lib/hcrypto/libtommath/bn_mp_radix_size.c

   1 #include <tommath.h>
   2 #ifdef BN_MP_RADIX_SIZE_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
   4  *
   5  * LibTomMath is a library that provides multiple-precision
   6  * integer arithmetic as well as number theoretic functionality.
   7  *
   8  * The library was designed directly after the MPI library by
   9  * Michael Fromberger but has been written from scratch with
  10  * additional optimizations in place.
  11  *
  12  * The library is free for all purposes without any express
  13  * guarantee it works.
  14  *
  15  * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
  16  */
  17
  18 /* returns size of ASCII reprensentation */
  19 int mp_radix_size (mp_int * a, int radix, int *size)
  20 {
  21   int     res, digs;
  22   mp_int  t;
  23   mp_digit d;
  24
  25   *size = 0;
  26
  27   /* special case for binary */
  28   if (radix == 2) {
  29     *size = mp_count_bits (a) + (a->sign == MP_NEG ? 1 : 0) + 1;
  30     return MP_OKAY;
  31   }
  32
  33   /* make sure the radix is in range */
  34   if (radix < 2 || radix > 64) {
  35     return MP_VAL;
  36   }
  37
  38   if (mp_iszero(a) == MP_YES) {
  39     *size = 2;
  40     return MP_OKAY;
  41   }
  42
  43   /* digs is the digit count */
  44   digs = 0;
  45
  46   /* if it's negative add one for the sign */
  47   if (a->sign == MP_NEG) {
  48     ++digs;
  49   }
  50
  51   /* init a copy of the input */
  52   if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
  53     return res;
  54   }
  55
  56   /* force temp to positive */
  57   t.sign = MP_ZPOS;
  58
  59   /* fetch out all of the digits */
  60   while (mp_iszero (&t) == MP_NO) {
  61     if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
  62       mp_clear (&t);
  63       return res;
  64     }
  65     ++digs;
  66   }
  67   mp_clear (&t);
  68
  69   /* return digs + 1, the 1 is for the NULL byte that would be required. */
  70   *size = digs + 1;
  71   return MP_OKAY;
  72 }
  73
  74 #endif
  75
  76 /* $Source: /cvs/libtom/libtommath/bn_mp_radix_size.c,v $ */
  77 /* $Revision: 1.5 $ */
  78 /* $Date: 2006/12/28 01:25:13 $ */