base.text.Base64Encode Maven / Gradle / Ivy

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/**
 * Creative commons Attribution-NonCommercial license.
 *
 * http://creativecommons.org/licenses/by-nc/2.5/au/deed.en_GB
 *
 * NO WARRANTY IS GIVEN OR IMPLIED, USE AT YOUR OWN RISK.
 */
package base.text;

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

/**
 * Encode a string or a stream in base 64.
 */
public class Base64Encode {

	private static final int END_MARKER = -1;

	protected static final byte[] LOOKUP_MAP = {
		'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', '+', '/',
	};

	/**
	 * Encode a String in Base64 using default character encoding.
	 *
	 * @param string The string to encode.
	 * @return A base 64 encoded String.
	 */
	public static String encode(String string) {
		return encode(string.getBytes());
	}

	/**
	 * Encode bytes in Base64.
	 *
	 * @param bytes The data to encode.
	 * @return Encoded base 64 string.
	 */
	public static String encode(byte[] bytes) {
		ByteArrayInputStream in = new ByteArrayInputStream(bytes);
		int length = bytes.length;
		int mod;

		// Size of output buffer will be (bytes * (4/3)).
		if ((mod = length % 3) != 0){
			length += 3 - mod;
		}
		length = length * 4 / 3;
		ByteArrayOutputStream out = new ByteArrayOutputStream(length);
		try {
			encode(in, out);
		} catch (IOException x) {
			// Reading/writing to from Input/OutputStream should not
			// ever fail, so passing up (and hence requiring handling of)
			// an IOException is not useful. IF an IOException ever occurs
			// something really strange is going on. (Hence RuntimeException)
			throw new RuntimeException(x);
		}
		return new String(out.toByteArray());
	}

	/**
	 * Encode data from the InputStream to the OutputStream in Base64.
	 *
	 * @param in Stream from which to read data that needs to be encoded.
	 * @param out Stream to which to write encoded data.
	 * @throws IOException if there is a problem reading or writing.
	 *
	 */
	public static void encode(InputStream in, OutputStream out) throws IOException {
		int[] inBuffer = new int[3];

		boolean done = false;
		while (!done && (inBuffer[0] = in.read()) != END_MARKER) {
			// Fill the buffer
			inBuffer[1] = in.read();
			inBuffer[2] = in.read();

			/*
			 * The first byte of input is valid but must check other two bytes
			 * are not equal to END_MARKER. Each set of three bytes add up to 24
			 * bits, the 24 bits are split up into 4 bytes of 6 bits and
			 * converted to ascii characters.
			 *
			 * If there are not enough bytes to make a 24 bit group, the
			 * remaining ascii characters are converted to the = character.
			 */

			// Byte 1: first six bits of first byte
			out.write(LOOKUP_MAP[inBuffer[0] >> 2]);
			if (inBuffer[1] != END_MARKER) {
				// Byte 2: last two bits of first byte, first four bits of
				// second byte
				out.write(LOOKUP_MAP[((inBuffer[0] << 4) & 0x30) | (inBuffer[1] >> 4)]);
				if (inBuffer[2] != END_MARKER) {
					// Byte 3: last four bits of second byte, first two bits of
					// third byte
					out.write(LOOKUP_MAP[((inBuffer[1] << 2) & 0x3c) | (inBuffer[2] >> 6)]);
					// Byte 4: last six bits of third byte
					out.write(LOOKUP_MAP[inBuffer[2] & 0x3F]);
				} else {
					// Byte 3: last four bits of second byte
					out.write(LOOKUP_MAP[((inBuffer[1] << 2) & 0x3c)]);
					// Output = if no more characters to write
					out.write('=');
					done = true;
				}
			} else {
				// Byte 2: last two bits of first byte
				out.write(LOOKUP_MAP[((inBuffer[0] << 4) & 0x30)]);
				// Output = if no more characters to write
				out.write('=');
				out.write('=');
				done = true;
			}
		}
		out.flush();
	}

}