Base64Encoder.java

package org.herac.tuxguitar.util;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

import org.apache.log4j.Logger;

public class Base64Encoder {

  /** The Logger for this class. */
  public static final transient Logger LOG = Logger
      .getLogger(Base64Encoder.class);

  private static final int BUFFER_SIZE = 1024;

  private static byte ENCODING[] = { (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) '/', (byte) '=' };

  public static byte[] encode(byte[] bytes) {
    try {

      ByteArrayInputStream in = new ByteArrayInputStream(bytes);
      ByteArrayOutputStream out = new ByteArrayOutputStream();

      byte buffer[] = new byte[BUFFER_SIZE];
      int got = -1;
      int off = 0;
      int count = 0;
      while ((got = in.read(buffer, off, BUFFER_SIZE - off)) > 0) {
        if ((got + off) >= 3) {
          got += off;
          off = 0;
          while (off + 3 <= got) {
            int c1 = get1(buffer, off);
            int c2 = get2(buffer, off);
            int c3 = get3(buffer, off);
            int c4 = get4(buffer, off);
            switch (count) {
            case 73:
              out.write(ENCODING[c1]);
              out.write(ENCODING[c2]);
              out.write(ENCODING[c3]);
              out.write('\n');
              out.write(ENCODING[c4]);
              count = 1;
              break;
            case 74:
              out.write(ENCODING[c1]);
              out.write(ENCODING[c2]);
              out.write('\n');
              out.write(ENCODING[c3]);
              out.write(ENCODING[c4]);
              count = 2;
              break;
            case 75:
              out.write(ENCODING[c1]);
              out.write('\n');
              out.write(ENCODING[c2]);
              out.write(ENCODING[c3]);
              out.write(ENCODING[c4]);
              count = 3;
              break;
            case 76:
              out.write('\n');
              out.write(ENCODING[c1]);
              out.write(ENCODING[c2]);
              out.write(ENCODING[c3]);
              out.write(ENCODING[c4]);
              count = 4;
              break;
            default:
              out.write(ENCODING[c1]);
              out.write(ENCODING[c2]);
              out.write(ENCODING[c3]);
              out.write(ENCODING[c4]);
              count += 4;
              break;
            }
            off += 3;
          }

          for (int i = 0; i < 3; i++) {
            buffer[i] = (i < got - off) ? buffer[off + i] : ((byte) 0);
          }
          off = got - off;
        } else {
          off += got;
        }
      }

      switch (off) {
      case 1:
        out.write(ENCODING[get1(buffer, 0)]);
        out.write(ENCODING[get2(buffer, 0)]);
        out.write('=');
        out.write('=');
        break;
      case 2:
        out.write(ENCODING[get1(buffer, 0)]);
        out.write(ENCODING[get2(buffer, 0)]);
        out.write(ENCODING[get3(buffer, 0)]);
        out.write('=');
      }

      return out.toByteArray();

    } catch (Throwable throwable) {
      LOG.error(throwable);
    }

    return bytes;
  }

  private static int get1(byte buf[], int off) {
    return (buf[off] & 0xfc) >> 2;
  }

  private static int get2(byte buf[], int off) {
    return ((buf[off] & 0x3) << 4) | ((buf[off + 1] & 0xf0) >>> 4);
  }

  private static int get3(byte buf[], int off) {
    return ((buf[off + 1] & 0x0f) << 2) | ((buf[off + 2] & 0xc0) >>> 6);
  }

  private static int get4(byte buf[], int off) {
    return buf[off + 2] & 0x3f;
  }
}