(byte[]).
Params:
bytes – input stream
wide – wide prefix?
See Also:
InstructionList/**
     * Read needed data (e.g. index) from file. Conversion to a
     * InstructionHandle is done in InstructionList(byte[]).
     *
     * @param bytes input stream
     * @param wide wide prefix?
     * @see InstructionList
     */
    @Override
    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
        super.setLength(3);
        index = bytes.readShort();
    }

    
Returns:
target offset in byte code/**
     * @return target offset in byte code
     */
    public final int getIndex() {
        return index;
    }

    
Returns:
target of branch instruction/**
     * @return target of branch instruction
     */
    public InstructionHandle getTarget() {
        return target;
    }

    
Set branch target
Params:
target – branch target/**
     * Set branch target
     *
     * @param target branch target
     */
    public void setTarget(final InstructionHandle target) {
        notifyTarget(this.target, target, this);
        this.target = target;
    }

    
Used by BranchInstruction, LocalVariableGen, CodeExceptionGen,
LineNumberGen
/**
     * Used by BranchInstruction, LocalVariableGen, CodeExceptionGen,
     * LineNumberGen
     */
    static void notifyTarget(final InstructionHandle old_ih, final InstructionHandle new_ih,
            final InstructionTargeter t) {
        if (old_ih != null) {
            old_ih.removeTargeter(t);
        }
        if (new_ih != null) {
            new_ih.addTargeter(t);
        }
    }

    
Params:
old_ih – old target
new_ih – new target/**
     * @param old_ih old target
     * @param new_ih new target
     */
    @Override
    public void updateTarget(final InstructionHandle old_ih, final InstructionHandle new_ih) {
        if (target == old_ih) {
            setTarget(new_ih);
        } else {
            throw new ClassGenException("Not targeting " + old_ih + ", but " + target);
        }
    }

    
Returns:
true, if ih is target of this instruction/**
     * @return true, if ih is target of this instruction
     */
    @Override
    public boolean containsTarget(final InstructionHandle ih) {
        return target == ih;
    }

    
Inform target that it's not targeted anymore.
/**
     * Inform target that it's not targeted anymore.
     */
    @Override
    void dispose() {
        setTarget(null);
        index = -1;
        position = -1;
    }

    
Returns:
the position
Since:
6.0/**
     * @return the position
     * @since 6.0
     */
    protected int getPosition() {
        return position;
    }

    
Params:
position – the position to set
Since:
6.0/**
     * @param position the position to set
     * @since 6.0
     */
    protected void setPosition(final int position) {
        this.position = position;
    }

    
Params:
index – the index to set
Since:
6.0/**
     * @param index the index to set
     * @since 6.0
     */
    protected void setIndex(final int index) {
        this.index = index;
    }

}