diff options
Diffstat (limited to 'src/numthry.cpp')
| -rw-r--r-- | src/numthry.cpp | 28 |
1 files changed, 22 insertions, 6 deletions
diff --git a/src/numthry.cpp b/src/numthry.cpp index 2b900e96c..9f05b6114 100644 --- a/src/numthry.cpp +++ b/src/numthry.cpp @@ -1,9 +1,10 @@ /************************************************* * Number Theory Source File * -* (C) 1999-2007 Jack Lloyd * +* (C) 1999-2008 Jack Lloyd * *************************************************/ #include <botan/numthry.h> +#include <botan/bit_ops.h> #include <algorithm> namespace Botan { @@ -73,12 +74,27 @@ u32bit miller_rabin_test_iterations(u32bit bits, bool verify) *************************************************/ u32bit low_zero_bits(const BigInt& n) { - if(n.is_zero()) return 0; + if(n.is_negative() || n.is_zero()) return 0; - u32bit bits = 0, max_bits = n.bits(); - while((n.get_bit(bits) == 0) && bits < max_bits) - ++bits; - return bits; + u32bit low_zero = 0; + + if(n.is_positive() && n.is_nonzero()) + { + for(u32bit i = 0; i != n.size(); ++i) + { + word x = n[i]; + + if(x) + { + low_zero += __builtin_ctzl(x); + break; + } + else + low_zero += BOTAN_MP_WORD_BITS; + } + } + + return low_zero; } /************************************************* |