diff --git a/libcxx/include/__format/buffer.h b/libcxx/include/__format/buffer.h
--- a/libcxx/include/__format/buffer.h
+++ b/libcxx/include/__format/buffer.h
@@ -11,11 +11,15 @@
#define _LIBCPP___FORMAT_BUFFER_H
#include <__algorithm/copy_n.h>
+#include <__algorithm/max.h>
+#include <__algorithm/min.h>
#include <__algorithm/unwrap_iter.h>
#include <__config>
+#include <__format/format_to_n_result.h>
#include <__format/formatter.h> // for __char_type TODO FMT Move the concept?
#include <__iterator/back_insert_iterator.h>
#include <__iterator/concepts.h>
+#include <__iterator/incrementable_traits.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/wrap_iter.h>
#include <__utility/move.h>
@@ -27,6 +31,9 @@
# pragma GCC system_header
#endif
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 17
@@ -278,10 +285,108 @@
size_t __size_{0};
};
+/// The base of a buffer that counts and limits the number of insertions.
+template <class _OutIt, __formatter::__char_type _CharT, bool>
+requires(output_iterator<_OutIt, const _CharT&>) struct _LIBCPP_TEMPLATE_VIS
+ __format_to_n_buffer_base {
+ using _Size = iter_difference_t<_OutIt>;
+
+public:
+ _LIBCPP_HIDE_FROM_ABI explicit __format_to_n_buffer_base(_OutIt __out_it,
+ _Size __n)
+ : __writer_(_VSTD::move(__out_it)), __n_(_VSTD::max(_Size(0), __n)) {}
+
+ _LIBCPP_HIDE_FROM_ABI void flush(_CharT* __ptr, size_t __size) {
+ if (_Size(__size_) <= __n_)
+ __writer_.flush(__ptr, _VSTD::min(_Size(__size), __n_ - __size_));
+ __size_ += __size;
+ }
+
+protected:
+ __internal_storage<_CharT> __storage_;
+ __output_buffer<_CharT> __output_{__storage_.begin(), __storage_.capacity(),
+ this};
+ typename __writer_selector<_OutIt, _CharT>::type __writer_;
+
+ _Size __n_;
+ _Size __size_{0};
+};
+
+/// The base of a buffer that counts and limits the number of insertions.
+///
+/// This version is used when \c __enable_direct_output<_OutIt, _CharT> == true.
+///
+/// This class limits the size available the the direct writer so it will not
+/// exceed the maximum number of code units.
+template <class _OutIt, __formatter::__char_type _CharT>
+requires(output_iterator<_OutIt, const _CharT&>) class _LIBCPP_TEMPLATE_VIS
+ __format_to_n_buffer_base<_OutIt, _CharT, true> {
+ using _Size = iter_difference_t<_OutIt>;
+
+public:
+ _LIBCPP_HIDE_FROM_ABI explicit __format_to_n_buffer_base(_OutIt __out_it,
+ _Size __n)
+ : __output_(_VSTD::__unwrap_iter(__out_it), __n, this),
+ __writer_(_VSTD::move(__out_it)) {
+ if (__n <= 0) [[unlikely]]
+ __output_.reset(__storage_.begin(), __storage_.capacity());
+ }
+
+ _LIBCPP_HIDE_FROM_ABI void flush(_CharT* __ptr, size_t __size) {
+ // A flush to the direct writer happens in two occasions:
+ // - The format function has written the maximum number of allowed code
+ // units. At this point it's no longer valid to write to this writer. So
+ // switch to the internal storage. This internal storage doesn't need to
+ // be written anywhere so the flush for that storage writes no output.
+ // - The format_to_n function is finished. In this case there's no need to
+ // switch the buffer, but for simplicity the buffers are still switched.
+ // When the __n <= 0 the constructor already switched the buffers.
+ if (__size_ == 0 && __ptr != __storage_.begin()) {
+ __writer_.flush(__ptr, __size);
+ __output_.reset(__storage_.begin(), __storage_.capacity());
+ }
+
+ __size_ += __size;
+ }
+
+protected:
+ __internal_storage<_CharT> __storage_;
+ __output_buffer<_CharT> __output_;
+ __writer_direct<_OutIt, _CharT> __writer_;
+
+ _Size __size_{0};
+};
+
+/// The buffer that counts and limits the number of insertions.
+template <class _OutIt, __formatter::__char_type _CharT>
+requires(output_iterator<_OutIt, const _CharT&>) struct _LIBCPP_TEMPLATE_VIS
+ __format_to_n_buffer final
+ : public __format_to_n_buffer_base<
+ _OutIt, _CharT, __enable_direct_output<_OutIt, _CharT>> {
+ using _Base =
+ __format_to_n_buffer_base<_OutIt, _CharT,
+ __enable_direct_output<_OutIt, _CharT>>;
+ using _Size = iter_difference_t<_OutIt>;
+
+public:
+ _LIBCPP_HIDE_FROM_ABI explicit __format_to_n_buffer(_OutIt __out_it,
+ _Size __n)
+ : _Base(_VSTD::move(__out_it), __n) {}
+ _LIBCPP_HIDE_FROM_ABI auto make_output_iterator() {
+ return this->__output_.make_output_iterator();
+ }
+
+ _LIBCPP_HIDE_FROM_ABI format_to_n_result<_OutIt> result() && {
+ this->__output_.flush();
+ return {_VSTD::move(this->__writer_).out(), this->__size_};
+ }
+};
} // namespace __format
#endif //_LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
+_LIBCPP_POP_MACROS
+
#endif // _LIBCPP___FORMAT_BUFFER_H
diff --git a/libcxx/include/format b/libcxx/include/format
--- a/libcxx/include/format
+++ b/libcxx/include/format
@@ -362,31 +362,27 @@
}
#endif
+template <class _Context, class _OutIt, class _CharT>
+_LIBCPP_HIDE_FROM_ABI format_to_n_result<_OutIt> __vformat_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n,
+ basic_string_view<_CharT> __fmt,
+ basic_format_args<_Context> __args) {
+ __format::__format_to_n_buffer<_OutIt, _CharT> __buffer{_VSTD::move(__out_it), __n};
+ _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 <output_iterator<const char&> _OutIt, class... _Args>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT format_to_n_result<_OutIt>
-format_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n, string_view __fmt,
- const _Args&... __args) {
- // TODO FMT Improve PoC: using std::string is inefficient.
