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Diffstat (limited to '')
-rw-r--r-- | third_party/heimdal/lib/hcrypto/libtommath/bn_mp_cnt_lsb.c | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_cnt_lsb.c b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_cnt_lsb.c new file mode 100644 index 0000000..4b2d206 --- /dev/null +++ b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_cnt_lsb.c @@ -0,0 +1,37 @@ +#include "tommath_private.h" +#ifdef BN_MP_CNT_LSB_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis */ +/* SPDX-License-Identifier: Unlicense */ + +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_IS_ZERO(a)) { + return 0; + } + + /* scan lower digits until non-zero */ + for (x = 0; (x < a->used) && (a->dp[x] == 0u); x++) {} + q = a->dp[x]; + x *= MP_DIGIT_BIT; + + /* now scan this digit until a 1 is found */ + if ((q & 1u) == 0u) { + do { + qq = q & 15u; + x += lnz[qq]; + q >>= 4; + } while (qq == 0u); + } + return x; +} + +#endif |