Mercurial > dropbear
view libtommath/bn_mp_2expt.c @ 367:c046b66b76cd channel-fix
propagate from branch 'au.asn.ucc.matt.dropbear' (head 31dcd7a22983ef19d6c63248e415e71d292dd0ec)
to branch 'au.asn.ucc.matt.dropbear.channel-fix' (head 7559a8cc4f6abe2338636f2aced3a395a79c172c)
author | Matt Johnston <matt@ucc.asn.au> |
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date | Thu, 12 Oct 2006 03:01:10 +0000 |
parents | eed26cff980b |
children | 5ff8218bcee9 |
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#include <tommath.h> #ifdef BN_MP_2EXPT_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 */ /* computes a = 2**b * * Simple algorithm which zeroes the int, grows it then just sets one bit * as required. */ int mp_2expt (mp_int * a, int b) { int res; /* zero a as per default */ mp_zero (a); /* grow a to accomodate the single bit */ if ((res = mp_grow (a, b / DIGIT_BIT + 1)) != MP_OKAY) { return res; } /* set the used count of where the bit will go */ a->used = b / DIGIT_BIT + 1; /* put the single bit in its place */ a->dp[b / DIGIT_BIT] = ((mp_digit)1) << (b % DIGIT_BIT); return MP_OKAY; } #endif