История изменений

(define (whitening in-port out-port)
  (let rloop ([bits 0]
              [bit 0])
    (let ([in (read-u8 in-port)])
      (unless (eof-object? in)
        (let loop ([mask-shift 0]
                   [bits bits]
                   [bit bit])
          (cond
           [(= mask-shift 8)
            (rloop bits bit)]
           [(= bit 8)
            (write-u8 bits out-port)
            (loop mask-shift 0 0)]
           [else
            (let ([ms (+ mask-shift 2)])
              (case (bitwise-and 3 (arithmetic-shift in (- mask-shift)))
                [(0 3) (loop ms bits bit)]
                [(1)   (loop ms bits (+ bit 1))]
                [(2)   (loop ms
                             (bitwise-ior bits (arithmetic-shift 1 bit))
                             (+ bit 1))]))]))))))     

(define (whitening in-port out-port)
  (let rloop ([bits 0]
              [bit 0])
    (let ([in (read-u8 in-port)])
      (if (eof-object? in) '()
          (let loop ([mask-shift 0]
                     [bits bits]
                     [bit bit])
            (cond
             [(= mask-shift 8)
              (rloop bits bit)]
             [(= bit 8)
              (write-u8 bits out-port)
              (loop mask-shift 0 0)]
             [else
              (let ([ms (+ mask-shift 2)])
                (case (bitwise-and 3 (arithmetic-shift in (- mask-shift)))
                  [(0 3) (loop ms bits bit)]
                  [(1)   (loop ms bits (+ bit 1))]
                  [(2)   (loop ms
                               (bitwise-ior bits (arithmetic-shift 1 bit))
                               (+ bit 1))]))]))))))