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 static org.apache.distributedlog.LogRecordSet.METADATA_COMPRESSION_MASK;
  import static org.apache.distributedlog.LogRecordSet.METADATA_VERSION_MASK;
  import static org.apache.distributedlog.LogRecordSet.VERSION;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.util.ReferenceCountUtil;
  import java.io.IOException;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.distributedlog.io.CompressionCodec;
  import org.apache.distributedlog.io.CompressionCodec.Type;
  import org.apache.distributedlog.io.CompressionUtils;
  
  /**
   * Record reader to read records from an enveloped entry buffer.
   */
  @Slf4j
  class EnvelopedRecordSetReader implements LogRecordSet.Reader {
  
      private final long logSegmentSeqNo;
      private final long entryId;
      private final long transactionId;
      private final long startSequenceId;
      private int numRecords;
      private final ByteBuf reader;
  
      // slot id
      private long slotId;
      private int position;
  
      EnvelopedRecordSetReader(long logSegmentSeqNo,
                               long entryId,
                               long transactionId,
                               long startSlotId,
                               int startPositionWithinLogSegment,
                               long startSequenceId,
                               ByteBuf src)
              throws IOException {
          this.logSegmentSeqNo = logSegmentSeqNo;
          this.entryId = entryId;
          this.transactionId = transactionId;
          this.slotId = startSlotId;
          this.position = startPositionWithinLogSegment;
          this.startSequenceId = startSequenceId;
  
          // read data
          int metadata = src.readInt();
          int version = metadata & METADATA_VERSION_MASK;
          if (version != VERSION) {
              throw new IOException(String.format("Version mismatch while reading. Received: %d,"
                  + " Required: %d", version, VERSION));
          }
          int codecCode = metadata & METADATA_COMPRESSION_MASK;
          this.numRecords = src.readInt();
          int decompressedDataLen = src.readInt();
          int compressedDataLen = src.readInt();
          ByteBuf compressedBuf = src.slice(src.readerIndex(), compressedDataLen);
          try {
              if (Type.NONE.code() == codecCode && decompressedDataLen != compressedDataLen) {
                  throw new IOException("Inconsistent data length found for a non-compressed record set : decompressed = "
                          + decompressedDataLen + ", actual = " + compressedDataLen);
              }
              CompressionCodec codec = CompressionUtils.getCompressionCodec(Type.of(codecCode));
              this.reader = codec.decompress(compressedBuf, decompressedDataLen);
          } finally {
              ReferenceCountUtil.release(compressedBuf);
          }
          if (numRecords == 0) {
              ReferenceCountUtil.release(this.reader);
          }
      }
  
      @Override
      public LogRecordWithDLSN nextRecord() throws IOException {
          if (numRecords <= 0) {
              return null;
          }
  
          int recordLen = reader.readInt();
          ByteBuf recordBuf = reader.slice(reader.readerIndex(), recordLen);
          reader.readerIndex(reader.readerIndex() + recordLen);
  
          DLSN dlsn = new DLSN(logSegmentSeqNo, entryId, slotId);
          LogRecordWithDLSN record =
                  new LogRecordWithDLSN(dlsn, startSequenceId);
          record.setPositionWithinLogSegment(position);
          record.setTransactionId(transactionId);
          record.setPayloadBuf(recordBuf, true);
  
          ++slotId;
          ++position;
          --numRecords;
  
          // release the record set buffer when exhausting the reader
          if (0 == numRecords) {
              ReferenceCountUtil.release(this.reader);
          }
  
          return record;
      }
  
      @Override
      public void release() {
          if (0 != numRecords) {
              numRecords = 0;
              ReferenceCountUtil.release(reader);
          }
      }
  }
  