;;;;;;;;; From (r6rs bytevectores) begin ;;;;;;;;;;

;;; Copyright 2015 William D Clinger.
;;;
;;; Permission to copy this software, in whole or in part, to use this
;;; software for any lawful purpose, and to redistribute this software
;;; is granted subject to the restriction that all copies made of this
;;; software must include this copyright and permission notice in full.
;;;
;;; I also request that you send me a copy of any improvements that you
;;; make to this software so that they may be incorporated within it to
;;; the benefit of the Scheme community.
;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(define-syntax bytevector:div
    (syntax-rules ()
         ((_ x y) (quotient x y))))

(define-syntax bytevector:mod
    (syntax-rules ()
         ((_ x y) (remainder x y))))

(define-syntax unspecified
    (syntax-rules ()
         ((_) (if #f #f))))

(define (bytevector-uint-ref bytevector index endness size)
  (case endness
    ((big)
     (do ((i 0 (+ i 1))
          (result 0 (+ (* 256 result)
                       (bytevector-u8-ref bytevector (+ index i)))))
       ((>= i size)
        result)))
    ((little)
     (do ((i (- size 1) (- i 1))
          (result 0 (+ (* 256 result)
                       (bytevector-u8-ref bytevector (+ index i)))))
       ((< i 0)
        result)))
    (else (error "bytevector-uint-ref error: Unknown endianness" endness))))

(define (bytevector-uint-set! bytevector index val endness size)
    (case endness
         ((little)
              (do ((i 0 (+ i 1))
                            (val val (bytevector:div val 256)))
                        ((>= i size)
                                  (unspecified))
                              (bytevector-u8-set! bytevector (+ index i) (bytevector:mod val 256))))
            ((big)
                 (do ((i (- size 1) (- i 1))
                               (val val (bytevector:div val 256)))
                           ((< i 0)
                                     (unspecified))
                                 (bytevector-u8-set! bytevector (+ index i) (bytevector:mod val 256))))
               (else
                     (bytevector-uint-set! bytevector index val (native-endianness) size))))

;;;;;;;;; From (r6rs bytevectores) end ;;;;;;;;;;