Here you can find the source of encode(@Nonnull byte[] input)
public static String encode(@Nonnull byte[] input)
/*/*from ww w.j a va 2s . c o m*/ * Copyright 2011 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import javax.annotation.Nonnull; import com.google.common.base.Charsets; public class Main{ private static final char[] ALPHABET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ$*+-./:" .toCharArray(); public static String encode(@Nonnull byte[] input) { if (input.length == 0) return ""; input = copyOfRange(input, 0, input.length); // Count leading zeroes. int zeroCount = 0; while (zeroCount < input.length && input[zeroCount] == 0) ++zeroCount; // The actual encoding. final byte[] temp = new byte[input.length * 2]; int j = temp.length; int startAt = zeroCount; while (startAt < input.length) { byte mod = divmod43(input, startAt); if (input[startAt] == 0) ++startAt; temp[--j] = (byte) ALPHABET[mod]; } // Strip extra '1' if there are some after decoding. while (j < temp.length && temp[j] == ALPHABET[0]) ++j; // Add as many leading '1' as there were leading zeros. while (--zeroCount >= 0) temp[--j] = (byte) ALPHABET[0]; final byte[] output = copyOfRange(temp, j, temp.length); return new String(output, Charsets.US_ASCII); } private static byte[] copyOfRange(final byte[] source, final int from, final int to) { final byte[] range = new byte[to - from]; System.arraycopy(source, from, range, 0, range.length); return range; } private static byte divmod43(final byte[] number, final int startAt) { int remainder = 0; for (int i = startAt; i < number.length; i++) { final int digit256 = (int) number[i] & 0xFF; final int temp = remainder * 256 + digit256; number[i] = (byte) (temp / 43); remainder = temp % 43; } return (byte) remainder; } }