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}