SeptetPackingInputStream.java

/*
 * Copyright (c) 2020, Stein Eldar Johnsen
 *
 * 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
 *
 *   http://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 net.morimekta.io;

import java.io.IOException;
import java.io.InputStream;

/**
 * An input stream that reads septets (7-bit values) from a bit-packed
 * underlying stream. Each {@link #read()} call returns a 7-bit value,
 * making this the counterpart to {@link SeptetPackingOutputStream}.
 */
public class SeptetPackingInputStream extends InputStream {
    private BitPackingInputStream in;

    /**
     * Create a septet packing input stream.
     *
     * @param in Input stream to read packed bytes from.
     */
    public SeptetPackingInputStream(InputStream in) {
        this.in = in instanceof BitPackingInputStream
                  ? (BitPackingInputStream) in
                  : new BitPackingInputStream(in);
    }

    @Override
    public int read() throws IOException {
        if (in == null) {
            throw new IOException("Reading from closed stream");
        }
        return in.readBits(7);
    }

    @Override
    public int available() throws IOException {
        return in == null ? 0 : in.available(7);
    }

    @Override
    public void close() throws IOException {
        if (in != null) {
            try {
                in.close();
            } finally {
                in = null;
            }
        }
    }
}