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Diffstat (limited to 'libtommath/bn_mp_read_radix.c')
-rw-r--r-- | libtommath/bn_mp_read_radix.c | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/libtommath/bn_mp_read_radix.c b/libtommath/bn_mp_read_radix.c new file mode 100644 index 0000000..4b92589 --- /dev/null +++ b/libtommath/bn_mp_read_radix.c @@ -0,0 +1,88 @@ +#include <tommath.h> +#ifdef BN_MP_READ_RADIX_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis + * + * LibTomMath is a library that provides multiple-precision + * integer arithmetic as well as number theoretic functionality. + * + * The library was designed directly after the MPI library by + * Michael Fromberger but has been written from scratch with + * additional optimizations in place. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com + */ + +/* read a string [ASCII] in a given radix */ +int mp_read_radix (mp_int * a, const char *str, int radix) +{ + int y, res, neg; + char ch; + + /* zero the digit bignum */ + mp_zero(a); + + /* make sure the radix is ok */ + if (radix < 2 || radix > 64) { + return MP_VAL; + } + + /* if the leading digit is a + * minus set the sign to negative. + */ + if (*str == '-') { + ++str; + neg = MP_NEG; + } else { + neg = MP_ZPOS; + } + + /* set the integer to the default of zero */ + mp_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 = (char) ((radix < 36) ? toupper ((unsigned char) *str) : *str); + for (y = 0; y < 64; y++) { + if (ch == mp_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) { + if ((res = mp_mul_d (a, (mp_digit) radix, a)) != MP_OKAY) { + return res; + } + if ((res = mp_add_d (a, (mp_digit) y, a)) != MP_OKAY) { + return res; + } + } else { + break; + } + ++str; + } + + /* if an illegal character was found, fail. */ + + if ( *str != '\0' ) { + mp_zero( a ); + return MP_VAL; + } + + /* set the sign only if a != 0 */ + if (mp_iszero(a) != 1) { + a->sign = neg; + } + return MP_OKAY; +} +#endif |