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author | William Joye <wjoye@cfa.harvard.edu> | 2017-09-22 18:57:19 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2017-09-22 18:57:19 (GMT) |
commit | 2aff4a96fa0286d875bddec0019648e2c6431cbc (patch) | |
tree | f7a9a4800a3f3ad4b77470b8383529176d8b7181 /tcl8.6/libtommath/bn_mp_mul_2.c | |
parent | 3fa8e6dc88e8041b6cb88d1b1e9c05676d3346b7 (diff) | |
parent | 29ccecd87709feda60d191f6aaba324ccad91f55 (diff) | |
download | blt-2aff4a96fa0286d875bddec0019648e2c6431cbc.zip blt-2aff4a96fa0286d875bddec0019648e2c6431cbc.tar.gz blt-2aff4a96fa0286d875bddec0019648e2c6431cbc.tar.bz2 |
Merge commit '29ccecd87709feda60d191f6aaba324ccad91f55' as 'tcl8.6'
Diffstat (limited to 'tcl8.6/libtommath/bn_mp_mul_2.c')
-rw-r--r-- | tcl8.6/libtommath/bn_mp_mul_2.c | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/tcl8.6/libtommath/bn_mp_mul_2.c b/tcl8.6/libtommath/bn_mp_mul_2.c new file mode 100644 index 0000000..2ca6022 --- /dev/null +++ b/tcl8.6/libtommath/bn_mp_mul_2.c @@ -0,0 +1,78 @@ +#include <tommath.h> +#ifdef BN_MP_MUL_2_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@gmail.com, http://math.libtomcrypt.com + */ + +/* b = a*2 */ +int mp_mul_2(mp_int * a, mp_int * b) +{ + int x, res, oldused; + + /* grow to accomodate result */ + if (b->alloc < a->used + 1) { + if ((res = mp_grow (b, a->used + 1)) != MP_OKAY) { + return res; + } + } + + oldused = b->used; + b->used = a->used; + + { + register mp_digit r, rr, *tmpa, *tmpb; + + /* alias for source */ + tmpa = a->dp; + + /* alias for dest */ + tmpb = b->dp; + + /* carry */ + r = 0; + for (x = 0; x < a->used; x++) { + + /* get what will be the *next* carry bit from the + * MSB of the current digit + */ + rr = *tmpa >> ((mp_digit)(DIGIT_BIT - 1)); + + /* now shift up this digit, add in the carry [from the previous] */ + *tmpb++ = ((*tmpa++ << ((mp_digit)1)) | r) & MP_MASK; + + /* copy the carry that would be from the source + * digit into the next iteration + */ + r = rr; + } + + /* new leading digit? */ + if (r != 0) { + /* add a MSB which is always 1 at this point */ + *tmpb = 1; + ++(b->used); + } + + /* now zero any excess digits on the destination + * that we didn't write to + */ + tmpb = b->dp + b->used; + for (x = b->used; x < oldused; x++) { + *tmpb++ = 0; + } + } + b->sign = a->sign; + return MP_OKAY; +} +#endif |