/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.bcel.util;

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;

/**
 * Utility class that implements a sequence of bytes which can be read via the 'readByte()' method. This is used to
 * implement a wrapper for the Java byte code stream to gain some more readability.
 */
public final class ByteSequence extends DataInputStream {

    private static final class ByteArrayStream extends ByteArrayInputStream {

        ByteArrayStream(final byte[] bytes) {
            super(bytes);
        }

        int getPosition() {
            // pos is protected in ByteArrayInputStream
            return pos;
        }

        void unreadByte() {
            if (pos > 0) {
                pos--;
            }
        }
    }

    private final ByteArrayStream byteStream;

    /**
     * Constructs a ByteSequence.
     *
     * @param bytes the byte array.
     */
    public ByteSequence(final byte[] bytes) {
        super(new ByteArrayStream(bytes));
        byteStream = (ByteArrayStream) in;
    }

    /**
     * Gets the current index.
     *
     * @return the current index.
     */
    public int getIndex() {
        return byteStream.getPosition();
    }

    /**
     * Unreads the last byte.
     */
    void unreadByte() {
        byteStream.unreadByte();
    }
}
