;;;
;;; logutil.scm - logical (bitwise) operations.  to be autoloaded.
;;;
;;;   Copyright (c) 2000-2025  Shiro Kawai  <shiro@acm.org>
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(select-module gauche)

;; SLIB compatible interface.

(define (logtest . args)  ;; can be optimized for two-arg case
  (not (zero? (apply logand args))))

(define (logbit? index n)
  (not (zero? (logand n (ash 1 index)))))

(define (copy-bit index from bit)
  (if bit
    (logior (ash 1 index) from)
    (logand (lognot (ash 1 index)) from)))

(define (bit-field n start end)
  (assume-type start <integer>)
  (assume-type end <integer>)
  (if (< start end)
    (let1 mask (- (ash 1 (- end start)) 1)
      (logand (ash n (- start)) mask))
    0))

(define (copy-bit-field to from start end)
  (assume-type start <integer>)
  (assume-type end <integer>)
  (if (< start end)
    (let1 mask (- (ash 1 (- end start)) 1)
      (logior (logand to (lognot (ash mask start)))
              (ash (logand from mask) start)))
    from))
