content: package com.alipay.api.kms.aliyun.utils;
  
  public class Base64Utils {
      private static final String BASE64_CODE = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
              + "abcdefghijklmnopqrstuvwxyz" + "0123456789" + "+/";
  
      private static byte[] zeroPad(int length, byte[] bytes) {
          byte[] padded = new byte[length];
          System.arraycopy(bytes, 0, padded, 0, bytes.length);
          return padded;
      }
  
      public synchronized static String encode(byte[] buff) {
          StringBuilder strBuilder = new StringBuilder("");
          int paddingCount = (3 - (buff.length % 3)) % 3;
          byte[] stringArray = zeroPad(buff.length + paddingCount, buff);
          for (int i = 0; i < stringArray.length; i += 3) {
              int j = ((stringArray[i] & 0xff) << 16) +
                      ((stringArray[i + 1] & 0xff) << 8) +
                      (stringArray[i + 2] & 0xff);
              strBuilder.append(BASE64_CODE.charAt((j >> 18) & 0x3f));
              strBuilder.append(BASE64_CODE.charAt((j >> 12) & 0x3f));
              strBuilder.append(BASE64_CODE.charAt((j >> 6) & 0x3f));
              strBuilder.append(BASE64_CODE.charAt(j & 0x3f));
          }
          int intPos = strBuilder.length();
          for (int i = paddingCount; i > 0; i--) {
              strBuilder.setCharAt(intPos - i, '=');
          }
  
          return strBuilder.toString();
      }
  }
  