Mercurial > dropbear
diff libtommath/bn_mp_radix_size.c @ 284:eed26cff980b
propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583)
to branch 'au.asn.ucc.matt.dropbear' (head fff0894a0399405a9410ea1c6d118f342cf2aa64)
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 08 Mar 2006 13:23:49 +0000 |
parents | |
children | 5ff8218bcee9 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/libtommath/bn_mp_radix_size.c Wed Mar 08 13:23:49 2006 +0000 @@ -0,0 +1,74 @@ +#include <tommath.h> +#ifdef BN_MP_RADIX_SIZE_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, [email protected], http://math.libtomcrypt.org + */ + +/* returns size of ASCII reprensentation */ +int mp_radix_size (mp_int * a, int radix, int *size) +{ + int res, digs; + mp_int t; + mp_digit d; + + *size = 0; + + /* special case for binary */ + if (radix == 2) { + *size = mp_count_bits (a) + (a->sign == MP_NEG ? 1 : 0) + 1; + return MP_OKAY; + } + + /* make sure the radix is in range */ + if (radix < 2 || radix > 64) { + return MP_VAL; + } + + if (mp_iszero(a) == MP_YES) { + *size = 2; + return MP_OKAY; + } + + /* digs is the digit count */ + digs = 0; + + /* if it's negative add one for the sign */ + if (a->sign == MP_NEG) { + ++digs; + } + + /* init a copy of the input */ + if ((res = mp_init_copy (&t, a)) != MP_OKAY) { + return res; + } + + /* force temp to positive */ + t.sign = MP_ZPOS; + + /* fetch out all of the digits */ + while (mp_iszero (&t) == MP_NO) { + if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) { + mp_clear (&t); + return res; + } + ++digs; + } + mp_clear (&t); + + /* return digs + 1, the 1 is for the NULL byte that would be required. */ + *size = digs + 1; + return MP_OKAY; +} + +#endif