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author | William Joye <wjoye@cfa.harvard.edu> | 2016-12-21 22:56:22 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2016-12-21 22:56:22 (GMT) |
commit | d1a6de55efc90f190dee42ab8c4fa9070834e77d (patch) | |
tree | ec633f5608ef498bee52a5f42c12c49493ec8bf8 /tcl8.6/libtommath/bn_mp_cnt_lsb.c | |
parent | 5514e37335c012cc70f5b9aee3cedfe3d57f583f (diff) | |
parent | 98acd3f494b28ddd8c345a2bb9311e41e2d56ddd (diff) | |
download | blt-d1a6de55efc90f190dee42ab8c4fa9070834e77d.zip blt-d1a6de55efc90f190dee42ab8c4fa9070834e77d.tar.gz blt-d1a6de55efc90f190dee42ab8c4fa9070834e77d.tar.bz2 |
Merge commit '98acd3f494b28ddd8c345a2bb9311e41e2d56ddd' as 'tcl8.6'
Diffstat (limited to 'tcl8.6/libtommath/bn_mp_cnt_lsb.c')
-rw-r--r-- | tcl8.6/libtommath/bn_mp_cnt_lsb.c | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/tcl8.6/libtommath/bn_mp_cnt_lsb.c b/tcl8.6/libtommath/bn_mp_cnt_lsb.c new file mode 100644 index 0000000..f205e8c --- /dev/null +++ b/tcl8.6/libtommath/bn_mp_cnt_lsb.c @@ -0,0 +1,49 @@ +#include <tommath.h> +#ifdef BN_MP_CNT_LSB_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 + */ + +static const int lnz[16] = { + 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0 +}; + +/* Counts the number of lsbs which are zero before the first zero bit */ +int mp_cnt_lsb(const mp_int *a) +{ + int x; + mp_digit q, qq; + + /* easy out */ + if (mp_iszero(a) == 1) { + return 0; + } + + /* scan lower digits until non-zero */ + for (x = 0; x < a->used && a->dp[x] == 0; x++); + q = a->dp[x]; + x *= DIGIT_BIT; + + /* now scan this digit until a 1 is found */ + if ((q & 1) == 0) { + do { + qq = q & 15; + x += lnz[qq]; + q >>= 4; + } while (qq == 0); + } + return x; +} + +#endif |