    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 */
    017package org.apache.bcel.verifier.statics;
    018
    019import java.util.Hashtable;
    020
    021import org.apache.bcel.generic.Type;
    022import org.apache.bcel.verifier.exc.LocalVariableInfoInconsistentException;
    023
    024/**
    025 * A utility class holding the information about the name and the type of a local variable in a given slot (== index).
    026 * This information often changes in course of byte code offsets.
    027 */
    028public class LocalVariableInfo {
    029
    030    /** The types database. KEY: String representing the offset integer. */
    031    private final Hashtable<String, Type> types = new Hashtable<>();
    032
    033    /** The names database. KEY: String representing the offset integer. */
    034    private final Hashtable<String, String> names = new Hashtable<>();
    035
    036    /**
    037     * Adds information about name and type for a given offset.
    038     *
    039     * @throws LocalVariableInfoInconsistentException if the new information conflicts with already gathered information.
    040     */
    041    private void add(final int offset, final String name, final Type t) throws LocalVariableInfoInconsistentException {
    042        if (getName(offset) != null && !getName(offset).equals(name)) {
    043            throw new LocalVariableInfoInconsistentException(
    044                "At bytecode offset '" + offset + "' a local variable has two different names: '" + getName(offset) + "' and '" + name + "'.");
    045        }
    046        if (getType(offset) != null && !getType(offset).equals(t)) {
    047            throw new LocalVariableInfoInconsistentException(
    048                "At bytecode offset '" + offset + "' a local variable has two different types: '" + getType(offset) + "' and '" + t + "'.");
    049        }
    050        setName(offset, name);
    051        setType(offset, t);
    052    }
    053
    054    /**
    055     * Adds some information about this local variable (slot).
    056     *
    057     * @param name variable name
    058     * @param startPc Range in which the variable is valid.
    059     * @param length length of ...
    060     * @param type variable type
    061     *
    062     * @throws LocalVariableInfoInconsistentException if the new information conflicts with already gathered information.
    063     */
    064    public void add(final String name, final int startPc, final int length, final Type type) throws LocalVariableInfoInconsistentException {
    065        for (int i = startPc; i <= startPc + length; i++) { // incl/incl-notation!
    066            add(i, name, type);
    067        }
    068    }
    069
    070    /**
    071     * Returns the name of the local variable that uses this local variable slot at the given bytecode offset. Care for
    072     * legal bytecode offsets yourself, otherwise the return value might be wrong. May return 'null' if nothing is known
    073     * about the type of this local variable slot at the given bytecode offset.
    074     *
    075     * @param offset bytecode offset.
    076     * @return the name of the local variable that uses this local variable slot at the given bytecode offset.
    077     */
    078    public String getName(final int offset) {
    079        return names.get(Integer.toString(offset));
    080    }
    081
    082    /**
    083     * Returns the type of the local variable that uses this local variable slot at the given bytecode offset. Care for
    084     * legal bytecode offsets yourself, otherwise the return value might be wrong. May return 'null' if nothing is known
    085     * about the type of this local variable slot at the given bytecode offset.
    086     *
    087     * @param offset bytecode offset.
    088     * @return the type of the local variable that uses this local variable slot at the given bytecode offset.
    089     */
    090    public Type getType(final int offset) {
    091        return types.get(Integer.toString(offset));
    092    }
    093
    094    /**
    095     * Adds a name of a local variable and a certain slot to our 'names' (Hashtable) database.
    096     */
    097    private void setName(final int offset, final String name) {
    098        names.put(Integer.toString(offset), name);
    099    }
    100
    101    /**
    102     * Adds a type of a local variable and a certain slot to our 'types' (Hashtable) database.
    103     */
    104    private void setType(final int offset, final Type t) {
    105        types.put(Integer.toString(offset), t);
    106    }
    107}