diff options
| -rw-r--r-- | include/bit_ops.h | 13 | ||||
| -rw-r--r-- | src/numthry.cpp | 2 |
2 files changed, 13 insertions, 2 deletions
diff --git a/include/bit_ops.h b/include/bit_ops.h index 42b922620..ca6fb7d5d 100644 --- a/include/bit_ops.h +++ b/include/bit_ops.h @@ -13,7 +13,6 @@ namespace Botan { /************************************************* * Return true iff arg is 2**n for some n > 0 * * T should be an unsigned integer type * -* *************************************************/ template<typename T> inline bool power_of_2(T arg) @@ -71,6 +70,18 @@ inline u32bit hamming_weight(T n) return weight; } +/************************************************* +* Count the trailing zero bits in n * +*************************************************/ +template<typename T> +inline int ctz(T n) + { + for(int i = 0; i != 8*sizeof(T); ++i) + if((n >> i) & 0x01) + return i; + return 8*sizeof(T); + } + } #endif diff --git a/src/numthry.cpp b/src/numthry.cpp index 9f05b6114..ffd523e82 100644 --- a/src/numthry.cpp +++ b/src/numthry.cpp @@ -86,7 +86,7 @@ u32bit low_zero_bits(const BigInt& n) if(x) { - low_zero += __builtin_ctzl(x); + low_zero += ctz(x); break; } else |