BASE64 Encoder Stream
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/*
* @(#)BASE64EncoderStream.java 1.10 07/05/04
*/
import java.io.*;
/**
* This class implements a BASE64 encoder. It is implemented as
* a FilterOutputStream, so one can just wrap this class around
* any output stream and write bytes into this filter. The encoding
* is done as the bytes are written out.
*
* @author John Mani
* @author Bill Shannon
*/
public class BASE64EncoderStream extends FilterOutputStream {
private byte[] buffer; // cache of bytes that are yet to be encoded
private int bufsize = 0; // size of the cache
private byte[] outbuf; // line size output buffer
private int count = 0; // number of bytes that have been output
private int bytesPerLine; // number of bytes per line
private int lineLimit; // number of input bytes to output bytesPerLine
private boolean noCRLF = false;
private static byte[] newline = new byte[] { '\r', '\n' };
/**
* Create a BASE64 encoder that encodes the specified output stream.
*
* @param out the output stream
* @param bytesPerLine number of bytes per line. The encoder inserts
* a CRLF sequence after the specified number of bytes,
* unless bytesPerLine is Integer.MAX_VALUE, in which
* case no CRLF is inserted. bytesPerLine is rounded
* down to a multiple of 4.
*/
public BASE64EncoderStream(OutputStream out, int bytesPerLine) {
super(out);
buffer = new byte[3];
if (bytesPerLine == Integer.MAX_VALUE || bytesPerLine < 4) {
noCRLF = true;
bytesPerLine = 76;
}
bytesPerLine = (bytesPerLine / 4) * 4; // Rounded down to 4n
this.bytesPerLine = bytesPerLine; // save it
lineLimit = bytesPerLine / 4 * 3;
if (noCRLF) {
outbuf = new byte[bytesPerLine];
} else {
outbuf = new byte[bytesPerLine + 2];
outbuf[bytesPerLine] = (byte)'\r';
outbuf[bytesPerLine + 1] = (byte)'\n';
}
}
/**
* Create a BASE64 encoder that encodes the specified input stream.
* Inserts the CRLF sequence after outputting 76 bytes.
*
* @param out the output stream
*/
public BASE64EncoderStream(OutputStream out) {
this(out, 76);
}
/**
* Encodes <code>len</code> bytes from the specified
* <code>byte</code> array starting at offset <code>off</code> to
* this output stream.
*
* @param b the data.
* @param off the start offset in the data.
* @param len the number of bytes to write.
* @exception IOException if an I/O error occurs.
*/
public synchronized void write(byte[] b, int off, int len)
throws IOException {
int end = off + len;
// finish off incomplete coding unit
while (bufsize != 0 && off < end)
write(b[off++]);
// finish off line
int blen = ((bytesPerLine - count) / 4) * 3;
if (off + blen < end) {
// number of bytes that will be produced in outbuf
int outlen = encodedSize(blen);
if (!noCRLF) {
outbuf[outlen++] = (byte)'\r';
outbuf[outlen++] = (byte)'\n';
}
out.write(encode(b, off, blen, outbuf), 0, outlen);
off += blen;
count = 0;
}
// do bulk encoding a line at a time.
for (; off + lineLimit < end; off += lineLimit)
out.write(encode(b, off, lineLimit, outbuf));
// handle remaining partial line
if (off + 3 < end) {
blen = end - off;
blen = (blen / 3) * 3; // round down
// number of bytes that will be produced in outbuf
int outlen = encodedSize(blen);
out.write(encode(b, off, blen, outbuf), 0, outlen);
off += blen;
count += outlen;
}
// start next coding unit
for (; off < end; off++)
write(b[off]);
}
/**
* Encodes <code>b.length</code> bytes to this output stream.
*
* @param b the data to be written.
* @exception IOException if an I/O error occurs.
*/
public void write(byte[] b) throws IOException {
write(b, 0, b.length);
}
/**
* Encodes the specified <code>byte</code> to this output stream.
*
* @param c the <code>byte</code>.
* @exception IOException if an I/O error occurs.
