fp_read_radix.c   [plain text]

/* TomsFastMath, a fast ISO C bignum library.
 * 
 * This project is meant to fill in where LibTomMath
 * falls short.  That is speed ;-)
 *
 * This project is public domain and free for all purposes.
 * 
 * Tom St Denis, tomstdenis@gmail.com
 */
#include <tfm.h>

int fp_read_radix(fp_int *a, char *str, int radix)
{
  int     y, neg;
  char    ch;

  /* make sure the radix is ok */
  if (radix < 2 || radix > 64) {
    return FP_VAL;
  }

  /* if the leading digit is a
   * minus set the sign to negative.
   */
  if (*str == '-') {
    ++str;
    neg = FP_NEG;
  } else {
    neg = FP_ZPOS;
  }

  /* set the integer to the default of zero */
  fp_zero (a);

  /* process each digit of the string */
  while (*str) {
    /* if the radix < 36 the conversion is case insensitive
     * this allows numbers like 1AB and 1ab to represent the same  value
     * [e.g. in hex]
     */
    ch = *str;
    /*
     * Don't use toupper() because it tends to pull in tons of locale stuff
     */
    if (radix < 36  &&  ch >= 'a'  &&  ch <= 'z')
        ch = ch - 'a' + 'A';
    for (y = 0; y < 64; y++) {
      if (ch == fp_s_rmap[y]) {
         break;
      }
    }

    /* if the char was found in the map
     * and is less than the given radix add it
     * to the number, otherwise exit the loop.
     */
    if (y < radix) {
      fp_mul_d (a, (fp_digit) radix, a);
      fp_add_d (a, (fp_digit) y, a);
    } else {
      break;
    }
    ++str;
  }

  /* set the sign only if a != 0 */
  if (fp_iszero(a) != FP_YES) {
     a->sign = neg;
  }
  return FP_OKAY;
}

/* $Source: /cvs/libtom/tomsfastmath/src/bin/fp_read_radix.c,v $ */
/* $Revision: 1.1 $ */
/* $Date: 2006/12/31 21:25:53 $ */