Base64Decoder.java

/*
 *  Copyright (C) 2011 in-somnia
 * 
 *  This file is part of JAAD.
 * 
 *  JAAD is free software; you can redistribute it and/or modify it 
 *  under the terms of the GNU Lesser General Public License as 
 *  published by the Free Software Foundation; either version 3 of the 
 *  License, or (at your option) any later version.
 *
 *  JAAD is distributed in the hope that it will be useful, but WITHOUT 
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
 *  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General 
 *  Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library.
 *  If not, see <http://www.gnu.org/licenses/>.
 */
package net.sourceforge.jaad.mp4.boxes.impl.fd;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PushbackInputStream;

/**
 * A BASE64 character decoder.
 */
class Base64Decoder {

	/*private static final char[] CHAR_ARRAY = {
	//       0   1   2   3   4   5   6   7
	'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
	};*/
	//CHAR_CONVERT_ARRAY[CHAR_ARRAY[i]] = i;
	private static final byte[] CHAR_CONVERT_ARRAY = {
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57,
		58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
		9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1,
		-1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
		39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, 0
	};

	public static byte[] decode(byte[] b) {
		ByteArrayInputStream in = new ByteArrayInputStream(b);
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int i;

		PushbackInputStream ps = new PushbackInputStream(in);
		try {
			while(true) {
				for(i = 0; (i+4)<72; i += 4) {
					decodeAtom(ps, out, 4);
				}
				if((i+4)==72) decodeAtom(ps, out, 4);
				else decodeAtom(ps, out, 72-i);
			}
		}
		catch(IOException e) {
		}
		return out.toByteArray();
	}

	private static void decodeAtom(InputStream in, OutputStream out, int rem) throws IOException {
		if(rem<2) throw new IOException();

		int i;
		do {
			i = in.read();
			if(i==-1) throw new IOException();
		}
		while(i=='\n'||i=='\r');

		final byte[] buf = new byte[4];
		buf[0] = (byte) i;

		i = readFully(in, buf, 1, rem-1);
		if(i==-1) throw new IOException();

		if(rem>3&&buf[3]=='=') rem = 3;
		if(rem>2&&buf[2]=='=') rem = 2;

		byte a = -1, b = -1, c = -1, d = -1;
		switch(rem) {
			case 4:
				d = CHAR_CONVERT_ARRAY[buf[3]&0xff];
			case 3:
				c = CHAR_CONVERT_ARRAY[buf[2]&0xff];
			case 2:
				b = CHAR_CONVERT_ARRAY[buf[1]&0xff];
				a = CHAR_CONVERT_ARRAY[buf[0]&0xff];
				break;
		}

		switch(rem) {
			case 2:
				out.write((byte) (((a<<2)&0xfc)|((b>>>4)&3)));
				break;
			case 3:
				out.write((byte) (((a<<2)&0xfc)|((b>>>4)&3)));
				out.write((byte) (((b<<4)&0xf0)|((c>>>2)&0xf)));
				break;
			case 4:
				out.write((byte) (((a<<2)&0xfc)|((b>>>4)&3)));
				out.write((byte) (((b<<4)&0xf0)|((c>>>2)&0xf)));
				out.write((byte) (((c<<6)&0xc0)|(d&0x3f)));
				break;
		}
		return;
	}

	private static int readFully(InputStream in, byte[] b, int off, int len) throws IOException {
		for(int i = 0; i<len; i++) {
			int q = in.read();
			if(q==-1) return ((i==0) ? -1 : i);
			b[i+off] = (byte) q;
		}
		return len;
	}
}