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      1 #include <tommath.h>
      2 #ifdef BN_MP_TORADIX_N_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 (at) gmail.com, http://math.libtomcrypt.com
     16  */
     17 
     18 /* stores a bignum as a ASCII string in a given radix (2..64)
     19  *
     20  * Stores upto maxlen-1 chars and always a NULL byte
     21  */
     22 int mp_toradix_n(mp_int * a, char *str, int radix, int maxlen)
     23 {
     24   int     res, digs;
     25   mp_int  t;
     26   mp_digit d;
     27   char   *_s = str;
     28 
     29   /* check range of the maxlen, radix */
     30   if (maxlen < 2 || radix < 2 || radix > 64) {
     31     return MP_VAL;
     32   }
     33 
     34   /* quick out if its zero */
     35   if (mp_iszero(a) == MP_YES) {
     36      *str++ = '0';
     37      *str = '\0';
     38      return MP_OKAY;
     39   }
     40 
     41   if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
     42     return res;
     43   }
     44 
     45   /* if it is negative output a - */
     46   if (t.sign == MP_NEG) {
     47     /* we have to reverse our digits later... but not the - sign!! */
     48     ++_s;
     49 
     50     /* store the flag and mark the number as positive */
     51     *str++ = '-';
     52     t.sign = MP_ZPOS;
     53 
     54     /* subtract a char */
     55     --maxlen;
     56   }
     57 
     58   digs = 0;
     59   while (mp_iszero (&t) == 0) {
     60     if (--maxlen < 1) {
     61        /* no more room */
     62        break;
     63     }
     64     if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
     65       mp_clear (&t);
     66       return res;
     67     }
     68     *str++ = mp_s_rmap[d];
     69     ++digs;
     70   }
     71 
     72   /* reverse the digits of the string.  In this case _s points
     73    * to the first digit [exluding the sign] of the number
     74    */
     75   bn_reverse ((unsigned char *)_s, digs);
     76 
     77   /* append a NULL so the string is properly terminated */
     78   *str = '\0';
     79 
     80   mp_clear (&t);
     81   return MP_OKAY;
     82 }
     83 
     84 #endif
     85 
     86 /* $Source: /cvs/libtom/libtommath/bn_mp_toradix_n.c,v $ */
     87 /* $Revision: 1.4 $ */
     88 /* $Date: 2006/03/31 14:18:44 $ */
     89