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.kafka.common.record;
  
  import org.apache.kafka.common.errors.CorruptRecordException;
  import org.apache.kafka.common.utils.Utils;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.ByteBuffer;
  
  import static org.apache.kafka.common.record.Records.HEADER_SIZE_UP_TO_MAGIC;
  import static org.apache.kafka.common.record.Records.LOG_OVERHEAD;
  import static org.apache.kafka.common.record.Records.MAGIC_OFFSET;
  import static org.apache.kafka.common.record.Records.SIZE_OFFSET;
  
  public class RemoteLogInputStream implements LogInputStream<RecordBatch> {
      private final InputStream inputStream;
      // LogHeader buffer up to magic.
      private final ByteBuffer logHeaderBuffer = ByteBuffer.allocate(HEADER_SIZE_UP_TO_MAGIC);
  
      public RemoteLogInputStream(InputStream inputStream) {
          this.inputStream = inputStream;
      }
  
      @Override
      public RecordBatch nextBatch() throws IOException {
          logHeaderBuffer.clear();
          Utils.readFully(inputStream, logHeaderBuffer);
  
          if (logHeaderBuffer.position() < HEADER_SIZE_UP_TO_MAGIC)
              return null;
  
          logHeaderBuffer.rewind();
          int size = logHeaderBuffer.getInt(SIZE_OFFSET);
  
          // V0 has the smallest overhead, stricter checking is done later
          if (size < LegacyRecord.RECORD_OVERHEAD_V0)
              throw new CorruptRecordException(String.format("Found record size %d smaller than minimum record " +
                                                                     "overhead (%d).", size, LegacyRecord.RECORD_OVERHEAD_V0));
  
          // Total size is: "LOG_OVERHEAD + the size of the rest of the content"
          int bufferSize = LOG_OVERHEAD + size;
          // buffer contains the complete payload including header and records.
          ByteBuffer buffer = ByteBuffer.allocate(bufferSize);
  
          // write log header into buffer
          buffer.put(logHeaderBuffer);
  
          // write the records payload into the buffer
          Utils.readFully(inputStream, buffer);
          if (buffer.position() != bufferSize)
              return null;
          buffer.rewind();
  
          byte magic = logHeaderBuffer.get(MAGIC_OFFSET);
          MutableRecordBatch batch;
          if (magic > RecordBatch.MAGIC_VALUE_V1)
              batch = new DefaultRecordBatch(buffer);
          else
              batch = new AbstractLegacyRecordBatch.ByteBufferLegacyRecordBatch(buffer);
  
          return batch;
      }
  }
  