view tomsfastmath/src/bit/fp_count_bits.c @ 645:8622ee48fab5 dropbear-tfm

- Work around broken asm constraint behaviour on 32bit x86 OS X
author Matt Johnston <matt@ucc.asn.au>
date Wed, 30 Nov 2011 22:27:26 +0800
parents a362b62d38b2
children
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/* TomsFastMath, a fast ISO C bignum library.
 * 
 * This project is meant to fill in where LibTomMath
 * falls short.  That is speed ;-)
 *
 * This project is public domain and free for all purposes.
 * 
 * Tom St Denis, [email protected]
 */
#include <tfm.h>

int fp_count_bits (fp_int * a)
{
  int     r;
  fp_digit q;

  /* shortcut */
  if (a->used == 0) {
    return 0;
  }

  /* get number of digits and add that */
  r = (a->used - 1) * DIGIT_BIT;

  /* take the last digit and count the bits in it */
  q = a->dp[a->used - 1];
  while (q > ((fp_digit) 0)) {
    ++r;
    q >>= ((fp_digit) 1);
  }
  return r;
}

/* $Source$ */
/* $Revision$ */
/* $Date$ */