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;;;
;;; deflate-stream.lisp
;;;
;;; Created: 2005-03-12 by Zach Beane <xach@xach.com>
;;;
;;; An interface to the DEFLATE data compression format. See the
;;; "packages.lisp" file for the public interface.
;;;
;;; Copyright (c) 2005 Zachary Beane, All Rights Reserved
;;;
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;;
;;; * Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;;
;;; * Redistributions in binary form must reproduce the above
;;; copyright notice, this list of conditions and the following
;;; disclaimer in the documentation and/or other materials
;;; provided with the distribution.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE AUTHOR 'AS IS' AND ANY EXPRESSED
;;; OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
;;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
;;; ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
;;; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
;;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
;;; GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
;;; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
;;; WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;;
;;; $Id: deflate-stream.lisp,v 1.11 2005/04/01 21:57:24 xach Exp $
(in-package :salza-deflate)
(declaim (inline deflate-stream-buffer))
(declaim (inline deflate-stream-pos))
(declaim (inline deflate-stream-byte))
(declaim (inline deflate-stream-end))
(declaim (inline deflate-stream-bits-left))
(define-condition deflate-stream-buffer-full ()
((deflate-stream :initarg :deflate-stream :reader deflate-stream-buffer-full-deflate-stream)))
(defvar *compressor-buffer-size* 65536)
(defstruct (deflate-stream
(:constructor
%make-deflate-stream (buffer pos end callback)))
(buffer nil :type (or octet-vector null))
(callback nil :type (or function null))
(pos 0 :type buffer-offset)
(end 0 :type buffer-offset)
(byte 0 :type octet)
(bits-left 8 :type octet)
(compress-buffer (make-array *compressor-buffer-size* :element-type 'octet)
:type (simple-array octet))
(compress-pos 0 :type buffer-offset)
(compress-positions (make-fixhash-table)))
(defun default-callback (deflate-stream)
(cerror "Resume output"
'deflate-stream-buffer-full
:deflate-stream deflate-stream))
(defun make-deflate-stream (buffer
&key (pos 0) end (callback #'default-callback))
(check-type buffer octet-vector)
(setf end (or end (length buffer)))
(%make-deflate-stream buffer pos end callback))
(defmethod print-object ((object deflate-stream) stream)
(print-unreadable-object (object stream :type t :identity t)
(format stream "~D/~D ~D ~D/8"
(deflate-stream-pos object)
(deflate-stream-end object)
(deflate-stream-byte object)
(deflate-stream-bits-left object))))
(defun write-bits (code length deflate-stream)
"Save LENGTH low bits of CODE to the buffer of DEFLATE-STREAM. If the end
of the deflate-stream buffer is reached, raise a continuable error of type
DEFLATE-STREAM-BUFFER-FULL."
(declare (type (unsigned-byte 24) code)
(type (integer 0 24) length)
(type deflate-stream deflate-stream)
(optimize (speed 3) (safety 0) (debug 0)))
(let ((byte (deflate-stream-byte deflate-stream))
(bits-left (deflate-stream-bits-left deflate-stream))
(pos (deflate-stream-pos deflate-stream))
(buffer (deflate-stream-buffer deflate-stream))
(end (deflate-stream-end deflate-stream)))
(declare (type octet-vector buffer)
(type (integer 0 8) bits-left)
(type (integer 0 255) byte)
(type buffer-offset pos end))
(flet ((output-byte ()
(setf (aref buffer pos) byte)
(incf pos)
(loop
(when (< pos end) (return))
(setf (deflate-stream-pos deflate-stream) pos)
(funcall (the function (deflate-stream-callback deflate-stream))
deflate-stream)
(setf buffer (deflate-stream-buffer deflate-stream)
pos (deflate-stream-pos deflate-stream)))))
(declare (inline output-byte))
(tagbody
loop
(cond ((> length bits-left)
(setf byte
(logior byte
(logand #xFF (ash code (- 8 bits-left)))))
(output-byte)
(decf length bits-left)
(setf code (ash code (- bits-left)))
(setf bits-left 8
byte 0)
(go loop))
((= length bits-left)
(setf byte (logior byte
(logand #xFF (ash code (- 8 bits-left)))))
(output-byte)
(setf bits-left 8
byte 0))
(t
(setf byte (logior byte (logand #xFF (ash code (- 8 bits-left)))))
(decf bits-left length))))
(setf (deflate-stream-bits-left deflate-stream) bits-left
(deflate-stream-byte deflate-stream) byte
(deflate-stream-pos deflate-stream) pos))))
(defconstant +deflate-fixed-tables-code+ #b01)
(defun write-block-header (deflate-stream)
;; The block header
;; BFINAL is always set, since right now dynamic codes are not
;; supported so we never need to start a new block
(write-bits 1 1 deflate-stream)
(write-bits +deflate-fixed-tables-code+ 2 deflate-stream))
(defun flush-deflate-stream (deflate-stream)
"If there is a pending unwritten byte in the deflate-stream, save it and
advance the stream position."
(when (< (deflate-stream-bits-left deflate-stream) 8)
(setf (aref (deflate-stream-buffer deflate-stream) (deflate-stream-pos deflate-stream))
(deflate-stream-byte deflate-stream))
(setf (deflate-stream-byte deflate-stream) 0
(deflate-stream-bits-left deflate-stream) 8)
(incf (deflate-stream-pos deflate-stream))
(loop
(when (< (deflate-stream-pos deflate-stream)
(deflate-stream-end deflate-stream))
(return)))))
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