Merge branch 'no-exceptional-control-flow' of github.com:Ethsnarks/libfqfft into no-exceptional-control-flow

Author: HarryR

libfqfft/evaluation_domain/domains/basic_radix2_domain.tcc

@@ -35,11 +35,11 @@ bool basic_radix2_domain<FieldT>::valid_for_size(const size_t m)
 
         if (logm > FieldT::s)
             return false;
-
-        if (m != 1u << logm)
-            return false;
     }
 
+    if( get_root_of_unity_will_throw<FieldT>(m) )
+        return false;
+
     return true;
 }
 

libfqfft/evaluation_domain/domains/extended_radix2_domain.tcc

@@ -30,15 +30,12 @@ bool extended_radix2_domain<FieldT>::valid_for_size(const size_t m)
 
         if (logm != (FieldT::s + 1))
             return false;
+    }
 
-        size_t small_m = m / 2;
-
-        if (small_m > FieldT::s)
-            return false;
+    size_t small_m = m / 2;
 
-        if (m != (1u << small_m))
-            return false;
-    }
+    if( get_root_of_unity_will_throw<FieldT>(small_m) )
+        return false;
 
     return true;
 }

libfqfft/evaluation_domain/domains/step_radix2_domain.tcc

@@ -29,17 +29,13 @@ bool step_radix2_domain<FieldT>::valid_for_size(const size_t m)
     if (small_m != 1ul<<libff::log2(small_m))
         return false;
 
-    // Will `get_root_of_unity` throw?
-    if (!std::is_same<FieldT, libff::Double>::value)
-    {
-        const size_t logm = libff::log2(m);
-
-        if (m != (1u << logm))
-            return false;
+    // omega
+    if( get_root_of_unity_will_throw<FieldT>(1ul<<libff::log2(m)) )
+        return false;
 
-        if (logm > FieldT::s)
-            return false;
-    }
+    // small_omega
+    if( get_root_of_unity_will_throw<FieldT>(1ul<<libff::log2(small_m)) )
+        return false;
 
     return true;
 }

libfqfft/evaluation_domain/evaluation_domain.hpp

@@ -27,9 +27,34 @@
 #define EVALUATION_DOMAIN_HPP_
 
 #include <vector>
+#include <libff/common/double.hpp>
 
 namespace libfqfft {
 
+template<typename FieldT>
+typename std::enable_if<std::is_same<FieldT, libff::Double>::value, bool>::type
+get_root_of_unity_will_throw(const size_t n)
+{
+    return false;
+}
+
+
+template<typename FieldT>
+typename std::enable_if<!std::is_same<FieldT, libff::Double>::value, bool>::type
+get_root_of_unity_will_throw(const size_t n)
+{
+    const size_t logn = libff::log2(n);
+
+    if (n != (1u << logn))
+        return true;
+
+    if (logn > FieldT::s)
+        return true;
+
+    return false;
+}
+
+
 /**
  * An evaluation domain.
  */