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 *      http://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 Windows line endings, CRLF.
028 *
029 * @since 2.5
030 */
031public class WindowsLineEndingInputStream  extends InputStream {
032
033    private boolean slashRSeen;
034
035    private boolean slashNSeen;
036
037    private boolean injectSlashN;
038
039    private boolean eofSeen;
040
041    private final InputStream target;
042
043    private final boolean ensureLineFeedAtEndOfFile;
044
045    /**
046     * Creates an input stream that filters another stream
047     *
048     * @param in                        The input stream to wrap
049     * @param ensureLineFeedAtEndOfFile true to ensure that the file ends with CRLF
050     */
051    public WindowsLineEndingInputStream(final InputStream in, final boolean ensureLineFeedAtEndOfFile) {
052        this.target = in;
053        this.ensureLineFeedAtEndOfFile = ensureLineFeedAtEndOfFile;
054    }
055
056    /**
057     * Reads the next item from the target, updating internal flags in the process
058     * @return the next int read from the target stream
059     * @throws IOException upon error
060     */
061    private int readWithUpdate() throws IOException {
062        final int target = this.target.read();
063        eofSeen = target == EOF;
064        if (eofSeen) {
065            return target;
066        }
067        slashRSeen = target == CR;
068        slashNSeen = target == LF;
069        return target;
070    }
071
072    /**
073     * {@inheritDoc}
074     */
075    @Override
076    public int read() throws IOException {
077        if (eofSeen) {
078            return eofGame();
079        }
080        if (injectSlashN) {
081            injectSlashN = false;
082            return LF;
083        }
084        final boolean prevWasSlashR = slashRSeen;
085        final int target = readWithUpdate();
086        if (eofSeen) {
087            return eofGame();
088        }
089        if ((target == LF) && !prevWasSlashR) {
090            injectSlashN = true;
091            return CR;
092        }
093        return target;
094    }
095
096    /**
097     * Handles the EOF-handling at the end of the stream
098     * @return The next char to output to the stream
099     */
100    private int eofGame() {
101        if (!ensureLineFeedAtEndOfFile) {
102            return EOF;
103        }
104        if (!slashNSeen && !slashRSeen) {
105            slashRSeen = true;
106            return CR;
107        }
108        if (!slashNSeen) {
109            slashRSeen = false;
110            slashNSeen = true;
111            return LF;
112        }
113        return EOF;
114    }
115
116    /**
117     * Closes the stream. Also closes the underlying stream.
118     * @throws IOException upon error
119     */
120    @Override
121    public void close() throws IOException {
122        super.close();
123        target.close();
124    }
125
126    /**
127     * {@inheritDoc}
128     */
129    @Override
130    public synchronized void mark(final int readlimit) {
131        throw UnsupportedOperationExceptions.mark();
132    }
133}