/*

 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * @(#)QPDecoderStream.java   1.9 02/04/02

 */

package com.sun.xml.internal.messaging.saaj.packaging.mime.util;

import java.io.*;

/**

 * This class implements a QP Decoder. It is implemented as

 * a FilterInputStream, so one can just wrap this class around

 * any input stream and read bytes from this filter. The decoding

 * is done as the bytes are read out.

 *

 * @author John Mani

 */

public class QPDecoderStream extends FilterInputStream {

    protected byte[] ba = new byte[2];

    protected int spaces = 0;

    /**

     * Create a Quoted Printable decoder that decodes the specified

     * input stream.

     * @param in        the input stream

     */

    public QPDecoderStream(InputStream in) {

        super(new PushbackInputStream(in, 2)); // pushback of size=2

    }

    /**

     * Read the next decoded byte from this input stream. The byte

     * is returned as an <code>int</code> in the range <code>0</code>

     * to <code>255</code>. If no byte is available because the end of

     * the stream has been reached, the value <code>-1</code> is returned.

     * This method blocks until input data is available, the end of the

     * stream is detected, or an exception is thrown.

     *

     * @return     the next byte of data, or <code>-1</code> if the end of the

     *             stream is reached.

     * @exception  IOException  if an I/O error occurs.

     */

    public int read() throws IOException {

        if (spaces > 0) {

            // We have cached space characters, return one

            spaces--;

            return ' ';

        }

        int c = in.read();

        if (c == ' ') {

            // Got space, keep reading till we get a non-space char

            while ((c = in.read()) == ' ')

                spaces++;

            if (c == '\r' || c == '\n' || c == -1)

                // If the non-space char is CR/LF/EOF, the spaces we got

                // so far is junk introduced during transport. Junk 'em.

                spaces = 0;

            else {

                // The non-space char is NOT CR/LF, the spaces are valid.

                ((PushbackInputStream)in).unread(c);

                c = ' ';

            }

            return c; // return either <SPACE> or <CR/LF>

        }

        else if (c == '=') {

            // QP Encoded atom. Decode the next two bytes

            int a = in.read();

            if (a == '\n') {

                /* Hmm ... not really confirming QP encoding, but lets

                 * allow this as a LF terminated encoded line .. and

                 * consider this a soft linebreak and recurse to fetch

                 * the next char.

                 */

                return read();

            } else if (a == '\r') {

                // Expecting LF. This forms a soft linebreak to be ignored.

                int b = in.read();

                if (b != '\n')

                    /* Not really confirming QP encoding, but

                     * lets allow this as well.

                     */

                    ((PushbackInputStream)in).unread(b);

                return read();

            } else if (a == -1) {

                // Not valid QP encoding, but we be nice and tolerant here !

                return -1;

            } else {

                ba[0] = (byte)a;

                ba[1] = (byte)in.read();

                try {

                    return ASCIIUtility.parseInt(ba, 0, 2, 16);

                } catch (NumberFormatException nex) {

                    /*

                    System.err.println(

                        "Illegal characters in QP encoded stream: " +

                        ASCIIUtility.toString(ba, 0, 2)

                    );

                    */

                    ((PushbackInputStream)in).unread(ba);

                    return c;

                }

            }

        }

        return c;

    }

    /**

     * Reads up to <code>len</code> decoded bytes of data from this input stream

     * into an array of bytes. This method blocks until some input is

     * available.

     * <p>

     *

     * @param      buf   the buffer into which the data is read.

     * @param      off   the start offset of the data.

     * @param      len   the maximum number of bytes read.

     * @return     the total number of bytes read into the buffer, or

     *             <code>-1</code> if there is no more data because the end of

     *             the stream has been reached.

     * @exception  IOException  if an I/O error occurs.

     */

    public int read(byte[] buf, int off, int len) throws IOException {

        int i, c;

        for (i = 0; i < len; i++) {

            if ((c = read()) == -1) {

                if (i == 0) // At end of stream, so we should

                    i = -1; // return -1 , NOT 0.

                break;

            }

            buf[off+i] = (byte)c;

        }

        return i;

    }

    /**

     * Tests if this input stream supports marks. Currently this class

     * does not support marks

     */

    public boolean markSupported() {

        return false;

    }

    /**

     * Returns the number of bytes that can be read from this input

     * stream without blocking. The QP algorithm does not permit

     * a priori knowledge of the number of bytes after decoding, so

     * this method just invokes the <code>available</code> method

     * of the original input stream.

     */

    public int available() throws IOException {

        // This is bogus ! We don't really know how much

        // bytes are available *after* decoding

        return in.available();

    }

    /**** begin TEST program

    public static void main(String argv[]) throws Exception {

        FileInputStream infile = new FileInputStream(argv[0]);

        QPDecoderStream decoder = new QPDecoderStream(infile);

        int c;

        while ((c = decoder.read()) != -1)

            System.out.print((char)c);

        System.out.println();

    }

    *** end TEST program ****/

}