libs/libtommath/bn_mp_read_radix.c

   1 #include <tommath.h>
   2 #ifdef BN_MP_READ_RADIX_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 /* read a string [ASCII] in a given radix */
  19 int mp_read_radix (mp_int * a, const char *str, int radix)
  20 {
  21   int     y, res, neg;
  22   char    ch;
  23
  24   /* zero the digit bignum */
  25   mp_zero(a);
  26
  27   /* make sure the radix is ok */
  28   if (radix < 2 || radix > 64) {
  29     return MP_VAL;
  30   }
  31
  32   /* if the leading digit is a
  33    * minus set the sign to negative.
  34    */
  35   if (*str == '-') {
  36     ++str;
  37     neg = MP_NEG;
  38   } else {
  39     neg = MP_ZPOS;
  40   }
  41
  42   /* set the integer to the default of zero */
  43   mp_zero (a);
  44
  45   /* process each digit of the string */
  46   while (*str) {
  47     /* if the radix < 36 the conversion is case insensitive
  48      * this allows numbers like 1AB and 1ab to represent the same  value
  49      * [e.g. in hex]
  50      */
  51     ch = (char) ((radix < 36) ? toupper (*str) : *str);
  52     for (y = 0; y < 64; y++) {
  53       if (ch == mp_s_rmap[y]) {
  54          break;
  55       }
  56     }
  57
  58     /* if the char was found in the map
  59      * and is less than the given radix add it
  60      * to the number, otherwise exit the loop.
  61      */
  62     if (y < radix) {
  63       if ((res = mp_mul_d (a, (mp_digit) radix, a)) != MP_OKAY) {
  64          return res;
  65       }
  66       if ((res = mp_add_d (a, (mp_digit) y, a)) != MP_OKAY) {
  67          return res;
  68       }
  69     } else {
  70       break;
  71     }
  72     ++str;
  73   }
  74
  75   /* set the sign only if a != 0 */
  76   if (mp_iszero(a) != 1) {
  77      a->sign = neg;
  78   }
  79   return MP_OKAY;
  80 }
  81 #endif
  82
  83 /* $Source: /cvs/libtom/libtommath/bn_mp_read_radix.c,v $ */
  84 /* $Revision: 1.5 $ */
  85 /* $Date: 2006/12/28 01:25:13 $ */