protected void init(TsFileSequenceReader reader) throws IOException {
    if (currentChunkDataBuffer != null) {
      return;
    }
    Chunk chunk = reader.readMemChunk(offset);
    this.currentChunkDataBuffer = chunk.getData();
    this.currentChunkHeader = chunk.getHeader();
    this.encryptParam = chunk.getEncryptParam();
  }
It will receive a list of offset and execute sequential scan of TsFile for chunkData.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/read/filescan/impl/DiskChunkHandleImpl.java