    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.bcel.verifier.statics;
    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 the name and the type of a local variable in a given slot (== index).
    028 * This information often changes in course of byte code offsets.
    029 */
    030public class LocalVariableInfo {
    031
    032    /** The types database. KEY: String representing the offset integer. */
    033    private final Hashtable<String, Type> types = new Hashtable<>();
    034
    035    /** The names database. KEY: String representing the offset integer. */
    036    private final Hashtable<String, String> names = new Hashtable<>();
    037
    038    /**
    039     * Adds information about name and type for a given offset.
    040     *
    041     * @throws LocalVariableInfoInconsistentException if the new information conflicts with already gathered information.
    042     */
    043    private void add(final int offset, final String name, final Type t) throws LocalVariableInfoInconsistentException {
    044        if (getName(offset) != null && !getName(offset).equals(name)) {
    045            throw new LocalVariableInfoInconsistentException(
    046                "At bytecode offset '" + offset + "' a local variable has two different names: '" + getName(offset) + "' and '" + name + "'.");
    047        }
    048        if (getType(offset) != null && !getType(offset).equals(t)) {
    049            throw new LocalVariableInfoInconsistentException(
    050                "At bytecode offset '" + offset + "' a local variable has two different types: '" + getType(offset) + "' and '" + t + "'.");
    051        }
    052        setName(offset, name);
    053        setType(offset, t);
    054    }
    055
    056    /**
    057     * Adds some information about this local variable (slot).
    058     *
    059     * @param name variable name
    060     * @param startPc Range in which the variable is valid.
    061     * @param length length of ...
    062     * @param type variable type
    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}