Fix copy_str performance

fmtlib · Sep 1, 2021 · 10905c8 · 10905c8
1 parent 34caecd
commit 10905c8
Showing 1 changed file with 13 additions and 6 deletions.
diff --git a/include/fmt/core.h b/include/fmt/core.h
@@ -740,19 +740,26 @@ inline auto get_container(std::back_insert_iterator<Container> it)
 }
 
 template <typename Char, typename InputIt, typename OutputIt>
-FMT_CONSTEXPR auto copy_str(InputIt begin, InputIt end, OutputIt out)
+FMT_CONSTEXPR auto copy_str_constexpr(InputIt begin, InputIt end, OutputIt out)
     -> OutputIt {
   while (begin != end) *out++ = static_cast<Char>(*begin++);
   return out;
 }
 
-template <typename Char, FMT_ENABLE_IF(std::is_same<Char, char>::value)>
-FMT_CONSTEXPR auto copy_str(const Char* begin, const Char* end, Char* out)
-    -> Char* {
+template <typename Char, typename InputIt, typename OutputIt>
+FMT_CONSTEXPR auto copy_str(InputIt begin, InputIt end, OutputIt out)
+    -> OutputIt {
+  return copy_str_constexpr<Char>(begin, end, out);
+}
+
+template <typename Char, typename Tp, typename Up,
+FMT_ENABLE_IF(std::is_same<remove_reference_t<Tp>, Up>::value && is_char<Up>::value)>
+FMT_CONSTEXPR auto copy_str(Tp* begin, Tp* end, Up* out)
+    -> Up* {
   if (is_constant_evaluated())
-    return copy_str<Char, const Char*, Char*>(begin, end, out);
+    return copy_str_constexpr<Char>(begin, end, out);
   auto size = to_unsigned(end - begin);
-  memcpy(out, begin, size);
+  memcpy(out, begin, size * sizeof(Up));
   return out + size;
 }