/usr/share/common-lisp/source/salza2/chains.lisp is in cl-salza2 2.0.9-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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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)
(defun hash-value (input position)
(+ (* #.+rmax+ (aref input position))
(* #.+radix+ (aref input (logand #.+input-mask+ (+ position 1))))
(aref input (logand #.+input-mask+ (+ position 2)))))
(declaim (inline mod8191))
(defun mod8191 (z)
(declare (type (integer 0 3057705) z))
(let ((zz (+ (ash z -13) (logand #x1FFF z))))
(if (< zz #x1FFF)
zz
(- zz #x1FFF))))
(defun update-chains (input hashes chains start count)
(declare (type input-buffer input)
(type hashes-buffer hashes)
(type chains-buffer chains)
(type input-index start)
(type (integer 0 32768) count)
(optimize speed))
(when (< count 3)
(return-from update-chains))
(let* ((hash (hash-value input start))
(p0 start)
(p1 (logand (+ start 2) #xFFFF)))
(declare (type (integer 0 3057705) hash))
(loop
(let ((hash-index (mod8191 hash)))
;; Stuff the old hash index into chains at p0
(setf (aref chains p0) (aref hashes hash-index))
;; Stuff p0 into the hashes
(setf (aref hashes hash-index) p0)
;; Tentatively advance; if we hit the end, don't do the rest of
;; the hash update
(setf p1 (logand (1+ p1) #xFFFF))
(decf count)
(when (= count 2)
(return))
;; We're not at the end, so lop off the high, shift left, and
;; add the low to form a new hash value
(setf hash (- hash (* (aref input p0) 11881)))
(setf hash (* hash 109))
(setf p0 (logand (1+ p0) #xFFFF))
(setf hash (+ hash (aref input p1)))))))
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