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.KafkaException;
  import org.apache.kafka.common.errors.CorruptRecordException;
  import org.apache.kafka.common.record.AbstractLegacyRecordBatch.LegacyFileChannelRecordBatch;
  import org.apache.kafka.common.record.DefaultRecordBatch.DefaultFileChannelRecordBatch;
  import org.apache.kafka.common.utils.BufferSupplier;
  import org.apache.kafka.common.utils.CloseableIterator;
  import org.apache.kafka.common.utils.Utils;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.FileChannel;
  import java.util.Iterator;
  import java.util.Objects;
  
  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.OFFSET_OFFSET;
  import static org.apache.kafka.common.record.Records.SIZE_OFFSET;
  
  /**
   * A log input stream which is backed by a {@link FileChannel}.
   */
  public class FileLogInputStream implements LogInputStream<FileLogInputStream.FileChannelRecordBatch> {
      private int position;
      private final int end;
      private final FileRecords fileRecords;
      private final ByteBuffer logHeaderBuffer = ByteBuffer.allocate(HEADER_SIZE_UP_TO_MAGIC);
  
      /**
       * Create a new log input stream over the FileChannel
       * @param records Underlying FileRecords instance
       * @param start Position in the file channel to start from
       * @param end Position in the file channel not to read past
       */
      FileLogInputStream(FileRecords records,
                         int start,
                         int end) {
          this.fileRecords = records;
          this.position = start;
          this.end = end;
      }
  
      @Override
      public FileChannelRecordBatch nextBatch() throws IOException {
          FileChannel channel = fileRecords.channel();
          if (position >= end - HEADER_SIZE_UP_TO_MAGIC)
              return null;
  
          logHeaderBuffer.rewind();
          Utils.readFullyOrFail(channel, logHeaderBuffer, position, "log header");
  
          logHeaderBuffer.rewind();
          long offset = logHeaderBuffer.getLong(OFFSET_OFFSET);
          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) in file %s.", size, LegacyRecord.RECORD_OVERHEAD_V0, fileRecords.file()));
  
          if (position > end - LOG_OVERHEAD - size)
              return null;
  
          byte magic = logHeaderBuffer.get(MAGIC_OFFSET);
          final FileChannelRecordBatch batch;
  
          if (magic < RecordBatch.MAGIC_VALUE_V2)
              batch = new LegacyFileChannelRecordBatch(offset, magic, fileRecords, position, size);
          else
              batch = new DefaultFileChannelRecordBatch(offset, magic, fileRecords, position, size);
  
          position += batch.sizeInBytes();
          return batch;
      }
  
      /**
       * Log entry backed by an underlying FileChannel. This allows iteration over the record batches
       * without needing to read the record data into memory until it is needed. The downside
       * is that entries will generally no longer be readable when the underlying channel is closed.
       */
      public abstract static class FileChannelRecordBatch extends AbstractRecordBatch {
          protected final long offset;
          protected final byte magic;
          protected final FileRecords fileRecords;
          protected final int position;
          protected final int batchSize;
  
          private RecordBatch fullBatch;
          private RecordBatch batchHeader;
  
          FileChannelRecordBatch(long offset,
                                 byte magic,
                                 FileRecords fileRecords,
                                 int position,
                                 int batchSize) {
              this.offset = offset;
              this.magic = magic;
              this.fileRecords = fileRecords;
              this.position = position;
              this.batchSize = batchSize;
          }
  
          @Override
          public CompressionType compressionType() {
              return loadBatchHeader().compressionType();
          }
  
          @Override
          public TimestampType timestampType() {
              return loadBatchHeader().timestampType();
          }
  
          @Override
          public long checksum() {
              return loadBatchHeader().checksum();
          }
  
          @Override
          public long maxTimestamp() {
              return loadBatchHeader().maxTimestamp();
          }
  
          public int position() {
              return position;
          }
  
          @Override
          public byte magic() {
              return magic;
          }
  
          @Override
          public Iterator<Record> iterator() {
              return loadFullBatch().iterator();
          }
  
          @Override
          public CloseableIterator<Record> streamingIterator(BufferSupplier bufferSupplier) {
              return loadFullBatch().streamingIterator(bufferSupplier);
          }
  
          @Override
          public boolean isValid() {
              return loadFullBatch().isValid();
          }
  
          @Override
          public void ensureValid() {
              loadFullBatch().ensureValid();
          }
  
          @Override
          public int sizeInBytes() {
              return LOG_OVERHEAD + batchSize;
          }
  
          @Override
          public void writeTo(ByteBuffer buffer) {
              FileChannel channel = fileRecords.channel();
              try {
                  int limit = buffer.limit();
                  buffer.limit(buffer.position() + sizeInBytes());
                  Utils.readFully(channel, buffer, position);
                  buffer.limit(limit);
              } catch (IOException e) {
                  throw new KafkaException("Failed to read record batch at position " + position + " from " + fileRecords, e);
              }
          }
  
          protected abstract RecordBatch toMemoryRecordBatch(ByteBuffer buffer);
  
          protected abstract int headerSize();
  
          protected RecordBatch loadFullBatch() {
              if (fullBatch == null) {
                  batchHeader = null;
                  fullBatch = loadBatchWithSize(sizeInBytes(), "full record batch");
              }
              return fullBatch;
          }
  
          protected RecordBatch loadBatchHeader() {
              if (fullBatch != null)
                  return fullBatch;
  
              if (batchHeader == null)
                  batchHeader = loadBatchWithSize(headerSize(), "record batch header");
  
              return batchHeader;
          }
  
          private RecordBatch loadBatchWithSize(int size, String description) {
              FileChannel channel = fileRecords.channel();
              try {
                  ByteBuffer buffer = ByteBuffer.allocate(size);
                  Utils.readFullyOrFail(channel, buffer, position, description);
                  buffer.rewind();
                  return toMemoryRecordBatch(buffer);
              } catch (IOException e) {
                  throw new KafkaException("Failed to load record batch at position " + position + " from " + fileRecords, e);
              }
          }
  
          @Override
          public boolean equals(Object o) {
              if (this == o)
                  return true;
              if (o == null || getClass() != o.getClass())
                  return false;
  
              FileChannelRecordBatch that = (FileChannelRecordBatch) o;
  
              FileChannel channel = fileRecords == null ? null : fileRecords.channel();
              FileChannel thatChannel = that.fileRecords == null ? null : that.fileRecords.channel();
  
              return offset == that.offset &&
                      position == that.position &&
                      batchSize == that.batchSize &&
                      Objects.equals(channel, thatChannel);
          }
  
          @Override
          public int hashCode() {
              FileChannel channel = fileRecords == null ? null : fileRecords.channel();
  
              int result = Long.hashCode(offset);
              result = 31 * result + (channel != null ? channel.hashCode() : 0);
              result = 31 * result + position;
              result = 31 * result + batchSize;
              return result;
          }
  
          @Override
          public String toString() {
              return "FileChannelRecordBatch(magic: " + magic +
                      ", offset: " + offset +
                      ", size: " + batchSize + ")";
          }
      }
  }
  