Replace __builtin_ctzl with a new ctz function in bit_ops.h

1 files changed, 12 insertions, 1 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