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;;; rander.el -- possibly better random numbers, using rc16 as a RNG
;; Copyright (C) 1998 Ray Jones
;; Author: Ray Jones, rjones@pobox.com
;; Keywords: RNG, rc4, rc16, stream cipher
;; Created: 1998-04-14
;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program; if not, you can either send email to this
;; program's maintainer or write to: The Free Software Foundation,
;; Inc.; 675 Massachusetts Avenue; Cambridge, MA 02139, USA.
(require 'cl)
(require 'rc16)
(defvar *rander-file* (expand-file-name "~/.emacs.rander"))
(defvar *rander-file-length* 512)
;;; Initialization of the random state
;; generate a string with random information in it
(defun rander-noise-string ()
(concat
;; randomness from before
(if (file-readable-p *rander-file*)
(let ((buf nil))
(unwind-protect
(progn
(setq buf (generate-new-buffer "randerdata"))
(save-excursion
(set-buffer buf)
(insert-file-contents-literally *rander-file*)
(buffer-string)))
(if buf
(let ((kill-buffer-hook nil))
(kill-buffer buf))))))
;; allocation randomness
(if (boundp 'cons-cells-consed)
(apply 'concat
(mapcar 'int-to-string
(list cons-cells-consed
floats-consed
intervals-consed
misc-objects-consed
string-chars-consed
symbols-consed
vector-cells-consed)))
"")
;; time randomness
(apply 'concat (mapcar 'int-to-string (current-time)))
;; process randomness
(int-to-string (emacs-pid))))
;;; Mixin keypress randomness, on the fly
;; don't use this if your (current-time) is not fine grained in the
;; microseconds. or if your computer is particularly slow, and the
;; pre-command-hook stuff slows it down (unlikely).
(defvar *rander-use-keypress* t)
;; this number shouldn't be too high, as a call to (rander16) will
;; have to mixin up to this many values before actually returning
(defvar *rander-keypress-count* 128)
(defvar *rander-keypress-timings*
(and *rander-use-keypress*
(make-vector *rander-keypress-count* 0)))
(defvar *rander-keypress-have* 0)
(defun rander-store-key-time ()
"store keypress timings until we have filled the keypress timings buffer"
(when (< *rander-keypress-have* *rander-keypress-count*)
(aset *rander-keypress-timings*
*rander-keypress-have*
(nth 2 (current-time)))
(incf *rander-keypress-have*)))
(if *rander-use-keypress*
(add-hook 'pre-command-hook 'rander-store-key-time))
;;; main source of randomness, the rc16 generator
(defvar *rander-initialized* nil)
(defvar *rander-rc16-context* nil)
(defun rander-init ()
(setq *rander-rc16-context* (rc16-create-context))
(rc16-set-key *rander-rc16-context* (rander-noise-string))
(add-hook 'kill-emacs-hook 'rander-write-file)
(setq *rander-initialized* t))
(defun rander16 ()
(if (not *rander-initialized*)
(rander-init))
(when (and *rander-use-keypress*
(not (zerop *rander-keypress-have*)))
;; mixin all the keypresses we have stored to this point
(dotimes (idx *rander-keypress-have*)
(rc16-mixin *rander-rc16-context*
(aref *rander-keypress-timings* idx)))
;; reset the buffer
(setq *rander-keypress-have* 0))
;; return a random value
(rc16-short *rander-rc16-context*))
(defun rander-write-file ()
"write out a seed file for the next time rander is used. called at
the exit of emacs."
(let ((buf nil))
(unwind-protect
(progn
(setq buf (generate-new-buffer "randerdata"))
(save-excursion
(set-buffer buf)
(dotimes (count *rander-file-length*)
(insert (logand ?\xff (rander16))))
(let ((backup-inhibited t))
(write-file *rander-file*))))
(if buf
(let ((kill-buffer-hook nil))
(kill-buffer buf))))))
(provide 'rander)
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