wip

src/scn/impl.cpp

@@ -3875,25 +3875,38 @@ class tm_reader {
     scan_error m_error{};
 };
 
-template <typename CharT, typename T, typename Context>
-auto chrono_scan_impl(std::basic_string_view<CharT> fmt_str, T& t, Context& ctx)
-    -> scan_expected<typename Context::iterator>
+template <typename CharT,
+          typename T,
+          typename Context,
+          typename Iterator,
+          typename Sentinel>
+auto chrono_scan_inner_impl(std::basic_string_view<CharT> fmt,
+                            T& t,
+                            Context& ctx,
+                            ranges::subrange<Iterator, Sentinel> rng)
+    -> scan_expected<Iterator>
 {
     {
-        SCN_TRY(it,
-                detail::internal_skip_classic_whitespace(ctx.range(), false));
+        SCN_TRY(it, detail::internal_skip_classic_whitespace(rng, false));
         ctx.advance_to(SCN_MOVE(it));
     }
-    auto r = detail::tm_reader<T, typename Context::range_type, CharT>(
-        ctx.range(), t, ctx.locale());
-    detail::parse_chrono_format_specs(fmt_str.data(),
-                                      fmt_str.data() + fmt_str.size(), r);
+
+    auto r = detail::tm_reader<T, ranges::subrange<Iterator, Sentinel>, CharT>(
+        rng, t, ctx.locale());
+    detail::parse_chrono_format_specs(fmt.data(), fmt.data() + fmt.size(), r);
     if (auto e = r.get_error(); SCN_UNLIKELY(!e)) {
         return unexpected(e);
     }
     return r.get_iterator();
 }
 
+template <typename CharT, typename T, typename Context>
+auto chrono_scan_impl(std::basic_string_view<CharT> fmt_str, T& t, Context& ctx)
+    -> scan_expected<typename Context::iterator>
+{
+    return chrono_scan_inner_impl(fmt_str, t, ctx, ctx.range());
+}
+
 template auto chrono_scan_impl(std::string_view, std::tm&, scan_context&)
     -> scan_expected<scan_context::iterator>;
 template auto chrono_scan_impl(std::string_view, tm_with_tz&, scan_context&)