    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.verifier.statics;
    019
    020
    021import java.util.Hashtable;
    022
    023import org.apache.bcel.generic.Type;
    024import org.apache.bcel.verifier.exc.LocalVariableInfoInconsistentException;
    025
    026/**
    027 * A utility class holding the information about
    028 * the name and the type of a local variable in
    029 * a given slot (== index). This information
    030 * often changes in course of byte code offsets.
    031 */
    032public class LocalVariableInfo{
    033
    034    /** The types database. KEY: String representing the offset integer. */
    035    private final Hashtable<String, Type> types = new Hashtable<>();
    036
    037    /** The names database. KEY: String representing the offset integer. */
    038    private final Hashtable<String, String> names = new Hashtable<>();
    039
    040    /**
    041     * Adds a name of a local variable and a certain slot to our 'names'
    042     * (Hashtable) database.
    043     */
    044    private void setName(final int offset, final String name) {
    045        names.put(Integer.toString(offset), name);
    046    }
    047
    048    /**
    049     * Adds a type of a local variable and a certain slot to our 'types'
    050     * (Hashtable) database.
    051     */
    052    private void setType(final int offset, final Type t) {
    053        types.put(Integer.toString(offset), t);
    054    }
    055
    056    /**
    057     * Returns the type of the local variable that uses this local variable slot at the given bytecode offset. Care for
    058     * legal bytecode offsets yourself, otherwise the return value might be wrong. May return 'null' if nothing is known
    059     * about the type of this local variable slot at the given bytecode offset.
    060     *
    061     * @param offset bytecode offset.
    062     * @return the type of the local variable that uses this local variable slot at the given bytecode offset.
    063     */
    064    public Type getType(final int offset) {
    065        return types.get(Integer.toString(offset));
    066    }
    067
    068    /**
    069     * Returns the name of the local variable that uses this local variable slot at the given bytecode offset. Care for
    070     * legal bytecode offsets yourself, otherwise the return value might be wrong. May return 'null' if nothing is known
    071     * about the type of this local variable slot at the given bytecode offset.
    072     *
    073     * @param offset bytecode offset.
    074     * @return the name of the local variable that uses this local variable slot at the given bytecode offset.
    075     */
    076    public String getName(final int offset) {
    077        return names.get(Integer.toString(offset));
    078    }
    079
    080    /**
    081     * Adds some information about this local variable (slot).
    082     *
    083     * @param name variable name
    084     * @param startPc Range in which the variable is valid.
    085     * @param length length of ...
    086     * @param type variable type
    087     *
    088     * @throws LocalVariableInfoInconsistentException if the new information conflicts
    089     *         with already gathered information.
    090     */
    091    public void add(final String name, final int startPc, final int length, final Type type)
    092            throws LocalVariableInfoInconsistentException {
    093        for (int i = startPc; i <= startPc + length; i++) { // incl/incl-notation!
    094            add(i, name, type);
    095        }
    096    }
    097
    098    /**
    099     * Adds information about name and type for a given offset.
    100     *
    101     * @throws LocalVariableInfoInconsistentException if the new information conflicts
    102     *         with already gathered information.
    103     */
    104    private void add(final int offset, final String name, final Type t) throws LocalVariableInfoInconsistentException {
    105        if (getName(offset) != null) {
    106            if (!getName(offset).equals(name)) {
    107                throw new LocalVariableInfoInconsistentException("At bytecode offset '" + offset
    108                        + "' a local variable has two different names: '" + getName(offset) + "' and '" + name + "'.");
    109            }
    110        }
    111        if (getType(offset) != null) {
    112            if (!getType(offset).equals(t)) {
    113                throw new LocalVariableInfoInconsistentException("At bytecode offset '" + offset
    114                        + "' a local variable has two different types: '" + getType(offset) + "' and '" + t + "'.");
    115            }
    116        }
    117        setName(offset, name);
    118        setType(offset, t);
    119    }
    120}