Mercurial > dropbear
diff bn_mp_reduce_2k_setup.c @ 282:91fbc376f010 libtommath-orig libtommath-0.35
Import of libtommath 0.35
From ltm-0.35.tar.bz2 SHA1 of 3f193dbae9351e92d02530994fa18236f7fde01c
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 08 Mar 2006 13:16:18 +0000 |
parents | |
children | 97db060d0ef5 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/bn_mp_reduce_2k_setup.c Wed Mar 08 13:16:18 2006 +0000 @@ -0,0 +1,43 @@ +#include <tommath.h> +#ifdef BN_MP_REDUCE_2K_SETUP_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 + */ + +/* determines the setup value */ +int mp_reduce_2k_setup(mp_int *a, mp_digit *d) +{ + int res, p; + mp_int tmp; + + if ((res = mp_init(&tmp)) != MP_OKAY) { + return res; + } + + p = mp_count_bits(a); + if ((res = mp_2expt(&tmp, p)) != MP_OKAY) { + mp_clear(&tmp); + return res; + } + + if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) { + mp_clear(&tmp); + return res; + } + + *d = tmp.dp[0]; + mp_clear(&tmp); + return MP_OKAY; +} +#endif