lib/hcrypto/libtommath/bn_mp_radix_size.c

   1 #include "tommath_private.h"
   2 #ifdef BN_MP_RADIX_SIZE_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
   4 /* SPDX-License-Identifier: Unlicense */
   5
   6 /* returns size of ASCII representation */
   7 mp_err mp_radix_size(const mp_int *a, int radix, int *size)
   8 {
   9    mp_err  err;
  10    int digs;
  11    mp_int   t;
  12    mp_digit d;
  13
  14    *size = 0;
  15
  16    /* make sure the radix is in range */
  17    if ((radix < 2) || (radix > 64)) {
  18       return MP_VAL;
  19    }
  20
  21    if (MP_IS_ZERO(a)) {
  22       *size = 2;
  23       return MP_OKAY;
  24    }
  25
  26    /* special case for binary */
  27    if (radix == 2) {
  28       *size = (mp_count_bits(a) + ((a->sign == MP_NEG) ? 1 : 0) + 1);
  29       return MP_OKAY;
  30    }
  31
  32    /* digs is the digit count */
  33    digs = 0;
  34
  35    /* if it's negative add one for the sign */
  36    if (a->sign == MP_NEG) {
  37       ++digs;
  38    }
  39
  40    /* init a copy of the input */
  41    if ((err = mp_init_copy(&t, a)) != MP_OKAY) {
  42       return err;
  43    }
  44
  45    /* force temp to positive */
  46    t.sign = MP_ZPOS;
  47
  48    /* fetch out all of the digits */
  49    while (!MP_IS_ZERO(&t)) {
  50       if ((err = mp_div_d(&t, (mp_digit)radix, &t, &d)) != MP_OKAY) {
  51          goto LBL_ERR;
  52       }
  53       ++digs;
  54    }
  55
  56    /* return digs + 1, the 1 is for the NULL byte that would be required. */
  57    *size = digs + 1;
  58    err = MP_OKAY;
  59
  60 LBL_ERR:
  61    mp_clear(&t);
  62    return err;
  63 }
  64
  65 #endif