001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.input;
018
019import static org.apache.commons.io.IOUtils.CR;
020import static org.apache.commons.io.IOUtils.EOF;
021import static org.apache.commons.io.IOUtils.LF;
022
023import java.io.IOException;
024import java.io.InputStream;
025
026/**
027 * A filtering input stream that ensures the content will have UNIX-style line endings, LF.
028 *
029 * @since 2.5
030 */
031public class UnixLineEndingInputStream extends AbstractLineEndingInputStream {
032
033    /**
034     * Constructs an input stream that filters another stream
035     *
036     * @param inputStream                        The input stream to wrap.
037     * @param lineFeedAtEos true to ensure that the file ends with LF.
038     */
039    public UnixLineEndingInputStream(final InputStream inputStream, final boolean lineFeedAtEos) {
040        super(inputStream, lineFeedAtEos);
041    }
042
043    /**
044     * Handles the end of stream condition.
045     *
046     * @param previousWasSlashCr Indicates if the last seen was a {@code \r}.
047     * @return The next char to output to the stream.
048     */
049    private int handleEos(final boolean previousWasSlashCr) {
050        if (previousWasSlashCr || !lineFeedAtEos) {
051            return EOF;
052        }
053        if (!atSlashLf) {
054            atSlashLf = true;
055            return LF;
056        }
057        return EOF;
058    }
059
060    /**
061     * {@inheritDoc}
062     */
063    @Override
064    public synchronized int read() throws IOException {
065        final boolean previousWasSlashR = atSlashCr;
066        if (atEos) {
067            return handleEos(previousWasSlashR);
068        }
069        final int target = readUpdate();
070        if (atEos) {
071            return handleEos(previousWasSlashR);
072        }
073        if (atSlashCr) {
074            return LF;
075        }
076
077        if (previousWasSlashR && atSlashLf) {
078            return read();
079        }
080
081        return target;
082    }
083
084    /**
085     * Reads the next item from the target, updating internal flags in the process
086     *
087     * @return the next int read from the target stream.
088     * @throws IOException If an I/O error occurs.
089     */
090    private int readUpdate() throws IOException {
091        final int target = this.in.read();
092        atEos = target == EOF;
093        if (atEos) {
094            return target;
095        }
096        atSlashCr = target == CR;
097        atSlashLf = target == LF;
098        return target;
099    }
100}