Mercurial > dropbear
view libtommath/bn_mp_gcd.c @ 1156:a8f4dade70e5
avoid getpass when not used
some systems (like android's bionic) do not provide getpass. you can
disable ENABLE_CLI_PASSWORD_AUTH & ENABLE_CLI_INTERACT_AUTH to avoid
its use (and rely on pubkey auth), but the link still fails because
the support file calls getpass. do not define this func if both of
those auth methods are not used.
author | Mike Frysinger <vapier@gentoo.org> |
---|---|
date | Wed, 21 Oct 2015 22:39:55 +0800 |
parents | 5ff8218bcee9 |
children | 60fc6476e044 |
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line source
#include <tommath.h> #ifdef BN_MP_GCD_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.com */ /* Greatest Common Divisor using the binary method */ int mp_gcd (mp_int * a, mp_int * b, mp_int * c) { mp_int u, v; int k, u_lsb, v_lsb, res; /* either zero than gcd is the largest */ if (mp_iszero (a) == MP_YES) { return mp_abs (b, c); } if (mp_iszero (b) == MP_YES) { return mp_abs (a, c); } /* get copies of a and b we can modify */ if ((res = mp_init_copy (&u, a)) != MP_OKAY) { return res; } if ((res = mp_init_copy (&v, b)) != MP_OKAY) { goto LBL_U; } /* must be positive for the remainder of the algorithm */ u.sign = v.sign = MP_ZPOS; /* B1. Find the common power of two for u and v */ u_lsb = mp_cnt_lsb(&u); v_lsb = mp_cnt_lsb(&v); k = MIN(u_lsb, v_lsb); if (k > 0) { /* divide the power of two out */ if ((res = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) { goto LBL_V; } if ((res = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) { goto LBL_V; } } /* divide any remaining factors of two out */ if (u_lsb != k) { if ((res = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) { goto LBL_V; } } if (v_lsb != k) { if ((res = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) { goto LBL_V; } } while (mp_iszero(&v) == 0) { /* make sure v is the largest */ if (mp_cmp_mag(&u, &v) == MP_GT) { /* swap u and v to make sure v is >= u */ mp_exch(&u, &v); } /* subtract smallest from largest */ if ((res = s_mp_sub(&v, &u, &v)) != MP_OKAY) { goto LBL_V; } /* Divide out all factors of two */ if ((res = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) { goto LBL_V; } } /* multiply by 2**k which we divided out at the beginning */ if ((res = mp_mul_2d (&u, k, c)) != MP_OKAY) { goto LBL_V; } c->sign = MP_ZPOS; res = MP_OKAY; LBL_V:mp_clear (&u); LBL_U:mp_clear (&v); return res; } #endif /* $Source: /cvs/libtom/libtommath/bn_mp_gcd.c,v $ */ /* $Revision: 1.4 $ */ /* $Date: 2006/03/31 14:18:44 $ */