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kc3-lang/libtommath/bn_mp_get_long_long.c

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  • Author : Francois Perrad
    Date : 2017-10-15 19:58:35
    Hash : f1d6c887
    Message : refactor cast

  • bn_mp_get_long_long.c
  • #include <tommath_private.h>
    #ifdef BN_MP_GET_LONG_LONG_C
    /* LibTomMath, multiple-precision integer library -- Tom St Denis
     *
     * LibTomMath is a library that provides multiple-precision
     * integer arithmetic as well as number theoretic functionality.
     *
     * The library was designed directly after the MPI library by
     * Michael Fromberger but has been written from scratch with
     * additional optimizations in place.
     *
     * The library is free for all purposes without any express
     * guarantee it works.
     *
     * Tom St Denis, tstdenis82@gmail.com, http://libtom.org
     */
    
    /* get the lower unsigned long long of an mp_int, platform dependent */
    unsigned long long mp_get_long_long(const mp_int *a)
    {
       int i;
       unsigned long long res;
    
       if (a->used == 0) {
          return 0;
       }
    
       /* get number of digits of the lsb we have to read */
       i = MIN(a->used, ((((int)sizeof(unsigned long long) * CHAR_BIT) + DIGIT_BIT - 1) / DIGIT_BIT)) - 1;
    
       /* get most significant digit of result */
       res = DIGIT(a, i);
    
    #if DIGIT_BIT < 64
       while (--i >= 0) {
          res = (res << DIGIT_BIT) | DIGIT(a, i);
       }
    #endif
       return res;
    }
    #endif