kc3-lang/libtommath/mp_to_radix.c

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• Hash : f8b2f5d6
  Author :
  Date : 2019-10-23T20:07:33
  

  s_mp_reverse is only used by mp_to_radix

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• mp_to_radix.c

• #include "tommath_private.h"
  #ifdef MP_TO_RADIX_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* reverse an array, used for radix code */
  static void s_mp_reverse(unsigned char *s, size_t len)
  {
     size_t   ix, iy;
     unsigned char t;
  
     ix = 0u;
     iy = len - 1u;
     while (ix < iy) {
        t     = s[ix];
        s[ix] = s[iy];
        s[iy] = t;
        ++ix;
        --iy;
     }
  }
  
  /* stores a bignum as a ASCII string in a given radix (2..64)
   *
   * Stores upto "size - 1" chars and always a NULL byte, puts the number of characters
   * written, including the '\0', in "written".
   */
  mp_err mp_to_radix(const mp_int *a, char *str, size_t maxlen, size_t *written, int radix)
  {
     size_t  digs;
     mp_err  err;
     mp_int  t;
     mp_digit d;
     char   *_s = str;
  
     /* check range of radix and size*/
     if (maxlen < 2u) {
        return MP_BUF;
     }
     if ((radix < 2) || (radix > 64)) {
        return MP_VAL;
     }
  
     /* quick out if its zero */
     if (mp_iszero(a)) {
        *str++ = '0';
        *str = '\0';
        if (written != NULL) {
           *written = 2u;
        }
        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 = 0u;
     while (!mp_iszero(&t)) {
        if (--maxlen < 1u) {
           /* no more room */
           err = MP_BUF;
           goto LBL_ERR;
        }
        if ((err = mp_div_d(&t, (mp_digit)radix, &t, &d)) != MP_OKAY) {
           goto LBL_ERR;
        }
        *str++ = s_mp_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';
     digs++;
  
     if (written != NULL) {
        *written = (a->sign == MP_NEG) ? (digs + 1u): digs;
     }
  
  LBL_ERR:
     mp_clear(&t);
     return err;
  }
  
  #endif
  

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