content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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.
   */
  package org.apache.distributedlog;
  
  import org.apache.bookkeeper.versioning.Version;
  import org.apache.bookkeeper.versioning.Versioned;
  import org.apache.distributedlog.util.DLUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Utility class for storing and reading
   * the max seen txid in zookeeper.
   */
  class MaxTxId {
      static final Logger LOG = LoggerFactory.getLogger(MaxTxId.class);
  
      private Version version;
      private long currentMax;
  
      MaxTxId(Versioned<byte[]> maxTxIdData) {
          if (null != maxTxIdData
                  && null != maxTxIdData.getValue()
                  && null != maxTxIdData.getVersion()) {
              this.version = maxTxIdData.getVersion();
              try {
                  this.currentMax = DLUtils.deserializeTransactionId(maxTxIdData.getValue());
              } catch (NumberFormatException e) {
                  LOG.warn("Invalid txn id stored in ", e);
                  this.currentMax = DistributedLogConstants.INVALID_TXID;
              }
          } else {
              this.currentMax = DistributedLogConstants.INVALID_TXID;
              if (null != maxTxIdData && null != maxTxIdData.getVersion()) {
                  this.version = maxTxIdData.getVersion();
              } else {
                  throw new IllegalStateException("Invalid MaxTxId found - " + maxTxIdData);
              }
          }
      }
  
      synchronized void update(Version version, long txId) {
          if (version.compare(this.version) == Version.Occurred.AFTER) {
              this.version = version;
              this.currentMax = txId;
          }
      }
  
      synchronized long get() {
          return currentMax;
      }
  
      public synchronized Versioned<Long> getVersionedData(long txId) {
          return new Versioned<Long>(Math.max(txId, get()), version);
      }
  
  }
  