*/
public synchronized void write(int c) throws IOException {
buffer[bufsize++] = (byte)c;
if (bufsize == 3) { // Encoding unit = 3 bytes
encode();
bufsize = 0;
}
}
/**
* Flushes this output stream and forces any buffered output bytes
* to be encoded out to the stream.
*
* @exception IOException if an I/O error occurs.
*/
public synchronized void flush() throws IOException {
if (bufsize > 0) { // If there's unencoded characters in the buffer ..
encode(); // .. encode them
bufsize = 0;
}
out.flush();
}
/**
* Forces any buffered output bytes to be encoded out to the stream
* and closes this output stream
*/
public synchronized void close() throws IOException {
flush();
if (count > 0 && !noCRLF) {
out.write(newline);
out.flush();
}
out.close();
}
/** This array maps the characters to their 6 bit values */
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
};
/**
* Encode the data stored in <code>buffer</code>.
* Uses <code>outbuf</code> to store the encoded
* data before writing.
*
* @exception IOException if an I/O error occurs.
*/
private void encode() throws IOException {
int osize = encodedSize(bufsize);
out.write(encode(buffer, 0, bufsize, outbuf), 0, osize);
// increment count
count += osize;
// If writing out this encoded unit caused overflow,
// start a new line.
if (count >= bytesPerLine) {
if (!noCRLF)
out.write(newline);
count = 0;
}
}
/**
* Base64 encode a byte array. No line breaks are inserted.
* This method is suitable for short strings, such as those
* in the IMAP AUTHENTICATE protocol, but not to encode the
* entire content of a MIME part.
*/
public static byte[] encode(byte[] inbuf) {
if (inbuf.length == 0)
return inbuf;
return encode(inbuf, 0, inbuf.length, null);
}
/**
* Internal use only version of encode. Allow specifying which
* part of the input buffer to encode. If outbuf is non-null,
* it's used as is. Otherwise, a new output buffer is allocated.
*/
private static byte[] encode(byte[] inbuf, int off, int size,
byte[] outbuf) {
if (outbuf == null)
outbuf = new byte[encodedSize(size)];
int inpos, outpos;
int val;
for (inpos = off, outpos = 0; size >= 3; size -= 3, outpos += 4) {
val = inbuf[inpos++] & 0xff;
val <<= 8;
val |= inbuf[inpos++] & 0xff;
val <<= 8;
val |= inbuf[inpos++] & 0xff;
outbuf[outpos+3] = (byte)pem_array[val & 0x3f];
val >>= 6;
outbuf[outpos+2] = (byte)pem_array[val & 0x3f];
val >>= 6;
outbuf[outpos+1] = (byte)pem_array[val & 0x3f];
val >>= 6;
outbuf[outpos+0] = (byte)pem_array[val & 0x3f];
}
// done with groups of three, finish up any odd bytes left
if (size == 1) {
val = inbuf[inpos++] & 0xff;
val <<= 4;
outbuf[outpos+3] = (byte)'='; // pad character;
outbuf[outpos+2] = (byte)'='; // pad character;
outbuf[outpos+1] = (byte)pem_array[val & 0x3f];
val >>= 6;
outbuf[outpos+0] = (byte)pem_array[val & 0x3f];
} else if (size == 2) {
val = inbuf[inpos++] & 0xff;
val <<= 8;
val |= inbuf[inpos++] & 0xff;
val <<= 2;
outbuf[outpos+3] = (byte)'='; // pad character;
outbuf[outpos+2] = (byte)pem_array[val & 0x3f];
val >>= 6;
outbuf[outpos+1] = (byte)pem_array[val & 0x3f];
val >>= 6;
outbuf[outpos+0] = (byte)pem_array[val & 0x3f];
}
return outbuf;
}
/**
* Return the corresponding encoded size for the given number
* of bytes, not including any CRLF.
*/
private static int encodedSize(int size) {
return ((size + 2) / 3) * 4;
}
/*** begin TEST program
public static void main(String argv[]) throws Exception {
FileInputStream infile = new FileInputStream(argv[0]);
BASE64EncoderStream encoder = new BASE64EncoderStream(System.out);
int c;
while ((c = infile.read()) != -1)
encoder.write(c);
encoder.close();
}
*** end TEST program **/
}
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