factor/extra/crypto/barrett/barrett.factor

USING: kernel math math.functions ;
IN: crypto.barrett

: barrett-mu ( n size -- mu )
    #! Calculates Barrett's reduction parameter mu
    #! size = word size in bits (8, 16, 32, 64, ...)
    ! over log2 1+ over / 2 * >r 2 swap ^ r> ^ swap / floor ;
    [
        [ log2 1+ ] [ / 2 * ] bi*
    ] [
        2^ rot ^ swap /i
    ] 2bi ;