[libc++][format][4/6] Improve formatted_size.
Use a specialized "buffer" to count the number of insertions instead of
using a `string` as storage type.
Depends on D110497.
Reviewed By: ldionne, #libc
Differential Revision: https://reviews.llvm.org/D110498
NOKEYCHECK=True
GitOrigin-RevId: fb9a692be5dd20db62c705bb371977dc30fb407f
diff --git a/include/__format/buffer.h b/include/__format/buffer.h
index 584345c..e5c3b9f 100644
--- a/include/__format/buffer.h
+++ b/include/__format/buffer.h
@@ -244,6 +244,29 @@
__output_buffer<_CharT> __output_;
typename __writer_selector<_OutIt, _CharT>::type __writer_;
};
+
+/// A buffer that counts the number of insertions.
+///
+/// Since \ref formatted_size only needs to know the size, the output itself is
+/// discarded.
+template <__formatter::__char_type _CharT>
+class _LIBCPP_TEMPLATE_VIS __formatted_size_buffer {
+public:
+ _LIBCPP_HIDE_FROM_ABI auto make_output_iterator() { return __output_.make_output_iterator(); }
+
+ _LIBCPP_HIDE_FROM_ABI void flush(const _CharT*, size_t __size) { __size_ += __size; }
+
+ _LIBCPP_HIDE_FROM_ABI size_t result() && {
+ __output_.flush();
+ return __size_;
+ }
+
+private:
+ __internal_storage<_CharT> __storage_;
+ __output_buffer<_CharT> __output_{__storage_.begin(), __storage_.capacity(), this};
+ size_t __size_{0};
+};
+
} // namespace __format
#endif //_LIBCPP_STD_VER > 17
diff --git a/include/format b/include/format
index 4ae98ce..9516278 100644
--- a/include/format
+++ b/include/format
@@ -392,19 +392,25 @@
}
#endif
+template <class _CharT>
+_LIBCPP_HIDE_FROM_ABI size_t __vformatted_size(basic_string_view<_CharT> __fmt, auto __args) {
+ __format::__formatted_size_buffer<_CharT> __buffer;
+ _VSTD::__format::__vformat_to(basic_format_parse_context{__fmt, __args.__size()},
+ _VSTD::__format_context_create(__buffer.make_output_iterator(), __args));
+ return _VSTD::move(__buffer).result();
+}
+
template <class... _Args>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT size_t
-formatted_size(string_view __fmt, const _Args&... __args) {
- // TODO FMT Improve PoC: using std::string is inefficient.
- return _VSTD::vformat(__fmt, _VSTD::make_format_args(__args...)).size();
+_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT size_t formatted_size(string_view __fmt,
+ const _Args&... __args) {
+ return _VSTD::__vformatted_size(__fmt, basic_format_args{_VSTD::make_format_args(__args...)});
}
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <class... _Args>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT size_t
-formatted_size(wstring_view __fmt, const _Args&... __args) {
- // TODO FMT Improve PoC: using std::string is inefficient.
- return _VSTD::vformat(__fmt, _VSTD::make_wformat_args(__args...)).size();
+_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT size_t formatted_size(wstring_view __fmt,
+ const _Args&... __args) {
+ return _VSTD::__vformatted_size(__fmt, basic_format_args{_VSTD::make_wformat_args(__args...)});
}
#endif
@@ -526,23 +532,28 @@
}
#endif
+template <class _CharT>
+_LIBCPP_HIDE_FROM_ABI size_t __vformatted_size(locale __loc, basic_string_view<_CharT> __fmt, auto __args) {
+ __format::__formatted_size_buffer<_CharT> __buffer;
+ _VSTD::__format::__vformat_to(
+ basic_format_parse_context{__fmt, __args.__size()},
+ _VSTD::__format_context_create(__buffer.make_output_iterator(), __args, _VSTD::move(__loc)));
+ return _VSTD::move(__buffer).result();
+}
+
template <class... _Args>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT size_t
-formatted_size(locale __loc, string_view __fmt, const _Args&... __args) {
- // TODO FMT Improve PoC: using std::string is inefficient.
- return _VSTD::vformat(_VSTD::move(__loc), __fmt,
- _VSTD::make_format_args(__args...))
- .size();
+_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT size_t formatted_size(locale __loc,
+ string_view __fmt,
+ const _Args&... __args) {
+ return _VSTD::__vformatted_size(_VSTD::move(__loc), __fmt, basic_format_args{_VSTD::make_format_args(__args...)});
}
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <class... _Args>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT size_t
-formatted_size(locale __loc, wstring_view __fmt, const _Args&... __args) {
- // TODO FMT Improve PoC: using std::string is inefficient.
- return _VSTD::vformat(_VSTD::move(__loc), __fmt,
- _VSTD::make_wformat_args(__args...))
- .size();
+_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT size_t formatted_size(locale __loc,
+ wstring_view __fmt,
+ const _Args&... __args) {
+ return _VSTD::__vformatted_size(_VSTD::move(__loc), __fmt, basic_format_args{_VSTD::make_wformat_args(__args...)});
}
#endif