Base64.java

package com.github.kristofa.brave.scribe;

import java.io.UnsupportedEncodingException;

/**
 * Adapted from <a href="https://github.com/square/okio/blob/master/okio/src/main/java/okio/Base64.java">okio</a>
 * @author Alexander Y. Kleymenov
 */
final class Base64 {
  private Base64() {
  }

  private static final byte[] MAP = new byte[] {
      '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', '+', '/'
  };

  static String encode(byte[] in) {
    int length = (in.length + 2) * 4 / 3;
    byte[] out = new byte[length];
    int index = 0, end = in.length - in.length % 3;
    for (int i = 0; i < end; i += 3) {
      out[index++] = MAP[(in[i] & 0xff) >> 2];
      out[index++] = MAP[((in[i] & 0x03) << 4) | ((in[i + 1] & 0xff) >> 4)];
      out[index++] = MAP[((in[i + 1] & 0x0f) << 2) | ((in[i + 2] & 0xff) >> 6)];
      out[index++] = MAP[(in[i + 2] & 0x3f)];
    }
    switch (in.length % 3) {
      case 1:
        out[index++] = MAP[(in[end] & 0xff) >> 2];
        out[index++] = MAP[(in[end] & 0x03) << 4];
        out[index++] = '=';
        out[index++] = '=';
        break;
      case 2:
        out[index++] = MAP[(in[end] & 0xff) >> 2];
        out[index++] = MAP[((in[end] & 0x03) << 4) | ((in[end + 1] & 0xff) >> 4)];
        out[index++] = MAP[((in[end + 1] & 0x0f) << 2)];
        out[index++] = '=';
        break;
    }
    try {
      return new String(out, 0, index, "US-ASCII");
    } catch (UnsupportedEncodingException e) {
      throw new AssertionError(e);
    }
  }
}