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 * 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 org.apache.james.mime4j;

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

/**
 * InputStream which converts <code>\r</code>
 * bytes not followed by <code>\n</code> and <code>\n</code> not 
 * preceded by <code>\r</code> to <code>\r\n</code>.
 *
 * 
 * @version $Id: EOLConvertingInputStream.java,v 1.4 2004/11/29 13:15:42 ntherning Exp $
 */
public class EOLConvertingInputStream extends InputStream {
    /** Converts single '\r' to '\r\n' */
    public static final int CONVERT_CR   = 1;
    /** Converts single '\n' to '\r\n' */
    public static final int CONVERT_LF   = 2;
    /** Converts single '\r' and '\n' to '\r\n' */
    public static final int CONVERT_BOTH = 3;

    private PushbackInputStream in = null;
    private int previous = 0;
    private int flags = CONVERT_BOTH;
    private int size = 0;
    private int pos = 0;
    private int nextTenPctPos;
    private int tenPctSize;
    private Callback callback;

    public interface Callback {
        public void report(int bytesRead);
    }

    /**
     * Creates a new <code>EOLConvertingInputStream</code>
     * instance converting bytes in the given <code>InputStream</code>.
     * The flag <code>CONVERT_BOTH</code> is the default.
     * 
     * @param in the <code>InputStream</code> to read from.
     */
    public EOLConvertingInputStream(InputStream _in) {
        super();
        in = new PushbackInputStream(_in, 2);
    }

    /**
     * Creates a new <code>EOLConvertingInputStream</code>
     * instance converting bytes in the given <code>InputStream</code>.
     * 
     * @param _in the <code>InputStream</code> to read from.
     * @param _size the size of the input stream (need not be exact)
     * @param _callback a callback reporting when each 10% of stream's size is reached
     */
    public EOLConvertingInputStream(InputStream _in, int _size, Callback _callback) {
        this(_in);
        size = _size;
        tenPctSize = size / 10;
        nextTenPctPos = tenPctSize;
        callback = _callback;
    }

    /**
     * Closes the underlying stream.
     * 
     * @throws IOException on I/O errors.
     */
    public void close() throws IOException {
        in.close();
    }
    
    private int readByte() throws IOException {
        int b = in.read();
        if (b != -1) {
            if (callback != null && pos++ == nextTenPctPos) {
                nextTenPctPos += tenPctSize;
                if (callback != null) {
                    callback.report(pos);
                }
            }
        }
        return b;
    }

    private void unreadByte(int c) throws IOException {
        in.unread(c);
        pos--;
    }

    /**
     * @see java.io.InputStream#read()
     */
    public int read() throws IOException {
        int b = readByte();
        
        if (b == -1) {
            pos = size;
            return -1;
        }
        
        if ((flags & CONVERT_CR) != 0 && b == '\r') {
            int c = readByte();
            if (c != -1) {
                unreadByte(c);
            }
            if (c != '\n') {
                unreadByte('\n');
            }
        } else if ((flags & CONVERT_LF) != 0 && b == '\n' && previous != '\r') {
            b = '\r';
            unreadByte('\n');
        }
        
        previous = b;
        
        return b;
    }

}