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.asterix.transaction.management.service.logging;
  
  import java.nio.ByteBuffer;
  import java.util.Arrays;
  
  import org.apache.asterix.common.transactions.ILogRecord.RecordReadStatus;
  import org.apache.asterix.common.transactions.LogRecord;
  import org.apache.commons.codec.binary.Hex;
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  public class LogBufferTailReader {
  
      private static final Logger LOGGER = LogManager.getLogger();
      private final ByteBuffer buffer;
      private final LogRecord logRecord;
      private int endOffset;
  
      public LogBufferTailReader(ByteBuffer buffer) {
          this.buffer = buffer;
          logRecord = new LogRecord();
      }
  
      public void initializeScan(int beginOffset, int endOffset) {
          this.endOffset = endOffset;
          buffer.position(beginOffset);
      }
  
      public LogRecord next() {
          if (buffer.position() == endOffset) {
              return null;
          }
          RecordReadStatus status = logRecord.readLogRecord(buffer);
          //underflow is not expected because we are at the very tail of the current log buffer
          if (status != RecordReadStatus.OK) {
              logReadFailure(status);
              throw new IllegalStateException("Unexpected log read status: " + status);
          }
          return logRecord;
      }
  
      private void logReadFailure(RecordReadStatus status) {
          final int bufferRemaining = endOffset - buffer.position();
          final byte[] remainingData = new byte[bufferRemaining];
          buffer.get(remainingData);
          final char[] hexData = Hex.encodeHex(remainingData);
          LOGGER.error(
                  "Unexpected read status {}, read Log: {},  buffer remaining at read: {}, buffer remaining content: {}",
                  status, bufferRemaining, logRecord.getLogRecordForDisplay(), Arrays.toString(hexData));
      }
  }
  