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 * 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

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 */

/*

 * @(#)BASE64DecoderStream.java       1.8 02/03/27

 */

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

import java.io.*;

/**

 * This class implements a BASE64 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

 * @author Bill Shannon

 */

public class BASE64DecoderStream extends FilterInputStream {

    private byte[] buffer;      // cache of decoded bytes

    private int bufsize = 0;    // size of the cache

    private int index = 0;      // index into the cache

    /**

     * Create a BASE64 decoder that decodes the specified input stream

     * @param in        the input stream

     */

    public BASE64DecoderStream(InputStream in) {

        super(in);

        buffer = new byte[3];

    }

    /**

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

     *             stream is reached.

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

     * @see        java.io.FilterInputStream#in

     */

    public int read() throws IOException {

        if (index >= bufsize) {

            decode(); // Fills up buffer

            if (bufsize == 0) // buffer is empty

                return -1;

            index = 0; // reset index into buffer

        }

        return buffer[index++] & 0xff; // Zero off the MSB

    }

    /**

     * 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; // Maybe later ..

    }

    /**

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

     * stream without blocking. However, this figure is only

     * a close approximation in case the original encoded stream

     * contains embedded CRLFs; since the CRLFs are discarded, not decoded

     */

    public int available() throws IOException {

         // This is only an estimate, since in.available()

         // might include CRLFs too ..

         return ((in.available() * 3)/4 + (bufsize-index));

    }

    /**

     * This character array provides the character to value map

     * based on RFC1521.

     */

    private final static char pem_array[] = {

        'A','B','C','D','E','F','G','H', // 0

        'I','J','K','L','M','N','O','P', // 1

        'Q','R','S','T','U','V','W','X', // 2

        'Y','Z','a','b','c','d','e','f', // 3

        'g','h','i','j','k','l','m','n', // 4

        'o','p','q','r','s','t','u','v', // 5

        'w','x','y','z','0','1','2','3', // 6

        '4','5','6','7','8','9','+','/'  // 7

    };

    private final static byte pem_convert_array[] = new byte[256];

    static {

        for (int i = 0; i < 255; i++)

            pem_convert_array[i] = -1;

        for(int i = 0; i < pem_array.length; i++)

            pem_convert_array[pem_array[i]] = (byte) i;

    }

    /* The decoder algorithm */

    private byte[] decode_buffer = new byte[4];

    private void decode() throws IOException {

        bufsize = 0;

        /*

         * We need 4 valid base64 characters before we start decoding.

         * We skip anything that's not a valid base64 character (usually

         * just CRLF).

         */

        int got = 0;

        while (got < 4) {

            int i = in.read();

            if (i == -1) {

                if (got == 0)

                    return;     // EOF before any data is ok

                throw new IOException("Error in encoded stream, got " + got);

            }

            if (i >= 0 && i < 256 && i == '=' || pem_convert_array[i] != -1)

                decode_buffer[got++] = (byte)i;

        }

        byte a, b;

        a = pem_convert_array[decode_buffer[0] & 0xff];

        b = pem_convert_array[decode_buffer[1] & 0xff];

        // The first decoded byte

        buffer[bufsize++] = (byte)(((a << 2) & 0xfc) | ((b >>> 4) & 3));

        if (decode_buffer[2] == '=') // End of this BASE64 encoding

            return;

        a = b;

        b = pem_convert_array[decode_buffer[2] & 0xff];

        // The second decoded byte

        buffer[bufsize++] = (byte)(((a << 4) & 0xf0) | ((b >>> 2) & 0xf));

        if (decode_buffer[3] == '=') // End of this BASE64 encoding

            return;

        a = b;

        b = pem_convert_array[decode_buffer[3] & 0xff];

        // The third decoded byte

        buffer[bufsize++] = (byte)(((a << 6) & 0xc0) | (b & 0x3f));

    }

    /**

     * Base64 decode a byte array.  No line breaks are allowed.

     * This method is suitable for short strings, such as those

     * in the IMAP AUTHENTICATE protocol, but not to decode the

     * entire content of a MIME part.

     *

     * NOTE: inbuf may only contain valid base64 characters.

     *       Whitespace is not ignored.

     */

    public static byte[] decode(byte[] inbuf) {

        int size = (inbuf.length / 4) * 3;

        if (size == 0)

            return inbuf;

        if (inbuf[inbuf.length - 1] == '=') {

            size--;

            if (inbuf[inbuf.length - 2] == '=')

                size--;

        }

        byte[] outbuf = new byte[size];

        int inpos = 0, outpos = 0;

        size = inbuf.length;

        while (size > 0) {

            byte a, b;

            a = pem_convert_array[inbuf[inpos++] & 0xff];

            b = pem_convert_array[inbuf[inpos++] & 0xff];

            // The first decoded byte

            outbuf[outpos++] = (byte)(((a << 2) & 0xfc) | ((b >>> 4) & 3));

            if (inbuf[inpos] == '=') // End of this BASE64 encoding

                return outbuf;

            a = b;

            b = pem_convert_array[inbuf[inpos++] & 0xff];

            // The second decoded byte

            outbuf[outpos++] = (byte)(((a << 4) & 0xf0) | ((b >>> 2) & 0xf));

            if (inbuf[inpos] == '=') // End of this BASE64 encoding

                return outbuf;

            a = b;

            b = pem_convert_array[inbuf[inpos++] & 0xff];

            // The third decoded byte

            outbuf[outpos++] = (byte)(((a << 6) & 0xc0) | (b & 0x3f));

            size -= 4;

        }

        return outbuf;

    }

    /*** begin TEST program ***

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

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

        BASE64DecoderStream decoder = new BASE64DecoderStream(infile);

        int c;

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

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

        System.out.flush();

    }

    *** end TEST program ***/

}