/usr/share/common-lisp/source/salza2/gzip.lisp is in cl-salza2 2.0.9-1.
This file is owned by root:root, with mode 0o644.
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;;; Copyright (c) 2007 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.
;;;
(in-package #:salza2)
(defvar *gzip-signature* (octet-vector #x1F #x8B)
"These two octets precede all data in the gzip format.")
(defconstant +gzip-fast-compression+ 4
"Code for gzip compression level. This is present only to create valid
gzip data; it has no meaning to the compressor and is only a hint to
the decompressor.")
;;; These are all used to create valid files, not to control or modify
;;; the compression process.
(defconstant +gzip-deflate-compression+ 8)
(defconstant +gzip-flags+ 0)
(defconstant +gzip-unix-os+ 3)
(defconstant +gzip-mtime+ 0)
(defun gzip-write-u32 (value compressor)
;; LSB
(write-octet (ldb (byte 8 0) value) compressor)
(write-octet (ldb (byte 8 8) value) compressor)
(write-octet (ldb (byte 8 16) value) compressor)
(write-octet (ldb (byte 8 24) value) compressor))
(defclass gzip-compressor (deflate-compressor)
((checksum
:initarg :checksum
:accessor checksum)
(data-length
:initarg :data-length
:accessor data-length))
(:default-initargs
:checksum (make-instance 'crc32-checksum)
:data-length 0))
(defmethod start-data-format :before ((compressor gzip-compressor))
(write-octet-vector *gzip-signature* compressor)
(write-octet +gzip-deflate-compression+ compressor)
(write-octet +gzip-flags+ compressor)
(gzip-write-u32 +gzip-mtime+ compressor)
(write-octet +gzip-fast-compression+ compressor)
(write-octet +gzip-unix-os+ compressor))
(defmethod process-input :after ((compressor gzip-compressor)
input start count)
(incf (data-length compressor) count)
(update (checksum compressor) input start count))
(defmethod finish-data-format :after ((compressor gzip-compressor))
(gzip-write-u32 (result (checksum compressor)) compressor)
(gzip-write-u32 (data-length compressor) compressor))
(defmethod reset :after ((compressor gzip-compressor))
(reset (checksum compressor))
(setf (data-length compressor) 0))
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