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 *   http://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 ****************************************************************/
019
020package org.apache.james.mime4j.io;
021
022import org.apache.james.mime4j.util.ByteArrayBuffer;
023
024import java.io.FilterInputStream;
025import java.io.IOException;
026import java.io.InputStream;
027
028/**
029 * Input stream capable of reading lines of text.
030 */
031public abstract class LineReaderInputStream extends FilterInputStream {
032
033    protected LineReaderInputStream(InputStream in) {
034        super(in);
035    }
036
037    /**
038     * Reads one line of text into the given {@link ByteArrayBuffer}.
039     *
040     * @param dst Destination
041     * @return number of bytes copied or <code>-1</code> if the end of
042     * the stream has been reached.
043     *
044     * @throws MaxLineLimitException if the line exceeds a limit on
045     *   the line length imposed by a subclass.
046     * @throws IOException in case of an I/O error.
047     */
048    public abstract int readLine(final ByteArrayBuffer dst)
049            throws MaxLineLimitException, IOException;
050
051    /**
052     * Tries to unread the last read line.
053     *
054     * Implementation may refuse to unread a new buffer until the previous
055     * unread one has been competely consumed.
056     *
057     * Implementations will directly use the byte array backed by buf, so
058     * make sure to not alter it anymore once this method has been called.
059     *
060     * @return true if the unread has been succesfull.
061     */
062    public abstract boolean unread(ByteArrayBuffer buf);
063
064}