BASE64 Decoder Stream from Sun Microsystems
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can obtain
* a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
* or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
* Sun designates this particular file as subject to the "Classpath" exception
* as provided by Sun in the GPL Version 2 section of the License file that
* accompanied this code. If applicable, add the following below the License
* Header, with the fields enclosed by brackets [] replaced by your own
* identifying information: "Portions Copyrighted [year]
* [name of copyright owner]"
*
* Contributor(s):
*
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
/*
* @(#)BASE64DecoderStream.java 1.16 07/05/04
*/
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 {
// buffer of decoded bytes for single byte reads
private byte[] buffer = new byte[3];
private int bufsize = 0; // size of the cache
private int index = 0; // index into the cache
// buffer for almost 8K of typical 76 chars + CRLF lines,
// used by getByte method. this buffer contains encoded bytes.
private byte[] input_buffer = new byte[78*105];
private int input_pos = 0;
private int input_len = 0;;
private boolean ignoreErrors = false;
/**
* Create a BASE64 decoder that decodes the specified input stream.
* The System property <code>mail.mime.base64.ignoreerrors</code>
* controls whether errors in the encoded data cause an exception
* or are ignored. The default is false (errors cause exception).
*
* @param in the input stream
*/
public BASE64DecoderStream(InputStream in) {
super(in);
try {
String s = System.getProperty("mail.mime.base64.ignoreerrors");
// default to false
ignoreErrors = s != null && !s.equalsIgnoreCase("false");
} catch (SecurityException sex) {
// ignore it
}
}
/**
* Create a BASE64 decoder that decodes the specified input stream.
*
* @param in the input stream
* @param ignoreErrors ignore errors in encoded data?
*/
public BASE64DecoderStream(InputStream in, boolean ignoreErrors) {
super(in);
this.ignoreErrors = ignoreErrors;
}
/**
* 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) {
bufsize = decode(buffer, 0, buffer.length);
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 {
// empty out single byte read buffer
int off0 = off;
while (index < bufsize && len > 0) {
buf[off++] = buffer[index++];
len--;
}
if (index >= bufsize)
bufsize = index = 0;
int bsize = (len / 3) * 3; // round down to multiple of 3 bytes
if (bsize > 0) {
int size = decode(buf, off, bsize);
off += size;
len -= size;
if (size != bsize) { // hit EOF?
if (off == off0) // haven't returned any data
return -1;
else // returned some data before hitting EOF
return off - off0;
}
}
// finish up with a partial read if necessary
for (; len > 0; len--) {
int c = read();
if (c == -1) // EOF
break;
buf[off++] = (byte)c;
}
if (off == off0) // haven't returned any data
return -1;
else // returned some data before hitting EOF
return off - off0;
}
/**
* 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. Most of the complexity here is dealing
* with error cases. Returns the number of bytes decoded, which
* may be zero. Decoding is done by filling an int with 4 6-bit
* values by shifting them in from the bottom and then extracting
* 3 8-bit bytes from the int by shifting them out from the bottom.
*
* @param outbuf the buffer into which to put the decoded bytes
* @param pos position in the buffer to start filling
* @param len the number of bytes to fill
* @return the number of bytes filled, always a multiple
* of three, and may be zero
* @exception IOException if the data is incorrectly formatted
*/
private int decode(byte[] outbuf, int pos, int len) throws IOException {
int pos0 = pos;
while (len >= 3) {
/*
* 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;
int val = 0;
while (got < 4) {
int i = getByte();
if (i == -1 || i == -2) {
boolean atEOF;
if (i == -1) {
if (got == 0)
return pos - pos0;
if (!ignoreErrors)
throw new IOException("Error in encoded stream: " +
"needed 4 valid base64 characters " +
"but only got " + got + " before EOF" +
recentChars());
atEOF = true; // don't read any more
} else { // i == -2
// found a padding character, we're at EOF
// XXX - should do something to make EOF "sticky"
if (got < 2 && !ignoreErrors)
throw new IOException("Error in encoded stream: " +
"needed at least 2 valid base64 characters," +
" but only got " + got +
" before padding character (=)" +
recentChars());
// didn't get any characters before padding character?
if (got == 0)
return pos - pos0;
atEOF = false; // need to keep reading
}
// pad partial result with zeroes
// how many bytes will we produce on output?
