package org.madore.damlengine;

import java.io.InputStream;
import java.io.IOException;

public final class Base64 {

    public static final char[] base64Alphabet = {
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
	'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
	'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
	'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
    };

    public static String encode(InputStream str) {
	byte[] inb = new byte[768];
	char[] outb = new char[1024];
	StringBuffer strbuf = new StringBuffer();
	try {
	    int len;
	    while ( ( len = str.read(inb) ) > 0 ) {
		for ( int i=0 ; 3*i<len ; i++ ) {
		    outb[4*i] = base64Alphabet[(inb[3*i]>>>2)&0x3f];
		    if ( 3*i+1 < len )
			outb[4*i+1] = base64Alphabet[(inb[3*i]&3)<<4 | ((inb[3*i+1]>>>4)&0xf)];
		    else
			outb[4*i+1] = base64Alphabet[(inb[3*i]&3)<<4];
		    if ( 3*i+2 < len )
			outb[4*i+2] = base64Alphabet[(inb[3*i+1]&0xf)<<2 | ((inb[3*i+2]>>>6)&0x3)];
		    else if ( 3*i+1 < len )
			outb[4*i+2] = base64Alphabet[(inb[3*i+1]&0xf)<<2];
		    else
			outb[4*i+2] = '=';
		    if ( 3*i+2 < len )
			outb[4*i+3] = base64Alphabet[(inb[3*i+2]&0x3f)];
		    else
			outb[4*i+3] = '=';
		}
		strbuf.append(outb, 0, ((len+2)/3)*4);
	    }
	} catch (IOException e) {
	    throw new RuntimeException(e);
	}
	return new String(strbuf);
    }

}