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}