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Diffstat (limited to 'libtommath/bn_mp_2expt.c')
-rw-r--r-- | libtommath/bn_mp_2expt.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/libtommath/bn_mp_2expt.c b/libtommath/bn_mp_2expt.c new file mode 100644 index 0000000..7c91937 --- /dev/null +++ b/libtommath/bn_mp_2expt.c @@ -0,0 +1,48 @@ +#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, tomstdenis@iahu.ca, 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 + +/* $Source: /root/tcl/repos-to-convert/tcl/libtommath/bn_mp_2expt.c,v $ */ +/* $Revision: 1.1.1.1.2.1 $ */ +/* $Date: 2005/09/26 20:16:53 $ */ |