Base64Encoder.java

package org.emergent.android.weave.client;

import java.io.IOException;
import java.io.OutputStream;

class Base64Encoder {

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

	protected byte padding = (byte) '=';

	/*
	 * set up the decoding table.
	 */
	protected final byte[] decodingTable = new byte[128];

	public Base64Encoder() {
		initialiseDecodingTable();
	}

	/**
	 * decode the base 64 encoded byte data writing it to the given output
	 * stream, whitespace characters will be ignored.
	 * 
	 * @return the number of bytes produced.
	 */
	public int decode(byte[] data, int off, int length, OutputStream out)
			throws IOException {
		byte b1, b2, b3, b4;
		int outLen = 0;

		int end = off + length;

		while (end > off) {
			if (!ignore((char) data[end - 1])) {
				break;
			}

			end--;
		}

		int i = off;
		int finish = end - 4;

		i = nextI(data, i, finish);

		while (i < finish) {
			b1 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b2 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b3 = decodingTable[data[i++]];

			i = nextI(data, i, finish);

			b4 = decodingTable[data[i++]];

			out.write((b1 << 2) | (b2 >> 4));
			out.write((b2 << 4) | (b3 >> 2));
			out.write((b3 << 6) | b4);

			outLen += 3;

			i = nextI(data, i, finish);
		}

		outLen += decodeLastBlock(out, (char) data[end - 4],
				(char) data[end - 3], (char) data[end - 2],
				(char) data[end - 1]);

		return outLen;
	}

	/**
	 * decode the base 64 encoded String data writing it to the given output
	 * stream, whitespace characters will be ignored.
	 * 
	 * @return the number of bytes produced.
	 */
	public int decode(String data, OutputStream out) throws IOException {
		byte b1, b2, b3, b4;
		int length = 0;

		int end = data.length();

		while (end > 0) {
			if (!ignore(data.charAt(end - 1))) {
				break;
			}

			end--;
		}

		int i = 0;
		int finish = end - 4;

		i = nextI(data, i, finish);

		while (i < finish) {
			b1 = decodingTable[data.charAt(i++)];

			i = nextI(data, i, finish);

			b2 = decodingTable[data.charAt(i++)];

			i = nextI(data, i, finish);

			b3 = decodingTable[data.charAt(i++)];

			i = nextI(data, i, finish);

			b4 = decodingTable[data.charAt(i++)];

			out.write((b1 << 2) | (b2 >> 4));
			out.write((b2 << 4) | (b3 >> 2));
			out.write((b3 << 6) | b4);

			length += 3;

			i = nextI(data, i, finish);
		}

		length += decodeLastBlock(out, data.charAt(end - 4),
				data.charAt(end - 3), data.charAt(end - 2),
				data.charAt(end - 1));

		return length;
	}

	private int decodeLastBlock(OutputStream out, char c1, char c2, char c3,
			char c4) throws IOException {
		byte b1, b2, b3, b4;

		if (c3 == padding) {
			b1 = decodingTable[c1];
			b2 = decodingTable[c2];

			out.write((b1 << 2) | (b2 >> 4));

			return 1;
		} else if (c4 == padding) {
			b1 = decodingTable[c1];
			b2 = decodingTable[c2];
			b3 = decodingTable[c3];

			out.write((b1 << 2) | (b2 >> 4));
			out.write((b2 << 4) | (b3 >> 2));

			return 2;
		} else {
			b1 = decodingTable[c1];
			b2 = decodingTable[c2];
			b3 = decodingTable[c3];
			b4 = decodingTable[c4];

			out.write((b1 << 2) | (b2 >> 4));
			out.write((b2 << 4) | (b3 >> 2));
			out.write((b3 << 6) | b4);

			return 3;
		}
	}

	/**
	 * encode the input data producing a base 64 output stream.
	 * 
	 * @return the number of bytes produced.
	 */
	public int encode(byte[] data, int off, int length, OutputStream out)
			throws IOException {
		int modulus = length % 3;
		int dataLength = (length - modulus);
		int a1, a2, a3;

		for (int i = off; i < off + dataLength; i += 3) {
			a1 = data[i] & 0xff;
			a2 = data[i + 1] & 0xff;
			a3 = data[i + 2] & 0xff;

			out.write(encodingTable[(a1 >>> 2) & 0x3f]);
			out.write(encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f]);
			out.write(encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f]);
			out.write(encodingTable[a3 & 0x3f]);
		}

		/*
		 * process the tail end.
		 */
		int b1, b2, b3;
		int d1, d2;

		switch (modulus) {
		case 0: /* nothing left to do */
			break;
		case 1:
			d1 = data[off + dataLength] & 0xff;
			b1 = (d1 >>> 2) & 0x3f;
			b2 = (d1 << 4) & 0x3f;

			out.write(encodingTable[b1]);
			out.write(encodingTable[b2]);
			out.write(padding);
			out.write(padding);
			break;
		case 2:
			d1 = data[off + dataLength] & 0xff;
			d2 = data[off + dataLength + 1] & 0xff;

			b1 = (d1 >>> 2) & 0x3f;
			b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
			b3 = (d2 << 2) & 0x3f;

			out.write(encodingTable[b1]);
			out.write(encodingTable[b2]);
			out.write(encodingTable[b3]);
			out.write(padding);
			break;
		}

		return (dataLength / 3) * 4 + ((modulus == 0) ? 0 : 4);
	}

	private boolean ignore(char c) {
		return (c == '\n' || c == '\r' || c == '\t' || c == ' ');
	}

	protected void initialiseDecodingTable() {
		for (int i = 0; i < encodingTable.length; i++) {
			decodingTable[encodingTable[i]] = (byte) i;
		}
	}

	private int nextI(byte[] data, int i, int finish) {
		while ((i < finish) && ignore((char) data[i])) {
			i++;
		}
		return i;
	}

	private int nextI(String data, int i, int finish) {
		while ((i < finish) && ignore(data.charAt(i))) {
			i++;
		}
		return i;
	}
}