    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}