 /// A class with unarchive function for xz archives.
 public class XZArchive: Archive {
 
-    private struct StreamHeader {
-        let checkType: Int
-        let flagsCRC: Int
-    }
-
     /**
      Unarchives xz archive stored in `archiveData`.
 

        return Data(bytes: out)
    }

    private static func processStreamHeader(_ pointerData: inout DataWithPointer) throws -> StreamHeader {
        // Check magic number.
        guard pointerData.intFromAlignedBytes(count: 6) == 0x005A587A37FD
            else { throw XZError.WrongMagic }

            else { throw XZError.WrongIndexCRC }
    }

    private static func processFooter(_ streamHeader: (checkType: Int, flagsCRC: Int),
                                      _ pointerData: inout DataWithPointer) throws {
        let footerCRC = pointerData.intFromAlignedBytes(count: 4)
        let storedBackwardSize = pointerData.alignedBytes(count: 4)
