;;; io/flate.lisp --- Compressed IO Interface

 ;; Use compression (ZSTD) with Lisp objects and streams.

 ;;; Commentary:

 ;; compression ref: https://www.xach.com/lisp/salza2/ (compression only)

 ;; decompression ref: https://github.com/sharplispers/chipz (decompression only)

 ;; The libraries above are the current state-of-the-art for compression and

 ;; decompression in Common Lisp. They are portable packages which depend on

 ;; gray streams. They loosely cover deflate, zlib, gzip, and bzip2 data.

 ;; The compression backends are themselves hand-coded in Common Lisp, making

 ;; them excellent reference material. However, we don't have much use for the

 ;; compression backend offered.

 ;; We intend to almost exclusively support Zstd compression and decompression

 ;; using our ZSTD FFI Lisp system, so we'll make a new library - FLATE - which

 ;; provides a shared zstd compression/decompression to Lisp objects and

 ;; streams.

 ;;; Code:

 (in-package :io/flate)

 ;;; Vars

 (defparameter *compression-buffer-size* 4096)

 (defparameter *decompression-buffer-size* 4096)

 ;;; Utils

 ;;; Proto

 (deferror compression-error (flate-error) () (:auto t))

 (deferror decompression-error (flate-error) () (:auto t))

 (defgeneric finish-compression (self))

 (defgeneric finish-decompression (self))

 ;; TODO 2024-06-08: maybe move this to generic io/stream protocol - 'RESET'

 (defgeneric reset-compressor (self))

 (defgeneric reset-decompressor (self))

 (defgeneric make-compressing-stream (compressor stream))

 (defgeneric make-decompressing-stream (decompressor stream))

 (defgeneric compress-object (self))

 (defgeneric decompress-object (self))

 (defgeneric compress (input state output))

 (defgeneric decompress (input state output))

 ;; decompress

 ;;; Compression

 ;; AKA 'DEFLATE'

 ;; compress-octet

 ;; compress-octet-vector

 ;; finish-compression (finish-output?)

 ;; with-compressor

 ;; reset-compressor

 ;; make-compressing-stream

 (defclass compressor ()

   ((input

     :initarg :input

     :accessor compressor-input)

    (start

     :initarg :start

     :accessor compressor-start)

    (end

     :initarg :end

     :accessor compressor-end)))

 (defclass compressing-stream (fundamental-binary-output-stream)

   ((compressor

     :initarg :compressor

     :accessor compressor)))

 ;;; Decompression

 ;; AKA 'INFLATE'

 ;; From chipz:

 ;; We provide several convenience functions for decompression:

 ;;

 ;; * decompress a buffer to a newly-consed buffer;

 ;; * decompress a stream to a newly-consed buffer;

 ;; * decompress a pathname to a newly-consed buffer;

 ;; * decompress a buffer to a user-specified buffer;

 ;; * decompress a buffer to a stream;

 ;; * decompress a stream to a stream.

 ;; * decompress a pathname to another pathname;

 ;; * decompress a pathname to a stream;

 ;;

 ;; We do not provide stream->buffer decompression, as we have no way of

 ;; knowing how much to read from the stream to fill the buffer, no way

 ;; of determining what to do with possible state left in the

 ;; INFLATE-STATE that we used, etc.  Application-specific logic will

 ;; have to handle those bits.

 ;; make-decompressing-stream

 ;; decompress-octet

 ;; decompress-octet-vector

 (defclass decompressor () ())

 (defclass decompressing-stream (fundamental-binary-input-stream)

   ((decompressor

     :initarg :compressor

     :accessor decompressor)))

 ;;; API

 ;; zstd-stream

 ;; zstd-file