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/*
 * Copyright (c) 1997, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0, which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

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



package com.sun.xml.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 int in the range 0 
     * to 255. If no byte is available because the end of 
     * the stream has been reached, the value -1 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 -1 if the end of the
     *             stream is reached.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    @Override
    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 len decoded bytes of data from this input stream
     * into an array of bytes. This method blocks until some input is
     * available.
     * 

* * @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 * -1 if there is no more data because the end of * the stream has been reached. * @exception IOException if an I/O error occurs. */ @Override 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 */ @Override 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 */ @Override 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. * * @param inbuf byte array to decode * * @return decoded byte array * * 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 ***/ }





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