LocalVariableGen

/*
 * 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 org.apache.bcel.Const;
import org.apache.bcel.classfile.LocalVariable;

/**
 * Represents a local variable within a method. It contains its scope, name and type. The generated LocalVariable object
 * can be obtained with getLocalVariable which needs the instruction list and the constant pool as parameters.
 *
 * @see LocalVariable
 * @see MethodGen
 */
public class LocalVariableGen implements InstructionTargeter, NamedAndTyped, Cloneable {

    private int index;
    private String name;
    private Type type;
    private InstructionHandle start;
    private InstructionHandle end;
    private int origIndex; // never changes; used to match up with LocalVariableTypeTable entries
    private boolean liveToEnd;

    /**
     * Generate a local variable that with index 'index'. Note that double and long variables need two indexs. Index indices
     * have to be provided by the user.
     *
     * @param index index of local variable
     * @param name its name
     * @param type its type
     * @param start from where the instruction is valid (null means from the start)
     * @param end until where the instruction is valid (null means to the end)
     */
    public LocalVariableGen(final int index, final String name, final Type type, final InstructionHandle start, final InstructionHandle end) {
        if (index < 0 || index > Const.MAX_SHORT) {
            throw new ClassGenException("Invalid index: " + index);
        }
        this.name = name;
        this.type = type;
        this.index = index;
        setStart(start);
        setEnd(end);
        this.origIndex = index;
        this.liveToEnd = end == null;
    }

    /**
     * Generates a local variable that with index 'index'. Note that double and long variables need two indexs. Index
     * indices have to be provided by the user.
     *
     * @param index index of local variable
     * @param name its name
     * @param type its type
     * @param start from where the instruction is valid (null means from the start)
     * @param end until where the instruction is valid (null means to the end)
     * @param origIndex index of local variable prior to any changes to index
     */
    public LocalVariableGen(final int index, final String name, final Type type, final InstructionHandle start, final InstructionHandle end,
        final int origIndex) {
        this(index, name, type, start, end);
        this.origIndex = origIndex;
    }

    @Override
    public Object clone() {
        try {
            return super.clone();
        } catch (final CloneNotSupportedException e) {
            throw new UnsupportedOperationException("Clone Not Supported", e); // never happens
        }
    }

    /**
     * @return true, if ih is target of this variable
     */
    @Override
    public boolean containsTarget(final InstructionHandle ih) {
        return start == ih || end == ih;
    }

    /**
     * Clear the references from and to this variable when it's removed.
     */
    void dispose() {
        setStart(null);
        setEnd(null);
    }

    /**
     * We consider to local variables to be equal, if the use the same index and are valid in the same range.
     */
    @Override
    public boolean equals(final Object o) {
        if (!(o instanceof LocalVariableGen)) {
            return false;
        }
        final LocalVariableGen l = (LocalVariableGen) o;
        return l.index == index && l.start == start && l.end == end;
    }

    public InstructionHandle getEnd() {
        return end;
    }

    public int getIndex() {
        return index;
    }

    public boolean getLiveToEnd() {
        return liveToEnd;
    }

    /**
     * Gets LocalVariable object.
     *
     * This relies on that the instruction list has already been dumped to byte code or that the 'setPositions' methods
     * has been called for the instruction list.
     *
     * Note that due to the conversion from byte code offset to InstructionHandle, it is impossible to tell the difference
     * between a live range that ends BEFORE the last insturction of the method or a live range that ends AFTER the last
     * instruction of the method. Hence the liveToEnd flag to differentiate between these two cases.
     *
     * @param cp constant pool
     */
    public LocalVariable getLocalVariable(final ConstantPoolGen cp) {
        int startPc = 0;
        int length = 0;
        if (start != null && end != null) {
            startPc = start.getPosition();
            length = end.getPosition() - startPc;
            if (end.getNext() == null && liveToEnd) {
                length += end.getInstruction().getLength();
            }
        }
        final int nameIndex = cp.addUtf8(name);
        final int signatureIndex = cp.addUtf8(type.getSignature());
        return new LocalVariable(startPc, length, nameIndex, signatureIndex, index, cp.getConstantPool(), origIndex);
    }

    @Override
    public String getName() {
        return name;
    }

    public int getOrigIndex() {
        return origIndex;
    }

    public InstructionHandle getStart() {
        return start;
    }

    @Override
    public Type getType() {
        return type;
    }

    @Override
    public int hashCode() {
        // If the user changes the name or type, problems with the targeter hashmap will occur.
        // Note: index cannot be part of hash as it may be changed by the user.
        return name.hashCode() ^ type.hashCode();
    }

    public void setEnd(final InstructionHandle end) { // TODO could be package-protected?
        BranchInstruction.notifyTarget(this.end, end, this);
        this.end = end;
    }

    public void setIndex(final int index) {
        this.index = index;
    }

    public void setLiveToEnd(final boolean liveToEnd) {
        this.liveToEnd = liveToEnd;
    }

    @Override
    public void setName(final String name) {
        this.name = name;
    }

    public void setStart(final InstructionHandle start) { // TODO could be package-protected?
        BranchInstruction.notifyTarget(this.start, start, this);
        this.start = start;
    }

    @Override
    public void setType(final Type type) {
        this.type = type;
    }

    @Override
    public String toString() {
        return "LocalVariableGen(" + name + ", " + type + ", " + start + ", " + end + ")";
    }

    /**
     * @param oldIh old target, either start or end
     * @param newIh new target
     */
    @Override
    public void updateTarget(final InstructionHandle oldIh, final InstructionHandle newIh) {
        boolean targeted = false;
        if (start == oldIh) {
            targeted = true;
            setStart(newIh);
        }
        if (end == oldIh) {
            targeted = true;
            setEnd(newIh);
        }
        if (!targeted) {
            throw new ClassGenException("Not targeting " + oldIh + ", but {" + start + ", " + end + "}");
        }
    }
}