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 *
032 * @version $Id: LocalVariableInfo.java 1749600 2016-06-21 20:43:38Z ggregory $
033 */
034public class LocalVariableInfo{
035
036    /** The types database. KEY: String representing the offset integer. */
037    private final Hashtable<String, Type> types = new Hashtable<>();
038    /** The names database. KEY: String representing the offset integer. */
039    private final Hashtable<String, String> names = new Hashtable<>();
040
041    /**
042     * Adds a name of a local variable and a certain slot to our 'names'
043     * (Hashtable) database.
044     */
045    private void setName(final int offset, final String name) {
046        names.put(Integer.toString(offset), name);
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
058     * variable slot at the given bytecode offset.
059     * Care for legal bytecode offsets yourself, otherwise the return value
060     * might be wrong.
061     * May return 'null' if nothing is known about the type of this local
062     * 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     * Returns the name of the local variable that uses this local
069     * variable slot at the given bytecode offset.
070     * Care for legal bytecode offsets yourself, otherwise the return value
071     * might be wrong.
072     * May return 'null' if nothing is known about the type of this local
073     * variable slot at the given bytecode offset.
074     */
075    public String getName(final int offset) {
076        return names.get(Integer.toString(offset));
077    }
078    /**
079     * Adds some information about this local variable (slot).
080     * @throws LocalVariableInfoInconsistentException if the new information conflicts
081     *         with already gathered information.
082     */
083    public void add(final String name, final int startpc, final int length, final Type t) throws LocalVariableInfoInconsistentException{
084        for (int i=startpc; i<=startpc+length; i++) { // incl/incl-notation!
085            add(i,name,t);
086        }
087    }
088
089    /**
090     * Adds information about name and type for a given offset.
091     * @throws LocalVariableInfoInconsistentException if the new information conflicts
092     *         with already gathered information.
093     */
094    private void add(final int offset, final String name, final Type t) throws LocalVariableInfoInconsistentException{
095        if (getName(offset) != null) {
096            if (! getName(offset).equals(name)) {
097                throw new LocalVariableInfoInconsistentException("At bytecode offset '"+offset+
098                    "' a local variable has two different names: '"+getName(offset)+"' and '"+name+"'.");
099            }
100        }
101        if (getType(offset) != null) {
102            if (! getType(offset).equals(t)) {
103                throw new LocalVariableInfoInconsistentException("At bytecode offset '"+offset+
104                    "' a local variable has two different types: '"+getType(offset)+"' and '"+t+"'.");
105            }
106        }
107        setName(offset, name);
108        setType(offset, t);
109    }
110}