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