// (got always < 4, so size always < 3)
int size = got - 1;
if (size == 0)
size = 1;
// handle the one padding character we've seen
got++;
val <<= 6;
while (got < 4) {
if (!atEOF) {
// consume the rest of the padding characters,
// filling with zeroes
i = getByte();
if (i == -1) {
if (!ignoreErrors)
throw new IOException(
"Error in encoded stream: " +
"hit EOF while looking for " +
"padding characters (=)" +
recentChars());
} else if (i != -2) {
if (!ignoreErrors)
throw new IOException(
"Error in encoded stream: " +
"found valid base64 character after " +
"a padding character (=)" +
recentChars());
}
}
val <<= 6;
got++;
}
// now pull out however many valid bytes we got
val >>= 8; // always skip first one
if (size == 2)
outbuf[pos + 1] = (byte)(val & 0xff);
val >>= 8;
outbuf[pos] = (byte)(val & 0xff);
// len -= size; // not needed, return below
pos += size;
return pos - pos0;
} else {
// got a valid byte
val <<= 6;
got++;
val |= i;
}
}
// read 4 valid characters, now extract 3 bytes
outbuf[pos + 2] = (byte)(val & 0xff);
val >>= 8;
outbuf[pos + 1] = (byte)(val & 0xff);
val >>= 8;
outbuf[pos] = (byte)(val & 0xff);
len -= 3;
pos += 3;
}
return pos - pos0;
}
/**
* Read the next valid byte from the input stream.
* Buffer lots of data from underlying stream in input_buffer,
* for efficiency.
*
* @return the next byte, -1 on EOF, or -2 if next byte is '='
* (padding at end of encoded data)
*/
private int getByte() throws IOException {
int c;
do {
if (input_pos >= input_len) {
try {
input_len = in.read(input_buffer);
} catch (EOFException ex) {
return -1;
}
if (input_len <= 0)
return -1;
input_pos = 0;
}
// get the next byte in the buffer
c = input_buffer[input_pos++] & 0xff;
// is it a padding byte?
if (c == '=')
return -2;
// no, convert it
c = pem_convert_array[c];
// loop until we get a legitimate byte
} while (c == -1);
return c;
}
/**
* Return the most recent characters, for use in an error message.
*/
private String recentChars() {
// reach into the input buffer and extract up to 10
// recent characters, to help in debugging.
String errstr = "";
int nc = input_pos > 10 ? 10 : input_pos;
if (nc > 0) {
errstr += ", the " + nc +
" most recent characters were: \"";
for (int k = input_pos - nc; k < input_pos; k++) {
char c = (char)(input_buffer[k] & 0xff);
switch (c) {
case '\r': errstr += "\\r"; break;
case '\n': errstr += "\\n"; break;
case '\t': errstr += "\\t"; break;
default:
if (c >= ' ' && c < 0177)
errstr += c;
else
errstr += ("\\" + (int)c);
}
}
errstr += "\"";
}
return errstr;
}
/**
* 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) {
int val;
int osize = 3;
val = pem_convert_array[inbuf[inpos++] & 0xff];
val <<= 6;
val |= pem_convert_array[inbuf[inpos++] & 0xff];
val <<= 6;
if (inbuf[inpos] != '=') // End of this BASE64 encoding
val |= pem_convert_array[inbuf[inpos++] & 0xff];
else
osize--;
val <<= 6;
if (inbuf[inpos] != '=') // End of this BASE64 encoding
val |= pem_convert_array[inbuf[inpos++] & 0xff];
else
osize--;
if (osize > 2)
outbuf[outpos + 2] = (byte)(val & 0xff);
val >>= 8;
if (osize > 1)
outbuf[outpos + 1] = (byte)(val & 0xff);
val >>= 8;
outbuf[outpos] = (byte)(val & 0xff);
outpos += osize;
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 ***/
}
Related examples in the same category