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.util;
020
021import java.io.ByteArrayInputStream;
022import java.io.DataInputStream;
023
024/**
025 * Utility class that implements a sequence of bytes which can be read via the 'readByte()' method. This is used to
026 * implement a wrapper for the Java byte code stream to gain some more readability.
027 */
028public final class ByteSequence extends DataInputStream {
029
030    private static final class ByteArrayStream extends ByteArrayInputStream {
031
032        ByteArrayStream(final byte[] bytes) {
033            super(bytes);
034        }
035
036        int getPosition() {
037            // pos is protected in ByteArrayInputStream
038            return pos;
039        }
040
041        void unreadByte() {
042            if (pos > 0) {
043                pos--;
044            }
045        }
046    }
047
048    private final ByteArrayStream byteStream;
049
050    /**
051     * Constructs a ByteSequence.
052     *
053     * @param bytes the byte array.
054     */
055    public ByteSequence(final byte[] bytes) {
056        super(new ByteArrayStream(bytes));
057        byteStream = (ByteArrayStream) in;
058    }
059
060    /**
061     * Gets the current index.
062     *
063     * @return the current index.
064     */
065    public int getIndex() {
066        return byteStream.getPosition();
067    }
068
069    /**
070     * Unreads the last byte.
071     */
072    void unreadByte() {
073        byteStream.unreadByte();
074    }
075}