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.util;
019
020import java.io.ByteArrayInputStream;
021import java.io.DataInputStream;
022
023/**
024 * Utility class that implements a sequence of bytes which can be read
025 * via the `readByte()' method. This is used to implement a wrapper for the
026 * Java byte code stream to gain some more readability.
027 *
028 */
029public final class ByteSequence extends DataInputStream {
030
031    private final ByteArrayStream byteStream;
032
033
034    public ByteSequence(final byte[] bytes) {
035        super(new ByteArrayStream(bytes));
036        byteStream = (ByteArrayStream) in;
037    }
038
039
040    public int getIndex() {
041        return byteStream.getPosition();
042    }
043
044
045    void unreadByte() {
046        byteStream.unreadByte();
047    }
048
049    private static final class ByteArrayStream extends ByteArrayInputStream {
050
051        ByteArrayStream(final byte[] bytes) {
052            super(bytes);
053        }
054
055        int getPosition() {
056            // pos is protected in ByteArrayInputStream
057            return pos;
058        }
059
060        void unreadByte() {
061            if (pos > 0) {
062                pos--;
063            }
064        }
065    }
066}