com.sun.xml.messaging.saaj.packaging.mime.util.BASE64DecoderStream Maven / Gradle / Ivy
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*/
/*
* @(#)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
*/
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.
*/
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 ***/
}