core/src/main/java/org/apache/james/mime4j/io/LineReaderInputStream.java

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 * 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   *
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package org.apache.james.mime4j.io;

import org.apache.james.mime4j.util.ByteArrayBuffer;

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

/**
 * Input stream capable of reading lines of text.
 */
public abstract class LineReaderInputStream extends FilterInputStream {

    protected LineReaderInputStream(InputStream in) {
        super(in);
    }

    /**
     * Reads one line of text into the given {@link ByteArrayBuffer}.
     *
     * @param dst Destination
     * @return number of bytes copied or <code>-1</code> if the end of
     * the stream has been reached.
     *
     * @throws MaxLineLimitException if the line exceeds a limit on
     *   the line length imposed by a subclass.
     * @throws IOException in case of an I/O error.
     */
    public abstract int readLine(final ByteArrayBuffer dst)
            throws MaxLineLimitException, IOException;

    /**
     * Tries to unread the last read line.
     *
     * Implementation may refuse to unread a new buffer until the previous
     * unread one has been competely consumed.
     *
     * Implementations will directly use the byte array backed by buf, so
     * make sure to not alter it anymore once this method has been called.
     *
     * @return true if the unread has been succesfull.
     */
    public abstract boolean unread(ByteArrayBuffer buf);

}