code: func newCompressingStoredFieldsReaderFrom(reader *CompressingStoredFieldsReader) *CompressingStoredFieldsReader {
  	return &CompressingStoredFieldsReader{
  		version:           reader.version,
  		fieldInfos:        reader.fieldInfos,
  		fieldsStream:      reader.fieldsStream.Clone(),
  		indexReader:       reader.indexReader.Clone(),
  		maxPointer:        reader.maxPointer,
  		chunkSize:         reader.chunkSize,
  		packedIntsVersion: reader.packedIntsVersion,
  		compressionMode:   reader.compressionMode,
  		decompressor:      reader.compressionMode.NewDecompressor(),
  		numDocs:           reader.numDocs,
  		bytes:             make([]byte, len(reader.bytes)),
  		closed:            false,
  	}
  }
docs: // used by clone