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;;; bitwise.scm --- The R6RS bitwise arithmetic operations library
;; Copyright (C) 2010 Free Software Foundation, Inc.
;;
;; This library is free software; you can redistribute it and/or
;; modify it under the terms of the GNU Lesser General Public
;; License as published by the Free Software Foundation; either
;; version 3 of the License, or (at your option) any later version.
;;
;; This library 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
;; Lesser General Public License for more details.
;;
;; You should have received a copy of the GNU Lesser General Public
;; License along with this library; if not, write to the Free Software
;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
(library (rnrs arithmetic bitwise (6))
(export bitwise-not
bitwise-and
bitwise-ior
bitwise-xor
bitwise-if
bitwise-bit-count
bitwise-length
bitwise-first-bit-set
bitwise-bit-set?
bitwise-copy-bit
bitwise-bit-field
bitwise-copy-bit-field
bitwise-arithmetic-shift
bitwise-arithmetic-shift-left
bitwise-arithmetic-shift-right
bitwise-rotate-bit-field
bitwise-reverse-bit-field)
(import (rnrs base (6))
(rnrs control (6))
(rename (only (guile) lognot
logand
logior
logxor
logcount
logbit?
modulo
ash)
(lognot bitwise-not)
(logand bitwise-and)
(logior bitwise-ior)
(logxor bitwise-xor)
(logcount bitwise-bit-count)
(ash bitwise-arithmetic-shift)))
(define (bitwise-if ei1 ei2 ei3)
(bitwise-ior (bitwise-and ei1 ei2) (bitwise-and (bitwise-not ei1) ei3)))
(define (bitwise-length ei)
(do ((result 0 (+ result 1))
(bits (if (negative? ei) (bitwise-not ei) ei)
(bitwise-arithmetic-shift bits -1)))
((zero? bits)
result)))
(define (bitwise-first-bit-set ei)
(define (bitwise-first-bit-set-inner bits count)
(cond ((zero? bits) -1)
((logbit? 0 bits) count)
(else (bitwise-first-bit-set-inner
(bitwise-arithmetic-shift bits -1) (+ count 1)))))
(bitwise-first-bit-set-inner ei 0))
(define (bitwise-bit-set? ei1 ei2) (logbit? ei2 ei1))
(define (bitwise-copy-bit ei1 ei2 ei3)
(bitwise-if (bitwise-arithmetic-shift-left 1 ei2)
(bitwise-arithmetic-shift-left ei3 ei2)
ei1))
(define (bitwise-bit-field ei1 ei2 ei3)
(bitwise-arithmetic-shift-right
(bitwise-and ei1 (bitwise-not (bitwise-arithmetic-shift-left -1 ei3)))
ei2))
(define (bitwise-copy-bit-field ei1 ei2 ei3 ei4)
(bitwise-if (bitwise-and (bitwise-arithmetic-shift-left -1 ei2)
(bitwise-not
(bitwise-arithmetic-shift-left -1 ei3)))
(bitwise-arithmetic-shift-left ei4 ei2)
ei1))
(define bitwise-arithmetic-shift-left bitwise-arithmetic-shift)
(define (bitwise-arithmetic-shift-right ei1 ei2)
(bitwise-arithmetic-shift ei1 (- ei2)))
(define (bitwise-rotate-bit-field ei1 ei2 ei3 ei4)
(let ((width (- ei3 ei2)))
(if (positive? width)
(let ((field (bitwise-bit-field ei1 ei2 ei3))
(count (modulo ei4 width)))
(bitwise-copy-bit-field
ei1 ei2 ei3
(bitwise-ior (bitwise-arithmetic-shift-left field count)
(bitwise-arithmetic-shift-right
field (- width count)))))
ei1)))
(define (bitwise-reverse-bit-field ei1 ei2 ei3)
(define (reverse-bit-field-recursive n1 n2 len)
(if (> len 0)
(reverse-bit-field-recursive
(bitwise-arithmetic-shift-right n1 1)
(bitwise-copy-bit (bitwise-arithmetic-shift-left n2 1) 0 n1)
(- len 1))
n2))
(let ((width (- ei3 ei2)))
(if (positive? width)
(let ((field (bitwise-bit-field ei1 ei2 ei3)))
(bitwise-copy-bit-field
ei1 ei2 ei3 (reverse-bit-field-recursive field 0 width)))
ei1))))