/home/ntakagi/work/tcl8.5.1/libtommath/bn_mp_read_radix.c Source File

00001 #include <tommath.h>
00002 #ifdef BN_MP_READ_RADIX_C
00003 /* LibTomMath, multiple-precision integer library -- Tom St Denis
00004  *
00005  * LibTomMath is a library that provides multiple-precision
00006  * integer arithmetic as well as number theoretic functionality.
00007  *
00008  * The library was designed directly after the MPI library by
00009  * Michael Fromberger but has been written from scratch with
00010  * additional optimizations in place.
00011  *
00012  * The library is free for all purposes without any express
00013  * guarantee it works.
00014  *
00015  * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
00016  */
00017 
00018 /* read a string [ASCII] in a given radix */
00019 int mp_read_radix (mp_int * a, const char *str, int radix)
00020 {
00021   int     y, res, neg;
00022   char    ch;
00023 
00024   /* zero the digit bignum */
00025   mp_zero(a);
00026 
00027   /* make sure the radix is ok */
00028   if (radix < 2 || radix > 64) {
00029     return MP_VAL;
00030   }
00031 
00032   /* if the leading digit is a 
00033    * minus set the sign to negative. 
00034    */
00035   if (*str == '-') {
00036     ++str;
00037     neg = MP_NEG;
00038   } else {
00039     neg = MP_ZPOS;
00040   }
00041 
00042   /* set the integer to the default of zero */
00043   mp_zero (a);
00044   
00045   /* process each digit of the string */
00046   while (*str) {
00047     /* if the radix < 36 the conversion is case insensitive
00048      * this allows numbers like 1AB and 1ab to represent the same  value
00049      * [e.g. in hex]
00050      */
00051     ch = (char) ((radix < 36) ? toupper (*str) : *str);
00052     for (y = 0; y < 64; y++) {
00053       if (ch == mp_s_rmap[y]) {
00054          break;
00055       }
00056     }
00057 
00058     /* if the char was found in the map 
00059      * and is less than the given radix add it
00060      * to the number, otherwise exit the loop. 
00061      */
00062     if (y < radix) {
00063       if ((res = mp_mul_d (a, (mp_digit) radix, a)) != MP_OKAY) {
00064          return res;
00065       }
00066       if ((res = mp_add_d (a, (mp_digit) y, a)) != MP_OKAY) {
00067          return res;
00068       }
00069     } else {
00070       break;
00071     }
00072     ++str;
00073   }
00074   
00075   /* if an illegal character was found, fail. */
00076 
00077   if ( *str != '\0' ) {
00078       mp_zero( a );
00079       return MP_VAL;
00080   }
00081 
00082   /* set the sign only if a != 0 */
00083   if (mp_iszero(a) != 1) {
00084      a->sign = neg;
00085   }
00086   return MP_OKAY;
00087 }
00088 #endif
00089 
00090 /* $Source: /cvsroot/tcl/libtommath/bn_mp_read_radix.c,v $ */
00091 /* Tom's revision is 1.4. */
00092 /* $Revision: 1.5 $ */
00093 /* $Date: 2006/12/01 00:31:32 $ */
00094