 @available(macOS 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *)
 extension compression_stream {
 
-  /**
-   Initialize a compression_stream struct
-
-   - Parameter operation: direction of operation
-   - Parameter algorithm: compression algorithm
-
-   - Throws: `FilterError.filterInitError` if `algorithm` is not supported by the Compression stream API
-   */
-  init(operation: FilterOperation, algorithm: Algorithm) throws {
+  /// Initialize a compression_stream struct
+  ///
+  /// - Parameter operation: direction of operation
+  /// - Parameter algorithm: compression algorithm
+  ///
+  /// - Throws: `FilterError.filterInitError` if `algorithm` is not supported
+  ///           by the Compression stream API
+  ///
+  internal init(operation: FilterOperation, algorithm: Algorithm) throws {
     self.init(dst_ptr: UnsafeMutablePointer<UInt8>.allocate(capacity:0),
               dst_size: 0,
               src_ptr: UnsafeMutablePointer<UInt8>.allocate(capacity:0),

  private var _eofReached: Bool = false // did we read end-of-file from the input?
  private var _endReached: Bool = false // did we reach end-of-file from the decoder stream?

  /**
   Initialize an input filter

   - Parameters:
   - operation: direction of operation
   - algorithm: compression algorithm
   - bufferCapacity: capacity of the internal data buffer
   - readFunc: called to read the input data

   - Throws: `FilterError.filterInitError` if filter initialization failed
   */
  public init(
    _ operation: FilterOperation,
    using algorithm: Algorithm,

  private let _writeFunc: (Data?) throws -> ()
  private var _finalized: Bool = false

  /// Initialize an output filter
  ///
  /// - Parameters:
  /// - operation: direction of operation
  /// - algorithm: compression algorithm
  /// - bufferCapacity: capacity of the internal data buffer
  /// - writeFunc: called to write the processed data
  ///
  /// - Throws: `FilterError.StreamInitError` if stream initialization failed
  public init(
    _ operation: FilterOperation,
    using algorithm: Algorithm,
