Optimize writing to buffers via back_insert_iterator

fmtlib · Sep 12, 2022 · 192859c · 192859c
1 parent e2f6d76
commit 192859c
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Showing 5 changed files with 16 additions and 16 deletions.
diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
@@ -427,7 +427,7 @@ auto write(OutputIt out, const std::tm& time, const std::locale& loc,
            char format, char modifier = 0) -> OutputIt {
   auto&& buf = get_buffer<Char>(out);
   do_write<Char>(buf, time, loc, format, modifier);
-  return get_iterator(buf);
+  return get_iterator(buf, out);
 }
 
 template <typename Char, typename OutputIt,

diff --git a/include/fmt/color.h b/include/fmt/color.h
@@ -566,7 +566,7 @@ OutputIt vformat_to(
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   auto&& buf = detail::get_buffer<Char>(out);
   detail::vformat_to(buf, ts, format_str, args);
-  return detail::get_iterator(buf);
+  return detail::get_iterator(buf, out);
 }
 
 /**

diff --git a/include/fmt/core.h b/include/fmt/core.h
@@ -1123,13 +1123,19 @@ template <typename T, typename OutputIt>
 auto get_buffer(OutputIt out) -> iterator_buffer<OutputIt, T> {
   return iterator_buffer<OutputIt, T>(out);
 }
+template <typename T, typename Buf,
+          FMT_ENABLE_IF(std::is_base_of<buffer<char>, Buf>::value)>
+auto get_buffer(std::back_insert_iterator<Buf> out) -> buffer<char>& {
+  return get_container(out);
+}
 
-template <typename Buffer>
-FMT_INLINE auto get_iterator(Buffer& buf) -> decltype(buf.out()) {
+template <typename Buf, typename OutputIt>
+FMT_INLINE auto get_iterator(Buf& buf, OutputIt) -> decltype(buf.out()) {
   return buf.out();
 }
-template <typename T> auto get_iterator(buffer<T>& buf) -> buffer_appender<T> {
-  return buffer_appender<T>(buf);
+template <typename T, typename OutputIt>
+auto get_iterator(buffer<T>&, OutputIt out) -> OutputIt {
+  return out;
 }
 
 template <typename T, typename Char = char, typename Enable = void>
@@ -1556,11 +1562,6 @@ FMT_END_DETAIL_NAMESPACE
 class appender : public std::back_insert_iterator<detail::buffer<char>> {
   using base = std::back_insert_iterator<detail::buffer<char>>;
 
-  template <typename T>
-  friend auto get_buffer(appender out) -> detail::buffer<char>& {
-    return detail::get_container(out);
-  }
-
  public:
   using std::back_insert_iterator<detail::buffer<char>>::back_insert_iterator;
   appender(base it) noexcept : base(it) {}
@@ -3224,10 +3225,9 @@ FMT_NODISCARD FMT_INLINE auto format(format_string<T...> fmt, T&&... args)
 template <typename OutputIt,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
 auto vformat_to(OutputIt out, string_view fmt, format_args args) -> OutputIt {
-  using detail::get_buffer;
-  auto&& buf = get_buffer<char>(out);
+  auto&& buf = detail::get_buffer<char>(out);
   detail::vformat_to(buf, fmt, args, {});
-  return detail::get_iterator(buf);
+  return detail::get_iterator(buf, out);
 }
 
 /**

diff --git a/include/fmt/format.h b/include/fmt/format.h
@@ -4276,7 +4276,7 @@ auto vformat_to(OutputIt out, const Locale& loc, string_view fmt,
   using detail::get_buffer;
   auto&& buf = get_buffer<char>(out);
   detail::vformat_to(buf, fmt, args, detail::locale_ref(loc));
-  return detail::get_iterator(buf);
+  return detail::get_iterator(buf, out);
 }
 
 template <typename OutputIt, typename Locale, typename... T,

diff --git a/include/fmt/xchar.h b/include/fmt/xchar.h
@@ -145,7 +145,7 @@ auto vformat_to(OutputIt out, const S& format_str,
     -> OutputIt {
   auto&& buf = detail::get_buffer<Char>(out);
   detail::vformat_to(buf, detail::to_string_view(format_str), args);
-  return detail::get_iterator(buf);
+  return detail::get_iterator(buf, out);
 }
 
 template <typename OutputIt, typename S, typename... Args,