Reduce the memory allocations

Signed-off-by: Vladislav Shchapov <vladislav@shchapov.ru>

include/fmt/core.h

@@ -2776,8 +2776,13 @@ template <typename Char>
 void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
                 typename vformat_args<Char>::type args, locale_ref loc = {});
 
+FMT_API void vprint(std::FILE* f, string_view format_str, format_args args,
+                    string_view suffix);
+FMT_API void vprint_mojibake(std::FILE*, string_view, format_args, string_view);
 FMT_API void vprint_mojibake(std::FILE*, string_view, format_args);
 #ifndef _WIN32
+inline void vprint_mojibake(std::FILE*, string_view, format_args, string_view) {
+}
 inline void vprint_mojibake(std::FILE*, string_view, format_args) {}
 #endif
 FMT_END_DETAIL_NAMESPACE
@@ -3021,7 +3026,9 @@ FMT_INLINE void print(std::FILE* f, format_string<T...> fmt, T&&... args) {
  */
 template <typename... T>
 FMT_INLINE void println(std::FILE* f, format_string<T...> fmt, T&&... args) {
-  return fmt::print(f, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
+  const auto& vargs = fmt::make_format_args(args...);
+  return detail::is_utf8() ? detail::vprint(f, fmt, vargs, {"\n", 1})
+                           : detail::vprint_mojibake(f, fmt, vargs, {"\n", 1});
 }
 
 /**

include/fmt/format-inl.h

@@ -1482,23 +1482,35 @@ FMT_FUNC void print(std::FILE* f, string_view text) {
 #endif
   detail::fwrite_fully(text.data(), 1, text.size(), f);
 }
+
+FMT_FUNC void vprint(std::FILE* f, string_view format_str, format_args args,
+                     string_view suffix) {
+  memory_buffer buffer;
+  detail::vformat_to(buffer, format_str, args);
+  buffer.append(suffix);
+  detail::print(f, {buffer.data(), buffer.size()});
+}
+
 }  // namespace detail
 
 FMT_FUNC void vprint(std::FILE* f, string_view format_str, format_args args) {
-  memory_buffer buffer;
+  detail::vprint(f, format_str, args, {});
-  detail::vformat_to(buffer, format_str, args);
-  detail::print(f, {buffer.data(), buffer.size()});
 }
 
 #ifdef _WIN32
 // Print assuming legacy (non-Unicode) encoding.
 FMT_FUNC void detail::vprint_mojibake(std::FILE* f, string_view format_str,
-                                      format_args args) {
+                                      format_args args, string_view suffix) {
   memory_buffer buffer;
   detail::vformat_to(buffer, format_str,
                      basic_format_args<buffer_context<char>>(args));
+  buffer.append(suffix);
   fwrite_fully(buffer.data(), 1, buffer.size(), f);
 }
+FMT_FUNC void detail::vprint_mojibake(std::FILE* f, string_view format_str,
+                                      format_args args) {
+  vprint_mojibake(f, format_str, args, {});
+}
 #endif
 
 FMT_FUNC void vprint(string_view format_str, format_args args) {

include/fmt/ostream.h

@@ -188,9 +188,22 @@ struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
 };
 
 inline void vprint_directly(std::ostream& os, string_view format_str,
-                            format_args args) {
+                            format_args args, string_view suffix) {
   auto buffer = memory_buffer();
   detail::vformat_to(buffer, format_str, args);
+  buffer.append(suffix);
+  detail::write_buffer(os, buffer);
+}
+
+template <typename Char>
+void vprint(std::basic_ostream<Char>& os,
+            basic_string_view<type_identity_t<Char>> format_str,
+            basic_format_args<buffer_context<type_identity_t<Char>>> args,
+            basic_string_view<type_identity_t<Char>> suffix) {
+  auto buffer = basic_memory_buffer<Char>();
+  detail::vformat_to(buffer, format_str, args);
+  buffer.append(suffix);
+  if (detail::write_ostream_unicode(os, {buffer.data(), buffer.size()})) return;
   detail::write_buffer(os, buffer);
 }
 
@@ -200,10 +213,7 @@ FMT_MODULE_EXPORT template <typename Char>
 void vprint(std::basic_ostream<Char>& os,
             basic_string_view<type_identity_t<Char>> format_str,
             basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  auto buffer = basic_memory_buffer<Char>();
+  detail::vprint(os, format_str, args, {});
-  detail::vformat_to(buffer, format_str, args);
-  if (detail::write_ostream_unicode(os, {buffer.data(), buffer.size()})) return;
-  detail::write_buffer(os, buffer);
 }
 
 /**
@@ -221,7 +231,7 @@ void print(std::ostream& os, format_string<T...> fmt, T&&... args) {
   if (detail::is_utf8())
     vprint(os, fmt, vargs);
   else
-    detail::vprint_directly(os, fmt, vargs);
+    detail::vprint_directly(os, fmt, vargs, {});
 }
 
 FMT_MODULE_EXPORT
@@ -234,7 +244,11 @@ void print(std::wostream& os,
 
 FMT_MODULE_EXPORT template <typename... T>
 void println(std::ostream& os, format_string<T...> fmt, T&&... args) {
-  print(os, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
+  const auto& vargs = fmt::make_format_args(args...);
+  if (detail::is_utf8())
+    detail::vprint(os, fmt, vargs, {"\n", 1});
+  else
+    detail::vprint_directly(os, fmt, vargs, {"\n", 1});
 }
 
 FMT_MODULE_EXPORT
@@ -242,7 +256,9 @@ template <typename... Args>
 void println(std::wostream& os,
              basic_format_string<wchar_t, type_identity_t<Args>...> fmt,
              Args&&... args) {
-  print(os, L"{}\n", fmt::format(fmt, std::forward<Args>(args)...));
+  detail::vprint(os, fmt,
+                 fmt::make_format_args<buffer_context<wchar_t>>(args...),
+                 {L"\n", 1});
 }
 
 FMT_END_NAMESPACE