fixup size literals

libraries/libfc/include/fc/utility.hpp

@@ -208,37 +208,39 @@ namespace fc {
   //TODO: these should really be consteval, but they're getting pulled in by a few of our c++17 compiled files
   namespace size_literals {
      namespace detail {
-        template <unsigned ShiftAmount>
-        constexpr unsigned long long to_bytes(const unsigned long long val) {
+        constexpr unsigned long long multiply_pow2(const unsigned long long val, const unsigned long long shift) {
+           if(shift >= std::numeric_limits<unsigned long long>::digits)
+              throw std::invalid_argument("exponent for pow2 too large");
+
            constexpr unsigned long long max_ull = std::numeric_limits<unsigned long long>::max();
-           constexpr unsigned long long multiplier = 1ull << ShiftAmount;
-           if(val > max_ull/multiplier)
+
+           if(val > (max_ull >> shift))
               throw std::invalid_argument("literal too large");
-           return val * multiplier;
+
+           return val << shift;
         }
      }
 
      constexpr unsigned long long operator""_KiB(const unsigned long long val) {
-        return detail::to_bytes<10>(val);
+        return detail::multiply_pow2(val, 10);
      }
      constexpr unsigned long long operator""_MiB(const unsigned long long val) {
-        return detail::to_bytes<20>(val);
+        return detail::multiply_pow2(val, 20);
      }
      constexpr unsigned long long operator""_GiB(const unsigned long long val) {
-        return detail::to_bytes<30>(val);
+        return detail::multiply_pow2(val, 30);
      }
      constexpr unsigned long long operator""_TiB(const unsigned long long val) {
-        return detail::to_bytes<40>(val);
+        return detail::multiply_pow2(val, 40);
      }
 
      constexpr unsigned long long operator""_pow2(const unsigned long long n) {
-        if(n >= std::numeric_limits<unsigned long long>::digits)
-           throw std::invalid_argument("exponent for _pow2 too large");
-        return 1ull << n;
+        return detail::multiply_pow2(1, n);
      }
 
      static_assert(4_MiB == 4*1024*1024);
      static_assert(16_pow2 == 64*1024);
+     static_assert(63_pow2 == 9223372036854775808ull);
   }
 
 }