kc3-lang/libtommath/bn_mp_to_radix.c

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• Hash : 642ef5b0
  Author :
  Date : 2019-09-07T19:07:17
  

  fix mp_to_radix remove an assignment which could overwrite the one with MP_VAL caused by a conflict between 2 recent commits - refactor with goto - return error if output-buffer is too small

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• bn_mp_to_radix.c

• #include "tommath_private.h"
  #ifdef BN_MP_TO_RADIX_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* stores a bignum as a ASCII string in a given radix (2..64)
   *
   * Stores upto maxlen-1 chars and always a NULL byte
   */
  mp_err mp_to_radix(const mp_int *a, char *str, size_t maxlen, int radix)
  {
     int     digs;
     mp_err  err;
     mp_int  t;
     mp_digit d;
     char   *_s = str;
  
     /* check range of the maxlen, radix */
     if ((maxlen < 2u) || (radix < 2) || (radix > 64)) {
        return MP_VAL;
     }
  
     /* quick out if its zero */
     if (MP_IS_ZERO(a)) {
        *str++ = '0';
        *str = '\0';
        return MP_OKAY;
     }
  
     if ((err = mp_init_copy(&t, a)) != MP_OKAY) {
        return err;
     }
  
     /* if it is negative output a - */
     if (t.sign == MP_NEG) {
        /* we have to reverse our digits later... but not the - sign!! */
        ++_s;
  
        /* store the flag and mark the number as positive */
        *str++ = '-';
        t.sign = MP_ZPOS;
  
        /* subtract a char */
        --maxlen;
     }
  
     digs = 0;
     while (!MP_IS_ZERO(&t)) {
        if (--maxlen < 1u) {
           /* no more room */
           err = MP_VAL;
           break;
        }
        if ((err = mp_div_d(&t, (mp_digit)radix, &t, &d)) != MP_OKAY) {
           goto LBL_ERR;
        }
        *str++ = mp_s_rmap[d];
        ++digs;
     }
  
     /* reverse the digits of the string.  In this case _s points
      * to the first digit [exluding the sign] of the number
      */
     s_mp_reverse((unsigned char *)_s, digs);
  
     /* append a NULL so the string is properly terminated */
     *str = '\0';
  
  LBL_ERR:
     mp_clear(&t);
     return err;
  }
  
  #endif
  

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