- string __str = _VSTD::vformat(__fmt, _VSTD::make_format_args(__args...));
- iter_difference_t<_OutIt> __s = __str.size();
- iter_difference_t<_OutIt> __m =
- _VSTD::clamp(__n, iter_difference_t<_OutIt>(0), __s);
- __out_it = _VSTD::copy_n(__str.begin(), __m, _VSTD::move(__out_it));
- return {_VSTD::move(__out_it), __s};
+_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT format_to_n_result<_OutIt>
+format_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n, string_view __fmt, const _Args&... __args) {
+ return _VSTD::__vformat_to_n<format_context>(_VSTD::move(__out_it), __n, __fmt, _VSTD::make_format_args(__args...));
}
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <output_iterator<const wchar_t&> _OutIt, class... _Args>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT format_to_n_result<_OutIt>
-format_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n, wstring_view __fmt,
- const _Args&... __args) {
- // TODO FMT Improve PoC: using std::string is inefficient.
- wstring __str = _VSTD::vformat(__fmt, _VSTD::make_wformat_args(__args...));
- iter_difference_t<_OutIt> __s = __str.size();
- iter_difference_t<_OutIt> __m =
- _VSTD::clamp(__n, iter_difference_t<_OutIt>(0), __s);
- __out_it = _VSTD::copy_n(__str.begin(), __m, _VSTD::move(__out_it));
- return {_VSTD::move(__out_it), __s};
+_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT format_to_n_result<_OutIt>
+format_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n, wstring_view __fmt, const _Args&... __args) {
+ return _VSTD::__vformat_to_n<wformat_context>(_VSTD::move(__out_it), __n, __fmt, _VSTD::make_wformat_args(__args...));
}
#endif
@@ -500,33 +496,30 @@
}
#endif
+template <class _Context, class _OutIt, class _CharT>
+_LIBCPP_HIDE_FROM_ABI format_to_n_result<_OutIt> __vformat_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n,
+ locale __loc, basic_string_view<_CharT> __fmt,
+ basic_format_args<_Context> __args) {
+ __format::__format_to_n_buffer<_OutIt, _CharT> __buffer{_VSTD::move(__out_it), __n};
+ _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 <output_iterator<const char&> _OutIt, class... _Args>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT format_to_n_result<_OutIt>
-format_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n, locale __loc,
- string_view __fmt, const _Args&... __args) {
- // TODO FMT Improve PoC: using std::string is inefficient.
- string __str = _VSTD::vformat(_VSTD::move(__loc), __fmt,
- _VSTD::make_format_args(__args...));
- iter_difference_t<_OutIt> __s = __str.size();
- iter_difference_t<_OutIt> __m =
- _VSTD::clamp(__n, iter_difference_t<_OutIt>(0), __s);
- __out_it = _VSTD::copy_n(__str.begin(), __m, _VSTD::move(__out_it));
- return {_VSTD::move(__out_it), __s};
+_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT format_to_n_result<_OutIt>
+format_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n, locale __loc, string_view __fmt, const _Args&... __args) {
+ return _VSTD::__vformat_to_n<format_context>(_VSTD::move(__out_it), __n, _VSTD::move(__loc), __fmt,
+ _VSTD::make_format_args(__args...));
}
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template <output_iterator<const wchar_t&> _OutIt, class... _Args>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT format_to_n_result<_OutIt>
-format_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n, locale __loc,
- wstring_view __fmt, const _Args&... __args) {
- // TODO FMT Improve PoC: using std::string is inefficient.
- wstring __str = _VSTD::vformat(_VSTD::move(__loc), __fmt,
- _VSTD::make_wformat_args(__args...));
- iter_difference_t<_OutIt> __s = __str.size();
- iter_difference_t<_OutIt> __m =
- _VSTD::clamp(__n, iter_difference_t<_OutIt>(0), __s);
- __out_it = _VSTD::copy_n(__str.begin(), __m, _VSTD::move(__out_it));
- return {_VSTD::move(__out_it), __s};
+_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_FORMAT format_to_n_result<_OutIt>
+format_to_n(_OutIt __out_it, iter_difference_t<_OutIt> __n, locale __loc, wstring_view __fmt, const _Args&... __args) {
+ return _VSTD::__vformat_to_n<wformat_context>(_VSTD::move(__out_it), __n, _VSTD::move(__loc), __fmt,
+ _VSTD::make_wformat_args(__args...));
}
#endif