Mercurial > hg > Members > anatofuz > MoarVM
diff 3rdparty/libtommath/bn_mp_expt_d_ex.c @ 0:2cf249471370
convert mercurial for git
author | Takahiro SHIMIZU <anatofuz@cr.ie.u-ryukyu.ac.jp> |
---|---|
date | Tue, 08 May 2018 16:09:12 +0900 |
parents | |
children |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/3rdparty/libtommath/bn_mp_expt_d_ex.c Tue May 08 16:09:12 2018 +0900 @@ -0,0 +1,83 @@ +#include <tommath_private.h> +#ifdef BN_MP_EXPT_D_EX_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, tstdenis82@gmail.com, http://libtom.org + */ + +/* calculate c = a**b using a square-multiply algorithm */ +int mp_expt_d_ex (mp_int * a, mp_digit b, mp_int * c, int fast) +{ + int res; + unsigned int x; + + mp_int g; + + if ((res = mp_init_copy (&g, a)) != MP_OKAY) { + return res; + } + + /* set initial result */ + mp_set (c, 1); + + if (fast != 0) { + while (b > 0) { + /* if the bit is set multiply */ + if ((b & 1) != 0) { + if ((res = mp_mul (c, &g, c)) != MP_OKAY) { + mp_clear (&g); + return res; + } + } + + /* square */ + if (b > 1) { + if ((res = mp_sqr (&g, &g)) != MP_OKAY) { + mp_clear (&g); + return res; + } + } + + /* shift to next bit */ + b >>= 1; + } + } + else { + for (x = 0; x < DIGIT_BIT; x++) { + /* square */ + if ((res = mp_sqr (c, c)) != MP_OKAY) { + mp_clear (&g); + return res; + } + + /* if the bit is set multiply */ + if ((b & (mp_digit) (((mp_digit)1) << (DIGIT_BIT - 1))) != 0) { + if ((res = mp_mul (c, &g, c)) != MP_OKAY) { + mp_clear (&g); + return res; + } + } + + /* shift to next bit */ + b <<= 1; + } + } /* if ... else */ + + mp_clear (&g); + return MP_OKAY; +} +#endif + +/* $Source$ */ +/* $Revision$ */ +/* $Date$ */