content: /**
   * Copyright 2020 Alibaba Group Holding Limited.
   *
   * <p>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
   *
   * <p>http://www.apache.org/licenses/LICENSE-2.0
   *
   * <p>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.
   */
  package com.alibaba.graphscope.groot.common.util;
  
  import java.security.SecureRandom;
  import java.util.Base64;
  
  public class UuidUtils {
  
      private static class SecureRandomHolder {
          static final SecureRandom INSTANCE = new SecureRandom();
      }
  
      public static String getBase64UUIDString() {
          byte[] bytes = new byte[16];
          SecureRandomHolder.INSTANCE.nextBytes(bytes);
          // UUID v4. (http://www.ietf.org/rfc/rfc4122.txt)
          // clear version of 4 msb
          bytes[6] &= 0x0f;
          // set version to 4
          bytes[6] |= 0x40;
          // clear variant of 2 msb
          bytes[8] &= 0x3f;
          // set variant
          bytes[8] |= 0x80;
          // return base64 encoding
          return Base64.getUrlEncoder().withoutPadding().encodeToString(bytes);
      }
  }
  