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;; Processing Unicode Files with ACL2
;; Copyright (C) 2005-2006 by Jared Davis <jared@cs.utexas.edu>
;;
;; 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 of the License, 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, write to the Free Software Foundation, Inc., 59 Temple
;; Place - Suite 330, Boston, MA 02111-1307, USA.
(in-package "ACL2")
(include-book "read-byte")
(include-book "read-file-bytes")
(include-book "nthcdr-bytes")
(set-state-ok t)
(defund take-bytes (n channel state)
(declare (xargs :guard (and (natp n)
(state-p state)
(symbolp channel)
(open-input-channel-p channel :byte state))))
(if (zp n)
(mv nil state)
(mv-let (a state)
(read-byte$ channel state)
(mv-let (x state)
(take-bytes (1- n) channel state)
(mv (cons a x) state)))))
(defthm state-p1-of-take-bytes
(implies (and (force (state-p1 state))
(force (symbolp channel))
(force (open-input-channel-p1 channel :byte state)))
(state-p1 (mv-nth 1 (take-bytes n channel state))))
:hints(("Goal" :in-theory (enable take-bytes))))
(defthm open-input-channel-p1-of-take-bytes
(implies (and (force (state-p1 state))
(force (symbolp channel))
(force (open-input-channel-p1 channel :byte state)))
(open-input-channel-p1 channel :byte (mv-nth 1 (take-bytes n channel state))))
:hints(("Goal" :in-theory (enable take-bytes))))
(defthm car-of-take-bytes
(implies (and (force (state-p1 state))
(force (symbolp channel))
(force (open-input-channel-p1 channel :byte state)))
(equal (car (take-bytes n channel state))
(simpler-take n (car (read-byte$-all channel state)))))
:hints(("Goal"
:in-theory (enable take take-bytes read-byte$-all)
:induct (take-bytes n channel state))))
(defthm mv-nth1-of-take-bytes$
(implies (and (force (state-p1 state))
(force (symbolp channel))
(force (open-input-channel-p1 channel :byte state)))
(equal (mv-nth 1 (take-bytes n channel state))
(nthcdr-bytes n channel state)))
:hints(("Goal" :in-theory (enable take-bytes nthcdr-bytes))))
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